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Field studies on soil ammonia (NH3) volatilization are restricted in many countries owing to the high costs commonly demanded for accurate quantification. We assessed the accuracy of a simple, open chamber design to capture NH3 under field conditions, as affected by different chamber placement schemes. Urea-15N was surface applied to lysimeters installed in the spaces between maize rows. Open chambers made from plastic bottles were installed on each lysimeter with variations in i) N rates (3, 8, 13, and 18 g m–2), ii) the height of the chamber above the soil surface (0, 5, and 10 mm), and iii) chamber relocation (static vs. dynamic). Reference lysimeters without chambers were used to measure NH3 losses by 15N-balance. Losses of NH3 -N accounted for more than 50% of the applied N. Relocation of the chambers had no impact on their NH3-trapping efficiencies, proving to be an unnecessary procedure. Variation in the height of the chambers above the soil surface affected the capture of NH3, but the results still maintained high linearity with the NH3 losses quantified by the reference method (R2 > 0.98). When the same placement scheme used in the introductory study describing the chamber was utilized (static and touching the soil surface), we found a trapping efficiency of 60%, which was very similar to that (57%) obtained in the previous study. Our results show that this simple, open chamber design can be used with satisfactory accuracy under field conditions, provided that simple, standardized procedures are warranted.

Radionuclide fallout during nuclear accidents on the land may impair the atmosphere, contaminate farmland soils and crops, and can even reach the groundwater. Previous research focused on the field distribution of deposited radionuclides in farmland soils, but details of the amounts of radionuclides in the plough layer and the changes in their proportional distribution in the soil profile with time are still inadequate. In this study, a lysimeter experiment was conducted to determine the vertical migration of 137Cs and 60Co in brown and aeolian sandy soils, collected from the farmlands adjoining Shidaowan Nuclear Power Plant (NPP) in eastern China, and to identify the factors influencing their migration depths in soil. At the end of the experiment (800 d), > 96% of added 137Cs and 60Co were retained in the top 0–20 cm soil layer of both soils; very little 137Cs or 60Co initially migrated to 20–30 cm, but their amounts at this depth increased with time. The migration depth of 137Cs was greater in the aeolian sandy soil than in the brown soil during 0–577 d, but at the end of the experiment, 137Cs migrated to the same depth (25 cm) in both soils. Three phases on the vertical migration rate (v) of 60Co in the aeolian sandy soil can be identified: an initial rapid movement (0–355 d, v = 219 ± 17 mm year–1), followed by a steady movement (355–577 d, v = 150 ± 24 mm year–1) and a very slow movement (577–800 d, v = 107 ± 7 mm year–1). In contrast, its migration rate in the brown soil (v = 133 ± 17 mm year–1) was steady throughout the 800-d experimental period. The migration of both 137Cs and 60Co in the two soils appears to be regulated by soil clay and silt fractions that provide most of the soil surface area, soil organic carbon (SOC), and soil pH, which were manifested by the solid-liquid distribution coefficient of 137Cs and 60Co. The results of this study suggest that most 137Cs and 60Co remained within the top layer (0–20 cm depth) of farmland soils following a simulated NPP accident, and little reached the subsurface (20–30 cm depth). Fixation of radionuclides onto clay minerals may limit their migration in soil, but some could be laterally distributed by soil erosion and taken up by crops, and migrate into groundwater in a high water table level area after several decades. Remediation measures, therefore, should focus on reducing their impact on the farmland soils, crops, and water.

Salinity represents a medium with high soluble salts where as sodicity represents a medium with high exchangeable sodium, low calcium and highly alkaline pH. Salinity and sodicity commonly occur together in salt-affected soils however physiological studies have mostly considered salinity alone ending up in poor field success of the selected genetic resources. Similarly, the role of root-mediated acidification in salt resistance is not known in wheat. Here six wheat genotypes were exposed to salinity (NaCl: 125 mM), low calcium (25% of non-treated control) and salinity + low calcium in solution culture. There were significant differences among the wheat genotypes for growth and leaf ionic composition under salinity, low calcium and salinity + low calcium treatments. The wheat genotypes SARC-1, 25-SAWSN-42 and Pasban-90 accumulated higher K+ and Ca2+ and lower Na+ and Cl− and were resistant to the combined stress of low calcium and salinity. These genotypes also showed higher root-mediated acidification under stress conditions. The wheat genotypes resistant to salinity + low calcium supply in solution culture also performed better in the saline-sodic soil in a lysimeter study. A genotype resistant to salinity alone accumulated lower Ca2+ and showed lower rhizosphere acidification potential and did not perform good in saline-sodic soil conditions. Therefore, root-mediated acidification potential and resistance to low calcium supply improves resistance of wheat to saline-sodic conditions. It is further suggested that screening of the wheat germplasm for saline-sodic soils should be carried out at salinity + low calcium to better simulate saline-sodic field conditions.

Perchloroethene (PCE) is a hazardous and persistent groundwater pollutant. Both treatment with nanoscaled zero-valent iron (nZVI) and biological degradation by bacteria have downsides. Distribution of nZVI underground is difficult and a high percentage of injected nZVI is consumed by anaerobic corrosion, forming H2 rather than being available for PCE dechlorination. On the other hand, microbial PCE degradation can suffer from the absence of H2. This can cause the accumulation of the hazardous metabolites cis-1,2-dichloroethene (DCE) or vinylchloride (VC). The combination of chemical and biological PCE degradation is a promising approach to overcome the disadvantages of each method alone. In this lysimeter study, artificial aquifers were created to test the influence of nZVI on anaerobic microbial PCE dechlorination by a commercially available culture containing Dehalococcoides spp. under field-like conditions. The effect of the combined treatment was investigated with molasses as an additional electron source and after cessation of molasses addition. The combination of nZVI and the Dehalococcoides spp. containing culture led to a PCE discharge in the lysimeter outflow that was 4.7 times smaller than that with nZVI and 1.6 times smaller than with bacterial treatment. Moreover, fully dechlorinated end-products showed an 11-fold increase compared to nZVI and a 4.2-fold increase compared to the microbial culture. The addition of nZVI to the microbial culture also decreased the accumulation of hazardous metabolites by 1.7 (cis-DCE) and 1.2 fold (VC). The stimulatory effect of nZVI on microbial degradation was most obvious after the addition of molasses was stopped.

The environmental properties of three geotechnical composites made by recycling wastes were investigated on a laboratory scale and in the field with the use of lysimeters designated for the revitalization of degraded mining sites. Composites were prepared by combining the mine waste with paper-mill sludge and foundry sand (Composite 1), with digestate from municipal waste and paper ash (Composite 2), and with coal ash, foundry slag and waste incineration bottom ash (Composite 3). The results of laboratory leaching tests proved that Composites 1 and 3 are environmentally acceptable, according to the legislative limits, as the potentially hazardous substances were immobilized, while in Composite 2, the legislative limits were exceeded. In the field lysimeters, the lowest rate of leaching was determined for optimally compacted Composites 1 and 3, while for Composite 2 the leaching of Cu was high. This study proved that optimally installed Composites 1 and 3 are environmentally acceptable for use in construction as an alternative to virgin materials, for the revitalization of degraded mining sites or, along with Composite 2, for closure operations with landfills. In this way, locally available waste streams are valorised and channelized into a beneficial and sustainable recycling practice.

The water balance and effectiveness of a landfill cover containing a liner from fine-grained dredged material (‘METHA-material’) and a drainage layer from sandy dredged material (‘METHA-sand’) from the Port of Hamburg (Northern Germany) was investigated for 20 years using two test fields (lysimeters), each 500 m2 in size. The layering within the standard design test field (FS) is identical to the layering of the cover on the landfill, whereas the alternative design test field (FA) was designed to provoke desiccation of the liner. The setup abstained from continuous side walls cutting through the liners in order to allow for material properties representative for the landfill cover, at the cost of possible minor lateral inflows or outflows, which were, however, considered negligible. By example of the lysimeter FA the risk of desiccation-induced failure of a liner from METHA-material under the given climate could be shown. In contrast, the discharges and hydro-chemical parameters measured for the lysimeter FS indicate continuous high efficiency of the liner until today. The average discharge below the liner was 14.9 mm/yr. The entire cover contributes to the good liner performance. Reason are (1) the low hydraulic conductivity of the liner (5 × 10−10 m/s) and its large thickness (1.5 m); (2) the increased stresses on the liner due to the 2.5 m thick overlaying cover; (3) the 1.0 m thick drainage layer from slowly-draining METHA-sand, allowing for a continuous nearly water-saturated fringe above the liner; and (4) the sufficient amount of plant available water in the recultivation layer.

Citrus latifolia is increasingly being cultivated in Mediterranean areas, where the need for precise irrigation implies a sound knowledge of the crop's water requirements, which is carried out by monitoring the tree water status in the plant-soil-atmosphere system. Two year-old lime trees (Citrus latifolia Tan. cv. Bearss) were cultivated in 45 L weighing pot-lysimeters filled with a clay-loam soil and equipped with soil water sensors for recording the real-time soil water status. Irrigation, drainage, pot weight, and agro-meteorological variables were also recorded in real-time. Plant water relations - stem (Ψ) and leaf (Ψ) water potentials, and leaf gas exchange - were periodically measured throughout the experiment. The automated irrigation protocol based on the volumetric soil water content was set to prevent tree water stress (with mean seasonal values of Ψ above -0.8 MPa and 7 μmol m s and 80 mmol m s, for net phtosynthesis and stomatal conductance, respectively). From the soil water pot balance, the computed fortnightly ET mean values throughout the growing season varied from 0.25 to 2.56 L plant day in winter and summer months, respectively. Maximum ET values occurred in July when evaporative demand was highest and lime fruits were in their most active growing phase. For day length, lime tree biomass changes were negligible, and the pot tree weight variations served for ET water balance validation (r=0.92***). The contribution of this work is that it establishes a scalable weighing lysimeter prototype for determining the ET of lime trees grown in Mediterranean semi-arid conditions, using real-time soil water balance monitoring managed by an irrigation automation protocol. This approach could be replicated for precise ET measurements in other crops., This research was supported by Spanish National Plan-FEDER-UE-AGL2016-77282-C03-1 R and PID2019-106226RB-C2 1/AEI/10.13039/ 501100011033, and Seneca Foundation of Region of Murcia (19903/ GERM/15) projects. Conesa M.R. acknowledges the postdoctoral financial support received from the Spanish Juan de la Cierva program (FJCI -2017 -32045)

In New Zealand, dairy farming faces increasing scrutiny for its environmental impacts, including those on soil carbon (C) stocks; hence, alternative management practices are required. One such practice is usage of deep-rooting forage, such as lucerne ( Medicago sativa L.). We measured the C and water exchange of two neighbouring lucerne fields on stony, well-drained soil for 3 years, following conversion from grassland. One field received irrigation and effluent; the other received neither. Net CO 2 exchange and evaporation were measured by eddy covariance, drainage and leaching with lysimeters, and water inputs with rain gauges. Biomass removal from harvesting and grazing was recorded by direct sampling. In the conversion year, irrigated lucerne was C-neutral despite two harvests and losses from the conversion process. In the 2nd and 3rd years combined, the biomass-C removal exceeded net CO 2 uptake, causing net losses of 450 g C m −2 and 210 g C m −2 for irrigated and non-irrigated lucerne, respectively. Leaching losses accounted for 1 to 9% of annual net C uptake from the atmosphere. The ratio of ecosystem respiration to gross photosynthetic productivity (GPP) increased from

To investigate carbon (C) and nitrogen (N) dynamics in seasonally frozen soils under saline and shallow groundwater supply conditions, in-situ lysimeter experiments with different groundwater table depths (WTD = 1.8 and 2.2 m) were conducted in Inner Mongolia, China during the wintertime of 2012–2013. Changes in soil organic C and total N in multiple layers during various periods, as well as their relationships with soil water, salt, and heat dynamics were analyzed. Accumulation of soil organic C and total N during freezing periods was strongly related to water and salt accumulation under temperature and water potential gradients. Water and salt showed direct influences on soil C and N dynamics by transporting them to upper layer and changing soil microbial activity. Salt accumulation in the upper layer during freezing and thawing of soil affected microbial activity by lowering osmotic potential, resulting in lower C/N ratio. Nitrogen in soil tended to be more mobile with water during freezing and thawing than organic C, and the groundwater table also served as a water source for consecutive upward transport of dissolved N and C. The changes in C and N in the upper 10 cm soil layer served as a good sign for identification of water and salt influences on soil microbial activity during freezing/thawing.

Perfluoroalkyl substances (PFASs) are a group of contaminants of concern in agricultural crops, but little is known of their accumulation or behavior in grains. We grew Japanese rice (Oryza sativa subsp. indica) in lysimeters irrigated with tap water or tap water plus simulated contaminated water for 2 years, then analyzed the roots, straw, unhulled rice, white rice, bran, soil, and water for PFASs residues. Total fluorine was measured by combustion ion chromatography. Estimated per-plant residue levels were 3.0 pg perfluorooctanesulfonic acid (PFOS) (bran: 0.5%, hull: 99.5%), 0.54 pg N-ethylperfluorooctanesulfonamide (N-EtFOSA) (white rice: 67%, hull: 33%), 1.2 pg perfluorobutanoic acid (PFBA) (white rice: 13%, bran: 7%, hull: 79%), 0.68 pg perfluoropentanoic acid (hull: 100%), 0.50 pg perfluorohexanoic acid (PFHxA) (white rice: 65%, bran: 16%, hull: 19%), 0.21 pg perfluoroheptanoic acid (hull: 100%), 0.25 pg perfluorooctanoic acid (PFOA) (hull: 100%), and 0.12 pg perfluorodecanoic acid (PFNA) (white rice: 81%, bran: 19%). Estimated daily PFASs intakes were1-3 ng perfluorooctanesulfonamide,1-7 ng N-EtFOSA, 1-2 ng PFBA,3-4 ng PFHxA, and 1-2 ng PFNA. Estimated PFOS, PFOA, and total PFASs in straw feed were 0.4, 0.1, and 2 kg yr

Current precipitation measurements are conducted largely by simple automatic rain gauges. Despite being error-prone and sometimes of questionable accuracy, the procedure is still widely used. In recent years new possibilities have emerged, which are based on different measuring principles. Although the application of alternative devices is increasing, its use in research is limited. In this study, precipitation measurements by different devices were compared, and systematic errors caused by individual characteristics were corrected. Data were collected by means of a monitoring network, which included a piezoelectric precipitation sensor mounted at 2.3 m, a standard tipping bucket at 1 m, and a weighable gravitation lysimeter at ground level. As measurements at ground level are considered as optimum, the records of the lysimeter were thereby determined as a reference. The results showed that precipitation measured by elevated rain gauges differed in total between −6.8% and +35% compared to rainfall measured by the lysimeter. The records correlated well, but the analyses indicated a strong influence of the precipitation intensity on the recorded amount of precipitation. The deviations between values of the rain gauges and those of the lysimeter increased with rainfall intensity. In general, the tipping bucket demonstrated negative error values and indicated an underestimation of precipitation compared to records at ground level, whereas the piezoelectric precipitation sensor showed an overestimation by highly positive error values. A subsequent precipitation correction through the linear scaling method improved significantly the raw data of the rain gauges.

For efficient irrigation management practices, an accurate prediction of water uptake in the root zone and soil information are foremost important. The present study deals with the identification and estimation of root water uptake (RWU) and soil hydraulic parameters using inverse modeling. These parameters were estimated by minimizing the difference between observed and model simulated soil moisture and deep percolation during the crop growth period. The linked simulation optimization model is tested for three different objective functions using hypothetically generated observed data. Results indicate that the optimizer with objective function defined by soil moisture, failed to provide unique estimate of RWU and soil hydraulic parameters. Further, it has been observed that with the objective function defined by deep percolation, soil hydraulic parameters were uniquely estimated but RWU parameter was not estimated accurately. However, with the objective function, that includes both soil moisture and deep percolation, these parameters were uniquely estimated. A Lysimeter experiments were conducted with four crops i.e. berseem (Trifolium alexandrinum), wheat (Triticum aestivum), maize (Zea mays) and pearl millet (Pennisetum glaucum). Daily monitoring of soil moisture and deep percolation along with soil and crop parameter measurements were done for model validation. Inversely estimated soil hydraulic parameters were found to be in close agreement with laboratory obtained values. The results indicate that specifically for soils with high hydraulic conductivity, the information about deep percolation along with soil moisture is necessary for inverse estimation of root and soil parameters simultaneously. The moisture depletion pattern and deep percolation corresponding to optimized parameters for these crops were found to be in close agreement with observed values.

Management of many crown and root diseases of turfgrasses includes the use of fungicides. The physicochemical properties of the fungicides used vary greatly, but most have low mobility and are not phloem mobile, which results in little active ingredient present in the basal and underground structures of turfgrass plants. Two studies were conducted in a laboratory setting to determine the effects of post-application irrigation amounts (0, 0.3, 0.6, 1.3, and 2.5 cm) on the distribution of 14C myclobutanil and 14C tebuconazole in a soil profile of 90% sand and 10% peat moss by volume. In addition, growth chamber experiments were conducted to examine the effect of post-application irrigation amount on azoxystrobin efficacy against summer patch (Magnaporthiopsis poae) in ‘Penn A-4’ creeping bentgrass (Agrostis stolonifera L.). The creeping bentgrass was treated with azoxystrobin and immediately irrigated with 0, 0.25, 0.3, or 0.6 cm of irrigation. Lastly, an in vitro fungicide sensitivity assay was conducted on three M. poae isolates to determine their sensitivities to two succinate dehydrogenase inhibitors (SDHIs), three demethylation inhibitors (DMIs), and four strobilurins (QoIs) to determine if fungicide concentrations in the soil profile reached levels high enough to suppress fungal growth. In both 14C experiments, more than 54% of the 14C was retained in the top 5 cm of soil for all irrigation treatments. For the 14C myclobutanil experiment, lysimeters treated with 2.5 cm of post-application irrigation resulted in 3.9% of 14C recovered in the 7.6–10.2 cm sampling depth, which was higher than all other irrigation treatments. Post-application irrigation at 2.5 cm in the 14C tebuconazole experiment yielded 6.3% of the 14C at the 7.6–10.2 cm sampling depth and 2.3% at the 10.2–12.7 cm sampling depth—recoveries at both depths were higher with 2.5 cm of irrigation than all other irrigation treatments. No 14C was detected below 12.7 cm for either experiment. Less disease was observed when azoxystrobin received post-application irrigation. Both 0.25 and 0.3 cm of post-application irrigation increased turf quality compared to no irrigation; moreover, 0.25 and 0.6 cm of post-application irrigation increased root length compared to no irrigation. In the in vitro fungicide sensitivity assay, isolates of M. poae were sensitive to all fungicides with only minor sensitivity to the SDHIs. In general, isolates were most sensitive to the QoIs with some variability in isolate sensitivities noted. Isolates of M. poae are sensitive to commonly used fungicides and efficacy is enhanced by post-application irrigation due to improved fungicide distribution into the soil profile.

Estimation of crop water needs plays a key role in the water resource management in arid and semi-arid regions. Actual evapotranspiration (ETa) becomes the key term in both water and energy balances at this point. In this work we focus on vineyard due to the significance of this crop for La Mancha region, Spain, with the greatest concentration of vineyards in the world. Eddy-covariance (EC) technique has been traditionally used for ground observations of ETa. One of the aims of this work is to assess the feasibility of an EC system under the challenging conditions of a small drip-irrigated vineyard in a semi-arid environment. Two-source energy balance modelling allows for ETa estimation, as well as soil evaporation (E) and canopy transpiration (T) partitioning, using radiometric temperatures as a basis. A Simplified version of this Two-Source Energy Balance approach (STSEB) has been previously tested in a variety of crops and environments. The second goal of this paper is to explore now the performance of the STSEB model in a vineyard structure. Two experiments were carried out during the growing season of 2014 and 2015 in a ˜4 ha row-crop drip-irrigated Tempranillo vineyard, in a semi-arid location in Castilla-La Mancha, Spain. As a novelty in this work, a 9-m2 monolithic large weighting lysimeter was available. An eddy-covariance flux tower was deployed together with net radiation and soil heat flux instrumentation. The residual technique was selected to force the closure after an analysis of the energy imbalance based on the comparison EC-Lysimeter. Good agreement between adjusted EC measurements and lysimeter data (RMSE of ±0.09 mm h−1 and ±0.5 mm d−1 at hourly and daily scales, respectively) supports the validity of eddy-covariance technique to monitor turbulent fluxes and accurate ETa in vineyards. A set of 5 thermal-infrared radiometers were assembled to guaranty an appropriate thermal characterization of the vineyard structure required in the STSEB approach. Surface energy fluxes were modeled every hour with average estimation errors lower than ±30 W m−2 for net radiation and soil heat flux, and around ±50 W m−2 for sensible and latent heat fluxes, with systematic deviations lower than 25 W m−2 in all fluxes. Comparison with lysimeter data showed an average underestimation of 0.04 mm d-1 with a RMSE value of ±0.6 mm d-1 in modeled daily ETa. In terms of accumulated ETa for the full experiments, an underestimation of 12% in 2014 and an overestimation of 7% in 2015 were observed. These results reinforce the feasibility of the STSEB approach to monitor hourly, daily and accumulated ETa in row-crops such as vineyards. Although no ground measurements were available to assess the partitioning, separated E–T values were obtained for the full campaigns, showing a significant ratio E/ETa of 0.35−0.40 for soil evaporation.

Biofuel demand is on the rise, yet there is limited information available about the likely implications of increased planting of cellulosic biofuel crops on water and nutrient fluxes. To help address this gap, this study quantifies subsurface water, nitrate, and dissolved phosphorus fluxes below feedstock crops managed for biofuel production on naturally well drained soils in southern Wisconsin. Automated equilibrium tension lysimeters were used to measure subsurface (below root zone) fluxes of water and nutrients below continuous corn (CC), monoculture switchgrass (SG), and hybrid poplar (HP) cropping systems for three years. Average water fluxes below SG were nearly double those below CC and HP. Most of this difference can be linked to seasonal events, particularly during late winter and early spring when subsurface water fluxes and increased soil moisture were observed below SG plots, likely due to enhanced macropore flow. Nitrate fluxes were approximately 14 times higher below CC than the 37.4 kg NO3-N/ha three year annual average observed for SG; the nitrate fluxes were negligible below HP despite similar nitrogen application rates. The high flux in one of the two CC plots is likely due to excessive manure applications prior to the study period; however, the nitrate loss potential from CC is much higher than the perennial crops. Dissolved reactive phosphorus (DRP) concentrations were very low below all three cropping systems (average of 0.076, 0.083, 0.034 mg/L in SG, CC, and HP respectively). For the cropping systems evaluated, nitrate fluxes were driven by concentration differences in leachate and not influenced by nominal differences in N fertilizer inputs, whereas DRP fluxes were mainly driven by water fluxes and therefore independent of phosphorus inputs and soil test phosphorus. The data in this paper provide a foundation to better understand differences in fluxes below different biofuel cropping systems.

Over half of the irrigated land in the US, 11.5 million ha, is irrigated with center pivot and linear move systems. Because of this, minor changes in the operation efficiency of these systems can have large impact on overall water conservation. The objective of this study was to evaluate the water application efficiency (WAE) of low and of mid elevation spray application (LESA and MESA) using catch can test and drainage lysimeters, and develop governing equations based on the weather variables. A three-year (2015–2017) field study was conducted at the Washington State University Research and Extension Center, near Prosser. Catch cans were used to collect the fraction of total irrigation-water applied that reached the ground surface as WAE and drainage lysimeters to measure the overall water loss (OAWL) and wind drift and evaporation losses (WDEL), (WDEL = 100-WAE). Air temperature (Ta), relative humidity (RH), short-wave global irradiance (Rg), wind speed (WS), and calculated vapor pressure deficit (VPD) were used as the input weather variables to mixed modeling technique. Results showed that on average 21% more irrigation-water reached the ground with LESA than with MESA systems. Lysimetric measurements showed on average a 16% efficiency difference between MESA and LESA. The monthly WAE differences between MESA and LESA increased from 12 to 30% during the hot summer months and thereafter decreased, from 30 to 9%. The warmer and drier year of 2015 had the highest annual average values of WDEL of 17% for LESA and 19% for MESA. Results indicated a relatively constant WAE for LESA regardless of weather conditions. Mixed modelling showed that VPD was the only significant predictor (P

Crop water productivity is one of the important aspects of water use of crop, most especially where water is a limiting factor. This study was carried out to assess and compare water relations and productivity of two lines of pearl millet grown on lysimeters with two soil types. The study was carried out at the lysimeter unit of the Department of Soil, Crop and Climate Sciences Experimental Farm, Kenilworth, University of the Free State, Bloemfontein. One row of the unit contains a Clovelly soil and the other row, Bainsvlei soil. The two lines of pearl millet used for the study were GCI 17, improved variety and Monyaloti, a local variety. Irrigation treatments were applied such that water was withheld at the beginning of different growth stages of the crop to impose water stress. These treatments were well-watered (WW), vegetative stage stress (VS), reproductive stage stress (RS), and grain-filling stage stress (GS). The treatments were replicated two times per line of pearl millet per soil type. The results show that the lowest leaf water potential was observed in the GS stress plants for both lines of pearl millet on Bainsvlei soil form. The highest stomatal conductance observed on Clovelly soil was around 400 mmol m−2 s−1 while it was around 300 mmol m−2 s-1 on Bainsvlei soil for the two lines of pearl millet. The highest and lowest grain yields for GCI 17 were from Clovelly soil. The highest grain yield for Monyaloti was 10.74 t ha-1from the WW found on Clovelly soil type while the lowest was 3.93 t ha-1 from GS found on Bainsvlei soil type. The mean water productivity for biomass (WPbm) of GCI 17 was 0.036 t ha−1 mm−1for both soil types while Monyaloti had WPbm of 0.037 and 0.035 t ha−1 mm−1 on Bainsvlei and Clovelly respectively. Clovelly soil type proved to exhibit high water productivity for grain yield production of pearl millet.

The effect of controlled drainage (CD) on nitrogen (N) losses from controlled irrigation (CI) paddy fields through subsurface drainage and ammonia volatilization (AV) was investigated by managing water table control levels (WTC) with a lysimeter equipped with an automatic water table control system. Three drainage treatments were implemented, namely, controlled water table depths 1–3. The increases of the WTC resulted in a high proportion of groundwater levels below the WTC, which reduced the subsurface outflow from CI paddy fields by 30.5% during the first week after fertilization. Total N concentrations in the 0–10 cm soil solution and subsurface drain water were higher as the WTC increased. The increase of the WTC during the first week after fertilization could effectively decrease the N losses from CI paddy fields by 9.5%, and the first weekly N losses through subsurface drainage and AV after fertilization were reduced by 17.2% and 9.3%, respectively. The large reductions in subsurface outflow decreased the first weekly N losses through subsurface drainage after fertilization. The retention time of shallow water in CI paddy fields was extended with the increases in WTC, which may reduce the first weekly AV losses after fertilization. Results show that the combination of CI and CD may be an effective water management method for mitigating N losses through subsurface drainage and AV after fertilization from paddy fields.

Most cultivated vineyards worldwide are located in semi-arid and arid regions with a limited water supply. Skilled vineyard water management is considered the main tool for controlling vegetative growth and grape quality and for ensuring vineyard sustainability. Imposing an appropriate drought stress at a suitable phenological stage can improve wine quality with almost no yield reduction. A comprehensive irrigation model enabling precise vineyard irrigation should be based on changes in vine water consumption as a function of climate conditions and canopy area. In 2011, six drainage lysimeters were constructed within a commercial 'Cabernet Sauvignon' vineyard located in the central mountains of Israel. Data were collected during six successive years from 2012 – 2017. The daily vine water consumption, ETc (L day−1), was calculated by subtracting the amount of collected drainage (over a 24 h period) from the amount of applied irrigation during the same time period. Seasonal water consumption (ETc) was 715 mm season−1 on average, while seasonal calculated reference evapotranspiration (ETo) was 1237 mm season−1 on average. Maximal crop coefficient (Kc) was 0.8 – 0.9, meaning that actual water consumption was lower than the calculated reference evapotranspiration. Maximal leaf area index (LAI) was 0.9 to 1.7 m2 m-2. The multi-seasonal linear correlation between LAI and Kc was strongly positive and significant. The robust multiyear relationship between LAI & Kc proves that measuring canopy area of wine grapevines is a reliable approach for estimating their Kc. The LAI to Kc relationship that we have established can be used as a basis for developing a comprehensive irrigation model for wine grapevines that integrates both climatic conditions and canopy area.

This study investigated the performance of simulated landfills with different biogas collection practices, including upward biogas collection only (LT) and both upward and downward biogas collection (LTB). A simulated landfill was constructed using a stainless steel lysimeter equipped with a compression unit. Upward gas flow was favored in uncompressed MSW when both upward and downward gas flows were allowed (LTB). By reducing void ratio, the preferential flow direction of biogas was changed to downward gas flow along with gravimetric leachate drainage. In LT, porched leachate was formed because high flow resistance by countercurrent gas-liquid flow affected moisture redistribution. It was considered that high pressure buildup in gas-filled pores of LT enhanced uneven moisture distribution and resulted in inhibiting methane production. The cumulative methane volume produced from LTB was 2.5 times as much as that of LT.

Canopy conductance (Gc) largely regulates carbon/water cycling and land–atmosphere interactions, but quantifying Gc using eddy flux data is limited by the difficulty of partitioning plant transpiration (T) and surface evaporation (E). We introduced an underlying water use efficiency (uWUE) method to partition evapotranspiration (ET) in an oasis maize ecosystem, and cross–compared with the Shuttleworth and Wallace (SW) model, the lysimeter and isotope measurements. We then estimated surface conductance (Gs) by ET and Gc by T partitioned using the uWUE method, followed by a performance evaluation on the Jarvis model parameterized with both Gs and Gc. The results showed that T/ET estimated by the uWUE method was close to the isotope method in the peak growing season of 2012, it showed similar seasonal variations with the lysimeter/eddy covariance method and the SW model throughout this growing season. Daily T partitioned by the uWUE method was in good agreement with the SW model from 2012 to 2015 (r2 = 0.91). Additionally, Gc had more significant seasonal variations than Gs. The Jarvis model parameterized with Gc exhibited superior performance than those with Gs. Our study suggests that the uWUE method can exclude influences of nonstomatal conductances, and will have great potential to provide more reasonable parameterization for simulation of plant stomata.

The accurate determination of crop evapotranspiration (ETc) is important for improving irrigation water use efficiency and optimizing fruit quality in solar greenhouses. Taking drip-irrigated tomato in a solar greenhouse as an example, this study simulated the variations of ETc by the Shuttleworth–Wallace (S–W) and Dual crop coefficient (Dual-Kc) models at initial, development, mid and late stages in 2015 and 2016 respectively. Continuous measurements of crop ETc with weighing lysimeter, and sap flow system combined with micro-lysimeter were used to validate the performance of two approaches. Results indicated that the total soil evaporation accounted for 25% of ETc over the whole growth period, and decreased gradually with the increasing of canopy coverage ratio. The locally developed basal crop coefficients values during the initial, mid, and late stages were 0.15, 0.94 and 0.65 in 2015, and 0.15, 1.02 and 0.70 in 2016, respectively. The variations of the estimated ETc from S–W and Dual-Kc models were similar to the measured ETc. The S–W model performed well in estimating ETc when LAI was between 0.5 and 2.7, but slightly overestimated and underestimated at initial and mid stages, respectively. Additionally, the performance of the S–W model was also better under different weather conditions as well as after irrigation. However, the Dual-Kc method was superior to the S–W model in estimating daily soil evaporation and daily plant transpiration. The good agreements were found between the predicted ETc using the Dual-Kc method and the measurements for the greenhouse tomato, with the coefficients of regression of 1.03 (R2=0.93) in 2015, and 0.96 (R2=0.93) in 2016. Therefore, the Dual-Kc method was finally recommended for estimating evapotranspiration of tomato cultivated in the solar greenhouse.

The aim of the present work was to assess the impact of raw slurry injection and band application of acidified slurry upon nitrate leaching in two different soils under Mediterranean conditions. A lysimeter experiment with a winter crop (oat - Avena sativa) was performed over three years presenting significant inter-annual precipitation variability. Four fertilization treatments using dairy cattle slurry were implemented. Nitrate leaching was estimated using nitrate concentration in soil solution assessed through ceramic suction cups and drainage calculated using the Agricultural System Root Zone Water Quality Model (RZWQM2). Results show that the RZWQM2 was able to predict drainage with an average efficiency of 89%. Cumulative drainage averaged 69 and 65% of the precipitation for the sandy and the sandy loam soils, respectively. The application of acidified slurry did not lead to any increase of nitrate leaching relative to band application or injection of raw slurry. Soil incorporation following soil application of acidified slurry is highly relevant regarding nitrate leaching since it significantly reduced nitrate leaching in more than 50% in the sandy soil and close to 40% in the sandy loam soil. A severe risk of pollution swapping was observed with slurry injection since it led to an increase of nitrate leaching relative to band application of raw or acidified slurry (more than 100% in the sandy soil and around 30% in the sandy loam soil for the rainiest year). According to the results, band application of acidified slurry is an efficient alternative to raw slurry injection to minimize nitrogen losses by leaching. Nevertheless, soil incorporation of acidified slurry, not necessary in terms of ammonia emissions, is strongly recommended to reduce nitrate leaching.

A 3-year field experiment was conducted in Aksu region in Northwest China to determine crop water use, suitable irrigation mode and actual crop coefficient (Kc) in drip-irrigated cotton fields. In the experiment, 12 non-weighing large lysimeters were used to measure cotton water use under various irrigation modes. Then a micro-lysimeter was placed in each large lysimeter to monitor soil evaporation (E). Adjustments were done for a number of factors (including irrigation, meteorology, plastic mulching, water stress and salinity stress) in order to compare FAO-adjusted Kc (Kc-FAO) with the local actual Kc (Kc-loc). The results showed that: 1) plastic mulching with 0.6 cover ratio and 37.5 mm drip irrigation quota gave a crop water requirement of 536.4 mm; which was suitable for the study area. Also Kc-loc were respectively 0.28, 0.97 and 0.31 for early, middle and late growth stages. 2) Kc-FAO generally reflected the trend in Kc-loc for the entire growing season. The suggested 0.1 adjusted coefficient under plastic mulching for the initial growth stage was relatively low, and was most rational for the study area when increased to 0.25. 3) E/ET ratio was low (19.1–24.5%) under mulching treatment and relatively high (27.7–32.7%) under non-mulching treatment. 4) While change in E/ETo ratio was linear or logarithmic, that in T/ETo ratio was a power function of the canopy cover. Also the two rates responded to the interaction effects of canopy cover and soil water content. The results could lay the basis for developing scientific, data-driven water-saving strategies in the study area and elsewhere.

Groundwater recharge by precipitation is often assumed by practitioners as well as scientists to be a slow process of filtration through layers of uniform texture analogous to Darcy’s law. In most basins, however, rainwater also finds its way through macropores and preferential pathways to the shallow unconfined aquifers within hours of falling. Recharge phases may extend over several days, increasing groundwater levels, stored volume and hence baseflows into adjoining rivers. In this study, groundwater recharge and storage are computed from baseflow as separated with a nonlinear reservoir algorithm from time series of daily flows at gauging stations in northern Germany. Results are compared to groundwater level fluctuation in the catchments and to daily seepage rates measured in a lysimeter station. Peak times of the fast transfer of rain water through the vadose zone are generally the same. However, while recharge from baseflow ends when baseflow assumes its typical recession, the attenuation of lysimeter seepage may last much longer. The volume of lysimeter seepage is generally higher than the recharge in catchments due not only to different vegetation but also to rim effects impeding direct runoff. Furthermore, the lysimeter walls allow vertical fluxes only. Without further evidence or improved devices, lysimeter seepage should therefore not be indicated as groundwater recharge for the site or catchment. Findings also indicate that the shape of derived recharge unit responses is practically time invariant but with a strong seasonal variation in the recharge-rainfall ratio of precipitation events.

Agriculture has contributed greatly to nitrogen (N) pollution globally. It is essential to study the causes and characteristics of N leaching to develop better N management strategies. A field experiment with cucumber–Chinese cabbage rotation was conducted in a typical open field for vegetable planting in northern China. The characteristics of N leaching were studied using the lysimeter method. The total N leaching (TNL) value under the conventional N application rate (780 kg ha−1 season−1) was 585.3 kg ha−1 for the entire vegetable year and it had a significantly positive correlation with the N application rate. Reduction of the N rate by 20% and 50% could decrease the TNL by 18.3% and 43.0% during the entire cucumber and cabbage season (including the fallow period), respectively. A 20% reduction in the N rate had no obvious impact on vegetable yields. The TNL was decreased by 2.6% throughout the year under a combined application of manure and chemical fertilizers. An amendment with a urease-inhibitor plus a nitrification-inhibitor, biochar, and straw could decrease TNL by 23.5%, 15.3%, and 7.1%, respectively, compared to that without amendments. A combined reduction of N and the irrigation rate by 20% showed a decrease of the TNL by 38.4%. The results showed that N leaching substantially contributed to the loss of fertilizer N in a typical vegetable field in northern China, where both the temperature and the rainfall were synchronized. Appropriate management practices can effectively reduce the TNL at different degrees without the negative impact on vegetable yields. These practices include the addition of synergists (urease inhibitors and nitrification inhibitors), the amendment with biochar or straw, and the reduction in both N rate and irrigation volume by 20%. Different measures can be adopted in the actual vegetable production according to the specific conditions.

A two-year summer maize irrigation experiment was conducted in soil lysimeters under a rain-shelter to analyze the effects of water repellency on soil moisture, evapotranspiration, crop growth, and yields. Soil water droplet penetration time (WDPT) was initially 1, 7, 9, 12 and 16 s, showing wettable or slight water repellency, denoted as the treatments CK, WR1, WR2, WR3, and WR4, respectively. Soil water storage dynamics were observed using the lysimeters. The WDPT and volumetric soil water content (θv) on surface soil was measured daily. The results revealed that WDPT values of all the five treatments increased significantly as the sowing days increased and reached peaks before the subsequent irrigation. However, the peak decreased as irrigation events increased. The maximum WDPT values of CK, WR1, WR2, WR3, and WR4 were 31, 2000, 2200, 2300 and 2355s during the entire crop growth period, and indicated more persistent water repellency than the initial conditions. During the two irrigations, θv decreased with the increase of WDPT. The daily and cumulative evapotranspiration at the early growth stage differed slightly but decreased from CK to WR4 at the later crop growth stages. Likewise, soil water storage increased. The higher water consumption of summer maize in CK resulted in lower soil water storage and good plant growth, thus in soils with higher WDPTs, the lower values of LAI, the mass of roots and leaves, and root lengths were noted. The crop growth decreased regularly with the increase in initial WDPT. The main reason was due to a decrease in soil water availability for the crop and impeded root water uptake as the initial WDPT increased. The variation in initial WDPTs had a significant impact on WUE. In conclusion, more persistent water repellent soils result in a decrease in summer maize growth.

Dune belts are crucial for the recharge of coastal aquifers. In spite of their hydrological relevance for the maintenance of precious natural wetland and wildlife environments and a range of other ecosystemservices, only limited knowledge of soil water dynamics in dune belts is currently available. This study presents soilwater balance components measured during one hydrological year using a high precision meteo-lysimeter with lower boundary control installed in a coastal dune belt under a dry subhumid climate in southern Spain close to the Atlantic Ocean. The site is equipped with a cylindrical lysimeter of 1 m2 surface and 1.50 m height (METER Group, Inc. USA) and a weighing resolution of 10 g, 2 SC650 soil moisture sensors (Campbell Scientific, Logan, UT) and 1 automatic meteorological station. The lower boundary condition at the bottom of the lysimeter is controlled at 1.4 m depth by a bidirectional peristaltic pump to maintain field conditions. Results show a recharge rate of 64% of the precipitation measured by the lysimeter. Diurnal oscillations of the measured upper boundary flow during days without rainfall represented vapor adsorption and real evaporation rates ranging between 0.3 and 0.4 mm/day and 0.4 and 0.6 mm/day, respectively throughout the whole year summing up an annual vapor adsorption of 77mm. The measured precipitation of the lysimeter exceeded pluviometer data by 13% as a result of vapor adsorption. The presented results provide a precise balance of soilwater components in a coastal dune belt including the relevant contribution of vapor flow., Unidad de Sevilla, Instituto Geológico y Minero de España, España, Departamento de Física Aplicada, Universidad de Córdoba, España, Centro Alameda del Obispo, Investigación y Formación Agraria y Pesquera, España, Instituto Geológico y Minero de España, España

In many developing countries water scarcity has led to the use of wastewater, often untreated, to irrigate a range of crops, including tuber crops such as potatoes (Solanum tuberosum L.). Untreated wastewater contains a wide range of contaminants, including heavy metals, which can find their way into the edible part of the crop, thereby posing a risk to human health. An experiment was undertaken to elucidate the fate and transport of six water-borne heavy metals (Cd, Cr, Cu, Fe, Pb and Zn), applied through irrigation water to a potato (cv. Russet Burbank) crop grown on sandy soil, having either received no biochar amendment or having top 0.10 m of soil amended with 1% (w/w) plantain peel biochar. A non-amended control, irrigated with tap water, along with the two contaminated water treatments were replicated three times in a completely randomized design carried out on nine outdoor PVC lysimeters of 1.0 m height and 0.45 m diameter. The potatoes were planted, irrigated at 10-day intervals, and leachate then collected. Soil samples collected two days after each irrigation showed that all heavy metals accumulated in the surface soil; Fe, Pb and Zn were detected at 0.1 m depth, while only Fe was detected at 0.3 m depth. Heavy metals were not detected in the leachate. Tested individually, all portions of the potato plant (tuber flesh, peel, leaf, stem and root) bore heavy metals. Biochar-amended soil significantly reduced only Cd and Zn concentrations in tuber flesh (69% and 33%, respectively) and peel compared to the non-amended wastewater control (p < 0.05). Heavy metal concentrations were significantly lower in the tuber flesh than in the peel, suggesting that when consuming potatoes grown under wastewater irrigation, the peel poses a higher health risk than the flesh.

This research tested the hypothesis that incorporation of Carbon-Rich Organic Matter Amendments (CROMA) into bare soil after winter forage grazing would immobilise urinary-nitrogen (N) and reduce nitrate-N (NO3−-N) leaching losses. In mid-winter (14 July 2016), 32 intact soil monolith lysimeters (500 mm diameter and 700 mm deep) received natural cow urine at the equivalent rate of 300 kg N ha−1, and CROMA treatments of either: (i) no CROMA (control), (ii) three rates of barley straw [2, 4 or 8 t carbon (C) ha-1; C/N ratio of 66:1], (iii) two rates of separated dairy effluent solids (2 or 4 t C ha-1; C/N ratio of 31:1), or (iv) two rates of spent woodchip bedding material (2 or 4 t C ha-1; C/N ratio of 29:1). Leaching was measured for periods of approximately 100 days after treatment (250 mm of leachate collected). Across all treatments, 98–99% of the N leached was in the form of NO3−-N. Incorporated barley straw and effluent solids were effective in reducing NO3−-N leaching losses by up to 25% compared to the control treatment. Spent woodchip bedding was shown to be ineffective, which was attributed to a high lignin content.

The sugarcane pre-sprouted plantlets (PSP) production system is an innovative method to enhance crop multiplication rates. This system is greenhouse-grown, where correct irrigation management is essential to maintain the production quality. The purpose of this study was to determine the water requirement of three cultivars (CTC9005HP, RB966928, and SP87365) of pre-sprouted sugarcane plantlets, in which crop evapotranspiration (ETc) is a function of the product of the crop coefficient (Kc) and reference evapotranspiration (ETo). Three specifically built PSP-weighing lysimeters were used to determine ETc, while ETo was calculated by the FAO-56 method, making it possible to assess Kc values during the PSP cycle production. The ETc ranged from 3 to 6.9 mm d−1 for CTC9005HP, 3.1 to 6.8 mm d−1 for RB966928, and 2.9 to 6.6 mm d−1 for SP87365. Daily Kc values increased from 1.00 to 1.46 for CTC9005HP, 1.02 to 1.53 for RB966928, and 1.02 to 1.49 for SP87365. This research makes evident the importance of assessing appropriate Kc values in order to estimate crop water requirements and irrigation needs. Therefore, these results are appropriate for proper irrigation management in a greenhouse-grown sugarcane PSP.

This paper presents the results of a lysimeter experiment in which a forest soil has been artificially spiked with rock fragments from natural copper (Cu) and cobalt (Co)-hills from Tenke-Fungurume (Democratic Republic of Congo). The Cu and Co contents of the percolating water have been analysed at repeated intervals and the impact of rock on the soil properties was evaluated at the end of the experiment. Five rocks were sampled in one copper hill. In natural conditions, these rock fragments located on the top of the hill are mixed to surface soil horizon along the slope through colluvial processes. The Cu and Co contents in rocks range respectively between 470 mg/kg (siliceous rock) and 140,000 mg/kg (shale) and between 450 mg/kg (dolostone) and 5300 mg/kg (shale). Rock fragments were mixed with two horizons (hemi-organic A with 2.7% total organic carbon (TOC), and mineral B with 0.3% TOC) of an acid (pH water The results show great differences between Cu and Co releases in the percolating solutions according to the nature of the rocks. The quantities released were correlated to the concentrations originally present in the unweathered rocks. Differences were also found between the A and B horizons, which indicate that the physicochemical properties of the soil influence reaction with the rocks. The differences between both horizons are mainly organic carbon content, cationic exchange capacity and nutrient content, which were higher in the A horizon. However, the pH of the A horizon was acidic compared with the B horizon. Significant correlations were found between extractable Cu and Co with concentrations of their leaching solution. Because of this, soluble Cu and Co extracted by CaCl2 can be regarded as vertical transfer risk prediction tools of Cu and Co in the soil.

We examined spatial variation in vertical 137Cs flux from the litter layer using lysimeters combined with copper-substituted Prussian blue in two forests (deciduous broad-leaved and Japanese cedar (Cryptomeria japonica)), approximately 40 km northwest of the Fukushima Daiichi Nuclear power plant. The study ran from August 2016 to February 2017 in three periods; summer (10 Aug–4 Oct), autumn (5 Oct–30 Nov) and winter (1 Dec–27 Feb). Twenty-five and 15 lysimeters were installed in the deciduous broad-leaved and the Japanese cedar sites within 400 and 300 m2 areas with 3–5 m intervals, respectively. The geometric means of the flux in the deciduous broad-leaved site were 0.51, 0.085 and 0.060 kBq/m2/month in summer, autumn and winter periods, respectively. In the Japanese cedar site, the mean fluxes were 0.45, 0.036 and 0.023 kBq/m2/month. The ratio of 137Cs flux during the survey period to litter 137Cs inventory was 6% and 1% on average in the deciduous broad-leaved and Japanese cedar sites, respectively. The 137Cs flux in the summer period was much larger than those in other periods, resulting from higher precipitation in the summer. Our fine scale observation with 5 m interval showed very large spatial variation in the 137Cs flux and the differences between maximum and minimum range from 8 to 104 times, but were mostly 20–25 times. The spatial variations in the 137Cs flux were affected positively by those in the litter 137Cs inventory and negatively by canopy openness.

The commonly observed lack of energy balance closure at eddy covariance flux tower sites represents an outstanding problem in micrometeorology and significantly compromises the value of eddy covariance latent and sensible heat flux measurements. Here we used concurrent lysimeter and eddy covariance evapotranspiration measurements to correct for the energy imbalance attributable to the eddy covariance latent heat flux measurements (32%) and then, by assuming that the Bowen ratio is correctly quantified by the eddy covariance method, attributed the remainder of the energy balance to the sensible heat flux (10%) and the available energy (58%). We discuss our findings with respect to the ongoing discussion on the causes of the energy imbalance and approaches to force energy balance closure.

The aim of this study was to determine the importance of below-ground (root) plant biomass and nitrogen (N) uptake with perennial cropping system (PCS) as a mechanism of reducing nitrate leaching. The experimental design was a split plot with main plot being cropping system [annual cropping system (ACS) versus PCS] and subplots being manure treatment [N-based liquid pig manure (LPM), N-based solid pig manure (SPM), and a control with no manure addition (CON)]. The ACS was seeded to barley (Hurdeum vulgare L.) and canola (Brassica napus L.) in the spring of 2014 and 2015, respectively, whereas the PCS was seeded to a mixture of timothy (Phleum protense L.) and orchard (Dactylis glomerata L.) grass in the fall of 2013. LPM and SPM were applied to meet N requirement of each crop in spring of each year. In 2014, above-ground and root biomass were collected at harvest and in 2015, above-ground and root biomass were collected at mid-season. The PCS had significantly greater root biomass and N uptake than ACS in both years. Root biomass in PCS ranged from 5.3–9.7 Mg ha−1 compared to a range of 1.1–1.5 Mg ha−1 in ACS. Consequently, root N uptake in PCS ranged from 43 to 118 kg N ha−1 in both years while that in ACS was 9–20 kg N ha−1. In 2014, PCS had significantly greater above-ground N than ACS, whereas in 2015, PCS had significantly greater above-ground N than ACS in the LPM only. This study shows that the differences in nitrate leaching between the two cropping systems as previously determined from field core lysimeters at the same plots was mainly due to differences in root N uptake (34–98 kg N ha−1) between the cropping systems rather than above-ground N uptake. It is important that studies comparing N losses by ACS and PCS should consider the role of plant root biomass in N recovery.

We conducted a small soil column penetration test and lysimeter experiment in four soils (Isohumosol, Ferrosol, Primosol, and Sandy soil), to generate a migration model for antimony (Sb) in soil based on the convection-diffusion equation. Variation of the Sb concentration was also simulated by the Artificial neural networks model (ANN) model. The convection-dispersion model will provide a reference for the transfer of Sb in the environment. The results agreed with the laboratory measurements with an R2 of 0.79–0.98 in the Isohumosol, Ferrosol, and Primosol. It was found that the convection-dispersion model could be used to explain the migration of Sb in soil. The areas of high potential ecological risk for the Ferrosol, Isohumosol, and Primosol soils were at the soil surface, and there was a low to moderate potential ecological risk for the deep soil profile. Artificial neural network model fitting results showed that Sb migration was rapid in Sandy soil because these soils have a weak Sb-adsorption capacity. The Sb concentration in the surface soil was much higher than at other soil depths. Little variation was observed in the Sandy soil and Isohumosol, indicating a weak Sb-adsorption capacity for these soils. The Sb migration model will help us to describe and predict Sb pollution in the soil environment, providing the basis for managing Sb-contaminated soil.

The vertical distribution of 137Cs in forest soil is important for predicting air dose rates and future cycling in forest ecosystems. However, there are many unexplained questions about the mechanisms of its downward migration. In this study, the 137Cs flux by rainfall infiltration was observed for three years from August 2017 using zero-tension lysimeters in a mature cedar forest where monitoring of the vertical distribution of 137Cs has been conducted since 2011. As a result, the 137Cs concentration in infiltrated water through the litter layer, 5 cm and 10 cm showed a tendency to be high in summer, but no such seasonal variation was found at 20 cm. Although the 137Cs inventory in the litter layer has been exponentially decreasing, the annual 137Cs fluxes in infiltrated water through the litter layer were almost the same in three years, and about 0.14–0.17% of the deposition density of 137Cs. Comparing these 137Cs fluxes with the apparent amounts of downward migration of 137Cs estimated from the change in the vertical distribution of 137Cs, the contribution rate of the infiltrated water to downward migration of 137Cs from litter to soil was calculated to be 8.5–17.7%. Similarly, the contribution rate in mineral soil layers was calculated to be 0.6–0.8% on a measured basis and estimated to be 3.0 ± 0.2% after correcting the amount of collected water, which is a problem with zero-tension lysimeter. It indicates that rainfall infiltration can explain a small part of the downward migration of 137Cs, thus further studies are required to clarify the contribution rate of remaining mechanisms such as advection-diffusion, colloidal transport, physical mixing, bioturbation, and growth and death of plant roots.

International audience; En France, les zones humides artificielles basées sur le sol pour l'évacuation des eaux usées traitées sont devenues une technique populaire pour à la fois réduire le débit vers les masses d'eau réceptrices de surface et effectuer des traitements complémentaires. Cette étude porte sur le devenir du phosphore dans trois sols différents, ainsi que son assimilation par . Le dispositif expérimental consistait en trois lysimètres contenant trois sols choisis pour être représentatifs de ceux que l'on trouve habituellement à proximité des stations d'épuration (c.-à-d. un loam limoneux Fluvisol , un loam sableux Fluvisol et un loam sablo-argileux Technosol). Les lysimètres sont des monolithes de sol non perturbés (1,5 m Phragmites australis 3 en volume), dont les masses sont contrôlées en continu afin d'obtenir un bilan massique d'eau précis. Les lysimètres ici ont été alimentés par intermittence pendant 3,5 jours, puis laissés au repos pendant 3,5 jours. L'expérience a duré 26 mois, dont 18 mois d'alimentation avec des sortants de phosphore (PO 4 Phragmites australis-P, TP) les flux entrants et sortants sont surveillés ainsi que la teneur en eau, la teneur en oxygène et le potentiel redox à différentes profondeurs. Les quantités de phosphore stockées dans les sols et assimilées dans les sols ont été mesurées. Le fractionnement du phosphore dans les sols a été réalisé pour mieux comprendre sa distribution et sa remobilisation potentielle . De faibles concentrations de phosphate ont été mesurées à la sortie des trois lysimètres, mettant ainsi en évidence une rétention satisfaisante du phosphore dans les trois sols (efficacités d'élimination >90%). Une quantité importante de phosphore peut être exportée par la récolte Phragmites australisparties aériennes (26 %, 17 % et 13 % de la masse annuelle de phosphore entrant pour le loam limoneux Fluvisol, le loam sableux Fluvisol et le loam argilo-sableux Technosol, respectivement). L'étape de fractionnement a permis de déterminer que le phosphore retenu dans le sol était principalement lié aux oxydes/hydroxydes de fer, au calcium et à l'argile. De plus, il s'est avéré préférable de maintenir des conditions oxydantes (aérobies) et un pH proche de la neutralité afin de maintenir des conditions dans lesquelles les complexes formés avec le phosphore restent stables.

The 2025 goal of the Chesapeake Bay Program is to reduce agriculture’s nitrogen (N) loading by 20% from 2014 values. Cover cropping is an important best management practice for recycling and conserving N in cropping systems that might otherwise be lost to groundwater via leaching and runoff. The reduction of N leaching by winter cover crops depends largely on precipitation, timing of planting, and the selection of the appropriate crop species. We compared nitrate-nitrogen (NO3-–N) leaching losses among forage radish (Raphanus sativus L.), cereal rye (Secale cereal L.), a forage radish+cereal rye mixture, and no-cover control. Replicated field trials were conducted at the University of Maryland Central Maryland Research and Education Center over 2016–2018. We collected porewater from 60 cm below the ground surface using porous cup lysimeters following rainfall events and used NO3-–N concentrations paired with the HYDRUS 1-D soil moisture model to compare N leaching losses (in kg N ha−1) among cover crop treatments. We show that mean soil porewater NO3-–N concentrations were higher (by 5x) in the no-cover control compared to rye and radish+rye treatments (P

Nitrate (NO3−) leaching in agroecosystems has caused much concern worldwide due to its negative environmental and health impacts. To evaluate the effect of fertilization on NO3− leaching and soil N accumulation, a two-year 15N tracing study was conducted in subtropical China with field lysimeters packed with non-destructive sampling red soil. 200 kg N ha−1 yr−1 urea (15N abundance of 10%) was applied for maize crops. Fertilization promoted NO3− leaching by 91.5 ± 6.1 and 57.9 ± 15.2 kg N ha−1 yr−1 at 20 and 100 cm depth, respectively. Soil organic nitrogen (SON) pool was the main NO3− source (>60%), especially at surface soil. Fertilizer contributed 19.4 ± 2.0 and 32.8 ± 1.9% to NO3− leaching. At 20 cm depth, besides NO3− leaching accelerated by fertilization during the crop growth period (51.8%), mineralization of SON also resulted in abundant NO3− leaching during the fallow period (48.2%). At 100 cm depth, NO3− leaching significantly increased with the fertilization year due to the continuous NO3− leaching and the delay of NO3− leaching by soil NO3− adsorption. After two-year fertilization, 55.3 ± 2.2% of the applied N accumulated in the soil, leading to a soil N pool increase of 110.0 ± 10.1 kg N ha−1 yr−1. If the fertilization was maintained, the continuous N accumulation poses a potential threat to groundwater quality or drinking water safety. In subtropical red soil regions, to reduce NO3− leaching, NO3− leaching during both the crop growth and fallow period should be taken seriously, and effective management practices, such as cover crops and intensive tile drainage systems, should be carried out to reduce the fertilizer N accumulation and the contribution of SON.

Alternate wetting and drying irrigation (AWD) affects soil and plant K availability in the paddy field. However, it is unclear how zeolite amendment alters soil K fixation, K utilization, and K balance in the paddy rice systems under AWD compared with continuous flooding irrigation (CF). A two-year lysimeter experiment with a split-plot design was used to evaluate the effect of irrigation regime and fertilization management in paddy fields in Donggang, northern coastal China in 2018 and 2019. The field experiment included two irrigation regimes (CF and AWD) as the main plots, and three zeolite/K managements (Z0K0, no added zeolite or K; Z5K30, 5 t ha–1 zeolite and 30 kg ha–1 K; Z0K60, no added zeolite and 60 kg ha–1 K) as the subplots. The results showed that zeolite mitigated the reductions in grain yield and aboveground biomass caused by water stress in AWD. Zeolite addition also caused soil K fixation under AWD, which reduced K leaching losses and avoided excessive K absorption by rice plants, thus contributing to sustainable rice production by preventing soil K depletion. The Z5K30 treatment had lower total K leaching losses and higher K partial factor productivity (the ability of rice to use K to produce yield) than the commonly used practice (Z0K60). Compared with Z0K60 under CF, the Z5K30 treatment under AWD produced higher grain yield, economic benefit, water use efficiency, and total K balance. Therefore, appropriate zeolite and K amendments could be economically and environmentally feasible for rice production under AWD conditions.

Intensification of agricultural management practices, including irrigation and addition of nitrogen (N) fertilizers, can lead to enhanced N leaching and loss of soil fertility. In New Zealand, expansion of the dairy industry has rapidly increased irrigated land area, particularly on shallow, stony soils of the Canterbury region that are prone to leaching, leading to degradation of surface- and ground-water quality and losses of soil N and carbon (C). In this study, we measure components of N balance for two adjacent fields of lucerne (Medicago sativa L., alfalfa) harvested for cut-and-carry feed and grazed in situ. One field was non-irrigated and one irrigated with both water and dairy effluent. Inputs from N fixation associated with the legume crop were quantified using a natural abundance isotopic approach. Drainage from the root zone and leaching were measured with 6 large lysimeters in each field. Leaching losses from non-irrigated lucerne were 7–30 kg N ha-1 y-1 with the largest losses occurring in a year with primarily grazing management. Losses from irrigated lucerne were 39–102 kg N ha-1 y-1, with the largest losses resulting from summer drainage events exacerbated by irrigation. Fixation of N was the largest input to both systems, contributing 192–257 kg N ha-1 y-1 for non-irrigated lucerne. Under irrigation, biomass production increased, but N uptake from effluent and soil stocks contributed to biomass N to a greater extent and fixation was 262–286 kg N ha-1 y-1. Management influenced N balance through inputs from animal excreta and effluent additions and exports through harvest and grazing removals. Management practices which reduce N losses from the soil are needed to minimize environmental impacts and protect soil fertility.

The main objective of this study was to assess the seasonal nutrients requirement of ‘Hass’ avocado trees grown in lysimeters, especially during flowering and the early period of fruit development that may affect later on the fruitlet abscission and determine crop yield. The experimental design included three fertigation treatments applying a fixed nutrient solution at three different starting dates of fertigation: (a) T1 – continuous fertigation, including macro nutrients (N-P -K) and micronutrients application, all over the year; (b) T2 – no fertilization (only irrigation) until 15 March, and fertigation as T1 since then; (c) T3 - no fertilization (only irrigation) until 15 May, and fertigation as T1 since then. Absence of fertilization during the winter period induced leaf-chlorosis while healthy, dense and plenteously green leaves characterized the fertilized trees (T1). The beneficial effect of early fertigation on fruit yield was statistically significant, mostly because of higher fruit number. Leaf analyses are commonly used in the avocado industry as a guide for fertilization yet; fruits rather than leaves are the main products of avocado orchards. Consequently, fruit rather than leaf analyses should determine fertilization management. Based on fruit growth data and nutrient concentration in the fruit, the N, P and K quantities removed by ‘Hass’ avocado fruit yield of 30 t ha−1 were 120, 25 and 240 kg ha−1. Taking into account common efficiency consideration (nutrient quantities removed by fruit yield divided by quantities added), the annual quantities of N, P and K required for attaining high quality avocado yield are 250–300, 80–120 and 500–600 kg ha−1, respectively. Thus, fertilization rate together with nutrient combination should be modified in order to insure optimal fruit development.

Nitrogen (N) leaching is an important factor that threatens groundwater safety in intensive greenhouse vegetable production regions. However, managing irrigation and fertilization to reduce nitrate leaching has rarely been carried out in long-term experiments. In this study, N leaching in two typical greenhouse vegetable systems (a cucumber-cucumber system in Shandong and a cucumber-tomato system in Ningxia) from 2008 to 2013 investigated should be studied using a lysimeter monitoring method. The total N fertilization rate was 0 to 2508 kg N ha−1 which included three treatments: no fertilizer (CK: 0 kg N ha-1), conventional treatment (CON: Shandong 2508 kg N ha-1 and Ningxia 2239 kg N ha-1) and reduced fertilizer application (RF: Shandong 2164 kg N ha-1 and Ningxia 1716 kg N ha-1). The irrigation amount was 590–2919 mm year-1 according to vegetable water demand. The results indicated that the annual total N leaching were 344.8 kg ha−1 (192.3–508.3 kg ha−1) in Shandong and 170.7 kg ha−1 (134.9–203.7 kg ha−1) in Ningxia for the CON treatments. Compared with CON treatment, RF significantly decreased ANLL, while simultaneously maintaining the yield and increasing the downward trend of the annual TN leaching factor (ANLF) year by year. Meanwhile, a concomitant annual cost reductions associated with the RF treatment estimated at $187 million USD for Shandong and $20 million USD for Ningxia. ANLL increased linearly with the N input (p

Net ecosystem exchange (NEE) of carbon dioxide (CO2) and water vapor (H2O) fluxes from irrigated grain sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.) fields in the Texas High Plains were quantified using the eddy covariance (EC) technique during 2014–2016 growing seasons and examined in terms of relevant controlling climatic variables. Eddy covariance measured evapotranspiration (ETEC) was also compared against lysimeter measured ET (ETLys). Daily peak (7-day averages) NEE reached approximately −12 g C m−2 for sorghum and −14.78 g C m−2 for maize. Daily peak (7-day averages) ETEC reached approximately 6.5 mm for sorghum and 7.3 mm for maize. Higher leaf area index (5.7 vs 4–4.5 m2 m−2) and grain yield (14 vs 8–9 t ha−1) of maize compared to sorghum caused larger magnitudes of NEE and ETEC in maize. Comparisons of ETEC and ETLys showed a strong agreement (R2 = 0.93–0.96), while the EC system underestimated ET by 15–24% as compared to lysimeter without any corrections or energy balance adjustments. Both NEE and ETEC were not inhibited by climatic variables during peak photosynthetic period even though diurnal peak values (~2-weeks average) of photosynthetic photon flux density (PPFD), air temperature (Ta), and vapor pressure deficit (VPD) had reached over 2000 μmol m−2 s−1, 30 °C, and 2.5 kPa, respectively, indicating well adaptation of both C4 crops in the Texas High Plains under irrigation. However, more sensitivity of NEE and H2O fluxes beyond threshold Ta and VPD for maize than for sorghum indicated higher adaptability of sorghum for the region. These findings provide baseline information on CO2 fluxes and ET for a minimally studied grain sorghum and offer a robust geographic comparison for maize outside the United States Corn Belt. However, longer-term measurements are required for assessing carbon and water dynamics of these globally important agro-ecosystems.

Agriculture is one of the largest anthropogenic contributors of phosphorus (P) to surface waters and reducing these P loads is a target set by many countries. One potential mitigation strategy could be to utilize biochar, functionalized by co-precipitating metal ions onto its surface to adsorb phosphates. We evaluated such an approach in a series of laboratory experiments and a three-year field lysimeter study. Leached phosphates were trapped in a 3-cm layer of a commercially available 20% hardwood/80% Norway spruce biochar, coated with magnetite and placed under the soil root zone. Langmuir maximum adsorption potential (Qmax) was 3.38 mg P g−1 biochar, as determined from batch adsorption studies performed at pH 6.5. Further laboratory experiments revealed that adsorption was strongly negatively correlated with pH (R2 = 0.995). In a laboratory column study using high flow rates, no difference was found in phosphate adsorption between coated biochar and the control (no biochar), after application of ammonium phosphate at a rate corresponding to 22 kg P ha−1. However, differences were observed at higher application rates (285 or 570 kg P ha−1). Calculation of a Fe:P molar ratio to evaluate the magnetite treatment method from laboratory (2:1) to lysimeter (248:1) suggested a relatively effective laboratory performance, but overall poor field efficiency. Nevertheless, biochar in the lysimeter study still reduced phosphate leaching from two organic soils, by 62% (P

The Diavik Waste Rock Project, located in a region of continuous permafrost in northern Canada, includes complementary field and laboratory experiments with the purpose of investigating scale-up techniques for the assessment of the geochemical evolution of mine waste rock at a large scale. As part of the Diavik project, medium-scale field experiments (∼1.5 m high active zone lysimeters) were conducted to assess the long term geochemical evolution and drainage of a low-sulfide waste rock under a relatively simple (i.e. constrained by the container) flow regime while exposed to atmospheric conditions. A conceptual model, including the most significant processes controlling the sulfide-mineral oxidation and weathering of the associated host minerals as observed in a laboratory humidity cell experiment, was developed as part of a previous modelling study. The current study investigated the efficacy of scaling the calibrated humidity cell model to simulate the geochemical evolution of the active zone lysimeter experiments. The humidity cell model was used to simulate the geochemical evolution of low-sulfide waste rock with S content of 0.053 wt.% and 0.035 wt.% (primarily pyrrhotite) in the active zone lysimeter experiments using the reactive transport code MIN3P. Water flow through the lysimeters was simulated using temporally variable infiltration estimated from precipitation measurements made within 200 m of the lysimeters. Flow parameters and physical properties determined during previous studies at Diavik were incorporated into the simulations to reproduce the flow regime. The geochemical evolution of the waste-rock system was simulated by adjustment of the sulfide-mineral content to reflect the values measured at the lysimeters. The temperature dependence of the geochemical system was considered using temperature measurements taken daily, adjacent to the lysimeters, to correct weathering rates according to the Arrhenius equation. The lysimeter simulations indicated that a model developed from simulations of laboratory humidity cell experiments, incorporating detailed representations of temporally variable temperature and water infiltration, can be scaled to provide a reasonable assessment of geochemical evolution of the medium-scale field experiments.

Canopy size has an important and direct influence on water consumption by raising maize (Zea mays L.) transpiration through increased stomata number on leaves and reducing soil evaporation through blocking solar radiation. Evapotranspiration of maize was determined between 2012 and 2013 by weighing lysimeters at National experimental station for precise agriculture in Beijing. The results showed that total water consumption was 386.3 mm and 366.2 mm for maize strain with large (L) and small canopy (S), respectively. From DAS 50 to DAS 80, the difference of water consumption between two maize strains enlarged at a higher rate than other periods, which was about 4.2 mm at intervals of 10 days. Both the highest periodical water consumption and daily water consumption occurred at the Mid-stage, which was 151.8 mm for L and 139.1 mm for S, 5.06 mm/day for L and 4.64 mm/day for S, respectively. The crop coefficient was 1.11 and 1.04 and seasonal crop coefficients at Initial stage, Mid-stage and Late stage were 0.46, 1.53, 1.22 and 0.44, 1.40, 1.09 for L and S, respectively. The duration when daily Kc was bigger than 1(Kc > 1) was 56 days for L and was 5 days more than that of S, respectively. Although bigger canopy consumed more water, a higher water use efficiency of L is not only for its higher averaged yield, but also for its more positive response of yield to ET increment than that of S between two years. The stable yield performance is helpful for a long-term high water use efficiency. The characteristics of water consumption for maize of different canopy size may help to optimize water utilization in semiarid region.

This article presents validation results of the grass Reference Evapotranspiration (ETo) product, which is provided operationally by the Satellite Applications Facility on Land Surface Analysis (LSA SAF). ETo is considered to be the evapotranspiration from a hypothetical extensive well-watered field covered with green grass (12 cm high and with 0.23 albedo), under the given down-welling short-wave radiation. The LSA SAF product is estimated from daily solar radiation at the surface via a methodology designed to be applicable to that well-defined reference surface. In line with its definition, the LSA SAF ETo product is based on estimates of the radiative energy available at the surface. Validation of ETo estimates is challenging, given the difficulties of finding reliable in situ measurements that meet the ETo definition. We show that for the site that matches closely the reference surface (Cabauw, The Netherlands), the LSA SAF product outperforms other commonly used methodologies, even when these use in situ observations as input. However, observations taken at other stations, located in areas that do not deviate greatly from the reference surface, put into evidence the high uncertainty in local measurements. It is shown that the LSA SAF ETo product follows well in situ values, with average differences of 0.3 mm/day or less for mid-latitude sites and of the order of 1 mm/day for the Spanish sites near Cordoba and Albacete. Local advection effects cannot be ignored in measurements performed in the latter stations, where summer conditions are mostly warm and dry. In situ ETo measurements performed in those cases with lysimeters within limited fields are higher than satellite estimates due to advection of warm dry air from the vicinity, which acts as an extra source of energy. It is shown that this effect can be parameterized as a function of near surface air temperature. However, it is argued that those local advection effects should not occur in the idealized surface referred above. In contrast to other ETo estimates, the LSA SAF product is not influenced by local aridity or advection effects, and therefore it is particularly appropriate for large scale climate assessments, including drought monitoring (e.g. by considering the ratio of actual and reference evapotranspiration). Additionally, it provides suitable estimates of irrigation requirements in support of water management.