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Difficulties in efficient utilization of seasonal precipitation cause limitations in yields and even total crop failure on rainfed farms in semi-arid East Africa. The objective of the present study was to find out if covering the soil with plant residue mulch at a semi-arid site could retain water in the soil between precipitation events and build dry spell resilience by reducing soil water evaporation and increasing infiltration to deeper soil. Covering soil with plant residue mulch was studied at a smallholder farm in semi-arid Kenya by continuously measuring volumetric soil moisture content with soil sensors at multiple depths in bare soil and in maize (Zea mays L.) plant residue mulched soil. A physically based one-dimensional soil moisture model was calibrated and used to estimate the effect of plant residue mulch on soil moisture over a two-year period (multiple growing seasons). The modelled multiyear time series provides an estimate of the effect residue mulches of different thicknesses have on soil moisture over time. The simple soil moisture model was able to estimate soil moisture in the effective root zone of maize. By comparing measured data from mulched and uncovered soil and by model prediction, it was demonstrated that maize residue mulch conserved soil moisture over time in the effective root zone of maize compared to bare soil. During the two-year period mulching increased the total amount of days when measured relative soil moisture (s) exceeded water stress limit of maize (s*) by 24%-46%. Moisture accumulated in the mulched profile, especially in the deeper layers of the effective root zone. Calculations indicated that further increasing mulch thickness (delta(m)) from 1 to 3 cm would have increased the total days when s > s* 59%. Furthermore, increasing delta(m) from 3 to 5 cm would have resulted in 25% increase in total days when s > s*. According to our calculations mulching (delta(m) > 1 cm) could have maintained s > s* throughout a 19 days dry spell that occurred during the measurement period. The demonstrated moisture conserving effect of mulch increases with delta(m), but availability of plant residue may set limits on mulch application rates. The results suggest that maize residue mulching is as an accessible and feasible method for conserving soil moisture in the effective root zone in dryland smallholder systems in East Africa.

Fuel consumption of various forage harvesting methods was assessed with a theoretical calculation model, which was validated with field measurements. The examined harvesting methods were tractor-powered forage harvester (TPFH), self-propelled forage harvester (SPFH), self-loading forage wagon (SLFW), and combined baling and wrapping (CBW). The results from the field measurements indicated that the model was working either well or satisfactorily with the examined methods, apart from the CBW method, which would require re-defining the model coefficients. Model sensitivity analysis indicated that variables such as yield level, working width and transportation distance have a significant effect on the fuel consumption. When the working width was increased from 3 m to 9 m, the fuel consumption of the examined methods decreased ca. 54-61%. Increasing the working width by windrowing was found recommended for all examined methods. In all, the most energy efficient method was SLFW, but it was also most sensitive to transportation distance. With the transportation distance of 10 km, the fuel consumption of the SLFW method was already 9-11 % higher compared to that of TPFH and SPFH methods. The strong effect of these variables may cause a wide variation in the fuel consumption of the examined methods, but the model can be used to standardize this effect. The results from this study can thus be used for approximate estimations of average fuel consumption of the examined forage harvesting methods.

Water deficit limits cassava (Manihot esculenta Crantz) productivity in drought-prone areas and alters the nutritive quality of the crop. Potassium (K) may mitigate the effects of water deficit and improve the nutritional content of cassava, which would alleviate malnutrition among the human population in the tropics who depend on cassava as a staple food. Pot experiments were conducted under controlled glasshouse conditions to investigate the influence of deficit irrigation and K fertigation on the nutritive and anti-nutritive quality of biofortified cassava during the early growth phase. Treatments initiated at 30 days after planting were three irrigation doses (30, 60, 100% pot capacity) that were split to five K (0.01, 1, 4, 16, and 32 mM) concentrations. Plants were harvested at 90 days after planting, and the starch, energy, carotenoid, crude protein, fiber, minerals, and cyanide concentration of the leaves and roots were determined. Irrigation and K treatments showed significant (P

Correction FRONTIERS IN MICROBIOLOGY Volume: 12 Article Number: 693341 DOI: 10.3389/fmicb.2021.693341 Published: MAY 20 2021 The soil-borne plant pathogens cause serious yield losses and are difficult to control. In suppressive soils, disease incidence remains low regardless of the presence of the pathogen, the host plant, and favorable environmental conditions. The potential to improve natural soil disease suppressiveness through agricultural management practices would enable sustainable and resilient crop production systems. Our aim was to study the impact of autumn tillage methods and crop sequence on the soil carbon status, fungistasis and yield in boreal climate. The disease suppression was improved by the long-term reduced and no tillage management practices with and without crop rotation. Compared to the conventional plowing, the non-inversion tillage systems were shown to change the vertical distribution of soil carbon fractions and the amount of microbial biomass by concentrating them on the soil surface. Crop sequence and the choice of tillage method had a combined effect on soil organic carbon (SOC) sequestration. The improved general disease suppression had a positive correlation with the labile carbon status and microbial biomass. From the most common Fusarium species, the predominantly saprophytic F. avenaceum was more abundant under non-inversion practice, whereas the opposite was true for the pathogenic ones. Our findings furthermore demonstrated the correlation of the soil fungistasis laboratory assay results and the prevalence of the pathogenic test fungus Fusarium culmorum on the crop cereals in the field. Our results indicate that optimized management strategies have potential to improve microbial related soil fungistasis in boreal climate.

Subsurface drain trenches are important pathways for water movement from the field surface to subsurface drains in low permeability clayey soils. The hydrological effects of trenches installed with well conducting backfill material and gravel inlet patches are difficult to study with only experimental methods. Computational three-dimensional soil water models provide additional tools to assess spatial processes of such drainage system. The objective was to simulate water flow pathways with 3-D FLUSH model in drain spacing and trench depth scale with two model configurations: (1) the total pore space of soil was treated as a single continuous pore system and (2) the total pore space was divided into mobile soil matrix and macropore systems. Both model configurations were parameterized almost solely with field data without calibration. Data on soil hydraulic properties and drain discharge measurements were available from a clayey subsurface drained agricultural field in southern Finland. The effect of soil hydraulic variability on water flow pathways was assessed by generating computational grids in which the hydraulic properties were sampled randomly from five measured soil sets. Both model configurations were suitable to describe the recorded drain discharge, when model was parameterized in finer scale than drain spacing and the parameterization described highly conductive subdomains such as macropores in a dual-permeability model or the trench in a single pore system model. Models produced similar hourly discharge and water balance results with randomly sampled soil hydraulic properties. The results provide a new view on consequences of soil heterogeneity on subsurface drainage. The practical implication of the results from different drainage scenarios is that gravel trench appears to be important only in soils with a poorly conductive subsoil layers without direct macropore connections to subsurface drains. Solely drain discharge data was not sufficient to determine the differences in water flow pathways between the two model configurations and more output variables, such as groundwater level, should be taken into account in making assessments on the effects of different drainage practices on field drainage capacity. (C) 2016 Elsevier B.V. All rights reserved.

This study characterized different polyethylene (PE) and polyvinyl chloride (PVC) plastic foil materials effectiveness for dew collection in arid field-conditions in Kenya. Dew yields were collected daily for one year. Ten dew collectors with four different plastic foils were setup in the experimental field. The cumulated dew yields ranged from 18.9 to 25.3 mm. The greatest cumulated dew yields were 25.3 mm (nightly mean 0.096 mm) and 24.3 mm (nightly mean 0.093) measured with PVC and OPUR coated collectors respectively. The lowest cumulated dew yields 18.9 mm (nightly mean 0.075 mm) and 19.1 mm (nightly mean 0.074 mm) were measured with PVC and PE coated collectors respectively. Dew provided a continuous water source during the dry season. The type of the surface material was not found to be a determining factor for the collected dew yield. The location of the collector at the experimental field had impact on the collected dew yields. We also compared harvested dew yields to measured meteorological parameters and calculated dew yields with the use of a diffusion model using the measured surface temperatures and coefficient of mass diffusion to evaluate the dew collecting potential under the prevailing conditions.

No-till is considered an agricultural practice beneficial for the environment as soil erosion is decreased compared to ploughed soils. For on overall evaluation of the benefits and disadvantages of this crop production method, understanding the soil nutrient cycle is also of importance. The study was designed to obtain information about gross soil nitrogen (N) process rates in boreal no-tilled and mouldboard ploughed spring barley (Hordeum vulgare L.) fields after autumn harvesting. In situ soil gross N transformation process rates were quantified for the 5 cm topsoil in 9 days’ incubation experiment using 15N pool dilution and tracing techniques and a numerical 15N tracing model. Gross N mineralization into ammonium (NH4 +) and NH4 + immobilization were the most important N transformation processes in the soils. The gross mineralization rate was 14% and NH4 + immobilization rate 64% higher in no-till than in ploughing. Regardless of the faster mineralization, the gross rate of NH4 + oxidation into nitrate (NO3 −) in no-till was one order of magnitude lower compared the ploughing. The results indicate that the no-tilled soils have the potential to decrease the risk for NO3 − leaching due to slower NH4 + oxidation.

Water outflow pathways affect environmental loads from agricultural fields, but the pathways and effects of terrain topography on their proportions and on drainage design are not known in detail. In this study, a long-term hydrological dataset and 3D FLUSH model were applied to a field-scale assessment of multi-yearly and seasonal water balance in two adjacent clayey subsurface drained agricultural fields with different slopes (1% and 5%). The model was calibrated and then run with an hourly time step of input data throughout five studied years, and it was able to reproduce the measured water balance components. The results suggested that macropore flow had an essential role in the field-scale hydrological processes in clayey agricultural fields. The model provided a quantification how terrain slope increased the amount of groundwater outflow and correspondingly decreased the amount of drain discharge. The implication is that the hydrological effects of topography of the field and surrounding areas should be taken into account when optimizing drainage intensities. Though most of the groundwater outflow occurred outside the growing periods, sustained groundwater outflow occurred throughout all seasons. A correspondence was observed between the near-saturated surface soil conditions and tillage layer runoff (TLR) events, which suggests that TLR events in high-latitude clayey fields are mainly triggered by saturation excess mechanism. During two springs (once in both field section) TLR was clearly higher than during other seasons, which was likely induced by soil frost. However, the model without computational schemes for frost-induced changes on soil hydraulic properties satisfactorily reproduced drain discharge during most spring periods, and the amount of measured TLR was low during most springs, which indicates that typically frost-induced changes on TLR generation may be small. However, inaccuracies in the quantification of TLR induced by snowmelt formed uncertainty to the estimate of the water balance components during snowmelt.

A growing scarcity of freshwater supplies threatens societies and their future wellbeing as demand for water in agriculture increases. Water deficit often interferes with crop growth in temperate regions. However, between season and within season spatial and temporal variations in precipitation are high. Finland has abundant, good-quality freshwater resources, but only 3% of arable land is irrigated, almost exclusively for horticultural production. We invited 14 stakeholders to participate in a panel to generate and evaluate potential strengths, weaknesses, opportunities and threats (SWOT), focusing on future needs, means and restrictions of agricultural water management systems in Finland. During the panel meeting the expert members considered relevance, strategies and timescales for development and implementation of irrigation systems and characterized six strengths, seven weaknesses, 11 opportunities and six threats. Opportunities received the highest general priority. The SWOT results are further considered in this article from the viewpoints of readiness to operate, justifications for viability of implementation of water management systems and institutional and socio-economic drivers and limitations. The stakeholder perspectives encourage us to take the initial step to open the dialogue with policy makers with a clear message that the numerous management options should be explored in the near future in order to develop a solid strategy to either shift from rainfed to irrigated arable farming or not.

Poor water retention capacity (WRC) and nutrient deficiency commonly limit crop yields in sandy soils. The use of biochar as a soil amendment has been previously reported to improve these limiting factors in subtropical and temperate soils. We studied the effects of biochar on soil properties and yield formation of spring wheat (Triticum aestivum L.) when applied together with inorganic fertiliser or meat bone meal (MBM) to an Endogleyic Umbrisol with a loamy sand texture in boreal conditions. In a two-year field experiment, biochar was applied at 0, 5, 10, 20 and 30 t ha−1 combined with three fertiliser treatments (unfertilised control, MBM and inorganic fertiliser) providing equal amounts of nitrogen (N), phosphorus (P) and potassium (K). Soil WRC and fertility as well as wheat yield, yield components and quality were analysed. Soil moisture content, leaf area index and leaf chlorophyll values (SPAD) were monitored during the experiment. Biochar increased the plant-available water content of the topsoil in the first year and reduced the bulk density in the second year after application. It also increased the contents of easily soluble K and soil organic C (SOC) in the 20 cm of topsoil, but had no effects on other soil nutrients, pH or moisture content. Biochar amendment decreased the soil NO3−-N content below control values in the first year but increased it significantly in the second year. The addition of biochar did not significantly affect the nitrogen uptake, grain yield or quality of wheat, possibly because of its low nutrient availability and the high organic matter content of the soil.

In northern clay soils, field drainage is needed to ensure suitable moisture conditions for crop growth and farming operations. Supplementary drainage installations improve the efficiency of old drainage systems, but the hydrological impacts of the drainage procedures are not comprehensively understood or quantified. The objective was to simulate the hydrological behavior of a clay field section and to quantify the effects of a supplementary drainage on the water balance of the field section. The study site, in southern Finland, was originally subsurface drained in 1952 with 32 m drain spacing. Supplementary drainage was installed in 2014, decreasing the drain spacing to 10.7 m. Simulations were carried out with a dual-permeability hydrological model and two model parametrizations describing the field hydrology (1) before and (2) after the supplementary drainage installation. The parameterizations were used for simulations of a nine-year period to quantify the hydrological impacts of the supplementary drainage. For the periods without snow on the ground, the modified Nash-Sutcliffe efficiency for daily drain discharge and topsoil layer runoff values ranged from 0.43 to 0.53 and from 0.44 to 0.53, respectively. During the original drainage setup scenario, the average annual drain discharge was lower (7.8% of precipitation) than topsoil layer runoff and groundwater outflow (10.3% and 26.4%, respectively). For the supplementary drainage scenario, most of the water outflow was through drain discharge and groundwater outflow (20.4% and 21.9%, respectively). The supplementary drainage installation increased the average annual drain discharge by a factor of 2.6, while the annual average topsoil layer runoff and groundwater outflow decreased by 75% and 18%, respectively. The supplementary drainage setup was found to expedite the drying of the field section in spring by 8 days on average compared to the original drainage setup.

Viljelykasvin sato vaihtelee usein lohkon sisällä. Täsmäviljelyllä on pyritty vastaamaan tähän vaihteluun, mutta siinä onnistumiseen tarvitaan tietoa satovaihtelun syistä. Maan ominaisuuksien, erityisesti maan vesitalouteen liittyvien, on useissa eri tutkimuksissa todettu vaikuttavan sadon vaihteluun. Sadanta, maan hyötykapasiteetti, hydraulinen vedenjohtavuus ja kapillaarisuus vaikuttavat yhdessä viljelykasvin satoon, Niiden vaikutus satoon riippuu sadannan määrästä, maan ominaisuuksista ja viljelykasvin veden tarpeesta. Tästä syystä maan ominaisuuksien vaikutus sadon vaihteluun ei välttämättä ilmene jokaisella kasvukaudella.Tässä tutkimuksessa sadon vaihtelua tarkasteltiin simuloimalla veden rajoittamaa potentiaalisen kevätvehnän (Triticum aestivum) biomassan kertymää paikkakohtaisesti kolmella eri lohkolla. Simuloinnissa käytettiin lohkoilta paikkakohtaisesti mitattuja maan ominaisuuksia ja maksimaalista biomassan kertymistä kuvaavaa kasvimallia. Biomassan kertymistä simuloitiin paikkakohtaisesti jokaisella lohkolla 1000 kasvukauden ajan. 1000 simuloidun kasvukauden välillä ainoa muuttuvana tekijänä oli sade, joka kausikohtaisesti luotiin omalla mallillaan. Sadon vaihtelun voimakkuutta arvioitiin menetelmällä, jossa biomassasadosta laskettiin lohkokohtainen keskisato ja ajallinen keskihajonta simuloiduille pisteille. Simuloitu biomassasato oli kaikilla lohkoilla huomattavasti keskimääräistä alhaisempi vähäsateisina vuosina, jolloin sato vaihteli hieman enemmän kuin sateisina vuosina. Käytetyllä menetelmän ja simulointituloksien avulla pystyttiin löytämään ne alueet lohkoilla, joilla sato suurella todennäköisyydellä poikkeaa lohkon keskisadosta. Menetelmää käytettäessä on kuitenkin otettava huomioon, että se ei erottele sellaisia pisteitä, joissa sato pysyy toistuvasti samalla tasolla, mutta poikkeaa lohkon keskisadosta. Täsmäviljelyä ajatellen tieto vakaasti satoa tuottavista paikoista olisi hyödyllinen riippumatta sadon tasosta.

Soil productivity and other soil functions are dependent on processes in the untilled subsoil. Undisturbed soil cores were collected at the 0.3- to 0.4-m depth from a heavy clay soil in Finland subjected to a single heavy traffic event by agricultural machinery three decades before sampling. Untrafficked control plots were used as a reference. Computed tomography (CT) scanning was performed on soil cores at a field-sampled field capacity water content. Gas diffusion and air permeability were measured when the soil cores were drained to −1000 hPa matric potential (air permeability also at −100 and −300 hPa). The air-filled pore space was measured with an air pycnometer and also calculated from mass balance and CT data. Gas diffusion and air permeability were also measured on a straight model tube and on autoclaved aerated concrete. The compaction treatment had not influenced soil total porosity but had significantly lowered the volume fraction of air-filled macropores at the matric potentials investigated. The compacted soil displayed significantly lower air permeability, while gas diffusivity was not affected. Our analyses indicate that this was due to a compaction-induced reduction in the cross-sectional area of vertical, arterial macropores and in the volume of marginal pores branching from these vertical pores. We observed non-Darcian air flow during air permeability measurements and thus suggest the use of a nonlinear regression technique based on measurements at several pressure differences to arrive at true Darcian air permeability. The tests on artificial materials supported the conclusions that the dominating pores in this clayey subsoil are nearly straight, vertical macropores.

A 6-month trial was carried out to study operational conditions and process dynamics in a system of six continuously fed aerated tank bioreactors grouped by serial connection. Feedback was with NH3-stripped solution after biological treatment, with the purpose of lowering the NH3 content of the feedback solution in order to improve the process. The fate of carbon and nutrients during treatment were determined, as well as the ammonia stripping performance of the biological treatment. The results of the study confirmed the dynamic nature of the serial system and indicated its resistance to process disturbances. The feedback of slurry resulted in a dilution effect and significantly reduced the carbon and nutrients concentrations in the first tank, increasing the treatment efficiency. Overall, after mechanical separation, low intensity aeration treatment and ammonia stripping, up to 61%, 67%, 79% and 83% average reductions of TS, Ntot, NH4(+)-N and Ptot, respectively, were reached.

We studied the effect of different biochar (BC) application rates on soil properties, crop growth dynamics and yield on a fertile sandy clay loam in boreal conditions. In a three-year field experiment conducted in Finland, the field was divided into three sub-experiments with a split-plot experimental design, one for each crop: wheat (Triticum aestivum), turnip rape (Brassica rapa), and faba bean (Vicia faba). The main plot factor was BC rate (0, 5 and 10 t DM ha−1) and the sub-plot factor was the N-P-K fertiliser rate. Soil physico-chemical properties as well as plant development, yield components and quality were investigated. BC addition did not significantly affect the soil chemical composition other than the increased C and initially increased K contents. Increased soil moisture content was associated with BC application, especially at the end of the growing seasons. BC decreased the N content of turnip rape and wheat biomass in 2010, thus possibly indicating an initial N immobilisation. In dry years, the seed number per plant was significantly higher in faba bean and turnip rape when grown with BC, possibly due to compensation for decreased plant density and relieved water deficit. However, the grain yields and N uptake with BC addition were not significantly different from the control in any year. Even though BC application to a fertile sandy clay loam in a boreal climate might have relieved transient water deficit and thereby supported yield formation of crops, it did not improve the yield or N uptake.

The crop growth is highly dependent on growth conditions which vary from year to year making precision farming challenging. In the present paper was first investigated whether varying soil physical properties reflect the within-field yield variation of small grain cereals and how do the variations in weather conditions between growing seasons affect the within-field yield variation. Secondly, the potential biomass accumulation of the crop in existing soil and weather conditions was simulated. The simulated and experimentally based site-specific total biomasses were compared in order to find out whether the soil data explains the observed variations in yield. Three experimental fields size of 3–4 ha were established to examine the spatio-temporal yield variation during three years. The clay content of soils was high (> 46%) and soils were classified as Stagni-Vertic Cambisols. Correlations between soil water retention properties and crop yield were studied. Top and subsoil saturated (SWC), field capacity (FC) and permanent wilting point (PWP) water content, and saturated hydraulic conductivity of soil (Ksat), were determined from 19 to 24 places on each field once during the three years experimental period. During growing seasons, soil moisture content and leaf area index (LAI) were determined at same places biweekly, and yield was harvested. Spring barley (Hordeum vulgare) was grown on two fields, and spring wheat (Triticum aestivum, 2 years) and spring oilseed rape (Brassica napus L., one year) were grown on the third field. The measured grain yields correlated with selected soil physical properties only in few cases. The observed spatial variation in the biomass was in most cases found to be higher than the simulated. Therefore, the above mentioned parameters were not enough to predict the yield correctly in case of high variations. There were other factors decreasing the observed yield e.g. lodging, cold summer, extremely high precipitation and slopes in field. According to our results it is evident that it is very difficult to predict site-specific biomass accumulation solely by soil properties in order, for instance, to fertilize in a site-specific manner. Therefore one needs to measure the crop during the growing season in order to simulate the biomass accumulation for precision farming purposes.

Recent farming machinery provides multiple ways to gather spatial information about soil and cultivated crop properties. However, collected information can not be used straight forward for decision making purposes due to complex relationships between crop growth, weather and soil properties. A quantitative analysis of yield data from three fields over three years was carried out to investigate the spatial and temporal trends. At first it was studied if varying soil water retention properties reflect the observed within-field yield variation of small grain cereals and whether the variations in weather conditions between growing seasons affect the within-field yield variation. Secondly, the potential biomass accumulation in existing soil with varying precipitation was simulated and analysed. The analysis results of the observed biomass yield and simulated biomass yield were compared. The variation in soil water retention properties was found to have an effect to yield variation. However, soil properties alone were concluded not to be enough to predict the yield and the yield variation correctly in case of high variations. There were other factors affecting the observed yield variation, e.g. lodging, cold summer, extremely high precipitation and the field topography. The prediction of site-specific biomass accumulation solely by soil properties was concluded to be impossible. Therefore crop observations were found necessary among the knowledge of soil properties in order to simulate the potential biomass accumulation for precision farming purposes.

Proper drainage practices to remove excess water are crucial for crop cultivation in the humid climatic conditions of the boreal areas. The objectives of this study were to close the water balance, to quantify the amount of groundwater outflow, to identify the effects of topography on drain discharge, and to determine the effects of different subsurface drain installation methods and spacing of drainage lines on water outflow components in a clayey agricultural field. Hydro-meteorological, soil and topographic data were available from paired field sections in southern Finland including two control sections and two sections where different subsurface drainage methods were applied. A 3D hydrological model (FLUSH) was applied to the whole field area for snow- and frost-free periods in three measurement years to decipher the hydrological effects of the drainage improvements. The simulated field area was 14 ha. Simulation results revealed that a steep slope outside of the field decreased drain discharge with 40% and increased groundwater outflow, which was quantified to be a major component of the water balance, approximately 9–15% of the precipitation. The model simulations demonstrated and quantified how drainage improvements in a treatment section affected the hydrology of an adjacent control section. This revealed that the sections shared a hydrological connection through subsurface flow processes. Such connection is typically neglected in the experimental comparison of measurement results from paired field sections. According to the simulations trenchless drain installation changed soil hydraulic properties by decreasing the volumetric fraction of connected soil macropores and by increasing the rate of water exchange between soil matrix and macropores. This affected more the dynamics than the absolute amount of drain discharge. The 3D model was useful in closing the water balance although the limitations were lack of data outside monitored sections and exclusion of snow and frost processes.

Agricultural management practices can have a significant effect on the emissions of nitrous oxide (N 2 O) from soils. The aim of this 2-year study was to investigate the effects of no-till (NT) and reduced tillage (RT) practices on annual fluxes of N 2 O from different soil types typical for the boreal region of northern Europe. We measured the fluxes of N 2 O in conventional tillage (CT) and NT at four sites of which two also had RT treatment. No-till and RT practices had been implemented 8–10 years before our study was initiated. Chamber measurements were carried out fortnightly in 2008–2010 on clayey (sites 1–3) and coarse (site 4) soils. Annual cumulative emissions of N 2 O varied from 2.4 to 8.3 in CT, 2.5–6.5 in RT and 4.9–10.2 kg N 2 O-N ha −1 in NT. High peaks in measured N 2 O fluxes occurred during and after thawing of the soil in April and after fertilization and high rain events. No-till or RT did not have any significant effects on soil C or N stocks or potential denitrification of the 0–20 cm soil layer. Dry bulk density and water-filled pore space (WFPS) were generally higher under NT compared to CT, most probably being the main reasons for the increased N 2 O emissions in the NT systems. Soil temperature varied less in NT by being higher during the colder periods of the year and slightly cooler during hot summer days. In conclusion, our results indicate that NT induces a risk of increased N 2 O emissions in clayey soils in small grain spring cereal agroecosystems in Northern European boreal climate.

Maatalous kohtaa ilmastonmuutoksen myötä entistä suurempia ympäristöhaasteita. Eroosio- ja ravinnekuorma vesistöihin kasvaa, mikäli talvet muuttuvat ennustetulla tavalla lauhemmiksi ja sateisemmiksi. Kasvipeitteisyys suojaa maan pintaa vähentäen eroosio- ja ravinnehuuhtoumariskiä, mutta kasvinjäte voi vaikeuttaa viljelyä ja luoda suotuisat olosuhteet maa- ja kasvinjätelevinteisille kasvitaudeille. SUCCESS-projekti toteutettiin osana MTT:n Muuttuva ilmasto ja maatalous tutkimusohjelmaa (2009–2012) ja Helsingin yliopiston Globaalin ympäristömuutoksen tutkimusohjelmaa (2008–2011). Tutkimuksen tavoitteena oli selvittää muokkausmenetelmien vaikutusta maaperämikrobistoon ja sen tuottamiin ekosysteemipalveluihin, kuten tautimikrobien tukahduttamis-kykyyn. Maanäytteenotto tehtiin kuudelta erilliseltä peltoalalta, joissa pitkäaikaisina (8–12 vuotta) muokkauskäsittelyinä olivat suorakylvö ja kyntö. Kokoomanäytteet (vähintään 20 kairallista/ruutu) otettiin muokkauskerroksesta ennen syyskyntöä kolmelta eri syvyydeltä 0–5, 5–10 ja 10–20 cm (2009). Näytteistä analysoitiin sieni- ja bakteerimikrobiyhteisöjen koostumus kolmella eri menetelmällä; PLFA rasvahapposormenjälki, PCR T-RFLP DNA-sormenjälki ja 454 FLX Titanium DNA-pyrosekvensoinnilla (Roche Applied science). Samanaikaisesti mitattiin laboratoriobiotestien avulla mallikasvitautisienen (punahome, Fusarium culmorum) kykyä kasvaa peltomaan päällä ja näin saatiin arvio maiden kasvitautien tukahduttamiskyvystä. Peltoalojen maaperän vaihtelusta riippumatta ja kaikilla käytettyillä mikrobiyhteisöjen kuvausmenetelmillä huomattiin, että suorakylvössä muodostuu selkeä syvyysgradientti mikrobioyhteisöihin. Vastaavaa gradienttia ei havaittu kyntökäsittelyssä. Suorakylvöruutujen syvyysgradientissa korostuivat etenkin suurimpien maaperän bakteeripääjaksojen suhteelliset osuudet (acidobakteerit, proteobakteerit ja aktinobakteerit) sekä nitriittiä nitraatiksi happettava Nitrospira pääjakso (Parittainen t-testi, Suorakylvö 0–5 vs. 10–20 cm, P

Täsmäviljelyn perustana on viljellä peltoa paikkakohtaisesti viljelykasvin tarpeiden mukaisesti. Vesi on yksi tärkeimmistä kasvin kasvua määrittävistä tekijöistä lämmön, auringon säteilyn ja ravinteiden ohella. Kasville käytettävissä olevan veden määrä määräytyy sateiden ja maan hydrologisten ominaisuuksien perusteella. Tästä syystä paikkakohtainen tieto maaperän ominaisuuksista on olennaista täsmäviljelyssä. Suomessa kasvuolot vaihtelevat paljon kasvukausien välillä, mikä heijastuu myös viljelykasvin kasvuun. Tämä puolestaan vaikeuttaa viljelypanosten määrän mitoittamista kuluvan kasvukauden oloja vastaavaksi. Tämä muodostuu ongelmaksi erityisesti lannoituksessa, joka on kevätviljoilla perinteisesti tehty kylvön yhteydessä, jolloin on mahdotonta ennustaa luotettavasti tulevan kasvukauden olosuhteita. Yksi mahdollinen ratkaisu voisi olla lannoitteen jakaminen kahdessa tai useammassa eri erässä. Tällöin myöhemmillä lannoituskerroilla pystyttäisiin ottamaan huomioon kasvukauden siihen astiset kasvuolot sekä myös säätämään lannoitteen määrää paikkakohtaisesti kasvien tarpeen mukaan. Säädön myötä tarvittavan lannoitteen määrä ei välttämättä kaikissa tapauksissa pienene, mutta se pystytään kohdentamaan niihin pellon osiin, joissa viljelykasvi kykenee sen parhaiten hyödyntämään. Jotta tällainen säätö olisi mahdollista, tarvitaan malli, jolla voidaan verrata havaittua kasvua maksimaaliseen kasvuun sekä estimoida kasvin tulevaa kasvua ja tarvetta kasvuresursseille. Maataloustieteiden laitoksella TOOLMOD projektissa yksi tutimuksen kohden on ollut täsmäviljelyn työkaluksi tarkoitettu kasvimalli, jota käytettiin myös tässä tutkimuksessa. Malli on rakenteeltaan mekanistinen ja sillä pystytään kuvaamaan C3-kasvien biomassan kertymistä. Malli on tarkoitettu työkaluksi, jolla pystytään mitoittamaan paikkakohtaista lisälannoituksen määrää kasvukauden aikana. Tarvittavan lisälannoituksen määrä määräytyisi mallin antaman kasvun sekä pellolla kasvustosta mitatun säteilyn käytön perusteella. Tässä tutkimuksessa tutkittiin kasvimallin toimivuutta paikkakohtaisesti MaSa-projektissa kerätyn aineiston avulla. Tutkimuksessa käytettiin kolmen eri savipellon havaintoja kolmelta peräkkäiseltä vuodelta. Aineiston avulla selvitetttiin kuinka suuri osuus pelloilta havaituista satovaihtelusta voidaan selittää maaperästä mitatuilla suureilla kyseisen mallin avulla.

Tavoiteltaessa “vihreämpää maataloutta” peltomaan mikrobiston toiminnan merkitys korostuu entisestään. Maaperämikrobisto vastaa kasvintähteiden hajotuksesta ja eloperäisessä muodossa olevien ravinteiden vapauttamisesta satokasvien käyttöön. Mykorritsasienet voivat kasvin kanssa muodostuvan ns. sienijuuren avulla tehostaa kasvien fosforin saantia ja suojata kasvia stressitekijöiltä (mm. kuivuus, kasvitaudit). Monimuotoisen mikrobiston on todettu parantavan maaperän luontaista tautisuppressiivisuutta (kasvitautimikrobien kasvun tukahduttaminen). Mikrobisto on runsainta kasvin juuristossa ja sen välittömässä läheisyydessä (”ritsosfääriefekti”). Kasvi luovuttaa yhteyttämistuotteitaan juurieritteiden muodossa ja muokkaa maaperän olosuhteita mikrobeille suotuisiksi. Monivuotisilla kasveilla juuriston koko suhteessa maan yläpuoliseen biomassaan on suurempi kuin yksivuotisilla kasveilla. Monivuotisilla kasveilla juuristo kasvaa koko kasvukauden, kun se yksivuotisilla on laajimmillaan tuleentumisen aikoihin. Kasvilajeilla on kuitenkin suuria eroja juuriston koossa ja juurieritteissä, ja vain osa lajeista kykenee muodostamaan sienijuuren mykorritsasienten kanssa. Tutkimustemme tavoitteena oli selvittää, voidaanko peltomaan mikrobistoon vaikuttaa viljelykierron ja kasvilajivalikoiman avulla. Esitykseen kootaan tuloksia kahdesta tutkimuksesta, jotka molemmat on toteutettu MTT Jokioisilla. MONIKASVI-hankkeen 3-vuotisessa kenttäkokeessa keskityimme juuriston ja sen ympäröivän maan mikrobistoon. Kokeessa oli mukana viisi yksivuotista (ohra (Hordeum vulgare), kinua (Chenopodium quinoa), camelina (Camelina sativa), pellava (Linum usitatissimum) ja tattari (Fagopyrum esculentum)) ja viisi monivuotista (timotei (Phleum pratense), kumina (Carum carvi), ruokohelpi (Phalaris arundinacea), värimorsinko (Isatis tinctoria), nokkonen (Urtica dioica)) viljelykasvia. SUCCESS-hankkeessa vertailimme maaperän mikrobistoa 4-vuotisessa viljelykierrossa (kevätvehnä, rypsi, ohra, herne) ja jatkuvassa kevätvehnän viljelyssä. Vertailussa olivat myös muokkausmenetelmät kyntö ja suorakylvö. Maaperämikrobiston koostumusta selvitettiin fosfolipidirasvahappojen (PLFA) ja neutraalilipidi-rasvahappojen (NLFA) analyysien avulla. MONIKASVI-hankkeessa selvitettiin arbuskelimykorritsojen esiintymistä myös muilla menetelmillä. SUCCESS-hankkeessa analysoitiin mikrobiston koostumusta molekyylibiologisilla menetelmillä, sekä selvitettiin mikrosienten esiintymistä oljessa. Peltomaan mikrobiston esiintymisessä oli suuria eroja kasvilajien välillä. Monivuotiset kasvit ylläpitivät runsaampaa mikrobistoa. Arbuskelimykorritsan esiintymiseen vaikutti ensisijaisesti kasvilajin ominaisuudet. Viljelykierrolla ja muokkausmenetelmällä voidaan edistää toivotunlaisen mikrobiston esiintymistä maassa.

Due to the high cost of fuel and labour associated with conventional tillage, and because of their advantageous environmental consequences, interest in reduced and zero tillage systems has increased. Direct drilling into zero tilled (ZT) soil of two spring barley ( Hordeum vulgare L.) cultivars (six-rowed Rolfi and two-rowed Saana), spring oats ( Avena sativa L., cultivar Roope), and spring wheat ( Triticum aestivum L., cultivar Kruunu) was compared with conventional tillage (CT) and drilling into ploughed soil. Two field experiments were conducted on clay soils (clay content > 50%) between latitudes 60° and 61° N. Seed and fertilizer were placed in the same row in ZT and in separate rows in CT. Oats was the most productive spring cereal species in ZT. Establishment of spring wheat was often poor. Barley was most vulnerable to water surplus during early growth and drought during late growth. High levels of crop residues caused problems in soil drying in spring and growth of monocultures of oats and wheat. A higher seeding rate was advantageous in zero tilled clay soil. The substantial grain yield decrease suggests need for improving ZT. Long-term trials are required to determine whether ZT suits clay soils as soil structure can change over time and weather conditions play a major role in the productivity of differently tilled soils.

Consideration of the environmental effects of the no-tillage practice should be made on the basis of its effects on both carbon and nitrogen cycles. There is a lack of data on the effects of the no-till management in the cool and humid climate and typical soil types of Northern Europe. We measured the fluxes of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) on conventionally ploughed agricultural soils and on respective soils that had been under no-till practice for 5–7 years. Ten chamber measurement investigations were carried out during a 10-month period on six pairs of tilled and no-till fields on clayey (Vertic Cambisols, three pairs), coarse (Eutric Regosols, two pairs), and organic (Dystric Histosols, one pair) soils located between latitudes 60° and 62° N. The results suggest that there is a risk of increased N2O emissions in the first years of no-till practice under small grain spring cereal cultivation in Northern European boreal climate. Carbon dioxide emissions measured as total ecosystem respiration were either unchanged, increased or decreased under no-till. Fluxes of CH4 were negligible and not affected by no-till practice. Dry bulk density and soil moisture were higher in no-till soils compared to annually mouldboard ploughed soils. Variation in the greenhouse gas fluxes was best explained by the content of carbon and nitrogen in the topsoil of 0–20 cm.

Suorakylvöön siirtyminen on vähentänyt maa-aineksen ja siihen sitoutuneen fosforin (P) huuhtoutumista savipelloilta vesistöihin, sillä kasvipeite suojaa maanpintaa sadepisaroiden iskuilta. Liukoisen fosforikuormitusriskin kasvu koetaan kuitenkin ongelmaksi, johon tässä tutkimuksessa etsittiin ratkaisua. Tutkimukseen otettiin maanäytteitä kahdelta savipellolta, joilla oli suorakylvettyjä, sänkimuokattuja ja kynnettyjä lohkoja. Osa lohkoista oli kalkittu ennen näytteenottoa ja osa oli kalkitsemattomia. Lisäksi osalle lohkoista oli levitetty kalsiumkarbonaattipitoista kuitua seitsemän vuotta ennen näytteenottoa, verranneruutujen ollessa ilman kuitulisäystä. Tutkimuksessa selvitettiin myös miten maanäytteiden pinnalle lisätty tuore kuitu vaikutti viikon muhituksessa maan valumaveden laatuun. Suorakylvöpeltojen pintakerroksissa oli alhainen pH ja korkea P-pitoisuus syvempiin kerroksiin nähden. Sänkimuokatuilla lohkoilla gradientit olivat loivempia ja kynnössä pitoisuuseroja muokkauskerroksessa ei ollut lainkaan. Kalkituilla suorakylvömailla pinnan pH oli selkeästi korkeampi kalkitsemattomiin lohkoihin nähden ja kuitukäsitellyillä lohkoillakin oli vielä seitsemän vuoden jälkeen nähtävissä kalkkipitoisen kuidun pH:ta nostava vaikutus. Suorakylvetyiltä ja kynnetyiltä pelloilta otettujen 20 cm korkeiden maapatsaiden läpi tulleen valumaveden liukoisen P:n pitoisuudet olivat samansuuruisia, mikä johtui todennäköisesti P:n pidättymisestä maapatsaaseen veden suodattuessa maan läpi. Kalkituilla suorakylvölohkoilla valumaveden liukoisen P:n pitoisuus oli alhaisempi kalkitsemattomiin lohkoihin verrattuna. Kuidulla ei ollut enää seitsemän vuotta levityksen jälkeen vaikutusta pintavalumavesien P-pitoisuuksiin. Kun maapatsaiden pinnalle lisättiin tuoretta kuitua, valumavesien sameus ja P-pitoisuudet vähenivät selkeästi. Kuitu ilmeisestikin toimi maan pinnalla katteena, joka vähensi sadepisaroiden iskujen hajottavaa vaikutusta. Suorakylvöpeltojen liukoisen P:n kuormitusriskin pienentäminen on monen tekijän summa. Lannoitukseen on kiinnitettävä enemmän huomiota kuin kyntöpelloilla, sillä pienetkin ylimäärät kertyvät muokkaamattomuuden seurauksena pellon pintaan. Kalkituksen merkitys korostuu suorakylvössä, jossa maan pintakerroksen happamoituminen vähentää P:n käyttökelpoisuutta kasveille. P:n kertymistä pellon pintakerrokseen voidaan ennaltaehkäistä optimoimalla lannoitus kasvien tarvetta vastaavaksi ja kalkitsemalla pinnastaan happamia suorakylvöpeltoja. Maan rakennetta tulisi vaalia; mitä tehokkaammin vesi imeytyy maahan, sitä pienemmäksi jää P:a pintakerroksesta uuttavan pintavalunnan osuus. Sängen ja kateaineiden avulla voidaan vähentää sadepisaroiden iskujen maapartikkeleita hajottavaa vaikutusta. Kuitulisäyksillä ja kalkitusaineilla voidaan edistää savimaan murujen flokkuloitumista ja vähentää P:n irtoamista maasta valumaveden mukaan. Kuidun pintalevitys on lupaava jatkotutkimusta edellyttävä menetelmä, jolla voitaisiin vähentää liukoisen P:n kuormitusriskiä.

Macroporosity of soil and earthworm abundance in relation to the distance from subsurface drain lines were determined to investigate the effect of subsurface drainage on the spatial variation of clay soil structure. Our hypothesis was that soil macroporosity near a drain line location would be greater than the macroporosity at a midpoint between two drain lines where the groundwater table remains theoretically at a higher level. The experimental site was located on a post-glacial clay soil classified as a very fine Aeric Cryaquept (Vertic Cambisol). The area of the field was 1 ha and the slope varied from 2 to 4%. Measurements of soil properties were carried out along four subsurface drain lines installed 50 years before soil sampling. In each drain line, vertical soil profiles were examined at different distances from the drain: (1) above the drain, (2) 2 m from the drain, and (3) midway between two drains (6–7 m from a drain). In each vertical profile, soil macroporosity, number of earthworm burrows and root channels, and saturated hydraulic conductivity ( K sat ) were determined in three soil layers to the depth of 50 cm. In addition, the field saturated hydraulic conductivity ( in situ ) and the number and fresh mass of earthworms were determined. The results showed that the number of earthworm burrows was 44% (90 burrows m −2 ) greater above a drain than at a distance of 6–7 m from the drain. There was also an indication of higher earthworm density above the subsurface drains than between them. The other measures of soil physical properties were not clearly related to distance from the drain. One reason for the small differences in soil properties in relation to drain position was probably the groundwater level that in our clay field varied less in relation to drain location than was expected. Spatial variation of the investigated soil properties was mostly explained by the slope of the field. Even though the groundwater table was shallower at the downslope part compared with the upslope part of the field, the number of biopores, K sat and the number of earthworms clearly increased downslope.

The rolling resistance and rutting incurred by towed flotation implement tyres were investigated on an arable clay soil in three different soil strength conditions. Three radial (600/55R26.5) and two bias ply (600/55–26.5) tyres were compared. Experimental wheel loads were in the 35.4–36.4 kN range. Tyre inflation pressures, representing typical field operation, and road transport applications were in 100–150 kPa and 150–200 kPa, respectively. Soil strength was determined from mean soil penetration resistance (CI0–15, in the layer 0–15 cm) and mean cohesion (C0–10, 0–10 cm). Wheel rolling resistance evaluated by the coefficient of rolling resistance (CRR), rut depth (RD), driving speed, and field gradient were measured with the tyres mounted on a test trailer hitched to a tractor. CI0–15 and C0–10 values predicted the sinkage and the resistance to travel motion on clay soil reasonably well. When the CI0–15 was less than 1 MPa and C0–10 was below 100 kPa, CRR and RD increased rapidly. On average, CRR was 20% lower for the radials than the bias plies. In soft conditions (CI0–15 ⩽ 0.48 MPa), the radials produced 15% shallower ruts than bias plies, and the CRR was lower and RD shallower with field inflation pressures than with road pressures used. According to our results, flotation tyres can be recommended to agricultural machines when the implement or trailer is used in soft soil conditions.

Conservation tillage has proved to be an effective option to reduce erosion and particulate phosphorus (PP) losses from fields to watercourses. However, it usually leads to the higher losses of P in dissolved reactive (DRP) form if P accumulates into the uppermost soil layer. In this study we investigated the influence of CaCO 3 -rich boardmill sludge (BMS, applied 7 years ago) on soil properties and percolate quality with soil samples as well as undisturbed soil columns taken from a long-term conservation-tilled clay field experiment. A short-term laboratory experiment was undertaken to evaluate whether newly added BMS (FS) can be used to improve the quality of percolate waters by reducing turbidity, PP and DRP. The hypothesis was that BMS reduces the risk of dissolved reactive phosphorus (DRP) leaching from conservation-tilled soil. BMS served as a liming agent and counteracted the no-till-induced acidification and accumulation of DRP in the surface soil layer. Surface soil pH was on average 0.3 units higher and soil Ca 500 mg kg −1 higher in the BMS-treated plots than in the plots without BMS. The ability of BMS to enhance the availability of P for plants may prevent the surface accumulation of P in NT cultivation. At the same time, BMS-induced increase in Ca and EC of the surface soil suppress the diffuse double layer by reducing P desorption and leaching risk. In the laboratory experiment, FS reduced percolate turbidity by 80% and PP and DRP concentrations by 62% and 50%, respectively. FS probably improved stability of soil aggregates in the laboratory experiment, obviously through enhanced microbial activity. The covering effect and infiltration of water through the 0–5 cm soil layer seemed to be crucial factors in reducing P losses. BMS proved to be a promising material for the applications to the conservation-tilled fields. The effect of BMS on microbes and immobilization of nutrients, should, however, be studied further in fields under a wider diversity of conditions.

No-till (NT) has proved to be an effective method to reduce erosion and losses of particulate phosphorus (PP) from fields to watercourses. However, the accumulation of P in the uppermost soil layer and the increased leaching risk of dissolved reactive phosphorus (DRP) in surface runoff reduce the environmental benefits of NT. The objective of this study was to determine whether the concentration of DRP in percolates could be decreased by mixing surface soil (0–5 cm) and deeper soil layers (5–20 cm) and how this affects erosion. We also tested the impact of high ionic strength on erosion from undisturbed and disturbed soil columns. Soil samples were collected from conventionally tilled (CT) and non-tilled (for 5 years) plots from a clay field (Vertic Cambisol) at 0–2.5, 2.5–10 and 10–20 cm depths. Moreover, undisturbed and disturbed soil columns representing the same plots were saturated with water in the laboratory and allowed to drain. The physico-chemical properties of the percolates were analysed to unravel the impact of cultivation methods and disruption of the aggregate structure. To see the effect of high ionic strength on detachment of soil particles, the soil columns were leached with ammonium acetate solution. The low pH of NT surface soil had enhanced the sorption of P and easily-soluble P had accumulated in the uppermost soil layer. Surprisingly, this enrichment did not increase the DRP concentration in the percolates when water percolated through the 0–5 or 0–20 cm soil layers. Disruption of the aggregate structure increased the turbidity and concentrations of suspended solids and PP in the percolates. In the NT samples, this action increased the concentration of DRP relatively more than in the CT samples. When the disturbed soil columns were leached with a solution of high ionic strength, the turbidity of the eluates was almost as low as before the breakage. To prevent erosion and the leaching of PP and DRP, we have to ensure an even water infiltration by improving the soil structure and by avoiding the disruption of stabilized aggregates. Ploughing the surface layer of NT soil can be recommended only if erosion from the field can be kept under control.

Macroporosity and its effect on runoff processes were studied on a sloping subdrained clay field (very fine Aeric Cryaquept) in Southern Finland. An extensive field campaign was carried out to measure the spatial variability of soil macroporosity and hydraulic properties. According to the field data, macropore conductivity decreased with depth and soil properties showed differences between the upper and lower parts of the field. A one-dimensional model (MACRO) was applied to quantify the effect of these differences on the hydrological response of the upper and lower field sites. Based on the measurements, five separate parameterizations characterizing the differences in soil structure between the measurement sites were formulated. The change in soil structure had a great effect on the relative proportions of simulated drain flow and surface runoff but influenced only slightly the total amount of runoff. Evapotranspiration and percolation were similar in all cases. Examining model simulations, measured runoff components and groundwater table suggested that a two- or three-dimensional modeling approach is necessary, when prediction of proportional fractions of drain flow and surface runoff, and simulation of groundwater level in a sloping field are of interest.

In the southern parts of Finland, 75% of the arable land area has subsurface drainage. Most of the subsurface drainage systems have been installed 40-50 years ago. At present, there is need to improve drainage efficiency of the old drainage systems. The aim of this study is to find out how the additional subsurface drainage affects groundwater table depth, discharge, nutrient load and crop yield. The study has been carried out at the experimental site in Jokioinen, in south-western Finland. The soil is heavy clay and the mean slope is 1%. The drain depth was 1.1 m and gravel was used as envelope material. Drain flow and tillage layer runoff from each field section have been continuously measured since May 2007. Concentrations of total nutrients and suspended solids have been determined from flow weighted composite water samples. Depth of the groundwater table and soil moisture have also been measured. According to the results, additional drainage decrease of groundwater level following snow melt and rainfall events was more rapid than before drainage. Additional drainage increased drain outflow and also nutrient loads from the drains. The results suggest that additional drainage did not affect the nutrient concentrations, apart from the peak in total nitrogen concentration in the first year after additional drainage.

No-tillage (NT) is a method adopted to reduce erosion and particulate phosphorus (P) load from arable land to watercourses. However, it has been found to increase the loss of dissolved P with surface runoff, but the reasons for that have rarely been examined in detail. The objective of the present study was to determine the chemical factors explaining this response by investigating the impact of NT on the type and distribution of P reserves as well as on organic carbon (C) in the 0–35 cm topsoil layer of clay soil profiles (Vertic Cambisols). Soil samples were taken from two experimental fields (Jokioinen and Aurajoki) at 0–5, 5–20 and 20–35 cm depths in conventionally tilled (CT) and non-tilled (for 4–5 years) plots. The plots had been cultivated and fertilized according to the common field practices in Finland (15–18 kg P and 100–128 kg N ha −1 year −1 ). Inorganic and organic P reserves characterized by a modified Chang and Jackson fractionation procedure were not significantly affected by the cultivation methods. However, in the uppermost soil layer (0–5 cm) in NT of the Jokioinen field, the labile P determined by water extraction (P w ) increased significantly, whereas the increase in P extracted with acid ammonium acetate (P AAC ) remained statistically insignificant. The increase in labile P coincided with a significant increase in organic carbon (C), which supports the theory that competition between organic anions and phosphate for the same sorption sites on oxide surfaces will enhance the lability of soil P. In the Aurajoki field with distinct soil cracking, P w and P AAC were not affected by NT in the uppermost soil layer, but they increased in the deepest soil layer (20–35 cm) concomitantly with an increase in Al-bound P and organic C. However, the increases were not statistically significant. In both fields, soil acidification due to the repeated application of N fertilizers at a shallow soil depth as well as the accumulation of organic C lowered pH of the uppermost soil layer in NT compared to the deeper soil layers. The results indicated that even short-term NT can increase the labile P in clay soil. However, further studies are needed to assess the long-term changes in lability of surface soil P and, consequently, the possible need for readjustment of the fertilization level in NT.

Methane (CH 4 ) oxidation in soils is the only known biological sink of CH 4 . The sink strength of agricultural soils is known to be affected by soil properties and agricultural practices. We studied fluxes of CH 4 in southern and northern Finland in arable soils with different texture and crops. The annual fluxes ranged from uptake of −1.2 kg CH 4 ha −1 to emission of 40 kg CH 4 ha −1 . The CH 4 oxidation decreased in the order loamy sand > well drained peat > clay > poorly drained peat. The more there were macropores or the less there were micropores in the soil, the higher was the mean annual CH 4 oxidation rate. Calculated on the basis of the soil type specific CH 4 flux rates from our study and the soil type distribution of Finnish agricultural soils, the total agricultural area in Finland would form an annual CH 4 sink of −19 Gg CO 2 equiv., which is 0.3% of the total reported greenhouse gas emissions from agriculture in 2004.

Raskas peltoliikenne on lisääntynyt merkittävästi maatalouden koneellistumisen myötä. Kokonaismassaltaan yli 30 t koneet eivät enää ole harvinaisia. Renkaasta maahan välittyvä kuorma aiheuttaa maan huokos- ja mururakenteen rikkoutumista sekä muokkauskerroksessa että sen alapuolella olevassa pohjamaassa. Muutokset voivat olla pitkäaikaisia ja ne voivat haitata maan viljelyä, pienentää satoa sekä lisätä peltoviljelyn ympäristökuormitusta. Maassa tapahtuviin muutoksiin vaikuttavat maan ominaisuuksien ja yksittäisten koneiden ohella käytettävät työmenetelmät ja koneketjut sekä töiden ajoitus ja niitä voidaan vähentää minimoimalla peltoliikenne, käyttämällä olosuhteisiin parhaiten soveltuvaa teknologiaa sekä oikeaa rengasvarustusta. R enkaan pintapaineen ylittäessä maan kantavuuden rengas alkaa upota ja maan pintakerros tiivistyy. Rengaskuorman kasvaessa sen tiivistävä vaikutus ulottuu myös maan syvempiin kerroksiin. Renkaan uppoutumista ja siitä aiheutuvaa vetovastusta voidaan vähentää alentamalla rengaspainetta, pienentämällä kuormaa, lisäämällä renkaan kokoa ja käyttämällä vyörenkaita. Maan rakennevaurioiden välttämiseksi on tunnettava erityyppisten renkaiden ominaisuudet ja maan tiivistymisherkkyys. Tässä tutkimuksessa selvitettiin kahden vyörenkaan ja yhden ristikudosrenkaan vaikutusta savimaan penetrometrivastukseen. Renkaiden koko oli 600/55–26.5. Rengaskuorma oli 3,7 Mg ja käytetyt paineet 100 kPa renkaalla 1, 120 kPa ja 200 kPa renkaalla 2 ja 200 kPa renkaalla 3. Rengaspaine mitoitettiin valmistajan tai maahantuojan ohjeiden mukaan sekä pelto- tai maantieajoon sopivaksi käytetyn rengaskuorman mukaisesti. Vertailu tehtiin ajamalla muokatulla pellolla ja mittaamalla maan tunkeumapaine (cone-indeksi) penetrometrillä renkaan urasta ja vertaamalla sitä tiivistämättömästä maasta mitattuihin arvoihin. Mittaukset tehtiin heti ajon jälkeen sekä seuraavan vuoden keväällä. Mittausten mukaan kerta-ajosta maan 0-15 cm pintakerros oli tiivistynyt. Vyörenkaalla korkea rengaspaine aiheutti muita renkaita selvästi voimakkaampaa tiivistymistä, joka oli mitattavissa vuoden kuluttua ajosta. Suuri rengaspaine pienentää maan ja renkaan välistä kosketusalaa vyörenkaalla ja pintapaine aiheuttaa maan pakkautumisen pehmeissä olosuhteissa.