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The study was carried out to derive pedotransfer (PTFs) and spectrotransfer (STF) functions to estimate soil organic matter (SOM) content measured by time-consuming and expensive Walkley–Black wet combustion (W-B), using SOM content obtained from loss on ignition (LOI) and spectra reflectance bands at visible (Vis) and near infrared (NIR) regions. In total, 171 soil samples were collected from calcareous soils of southern Iran. The SOM content of the samples was determined using W–B wet combustion (SOMW-B) and LOI at temperatures of 360 °C during 2 h (LOI360-2); 550 °C during 3 h (LOI550-3); and 375°C during 16 h (LOI375-16). For the spectroscopy method, partial least squares regression (SpectPLSR) and forward stepwise multiple linear regression (SpectSMLR) approaches were used for function development. The LOI360-2 procedure with R2val of 0.9 for the validation dataset provided the best match with SOMW-B content. Furthermore, the SpectSMLR provided a STF using spectral reflectance bands at 495, 730, 970, 1906, 2262 and 2342 nm which predicted SOMW-B with R2val of 0.87. Results indicated both the SpectSMLR and LOI360-2, as easy and inexpensive approaches, could be recommended to accurately assess SOM content of calcareous soils. [ABSTRACT FROM AUTHOR]

Soil hydraulic properties are often influenced by agricultural activities. Knowledge of such properties is needed to understand the effect of agricultural practices on the soil water regime and catchment hydrology. In the present study, we investigated the effects of three land use types including orchard field, OF (without plowing), annual cultivated field, ACF (with seasonal plowing), and perennial alfalfa field, PAF (without plowing) on the soil's water-conducting porosity at equivalent pore radius interval a to b, ε(a, b), sorptivity at applied tension ψ, Sψ, and macroscopic capillary length at tension interval ψi to ψi+1, λ(ψi, ψi+1) of calcareous soils. The mentioned hydraulic attributes were calculated from infiltration data obtained from tension-disk infiltration measurements at six tensions of 0–15 cm at 75 experimental locations (25 replications per land use). In general, it can be concluded that more macropores are present in the soils of PAF than in those of ACF and OF land uses, probably due to high organic matter content, long-term no-till conditions, positive effects of alfalfa root systems, low machinery/livestock traffic, and low soluble sodium content. In ACF, conventional tillage and high machinery traffic, and in OF excessive use of Na-rich manure fertilizers and high livestock traffic resulted in less macropores compared to PAF. [ABSTRACT FROM AUTHOR]

Assisted phytoremediation procedures have been widely employed as soil removal instrument of heavy metals from contaminated soils. Rhizosphere processes have a major impact on pb and Zn availability and its fractions in soils. The present study evaluates the effects of EDTA, citric acid (CA) and poultry manure extract (PME) on bioavailability and fractionation of pb, Zn in both the rhizosphere of sunflower (Helianthus annuus L.) and bulk soil. EDTA and CA were added to soils at the rates of 0, 0.5 and 1 mmol kg−1 soil and PME at 0, 0.5 and 1 g kg−1 soil as factorial in a completely randomized pattern with three replicates in greenhouse condition. Results showed that chelator application had a significant impact (p < 0.05) on pb, Zn extraction by different extractants and its fractions in soils. The order of concentrations of pb, Zn present in different fractions in soil treated by chelators was: oxides-bounded fraction > residual fraction > OM-bounded fraction > carbonate-bounded fraction > exchangeable fraction. Biochemical soil characteristics in the sunflower rhizosphere change resulting from its roots contributing to pb, Zn decline in mobile soil fractions, and change in soil pb, Zn fractions that are generally regarded as more stable. [ABSTRACT FROM AUTHOR]

To assess recharge through floodwater spreading, three wells, approx. 30 m deep, were dug in a 35-year-old basin in southern Iran. Hydraulic parameters of the layers were measured. One well was equipped with pre-calibrated time domain reflectometry (TDR) sensors. The soil moisture was measured continuously before and after events. Rainfall, ponding depth and the duration of the flooding events were also measured. Recharge was assessed by the soil water balance method, and by calibrated (inverse solution) HYDRUS-1D. The results show that the 15 wetting front was interrupted at a layer with fine soil accumulation over a coarse layer at the depth of approx. 4 m. This seemed to occur due to fingering flow. Estimation of recharge by the soil water balance and modelling approaches showed a downward water flux of 55 and 57% of impounded floodwater, respectively. [ABSTRACT FROM AUTHOR]

Poor soil fertility remains a threat to crop production and livelihoods in the Sahel. Understanding the impacts of proposed soil fertility management technologies on soil fertility status and millet yield is essential. We conducted a 2-year experiment to assess changes in selected physical properties of an Arenosol and their impacts on millet yields at Karabedji, Niger. Treatments consisted of four fertilizer rates applied on top and bottom farm types selected from a long-term experiment. Mixed-model analyses indicated considerable effects (P = 0.055) of fertilizer rates and farm types on soil structural stability being higher in the top farm than in the bottom farm type. Dexter’s soil physical quality index (S) varied significantly with soil depth. A significant correlation (R2 = 0.24) was found between the aggregate stability index andS. Plant available water recorded in fertilizer-treated soil was higher than the control and higher on the top farm than in the bottom farm. Fertilizer rates and farm types influenced millet yields. Moreover, we obtained positive relationships between millet yield and soil aggregate stability, and plant available water, thereby elucidating the significant role played by soil physical properties in influencing crop yields.Scan be a simple way for assessing the physical quality of Sahelian sandy soil. [ABSTRACT FROM AUTHOR]

Using basic soil properties could save time and costs in determining field capacity (FC) and permanent wilting point (PWP). The objectives of this study were to investigate the relationship between FC and PWP and basic soil properties, develop two new equations for estimating FC and PWP, and evaluating their performance as compared to some existing pedotransfer functions (PTFs) in predicting FC and PWP. For this purpose, 210 soil samples of UNSODA dataset and 45 soil samples of HYPRES dataset were used for development and validation of the PTF, respectively. Graphical exploration of relations between soil texture component, geometric mean particle-size diameter (dg), bulk density (BD), and organic matter (OM) with FC and/or PWP showed that relations of FC was nonlinearly related to percentage of clay (positive) and dg (negative) and relations of PWP was linearly and nonlinearly related to percentage of clay (positive) and dg (negative), respectively. Based on standardized independent variable weight (W), dg showed the highest influence on FC (W = 0.81), followed by percentage of clay (W = 0.70), OM and BD (W = 0.49). PWP was primarily affected by percentage of clay (W = 0.89) and dg (W = 0.64), whereas BD and OM withWof 0.30 were less effective. The two new functions suggested and evaluated for predicting FC and PWP had root mean squares error (RMSE) of 0.06 and 0.02 m3 m−3, geometric mean error (GMER) 1.03 and 1.10 m3 m−3and Akaike's information criterion (AIC) of −262 and −349, respectively. As such, their prediction performance was higher than that of other FC and PWP PTFs found in literature. [ABSTRACT FROM AUTHOR]

Using easily measurable soil properties could save time and cost for field capacity (FC) prediction. The objective of this study was to compare Mamdani fuzzy inference system (MFIS) and regression tree (RT) for FC predicting using such properties. One hundred and sixty-five soil samples from Unsaturated Soil hydraulic database data-set and 45 from Hydraulic Properties of European Soils data-set were used for the development and validation of MFIS and RT, respectively. Fuzzy rules and tree diagram based on the relationships between these predictor variables and the response variable FC were defined and 48 rules were written. Results showed a positive linear relevancy in terms of standardized independent variable weight,W*, between clay content and FC and negative linear relevancy between geometric mean particular size diameter (dg) and FC. Among predictor variables,dg(W* = 0.81) and bulk density (BD) (W* = 0.49) had the highest and lowest influence on FC, respectively. A tree diagram is presented for the prediction of FC using clay content,dg, and BD. Overall, based on statistical parameters, RT method (R2 = 0.78, geometric mean error (GME) = 1.02, mean error (ME) = 0.01 cm3 cm−3, and root mean square error (RMSE) = 0.04 cm3 cm−3) showed a higher performance than MFIS method (R2 = 0.72, GME = 1.16, ME = 0.08 cm3 cm−3, and RMSE = 0.06 cm3 cm−3) to predict FC. [ABSTRACT FROM AUTHOR]

Whether aggravated agricultural drought in the Sahel is related to a changing climate (meteorological drought, i.e., deficit of rainfall or unfavourable rainfall distribution) or to land use and land degradation (soil-water drought, i.e., decreased water infilitration and water holding capacity) is a much-debated issue. Global climate models and trend analysis show little agreement on how rainfall and meteorological drought are changing in the region, and research has increasingly attributed agricultural drought to an imbalanced rainwater distribution over the root zone caused by human-induced land degradation. This paper investigates the extent of both meteorological and soil-water drought on “laterite” soils in the Tillaberí region of Niger and their effect on millet (Pennisetum glaucum(L.) R. Br.) growth by combining monthly (1905–1996) and daily (1989–2010) rainfall analysis with analysis of the root zone water distribution under different management practices. The treatments include: zaï + manure (Z), demi-lunes + manure (DL), scarification + manure (SCAR), control + manure (CF) and control (C). Our findings suggest that increasing agricultural drought does not originate from a decreasing annual amount of rainfall. However, other daily rainfall parameters more important for crop biomass productivity than total rainfall amount, such as the number of dry spells, do appear to have recently worsened. Dry-spell analysis showed increased drought risks during the vegetative growth phase (0–40 DAS) and the vulnerable grain formation phase (90–110 DAS, Days After Sowing). The extremely low grain yields and values of soil-water storage below the critical value for water stress of the control treatments, moreover, confirm poor root zone water distribution. DL and Z however, show potential, to mitigate both dry spells and soil-water drought, as they induce an important increase of soil-water storage, resulting in higher grain yields. In order to optimize these water and soil conservation (WSC) techniques and to increase their potential for drought mitigation, the underlying features enabling increased soil-water storage, including water balance analysis, soil physical properties, nutrient management and system design, should be tackled in future studies. [ABSTRACT FROM PUBLISHER]

Conservation agriculture (CA) is often quoted as a beneficial resource-saving technique for dryland agriculture, but its large-scale implementation is frequently hindered by the lack of farmers’ acceptance. To date, few studies have investigated the impact of spatial factors, costs and benefits and regional agroecosystem differentiation on adoption of CA. This study, therefore, aims to assess the impact of these factors through a case study in the North Ethiopian Highlands. One hundred eight farmers of 11 villages surrounding an experimental plot were interviewed in order to identify their knowledge and acceptance of the technique. The results show that several spatial factors play a role in CA acceptance. The lack of knowledge on the resource-saving technique proved primarily dependent (R= –0.73) on spatial impedance with the innovation source and on the strength of sociospatial networks. Next, a consumer model showed that perceived costs and benefits seem to balance each other. Finally, some agronomic traditions were identified that are related to the regional agroecosystem, which are not favoring the implementation of zero-tillage practices. Since this study identified acceptance problems related to several spatial and regional factors, future CA adoption schemes must allow better regional differentiation optimized to local contexts and conditions. [ABSTRACT FROM AUTHOR]

The results of a 1990 soil survey of a salinized region in Darab Plain, southern Iran, were combined with soil sampling data taken in 2002 from the same locations and employed as a basis for salinity change detection in the region. New preprocessing of satellite imagery was used, along with statistical analysis of the digital number (DN)−salinity relationship, in order to determine salinization of the area. Removal of outliers on the basis of interfering land uses improved the correlations. Nonlinear regression (NLR) in the form y = a + bx α provided a suitable predictor of salinity (y, dS m−1) for both 1990 and 2002 based on DNs (x). Among the 12 tested methods of salinity classification in this study, the six salinity class method with intervals 0–4, 4–10, 10–32, 32–64, 64–80 and >80 dS m–1 was selected. A series of accuracy assessments through a trial-and-error procedure was the basis of the selection of the best method and led to a final accuracy of 91%. About 42% of the lands located on ‘no saline’ and ‘low salinity’ classes in 1990 had changed to the ‘medium’, ‘very high’ and ‘new agricultural land’ classes in 2002. [ABSTRACT FROM PUBLISHER]

Sandy soils, with low productivity, could be improved by compost application to sustain crop production. This study aimed to examine the effect of three compost types (vegetable, fruit and yard waste compost, garden waste compost, and spent mushroom compost) on basic properties of a loamy sand and greenhouse tomato productivity. Disturbed and intact soil samples were taken from a decade-long compost field experiment on loamy sand with three compost types at application rate of 30 m³ ha-1 yr-1 (7.5 ton ha-1 yr-1). The soils were characterized for chemical and physical properties. Tomato was planted in a greenhouse using soil samples from the field and vegetative and yield parameters (plant height, stem diameter, leaf number, and fruit yield), water productivity, and harvest index were evaluated. All compost types significantly increased soil total carbon, total nitrogen, pH, electrical conductivity and significantly decreased bulk density, with no effect on plant available water compared to the control. Fresh and dry fruit weights were significantly increased after compost addition. Plant height, leaf number, stem diameter, and total biomass did not significantly improve after compost addition. Spent mushroom compost had greater effect in improving tomato productivity. A decade-long application of composts on loamy sand improved basic chemical and physical properties which were reflected in increased fruit yield in tomato. Since no negative effect of compost was observed, we suggest that sandy soils may serve as a safe end use option for these composts and potentially support crop growth. [ABSTRACT FROM AUTHOR]

We assessed impact of 5 years continuous application of traditional tillage practices (no-till (NT), shallow tillage (ST) and ridging tillage (RT)) applied by smallholder farmers in central Tanzania. Soil samples were collected at two different soil depths to verify farmer' perceptions. At 0-15 cm, ANOVA showed no significant difference (p > 0.05) for tested parameters except total N which was significantly different and rich in NT. Whereas no significant difference were observed for chemical properties analysed at 15-30 cm, percentage clay, silt and sand content were significantly different (p < 0.05) over tillage practices with NT having more silt and clay. [ABSTRACT FROM AUTHOR]