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Jatropha and Pongamia are a potential source of biodiesel and grow in a wide range of agroclimatic zones and soil conditions. Data and knowledge available on water requirement of Jatropha and Pongamia are very scarce. Crop coefficients are important parameters used for assessing water requirement and irrigation scheduling. In the present study, crop coefficients of Jatropha and Pongamia were estimated using water balance approach. Temporal data on soil moisture at different depths in block plantations of Jatropha and Pongamia at International Crops Research Institute for the Semi-Arid Tropics ( ICRISAT) farm, Patancheru in India, were collected at 15 days interval between 2007 and 2010. Measured soil moisture data were analyzed using one-dimensional water balance model. Results showed that annual water requirement of Jatropha is 750 mm and of Pongamia is about 950 mm in semi-arid tropics. Crop coefficients of Jatropha ranged from 0.10 to 0.95 and of Pongamia from 0.30 to 1.10 depending on plant growth stage in different months. ICRISAT received 820 mm of rainfall in a normal year (data between 2001 and 2010) during the monsoon, of which 52% (430 mm) contributed to evapotranspiration ( ET), 34% (280 mm) was stored in soil, and 14% (110 mm) was lost through surface runoff. Stored soil moisture during monsoon season was subsequently utilized by the Jatropha and 270 mm converted into ET during nonmonsoonal period. Pongamia utilized stored soil moisture more effectively than Jatropha as it could remove water from deeper soil layers even at high levels of soil moisture suction. [ABSTRACT FROM AUTHOR]

Abstract: Paddy is commonly grown under flooded or submerged condition in which substantial amount of water is lost by different processes. Puddling is traditionally done to reduce water loss from lowland rice fields. Since the very step of puddling, rice root zone undergoes structural changes leading to the formation of a layered profile having a hydraulically less-conductive plow sole below the root zone. However, studies have shown that soil cracking and the presence of preferential flow paths in puddle fields defeat this purpose. Description of soil water regime in such a dynamic soil requires an in situ measurement method for soil hydraulic properties. A field experiment was conducted in twelve 30m2 plots during the rainy seasons (June to October) of 2004 and 2005 to evaluate a suitable method for estimating soil hydraulic properties of lowland paddy soil. Results showed that piezometric (pressure) heads installed in different soil layers responded to the drying and wetting cycles typically followed in transplanted rice and are observed as a part of monsoon climate in eastern India. The Marquardt–Levenberg algorithm built in the HYDRUS-1D simulation environment was used to inversely estimate soil hydraulic parameters. Estimated parameters revealed larger hydraulic conductivity for the compacted plow sole than those published in literature, which may have resulted from alternate wetting and drying typically observed under monsoon climate and earthworm burrows observed in our experimental field. Results from simulation studies suggest that both the single- and dual-porosity models could simulate water flow considerably well in lowland paddy field although the latter described pressure head time series data slightly better in about 50% of simulations. Similar performance of the single- vs. dual-porosity model may have resulted from estimating a seasonally mean soil hydraulic properties which include the effect of both preferential flow and matrix flow as the specific soil and boundary conditions prevailed. While water may have preferentially transported through the macropores during the wetting cycles in a near-saturated soil, it would have dominantly moved through soil matrix during the drying cycles. This study shows that simple piezometers may be combined with a simulation model to estimate hydraulic properties of different soil layers in a lowland paddy field. [Copyright &y& Elsevier]

Increasing amounts of potentially hazardous chemicals such as nitrate (NO3 −) arising from various agricultural operations are polluting soil and water ecosystems worldwide. In the present study, the perching process and the simultaneous movement of water and nitrate through lateritic soils under perched water table conditions were investigated through two field experiments. The piezometric head and soil matric suction at five depths as well as the perched water table fluctuations in nine vadose zone wells were monitored daily. Also, a 20mm pulse of calcium nitrate was displaced in two experimental plots (called ‘plot I’ and ‘plot II’) by maintaining a constant depth of water throughout the leaching period, and the leaching of nitrate was monitored at six soil depths and in all the observation wells at suitable time intervals. The results of saturated hydraulic conductivity and bulk density at different depths in plot II suggested that the soil profile is heterogeneous. The analysis of hydraulic head and soil matric suction data revealed that the top 1·25m of the soil profile responds rapidly to rainfall in both the plots, with plot I more permeable than plot II. Relatively long perching conditions at 1·71m depth in both the plots indicated the presence of a more effective water-resisting layer at this depth. The maximum nitrate concentration in soil water was found after 8–12h of leaching at shallower depths (up to 0·33m) and after 12–18h at greater depths. The enhanced rate of nitrate leaching in both the plots indicated the presence of macropores in the soil profile. Lateral flow due to perching conditions was also found to considerably affect the contamination process in lateritic soils. Furthermore, the dispersion coefficients of nitrate based on the breakthrough curves were found to range between 0·004 and 1·67m2/day, suggesting heterogeneity in the soil profile. Finally, it is concluded that the relatively shallow aquifers of the lateritic region are vulnerable to nitrate contamination due to the current practice of nitrogenous fertiliser application in agricultural fields. Long-term and large-scale field studies under actual field conditions, together with simulation modeling, are recommended to generalise the flow and transport behaviour in lateritic soils. [Copyright &y& Elsevier]

This paper presents a comparison of the predictive capability of three hydrological models, and a mean ensemble of these models, in a heavily influenced catchment in Peninsular India: GWAVA (Global Water AVailability Assessment) model, SWAT (Soil Water Assessment Tool) and VIC (Variable Infiltration Capacity) model. The performance of the three models and their ensemble were investigated in five sub-catchments in the upstream reaches of the Cauvery river catchment. Model performances for monthly streamflow simulations from 1983–2005 were analysed using Nash-Sutcliffe efficiency, Kling-Gupta efficiency and percent bias. The predictive capability for each model was compared, and the ability to accurately represent key catchment hydrological processes is discussed. This highlighted the importance of an accurate spatial representation of precipitation for input into hydrological models, and that comprehensive reservoir functionality is paramount to obtaining good results in this region. The performance of the mean ensemble was analysed to determine whether the application of a multi-model ensemble approach can be useful in overcoming the uncertainties associated with individual models. It was demonstrated that the ensemble mean has a better predictive ability in catchments with reservoirs than the individual models, with Nash-Sutcliffe values between 0.49 and 0.92. Therefore, utilising multiple models could be a suitable methodology to offset uncertainty in input data and poor reservoir operation functionality within individual models. [ABSTRACT FROM AUTHOR]

Summary: Soil and water are crucial resources for agriculture, especially in arid and semi-arid rain-fed areas, yet farm-level economic impacts and the factors influencing the adoption of measures for their conservation are little studied. The present study used data from 400 farm households to assess factors influencing the adoption of soil and water conservation measures (SWCMs) and their impacts on farm productivity and income in a semi-arid region of central India. We employed a probit model to determine the factors influencing the on-farm adoption of SWCMs and a propensity score matching technique for assessing their impacts. The findings indicate that farmer age and education, off-farm income, farm size and land ownership and access to training are key drivers of the adoption of SWCMs. SWCMs accentuated the input costs by INR 1689–2847 per ha during the rabi cropping season (October–February), but also increased crop productivity and net revenue from farming. The impact in the rabi season was less sensitive to the unobserved confounders than in the kharif season (June–September). Therefore, SWCMs could represent an important strategy for unlocking the cultivation potential of large rain-fed areas and for sustaining the livelihoods of farm households in the ecologically fragile arid and semi-arid tropics. [ABSTRACT FROM AUTHOR]

Large variability and uncertainty of rainfall are the main limiting factors for crop growth in rainfed agriculture. Agriculture water management interventions are considered as suitable adoption strategy to enhance crop yield, productivity and income in rainfed condition. Three-year experimental data collected at the International Crops Research Institute for the Semi- Arid Tropics, Patancheru, India are analysed to study the impact of in-situ interventions (tillage and crop residue) on field water balance and grain yield under the two different cropping systems (maize + chickpea sequential and maize/pigeon pea intercropping). One dimensional water balance model is calibrated to capture field hydrology (soil water, surface runoff). Weather data calibrated for 36 years showed that incorporating crop residues reduced surface runoff by 28% compared to control fields. However, the impact of tillage and residue treatment on soil water was not consistent throughout the growing period. Water productivity values for intercropping systems (WUE = 0.61 to 1.49 kg -3) were relatively higher compared to sequential cropping systems (WUE = 0.47 to 1.06 kg -3). Second crop in sequential cropping system often suffered from water stress that led to poor crop yield. However, a few rain events at the end of the monsoon period were beneficial to second crop. Simulation results indicated that the conservation agriculture could save up to 30% yield loss incurred due to water stress during deficit rainfall compared to conventional agricultural practices. [ABSTRACT FROM AUTHOR]