Crop coefficients of Jatropha

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

Water needs and productivity of Jatropha curcas in India: myths and facts

Jatropha curcas referred as a ‘wonder plant’ with low water requirement, which can be cultivated on wastelands in dry tropical conditions to provide oil seeds for biodiesel without competing for prime cropland. However, results from experiments and case studies in semi-arid tropical locations in India indicated that evapotranspiration (ET) demand for Jatropha ranges between 750 and 1000 mm under optimal conditions. Jatropha extracted water from soil layer 150 cm below with transpiration requirements of 600–800 mm with increasing age. The yield potential of current genotypes is low (2–3 ton/ha) for realizing the potential of Jatropha cultivation on wastelands subject to limited availability of nutrients and water. Jatropha curcas is drought tolerant, but contrary to belief, it is not a crop that requires less water: in fact, it requires 750–1000 mm water to achieve economic production. However, Jatropha curcas demonstrated good potential for enhancing green water use efficiency without adversely affecting the blue water component, and for promoting crop management options facilitating carbon sequestration and nutrient recycling when grown on degraded lands. Improved cultivars of Jatropha curcas with synchronized flowering to enable mechanical harvesting, along with improved land and water management, are needed for harnessing the potential of Jatropha as a commercially viable biofuel crop

A fitted numerical method for singularly perturbed parabolic reaction-diffusion problems

This paper treats a time-dependent singularly perturbed reaction-diffusion problem. We semidiscretize the problem in time by means of the classical backward Euler method. We develop a fitted operator finite difference method (FOFDM) to solve the resulting set of linear problems (one at each time level). We prove that the underlying fitted operator satisfies the maximum principle. This result is then used in the error analysis of the FOFDM. The method is shown to be first order convergent in time and second order convergent in space, uniformly with respect to the perturbation parameter. We test the method on several numerical examples to confirm our theoretical findings.Web of Scienc