Evaluation of crop production potential using long term simulated soil moisture in drought prone region of Bihar

Abstract

The quantum of plant available moisture storage in the soil profile plays a vital role in crop growth and development under rainfed condition. Understanding the variability of available Soil Moisture (SM) in the root zone on both spatial and temporal scales would be a reliable guide in effective and sustainable crop production program in rainfed region. In this paper, weekly available soil moisture in medium and fine textured soils in seven chronically drought prone districts, viz. Gaya, Aurangabad, Jahanabad, Kaimur, Nalanda, Nawada and Rohtas of Zone IIIB (part of south Bihar alluvial plains) of Bihar has been simulated through climatic water balance technique employing weekly total rainfall data for the period from 30 to 55 years, normal weekly Potential Evapotranspiration (PET) and Available Water Holding Capacity (AWC). Probabilities of available SM for 25, 50 and 75% of AWC m-1 depth have been estimated for these soils in various districts. Results revealed that under medium textured soil when SM at 50% of AWC was considered, Jahanabad district recorded the longest crop growing period among all the seven districts indicating greater degree of moisture availability and thus favouring greater crop production potential, whereas shortest growing period with least crop production potential was observed in Auranagabd and Nawada districts. In the fine textured soil, the highest crop production potential in terms of SM availability seemed to be achieved also in Jahanabad district and the lowest in Nalanda district. Significant negative correlations of dry spell with rainfall and SM were observed. Crop planning based on available SM has been suggested under various SM scenarios for this drought prone zone of Bihar. Findings of the study could be useful for scheduling supplemental irrigation. In most vulnerable districts such as Nalanda and Gaya having lesser availability of SM, intercropping of pigeon pea with maize sown in paired rows could be more remunerative cropping system.