Influence of catenary soils on water use efficiency and yield of rainfed soybean in Vidarbha region

Soybean is the popular kharif crop amongst farmers of Vidarbha region. However, fluctuations in productivity have been recorded even under normal rainfall conditions. This paper deals with the variations in WUE and yield of soybean under normal rainfall years as influenced by the soil/site characteristics and soil catenary sequence. The study area was in a micro-watershed with an area of 75 ha and located 22 km west of Nagpur in dry sub-humid ecosystem. During the period of study i.e. from 1990 to 1992 (all the three years), the annual rainfall received was normal. The geomorphic analysis of the soil catena identified six distinct geomorphic units namely hill top, escarpment, pediment, upper piedmont plain, lower piedmont plain and narrow valley. The studied soils were Lithic Haplustepts (P1) on pediment, Typic Haplustepts (P2) on upper piedmont, Vertic Haplustepts (P3) on lower piedmont and Typic Haplusterts (P4) occurring on narrow valley. Soybean (cv. JS-335) was sown in kharif in all the years during the third week of June. Recommended package of practices was adopted. The WUE varied from 2.26 to 9.31 kg ha^·1 mm^·1 between soils in a catena. Though similar amount of rainfall was received, highest average WUE of 8.17 kg ha^·1 mm^·1 was recorded in P3 while the lowest (2.79 kg ha^·1mm^·1) in P1. This indicates the influence of soil catena over WUE and moisture availability for crop growth. P3 also recorded the highest yield because of higher Ca²⁺/Mg²⁺ ratio of subsoils indicating better drainability and aeration of these soils. Thus, it is observed that the soil catenary sequence has a significant influence on crop yield apart from the climatic parameters. The study also suggests that P3 soils (Vertic Haplustepts) produce higher yield due to favourable soil characteristics and have to be preserved for posterity for a sustained production.