Growth, competition, yield advantage and economics in soybean/pigeonpea intercropping system in semi-arid tropics of India - I. Effect of subsoiling

Opinions differ on the necessity of deep tillage for sustaining crop productivity in the rainfed Vertisols of the semi-arid tropics of central India. We conducted a field experiment for 3 years (2000-2002) with a factorial combination of three cropping systems (sole soybean, sole pigeonpea and soybean/pigeonpea intercropping in 2:1 row ratio) and three tillage practices (conventional, conventional + subsoiling in alternate years and conventional + subsoiling every year). Objectives were (i) to examine the effect of subsoiling Vertisols on sustaining yield of soybean/pigeon pea intercropping, and (ii) to assess the frequency of subsoiling for realizing maximum yield and profit. Though there was a reduction in growth and yield of intercrops, higher soybean equivalent yield (SEY) and area-time equivalent ratio (ATER) value in soybean/ pigeonpea intercropping system as compared to sole soybean had a yield advantage. The average yield advantage in intercropping system was 60% higher than that from sole soybean. The yield advantage of intercropping system in terms of ATER was 7% greater with subsoiling than conventional tillage. The yield response to subsoiling was consistent over the period and on an average, subsoiling increased yield by 20%. The effect was associated with improved water storage and root length density. However, with respect to energy use efficiency and profit, the effect of subsoiling was comparable to conventional tillage. The variation in net return and benefit:cost ratio in subsoiling every year and subsoiling in alternate years in sole soybean and soybean/pigeonpea intercropping was not significant. However, in sole pigeon pea subsoiling every year out-yielded subsoiling in alternate years. The interactive effect of subsoiling and intercropping increased the yield by 21-25%. Thus, under tainted cropping where drought of unpredictable intensity and duration is a prevailing feature, soybean/pigeon pea intercropping could be a promising option, especially when combined with subsoiling in alternate years. (c) 2005 Elsevier B.V. All rights reserved.