Interspecific Interaction and Nutrient Use in Soybean/Sorghum Intercropping System

Abstract

Intercropping soybean (Glycine max L.) with sorghum (Sorghum bicolor L.) is common in the semiarid tropics of India. In most intercropping studies, little attention has been paid to belowground interaction and nutrient management other than N while assessing yield advantage. In a 5‐yr field experiment (2000–2004), we evaluated the impact of fertilizer and organic manures on below‐ and aboveground interaction, competitive ability, and economic viability of this intercropping at the Indian Institute of Soil Science, Bhopal for deep Vertisol (isohyperthermic Typic Haplustert) of central India. Above‐ and belowground growth components as well as biological activities were greatly improved in intercropped sorghum while the value of these except nitrate reductase (NR) activity, soil microbial biomass C (SMBC), and dehydrogenase activity (DHA) were reduced in intercropped soybean indicating interspecies competition between component crops. The increased NR activity, SMBC, and DHA in intercropped soybean revealed interspecies facilitation between the component crops. This showed that interspecies competition concurred with interspecies facilitation in this system. We observed that yield and land equivalent ratio (LER) of both the intercrops increased over sole crops though based on aggressivity and relative crowding coefficient (RCC), sorghum (+) is more competitive than soybean. Interaction of yield with different components indicated that three belowground components, i.e., NR activity in root (r = 0.62, r = 0.63, P < 0.05), root length density (r = 0.36, r = 0.33, P < 0.05), and SMBC (r = 0.71, r = 0.66, P < 0.05) of both intercrop soybean and intercrop sorghum, respectively, had the greater effect on yield advantage in the intercropping system. Soybean did not benefit from intercropping to the same degree as sorghum under N–P–K. Nutrient application influenced LER, RCC, and monetary advantage index and was found in the order of N–P–K plus farmyard manure (FYM) > N–P–K plus poultry manure (PM) > N–P–K plus phosphocompost (PC) > N–P–K > control. However, based on competition ratio, yield advantage was greater under N–P–K plus PM. The results suggest that sorghum is the major contributor to the mixture yield and that the integrated use of N–P–K plus FYM or N–P–K plus PM is an important nutrient management option for sustaining this intercropping system, particularly to benefit the legume component.

Effects of inter-specific interaction of nitrogen fertilizer and bean-maize cropping systems on quality of bean seed in Western Kenya

“…The decrease in root growth in the soil when N was applied was probably due to the high rate of N consumption by Maize. Similar findings have been reported by Ghosh (2006) in a sorghum/soybean intercrop system. This could be attributed to reduced light energy received by the beans.…”

“…This could be attributed to the combined soil N applied and N fixed by the Rhizobium bacteria in the beans roots which usually promotes the development of the crop at its sowing time and reproductive stages (Table 7) (Gorecki, 1983. Competition between maize and beans for N is also a factor because the latter can fix N (Wortman et al, 1991;Norman et al, 1996).Similar results were reported by Ghosh (2006) in a sorghum/soybean intercropping system. Intercropping systems are superior to sole cropping due to the spatial differences in the root mass which facilitates utilization of greater soil volume.…”

Intercropping affects the rate of decomposition of soil organic matter and root litter

“…A greater litter input results in a rejuvenation of SOM stock, increasing the proportion of relatively young, labile C in total soil C, thereby reducing the overall recalcitrance of SOM, and accelerating SOM decomposition. This mechanism might play a role in intercropping, because intercrops have greater aboveground biomass (Willey 1979;Lithourgidis et al 2011) and root biomass (Ghosh et al 2006;Yang et al 2010;Li et al 2011;Cong et al 2014a) than monocultures. In a recent 7-year study, we found that intercropping decreased the soil C/N ratio compared to the corresponding monocrops, regardless of the presence of legumes (Cong et al 2014a).…”

“…A reduction of N losses through leaching may drive a reduction in soil C/N ratio and, as a result, increase storage of N in SOM in intercrops (Cong et al 2014a). Greater root biomass production in intercrops compared to monocrops might also cause a change in SOM quality (Ghosh et al 2006;Yang et al 2010;Li et al 2011;Cong et al 2014a). The resulting greater root litter C input in soil would lead to a faster rejuvenation of the SOM pool with more labile SOM (since the start of the experiment, 7 years ago) resulting in a higher relative decomposition rate.…”

“…This higher production is attributed to an increase in total resource capture due to complementarity between the intercropped species (Hinsinger et al 2011), and to reduced impacts of pests, diseases and weeds (Liebman and Dyck 1993;Trenbath 1993;Zhu et al 2000). The greater biomass production aboveground is mirrored belowground (Ghosh et al 2006;Yang et al 2010;Li et al 2011;Cong et al 2014a) and a recent study showed that intercropping increases soil organic carbon (C) stocks (Cong et al 2014a). However, the increase in C stocks over 7 years of intercropping (4 %) was smaller compared to the estimated increases in yearly root litter input in intercrops as compared to monocrops (23 %) (Cong et al 2014a).…”