Intensifying cropping systems through doubled-up legumes in Eastern Zambia

Abstract

Declining soil fertility and negative impacts of climate effects threaten the food security of millions in Africa. Conservation Agriculture (CA) is a promising strategy to address these challenges. However, lack of viable economic entry points and short-term benefits for smallholders limit its adoption. Legume intensification can possibly increase the output per unit area, thus making the system more attractive. Rotations of maize with intensified legume systems were tested for three consecutive years under ridge and furrow (RF) tillage and CA to investigate: (a) increases in productivity of legumes and the subsequent maize crop; (b) changes in land equivalent ratios (LERs) and; (c) improved total system productivity. Results showed an increase in legume yields when growing two legumes simultaneously, leading to greater LERs (ranging between 1.13 and 1.29). However, there was only a significant season and not a main treatment effect as CA did not outperform RF in both phases of the rotation. Full populations of companion legumes improved overall system productivity, yielding 76.8 GJ ha^-1 in a more conducive season while sole cropping of pigeonpea yielded only 4.4 GJ ha^-1. We conclude that the doubled-up legumes systems have great potential to improve household food security when integrated into current smallholder farming.

Figure 1

Interactive effects of different crop management systems and legume combinations and populations with seasons on (a), (b) legume grain yield and (c), (d) legume biomass yield over the seasons of implementation: RF = ridge and furrow; CA = conservation agriculture; soleGn = sole groundnuts; solePp = sole pigeonpea; fullGN/halfPP = legume intercropping with full population of groundnut and half population of pigeon pea; and fullGN/fullPP = legume intercropping with full population of groundnut and full population of pigeon pea. Boxplots with different letters above them are significantly different from each other. The error bars represent the standard error of mean (SEM). The jittered dots represent the individual observations from each plot over the seasons.

Figure 2

Interactive effect of crop management systems and legume combinations and their different populations on legume biomass yield over the seasons of implementation: RF = ridge and furrow; CA = conservation agriculture; soleGn = sole groundnuts; solePp = sole pigeonpea; fullGN/halfPP = legume intercropping with full population of groundnut and half population of pigeon pea; and fullGN/fullPP = legume intercropping with full population of groundnut and full population of pigeon pea. Boxplots with different letters above them are significantly different from each other. The error bars represent the standard error of mean (SEM). The jittered dots represent the individual observations from each plot over the seasons.

Figure 3

Effect of different seasons on (a) maize grain and (b) biomass yield averaged across all sites. Boxplots with different letters above them are significantly different from each other. The error bars represent the standard error of mean (SEM). The jittered dots represent the individual observations from each plot over the seasons.

Figure 4

Interactive effects of (a) different crop management systems and (b) legume combinations and populations with the seasons on total system grain yield, total system biomass yield and overall total system yield (grain plus biomass) over the seasons of implementation: RF = ridge and furrow; CA = conservation agriculture; soleGn = sole groundnuts; solePp = sole pigeonpea; fullGN/halfPP = legume intercropping with full population of groundnut and half population of pigeon pea; and fullGN/fullPP = legume intercropping with full population of groundnut and full population of pigeon pea. The letters within each segment of the stacked columns denote significance for that segment for grain and biomass and the letters above the columns denote significance for overall total system yield. Stack segments and columns with different letters are significantly different from each other.