Is maize-cowpea intercropping a viable option for smallholder farms in the risky environments of semi-arid southern Africa?

Abstract

Intercropping cereals with legumes can potentially enhance productivity and soil fertility. There is limited experimental evidence on the mechanisms underlying benefits or risks in intercropping systems and belowground interactions in intercrops remain largely unstudied. Such understanding can inform strategies towards maximising returns to investments, particularly in poor fertility soils on smallholder farms in semi-arid areas of sub-Saharan Africa. Additive intercropping experiments were established covering several seasons (2010/ 11-2014/15) and different conditions (on-station and on-farm) to determine effects on soil chemical variables, root dynamics and yield of intercrops. Maize was planted with the first effective rains and received either no fertiliser or 40 kg N ha −1. Cowpea was planted on the same date as maize or three weeks after planting maize in intercrops or sole stands and received no fertiliser. End-of-season available N was highest (P < 0.05) under the late planted intercrop with 40 kg N ha −1 treatment in 2013/14. Addition of 40 kg N ha −1 significantly increased maize grain yield by 500-1100 kg ha −1 in the 2013/14 season. There was generally greater productivity and over-yielding in the intercrops compared with the sole crops; most intercrops had a land equivalent ratio > 1. Intercropping, however, resulted in compromised cowpea yields especially under the relay intercrop compared with the sole cowpea stands whilst maize yield was either not affected or improved. We attributed this to the lack of below-ground niche differentiation in root distribution between maize and cowpea. Maize-cowpea intercropping with low doses of N fertiliser resulted in over-yielding compared with monocropping. Intercropping proved to be a robust option across seasons and soil types, confirming that it is a promising option for resource-poor smallholders.

Mixed outcomes from conservation practices on soils and Striga-affected yields of a low-input, rice–maize system in Madagascar

“…The correlation of maize yield with soil fertility parameters supports previous suggestions by Vanlauwe et al (2014) that additional fertilizer application would be a necessary element of CA, to ensure that sustainability and profitability go hand in hand. Contrary to findings by Masvaya et al (2017) with maize-cowpea intercropping, the yields in the current study were generally not improved and were often even reduced when maize was intercropped with a legume, despite improvements in soil nitrogen concentration compared to conventional practice (measured after 4 years). Poor soil fertility and low addition of nutrients through poor-quality manure, in combination with increased interspecific competition, may have masked the positive effects of cover crops on maize yields.…”

Effects of maize residue and mineral nitrogen applications on maize yield in conservation-agriculture-based cropping systems of Southern Africa

“…The general decline of grain yields with increased duration of experimentation observed at all sites could partially be explained by differences in seasonal rainfall patterns. However, Masvaya et al (2017) suggest that this could be due to reduced N mineralization because of minimum soil disturbance and mulching practices under NT systems.…”

“…This suggests that a smallholder farmer achieves no additional grain yield gain with 90 kg N ha −1 and they can therefore target 30 kg N ha −1 investment in mineral fertilizer. In a mulched NT system under semiarid conditions, a study by Masvaya et al (2017) showed that 40 kg N ha −1 gives the highest yield with above average seasonal rainfall. Under sub-humid conditions of Kenya, results from Kitonyo et al (2018) showed that 80 and 120 kg N ha −1 give similar maize yield under 3 and 5 t ha −1 soil cover.…”

Quantifying the potential of ‘on-farm’ seed priming to increase crop performance in developing countries. A meta-analysis

“…Currently, in both rotational and intercropping systems, the adoption of legumes is largely discouraged due to poor establishments of the legume component. In rotation, legumes are commonly grown utilizing residual soil moisture remaining during the dry season, and with no additional fertilization, whilst in intercropping systems, the planting of a legume companion is delayed in order to avoid shading and competition (Masvaya et al 2017). Therefore, on-farm seed priming may ameliorate these unfavourable planting conditions and boost the benefits of cereal-legume cropping systems, e.g.…”