Exploring pigeonpea [Cajanus cajan (L.) Millspaugh] production as a new crop in South Africa nitrogen contribution and benefits under intercropping with maize (Zea mays L.).
Mathews, Cherian
Mathews, Cherian
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Abstract
Poor crop yield by smallholder farmers in South Africa is due to edaphic, environmental and biotic constraints similar to that exist across Sub-Saharan Africa. In this study, the inclusion of legume as a viable option to enhance soil productivity and increase food and nutritional security of household was testedusing pigeonpea [Cajanus cajan (L.) Millspaugh]. This drought-resistant grain legume was evaluated in three different intercropping patterns againstmonocultures of pigeonpea (ICEAP00040) and maize (ZM521) for their effect on biomass accumulation, N contribution, rhizosphere nutrient dynamics and C sequestration. The results showed that above-ground biomass accumulation in pigeonpea ranged from 7.5 to 13.5 t ha-1, with an observed reduction in biomass and grain yield under intercropping. The leaf drop was huge and positively correlated to biomass accumulation. Harvest index was much greater with intercropping. The shoot, whole-plant biomass and the grain yield of maize were unaltered by intercropping. Under intercropping, there was greater land-use efficiency (LER and ATER), and cash income benefit. The results also showed greater δ15N values of monocultured-pigeonpea that resulted in much lower %Ndfa than intercropped pigeonpea. The sole-cropped pigeonpea showed greater N uptake from soil. The %Ndfa values ranged from 40 to 98% across the three seasons. Soil analysis showed a decrease in rhizosphere pH and an increase in N, P, K, and SOC, but these increases were greater after monocropped pigeonpea, and lowest in maize monoculture. Over the three years, the amount of C sequestrated by pigeonpea-based cropping system ranged from 9.10 to 13.77 t. ha-1 compared with 2.71 t. ha-1 from sole-cropped maize. The residual benefit of pigeonpea to maize was evident from the greater increase in biomass, grain yield, harvest index, plant height, shelling percentage, 100-seed mass and cob size of maize following pigeonpea. The symbiotic N benefit of pigeonpea to maize was >40 kg ha-1, which yielded greater monetary benefit to the farmer. As expected, incremental supply of N resulted in greater values of the parameters evaluated, but with reduced net monetary returns. These data show that pigeonpea/maize intercropping represent a low-input, sustainable, and environmentally safe technology for increased productivity and profitability of smallholder cropping systems in Africa.
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Submitted in fulfilment of the requirements for the degree Doctor Technologiae in the Department of Crop Sciences, Faculty of Science at the Tshwane University of Technology
Date
2016-01-01
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Tshwane University of Technology
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Keywords
Pigeonpea, Crop, Monocropped, Nitrogen, Maize