Background/Question/Methods   Soil infertility is a major constraint to agricultural productivity in Sub-Saharan Africa. Crop legumes such as pigeonpea (Cajanus cajan), peanut (Arachis hypofea), and soybean (Glycine max), are important sources of biological nitrogen fixation, crucial to system sustainability in maize (Zea mays)-based cropping systems. It is necessary to study competition within and between crop species, and its effect on plant growth and productivity because intercropping may enhance resource use efficiency and overall grain yield, while suppressing some yield from the main staple crop of maize. The objectives of this study were to understand above-ground intra- and inter-specific competition in pigeonpea, to evaluate above-ground pigeonpea plant architecture, and study plant-arthropod interactions in these production systems. Data was collected from seven on-farm trials in Lilongwe, Malawi. Pigeonpea plants were grown in either a monoculture, or intercropped with soybean, peanut, or maize. Ten plants per plot x 4 systems were monitored at each farm trial site, for a total of 70 observations per cropping system. Data included plant height, the number of primary branches, the number of tillers, stem width, the number of open flowers, number of pods, number of insects present on the plants, and the type of insects present.

Results/Conclusions   Of the plant characteristics measured, only height and grain yield were shown to vary significantly between treatments. Results of a one-way ANOVA show height (p=0.05) and grain yield (p=0.01) are higher in sole crops than pigeonpea intercrops. Similarity in plant architecture and interactions with arthropods show that pigeonpea grown in an intercrop perform likewise to pigeonpea grown in a monoculture. Although variability was high (as is typical of on-farm studies), this suggests that inter- and intra-specific competition is moderate in diversification treatments for pigeonpea. Implications of this study are that crops such as corn, peanut, and soybean can be successfully intercropped with pigeonpea with minimal competition and only a slight reduction in yield. Compensation for grain yield reduction in pigeonpea intercrops may manifest from the added ecosystem functions of pigeonpea and other economic usages.