Intercropping desmodium and maize improves nitrogen and phosphorus availability and performance of maize in Kenya

Abstract

Abstract Low levels of nitrogen (N) and phosphorus (P) in soils in sub-Saharan Africa (SSA) limit maize (Zea mays) production in smallholder farms. We tested the hypothesis that desmodium (Desmodium intortum (Mill.) Urb.), a fodder legume, and food legumes commonly grown with maize in Western Kenya avail N and P and improve the performance of maize in intercrops. We measured available N and P in 15 cm topsoil at 4, 8 and 12 weeks after planting (WAP), and corresponding maize shoot weight in three seasons: 2017 long rains (LR), 2017 short rains (SR), and 2018 LR at Thomas Odhiambo Campus of icipe at Mbita Point in western Kenya. Treatments were additive 1:1 maize-legume intercrops; maize-bean (Phaseolus vulgaris L.), maize-cowpea (Vigna unguiculata (L.) Walp.), maize-crotalaria (Crotalaria ochroleuca G. Don), maize-desmodium, maize-green gram [Vigna radiata (L.) Wilczek] and maize-groundnut (Arachis hypogaea L.), and maize monocrop as a control, replicated four times in a complete randomized design. This experiment was established in 2003 and treatments were repeated every season on the same plot (for 31 seasons up to 2018 LR). At the beginning (year 2003), experimental plots were infested with 100 g of striga seeds per 250 g soil. Across the three last seasons corresponding to this study, we observed an increase in available N in maize-desmodium plots compared to maize monocrop plots. Available P measured at 4, 8 and 12 WAP in 2017 SR and at 4 WAP in 2018 LR was higher in maize-desmodium than in maize monocrop at the same sampling times (P