Contribution of Tithonia diversifolia to yield and nutrient uptake of maize in Malawian small-scale agriculture

Abstract

Locally available non-traditional green manure plants could potentially contribute to reversing the trend of declining soil fertility and raise maize yield in small-scale farms. In this study, Tithonia diversifolia was tested as a low cost green manure in Malawi. In a greenhouse incubation experiment, changes in soil nitrate (NO(3-), ammonium (NH4 +) and extractable phosphorus (Mehlich-3 P) were compared between treatments of T. diversifolia, Crotolaria juncea (sunhemp), Tephrosia vogelii, Mucuna utilis (velvet beans) and maize stover that were applied to the soil at an equivalent rate of 3 Mg dry matter ha−1. This was followed by a field study where three rates of T. diversifolia dry matter (1.5, 3.0, 4.5 Mg ha−1) were applied with or without triple superphosphate (TSP) supplement to maize grown at three locations in central and northern Malawi. The changes in laboratory incubated soil N03- and NH4 + levels were similar (P 0.05) among T. diversifolia, Tephrosia and Mucuna while the change in soil treated with maize stover was less and similar to that observed in bare soil. The greatest change in soil NO3- and NH4 + levels were induced by Crotolaria. In the field, the average maize yields were 4.6 Mg ha−1 at Chitedze, 3.1 Mg ha−1 at Bembeke and 1.1 Mg ha−1 at Champhira; The lowest T. diversifolia rate (1.5 Mg ha−1), increased maize yield over that obtained in the control plot by 41% at Bembeke, 122% at Chitedze and 162% at Champhira. Maize yields were increased with increasing T. diversifolia rates and the yields obtained with 3.0 and 4.5 Mg T. diversifolia ha−1 were similar to those obtained with 90 Mg N ha−1 as inorganic fertilizer. There was no obvious benefit from applying TSP in combination with T. diversifolia. Given the nutrient release and maize yield values with T. diversifolia, it should prove to be a good green manure that can be afforded by small-scale farmers in these regions of Malawi.