Grain yield, gravimetric moisture content, dry matter accumulation and chlorophyll production in maize-legume intercrop under minimum and conventional tillage systems

Abstract

Maize is a dominant crop in smallholder farming systems in the Limpopo province of South Africa, generally cultivated as intercrop with grain legumes. The major constraint in this cropping system is inadequate soil moisture during the growing season, which also limits nutrient availability to the component crops. The minimum tillage system has been reported to improve soil moisture availability on farmers’ fields but this has not yet been verified in an intercropping system in the province. The objective of this study was to quantify grain yield and chlorophyll production of intercropped maize, and to assess seasonal moisture availability under minimum tillage (MT) and conventional tillage (CT) systems. Dryland field experiments were conducted at two locations in the province namely, farmer’s field at Dalmada in 2002/2003 and 2003/2004 growing seasons and at the University of Limpopo Experimental farm at Syferkuil during the 2003/2004. The experimental design was a randomized complete block in split plot arrangement at all locations and seasons. Tillage systems consisting of conventional tillage and minimum tillage were the main plot treatments, whereas five different cropping systems namely, sole maize, and maize intercrop with cowpea (variety, Bechuana White), cowpea (variety, Agripers), Lablab bean (variety, Rongai) and Velvet bean were assigned as sub-plot treatments. Maize grain yield in 2002/2003 at Dalmada was significantly lower (357 kg/ha) under CT relative to 755kg/ha under MT. In 2003/2004 at Dalmada, grain yields under the two systems were similar, where as at Syferkuil, 15% higher grain yield results was obtained under MT. Minimum tillage systems resulted in higher number of maize cobs per plant at Dalmada in both growing seasons and weight per cob was higher under MT at both locations and seasons. At Dalmada, significantly higher soil moisture was recorded under the MT relative to the CT depending on depth and sampling dates. Chlorophyll content of the youngest fully expanded leaves of maize was generally higher under MT than CT, but this was observed only at the later stages of plant growth. The results also showed that the rate of senescence (reduced chlorophyll content in older leaves) was higher in maize plants grown under CT relative to those under MT. The minimum tillage system has shown the potential of being a superior system for dryland maize production, but further research involving additional locations is required to ascertain this fact.