Evaluation of tillage practices on selected soil chemical properties, maize yield and net return in O. R. Tambo District, South Africa

The costs of maize production per ha in the Eastern Cape Province are escalating due to an increase in mechanization and input costs. Conservation agriculture (CA) has been identified as one of the systems that can reduce costs of production and improve maize productivity. Most famers in the district still require tangible evidence on the benefits and impacts of minimal soil disturbance. Hence it was necessary to conduct this comparison between tillage practices on maize productivity. Ten projects under conventional tillage (CT) were randomly selected from maize cropping in three local municipalities of the Eastern Cape Province in South Africa. Minimum tillage (MT) demonstration fields on maize production measuring 1 to 5 ha were conducted in the aforementioned local municipalities and were compared to project under conventional tillage. Minimum tillage recorded an increase in P (46 mg/L) and K (227 mg/L) concentration; whereas Ca (395.6 mg/L) and Mg (406.75 mg/L) concentration were higher under conventional tillage at 0 to 10 cm soil sampling depth. Soil pH was not affected by tillage practices. Minimum tillage recorded an average increase in maize yield from 2.3 to 4.78 tons per ha compared to 4.16 tons per under conventional tillage. The greatest gross margin was observed from minimum tillage (US $273.92) compared to conventional tillage which had the lowest (US $207.02) gross margin. The short term comparison between the tillage practices revealed that minimum tillage had higher levels of P and K soil macro elements, increase in maize grain yield and subsequent high net benefits relative to conventional tillage. Therefore, it is necessary to scale up the adoption of minimum tillage in the district coupled with crop rotation and residue retention so that the majority of farmers can realize its benefits. Key words: Gross margin, tillage, nutrients, yield.