Abstract only

Rain-fed crop production systems in smallholder farming areas of Zimbabwe is characterised by low productivity due to inherent low fertility and low, erratic and poorly distributed rainfall. The study assessed the long term effects of conservation agriculture (CA) on soil organic carbon and grain yield. The study was conducted during the 2010/11 cropping season at sites located in natural region II (NRII) and natural region III (NRIII) receiving mean annual rainfall of 800 mm and 650 mm, respectively and characterised by both sandy and clayey soils. On each soil type, land use was categorised into conventional tillage (CT) using the mouldboard plough; undisturbed natural virgin soil (NS) at the field boundary; and conservation agriculture (CA). The CA based on hoe prepared basins was further divided into three subcategories based on duration of CA practice on the site: viz young CA (CA1) (less than 2 years), old CA (CA2) (5-7 years) and very old CA (CA3) (8 years or more). Each treatment was replicated four times at each site from four farmers with each farm representing a replicate. Organic carbon levels were found to be highest in NS clay soil NRII (1.85%) and lowest in CT sandy soil NR III (0.46 %) but on both sites soil organic carbon levels were in the order NS>CA3>CA2>CA1>CT. Maize grain yields were significantly correlated (p<0.05) to organic carbon levels in the soil in CA and CT treatments on both sites while grain yields declined in the order CA3> CA2>CA1>CT. Maize grain yield was thus highest in CA3 fields NRII (3.6 t/ha) and lowest in CT fields NR III (0.51t/ha). Weed biomass was high in NRII due to high rainfall received and for both sites was in the order CT>CA1>CA2>CA3. Weed biomass significantly influenced grain yield (p<0.05). Thus CA practised for a long time even in sandy soil, leads to improved soil organic carbon, reduction in weeds and an improvement in grain yield

Conservation Agriculture Program

English

Lucia Segura

INT3097

CIMMYT Staff Publications Collection