Crops and Soils
The purpose of the present study was to investigate the effects of seven maize (Zea mays)–fallow rotation and fallow residue management treatments on growth, maize yield and soil carbon within a savannah-forest farming zone of Ghana. Over a 4-year period, maize rotated with bare fallow (control) produced an average maize biomass and yield of 4·0 and 1·0 t/ha/yr, respectively. Maize rotated with elephant grass (Pennisetum purpureum) with the fallow grass residue burning produced an average maize biomass and yield of 8·0 and 2·0 t/ha/yr, respectively. The removal of the fallow grass biomass (9·0 t/ha/yr) by burning resulted in a low total residue (maize stover+fallow residue) returned to the soil (7·0 t/ha/yr). The total residue returned to the soil was 14·0 t/ha/yr. Despite the larger total residue returned to the soil by the incorporation treatment, the performance of the maize was not significantly different from that of the fallow residue burning treatment. Maize rotated with cowpea (Vigna unguiculata), mucuna (Mucuna pruriens) or pigeon pea (Cajanus cajan) produced similar maize biomass of 8·0 t/ha/yr and yields of 2·0 t/ha/yr, but with higher variability for the maize–cowpea rotation. Biomass produced by fallow cowpea, mucuna or pigeon pea were 4·0, 5·0 and 8·0 t/ha/yr, respectively, and total residues added to the soil were 13·0, 13·0 and 15·0 t/ha/yr, respectively. Maize–grass rotation with fertilizer application to the maize resulted in biomass and yield production of 11·0 and 3·0 t/ha/yr, respectively, and fallow grass production of 12·0 t/ha/yr. The total residue returned to the soil was 18·0 t/ha/yr. Soil organic carbon (SOC) declined under all treatments over time, with the control losing about 55% of the initial SOC by the end of the trial. The decline in SOC was 19% for the fertilized maize–grass rotation, but all other treatments lost between 33 and 44% SOC. Overall, the fertilized maize–grass and maize–pigeon pea rotations were identified as those that sustained relatively high maize yields, returned large residue amounts to the soil and minimized soil carbon loss.
(Received December 18 2008)
(Online publication February 26 2009)