Abstract
Optimum rice production in Nigeria is constrained by poor soil fertility and weed interference, which greatly reduce grain yield. In order to minimise competition for resources between upland rice and weeds, it is important to synchronise time of fertiliser application with period of weed removal. Information on harmonising the time of fertiliser application with period of weed interference in upland rice field is scarce. Therefore, response of upland rice cultivars to different weeding regimes and time of cattle dung application on loamy sand in Ibadan was investigated. The study was a 2x2x4 factorial arranged in split-split plot design with three replicates. There were two rice cultivars (NERICA2 and CG14), two cattle dung applications (Pre-cropping incorporation and split application at 4 and 8 Weeks After Transplanting (WAT) and four weeding regimes (0, 4 and 8, 8 and 12 and 4, 8 and 12 WAT) each assigned to the main plot, sub-plot and sub-sub-plot, respectively. Residual effect of the applied materials were also assessed. Data were collected on growth, dry matter and yield components. Data were analysed with descriptive statistics, regression and analysis of variance at P?0.05. Split application of cattle dung enhanced growth, dry matter and grain yield of upland NERICA 2and CG14 cultivars better than pre-cropping manure application. Similarly, weed removal at 8 and 12 WAT in NERICA2 plots supplied with split cattle dung resulted in highest grain yield (5.23 t/ha) but not significantly different from yield from CG14 (4.24 t/ha) that received a similar treatment. Grain yield was significantly related to weed biomass (r = 0.23). Two periods of weed removal at 8 and 12 weeks after transplanting were sufficient and adequate for minimising adverse effects of weed interference in upland rice field supplied cattle dung in split dosage. Upland rice cultivars benefitted from residual cattle dung previously applied in split dosage.
