2.5. Cropping system and experimental design
Five cropping systems namely, single-stand pearl millet, single-stand sorghum, single-stand rice, pearl millet mix-planted with rice and sorghum mix-planted with rice were tested in five different experiments to evaluate the mixed cropping concept (Table 1). Four of the experiments were conducted in 2014/2015 to test the survival and production analysis in a randomized complete block design with three replications. In the last experiment performed in 2015/2016 for grain production and analysis of land equivalent ratios, the cropping systems were tested under two flood treatments: non-flooded control (drained soil) and flood treatments, which were arranged in a split-plot design with eight replications, with the flood treatments being the main plots and cropping systems being the sub plots. In all the experiments, 3-week-old pearl millet and sorghum and 4-week-old rice seedlings were transplanted into field plots, at a soil depth of 5 cm with a constant spacing of 0.3 m × 0.3 m. In total, 10 and 18 hills per treatment were grown in the 2014/2015 and 2015/2016 experiments, respectively. Mixed cropping treatments had constant plant densities; the plant hills consisted of two plants, i.e. one pearl millet and one rice, and/or one sorghum and one rice but the control treatment had one plant per hill as sown in cell trays. The field size for each of the 2014/2015 experiments was 9 m × 7 m, while that for the 2015/2016 experiment was 32 m × 18 m. NERICA4 was transplanted as a border plant in each experiment. Moreover, before field transplanting compacted earth bands (0.5 m high × 1.0 m wide) were constructed around each experimental plot, and between main plot treatments in the last experiment to separate non-flooded control plots from the flooded treatment plots.