Abstract
Field experiments were conducted at the University farm of the University of Education, Winneba, Mampong-Ashanti Campus, Ghana, during the major rainy seasons of 2010 and 2011 to evaluate the growth, yield and productivity of a maize varietal intercropping system as influenced by relative times of planting (RTP) and row spacing. Three relative times of planting [(i) simultaneous, (ii) early-maturing maize (Akposoe) planted 10 days before medium-maturing maize (Obatanpa) and (iii) medium-maturing maize (Obatanpa) planted 10 days before early-maturing maize (Akposoe) were combined with two row spacings [(i) 80 cm and (ii) 100 cm] in a 3 x 2 factorial arranged in a randomized complete block design with three replications. Sole Akposoe and Obatanpa were included as checks and to compare the productivity of the varietal intercrop options with the sole crops. The relative times of planting, row spacing and their interaction did not significantly influence the days to 50% tasselling (DFT) and days to 50% silking (DFS) of both maize varieties in both seasons. In both seasons, the plant height and total dry matter (TDM) accumulation of sole Akposoe and Obatanpa were greater than when both were intercropped. Among the intercrops, the plant height and TDM accumulation of both varieties when planted simultaneously were similar to when planted 10 days before the other, but greater than when delayed 10 days, for both seasons. Akposoe and Obatanpa intercrops spaced at 80 cm row spacing produced higher plant height and TDM accumulation than the 100 cm row spaced plants in both years. The sole Akposoe and Obatanpa out-yielded their intercropped counterparts by 12-53 % in both seasons. For the intercrops, the grain yield of Akposoe planted simultaneously with Obatanpa (1.71-2.12 t/ha) was similar to Akposoe planted 10 days before (DB) Obatanpa (1.80-2.20 t/ha), but out-yielded Akposoe planted 10 days after (DA) Obatanpa by 5-28 % in both seasons. The grain yield of Obatanpa planted simultaneously with Akposoe (3.38-4.78 t/ha) were also similar to the grain yield of Obatanpa planted 10 days before Akposoe (3.28-3.83 t/ha), but were 4-41 % greater than the yield of Obatanpa planted 10 days after Akposoe in 2010 and 2011. The 80 cm row spacing yielded 8-24 % and 11-26 % in 2010 and 2011, respectively, higher than the 100 cm row spacing. The varietal intercrops had higher productivity or land use ratios (1.12-1.76 for RTP and 1.14-1.80 for row spacing); and therefore, were 12-80% more productive and biologically more efficient than the sole crops in both seasons. Maize varietal intercropping produced higher total yield and was more productive under rain-fed conditions.
