SummaryThe growth and development of maize and soya bean when grown in mixtures in different proportions and arrangements were studied at Samaru (11° 11' N, 38° E) and Yandev (07° 23' N, 09° 10' E) in the savannah belts of Nigeria. The crops were sown in both pure and mixed stands. The pure-stand densities were 513 plants/m2 for maize and 20·15 plants/m2 for soya bean. Mixtures were made in three proportions: additive (100:100), containing 100% of the sole crop population of each crop; semi-additive (67:67), containing 67% of each crop's sole population; and replacement (67:33 and 33:67), containing 67% of one crop's population to the other's 33%. The mixtures were formed either on the same ridge (in-ridge) or on different ridges (alternate ridge).Maize grain yield at Samuru was not significantly reduced in mixtures except where its proportion was reduced to 33% of its sole crop density. Seed yields in soya bean were significantly reduced in all mixtures, and when associated with maize density of not greater than 67%, soya bean was capable of 50% of its sole crop yield. At Yandev, late planting coupled with inadequate rainfall in the month following planting depressed seed yields in both crops, the sole crop yields being only 1·53 t/ha in maize and 0·24 t/ha in soya bean. Also maize appeared to be adversely affected in the mixtures at this location, the yields being significantly reduced in the mixtures irrespective of planting ratios.All mixtures, except 100:100 at Yandev, proved beneficial by producing land equivalent ratio (LER) values greater than one, while 67:67 proportions made higher gross returns than any of the sole crops at Samaru. In this experiment moderately high populations of each crop were found to be necessary to obtain beneficial yields from the mixtures. In this regard semi-additive mixtures, with 67% of each crop's pure stand population, appeared most appropriate.Incidence of maize streak was significantly lower in alternate ridge mixtures; otherwise the crop in the mixtures seemed to be little affected by pattern of plant arrangement; while soya bean was quite sensitive, its flowering and podding being significantly delayed in in-ridge mixtures at Yandev. The legume yields in this mixture were also slightly, though not significantly, adversely affected. Thus alternate ridge arrangement was more favourable.
