Plant Population Density Effects On Yield Of Sorghum Grown In A Dry-Land Farming System

Abstract

Plant population studies in arid regions are very sparse and not well documented. A prerequisite in growing a successful sorghum (Sorghum bicolor [L.] Moench) crop is to obtain an adequate plant population. The response of sorghum yield to plant population was examined in terms of both the number of plants per unit area and the arrangements of the plants on the row. Response of sorghum to factorial combinations of three intra-row spacings and two seeding rates was investigated from 1987 to 1989. The experiments were conducted on an alloctonus colluvial soil (calcareous sandy clay loam) in the Field Crop's Experimental Station, Rodat Horma, 25.0°N, Qatar under full irrigation conditions .The sorghum variety Sahania I was sown each year on 1 Sep and was harvested on 18 Jan. The experiments were set up in a split plot design with four replications. Yield depressions were recorded at high populations (166000 - 333000 plants ha1). The results show that an increase in plant density from a range of 53000 -106000 to 166000 - 333000 plants ha"1 had contributed to the reduction in final grain yield. There is no benefit for yield from intra-row spacings closer than 20 cm. Most of the yield differences were associated with differences in 1000-grain weight, head weight and grain yield per plant. These results contrast with responses to increasing population recorded in most previous studies and indicate that clear optimal plant ranges must be defined. When planting sorghum for higher yields under irrigation under Qatari conditions an optimal plant population of 83000 -106000 plants per ha is desired.