Abstract
Response of potato genotypes (Solanum tuberosum L.) to increase in planting density was examined. Three potato cultivars (Irish Cobbler, May Queen and Dejima) and two planting densities (5 and 10 plants per m2) were employed. Increase in planting density caused the main stem length to increase and the number of branches and the leaf area per plant to decrease irrespective of the cultivar. Stolon growth and number of stolons per plant was not affected by increase in planting density, but the percentage of productive stolons was decreased by increase in planting density. During the experimental period, all cultivars showed upward trends in crop growth rate (CGR), net assimilation rate (NAR), tuber growth rate (TGR) and economic assimilation rate (EAR) under both densities. Plants under high density had higher TGR and EAR values and achieved them at an earlier stage than those under low planting densities. Increase in planting density decreased the dry weights per plant of leaves, stems and tubers but it increased dry weights per unit area. Percentage of dry matter partitioned to the tubers was high under high planting density. High density increased total and marketable tuber yield per unit area but decreased per plant yield of all three cultivars. High density markedly reduced both average tuber weight and average marketable tuber weight. Dejima outyielded the other cultivars. Range of optimum planting densities for marketable tubers will be higher for Dejima than Irish Cobbler and May Queen.
