Published online by Cambridge University Press: 01 June 2000
Two separate experiments, in clay loam and loamy sand (prepared by mixing the clay loam with washed sand), were performed to determine the effects of sowing method and sodicity on the survival, ion uptake, grain yield and yield components of spring wheat (Triticum aestivum L.) cv. Kharchia- 65. Three sodicity levels (control, exchangeable sodium percentage (ESP) 5–7; low (ESP 18–20); high (ESP 39–40)) and four sowing methods (sowing dry and pre-germinated seed and transplanting of 16 and 21-day-old seedlings) were tested. In the control and at low sodicity, sowing method had no effect on plant survival, grain and straw dry weight per plant. However at high sodicity, these variables were lower in plants established from pre-germinated seed than in plants established from dry seed, the farmers' normal practice. In contrast, transplanted seedlings showed increased survival and had significantly higher grain and straw dry weight than plants established by sowing dry seed. Differences in grain yield between sowing method and sodicity treatments were mainly due to differences in the number of grains per plant. Although increasing sodicity was associated with higher concentration of Na+, and lower concentrations of K+, Ca2+, Mg2+ and lower K+/Na+ ratio in flag leaf sap, ion concentrations were unaffected by sowing method.
It is suggested that the increased survival and yield of transplanted seedlings is due to the fact that they are not exposed to sodicity during the sensitive stages of germination and emergence. In addition, their already established roots and shoots may be better able to capture the resources required to support their subsequent growth. The decreases in grain and straw dry weight per plant, and the increases in these parameters achieved by transplanting seedlings instead of sowing dry seed, were greater in clay loam than in loamy sand. Further studies are required to determine whether the responses to transplanting observed here also occur in sodic soils under field conditions, and to investigate the technical and economic feasibility of adopting this technique in commercial agriculture.