Agronomic evaluation of rice cultivars for rainfed conditions of Kerala

Abstract

Two field experiments were conducted at the Cropping Systems Research Centre, Karamana and one pot culture trial at the College of Agriculture, Vellayani during 1991 and 1992, to select a suitable rice variety and nutrient level required for maximum rice production in the rainfed wetlands of Southern Kerala. The influence of seed hardening in inducing stress tolerance was also studied. In the study, experiment I included a pot culture trial with six varieties, viz., Jaya, Culture -4, M-102, Rasi, Ravi and Tulasi and six methods of seed hardening viz., water, triazole, NaH2PO4, KCI, cowdung extract treatments and a control in two moisture regimes. The significant results of the study were tested in the field. Experiment 2 included these six varieties and three nutrient levels, viz., 100, 75 and 50 per cent of recommended dose for medium duration varieties (90 : 45 : 45 kg N, P2o5 and K2o) and was conducted as a factorial experiment in RBD during the first crop season of 1991 and 1992. The results of the germination study revealed that KCI concentration of 2.50 per cent was ideal for seed hardening. Seed hardening improved germination of all the varieties and water treatment registered the highest vigour index values. In pot culture, Culture – 4 with water treatment registered the highest biomass production, grain and straw yields. The variety, Jaya had the highest root weight and root : shoot ratio. Among the seed treatments, water, KCI and triazole treatments favourably influenced the yield attributes, yield, root parameters and root : shoot ratio. Increasing the moisture regime from 50 to 100 per cent available water enhanced the growth characters, RWC, chlorophyll and decreased the proline content. The subsequent field trial with the highest grain yielding varieties and seed treatments confirmed the superiority of Rasi and Tulasi for increased grain yield, net income and benefit : cost ratio. The different seed treatments also had favourable influence on the above characters. The results of experiment 2 revealed that M – 102 recorded the highest plant height during both the years, while, Tulasi and Rasi had higher tiller number. The varieties, M-102 and Rasi registered higher straw yield than the others. Increased nutrient levels improved growth characters and straw yield. Pooled analysis of grain yield revealed that the varieties, Jaya, Rasi and Tulasi were good yielders and 75 per cent of the recommended nutrient level was sufficient to obtain high grain yield under rainfed conditions. Increased RWC values were observed in the drought tolerant varieties, Ravi, Tulasi and Rasi and at increased nutrient levels. Proline eontent was unaffected by varieties and nutrient levels. The variety, Jaya registered the highest uptake of major nutrients during 1991 while, Tulasi, Rasi and M-102 had higher uptake than the others during 1992. The highest nutrient level recorded the maximum uptake during both the years. Among the varieties, Jaya, Tulasi, Culture – 4 and Rasi recorded high net income and benefit : cost ratio. Among the nutrient levels, the variation between 100 and 75 per cent recommended nutrient dose was not significant with regard to net income and benefit : cost ratio. Under rainfed conditions, 75 per cent of the recommended nutrient dose was sufficient for the varieties, Jaya, Rasi and Tulasi to obtain commensurate yield, net income and benefit : cost ratio. Moreover, the yield and economic returns could be increased by resorting to seed hardening methods.