Genetic yield potential of rice (Oryza sativa) through water saving and high-yielding SRI technology*

The system of rice intensification (SRI) that evolved in the 1980s in Madagascar is also gaining popularity in India. SRI saves not only the seed (a seed rate of 5–7 kg/ha as against 25–30 kg/ha for normal) but also saves water (35– 40%) as the fields are not inundated continuously. It leads to higher ripening ratio and increases yield by 10–25%. The varietal response to SRI and conventional cultivation is wide. Varieties differed in their genetic potential and all the varieties are not promising for SRI cultivation. There is need to develop/ identify varieties that give better response to SRI cultivation. Therefore, the present investigation on comparative evaluation of rice genotypes for yield and its components under SRI and conventional system was undertaken to identify suitable cultivars for SRI. The experimental materials consisted of 20 genotypes (released varieties and elite lines), including aromatic and hybrids. These were evaluated in two methods, viz SRI and conventional during rainy (kharif) season 2009 at CCSHAU, rice research station, Kaul situated at 290 51’ N, 760 39’ E and 230.87 m above msl in sub-tropical region of North India. The SRI method consisted of reduced seed rate of 5 kg/ha, young seedling (15-day old) transplanted with one seedling/hill in wide spacing of 25 + 25 cm and irrigation at five days interval up to 45 days after transplanting (DAT). In SRI the required dose of chemical fertilizers was supplemented with farmyard manure (as organic source) @ 15 tonnes/ha applied 30 days before transplanting. Conventional method comprised seed rate of 25 kg/ha, 25 days old seedlings transplanted with 2 seedlings/hill in narrow spacing of 15 + 15 cm and irrigation at 3 days interval up to 45 DAT with all the required nutrients (150 kg N, 60 kg P2O5 and 60 kg K2O/ha) supplied through inorganic fertilizers. After 54 DAT the irrigations were applied at 3 days interval in both the methods. Accordingly, the SRI and conventional method received 24 and 30 irrigations, respectively during the crop season (up to 90 DAT). Nursery of all genotypes was sown on 31 May for conventional cultivation and on 10 June for SRI while seedlings of both practices were transplanted on 26 June 2009. The experiment was laid out in a randomized complete block design (RBD) with two replications. Different combinations of spacing and seedling number per hill of each method were created termed as micro-environments (Luthera et al. 1974) (Table 1) to evaluate genotypes. Plot size was 1 m2/genotype/replication. Observations were recorded on days to 50% flowering and days to 75% maturity from the whole plot, while observations on grain yield/plant and biological yield/plant were recorded from five randomly selected plants in each plot. The data were analyzed statistically using the method suggested by Panse and Sukhatme (1967) and pooled G × E interaction analysis was done following Eberhart and Russell (1966) model. The analysis of variance revealed significant mean squares due to genotypes for all the characters studied indicating that genotypes differed among themselves and there existed considerable variability. Pooled analysis revealed