Response of rice (Oryza Sativa L.) cooking quality properties to nitrogen and potassium application.

In order to consider effects of various levels of nitrogen and potassium application on cooking quality traits of rice cultivars, an experiment was conducted in 2004 and 2005 using Tarrom (a local Iranian landrace) and Neda (an Iranian improved cultivar). In this experiment four levels of nitrogen fertilizer (0, 50, 100 and 150 kg N ha(-2) from urea source) and four levels of potassium fertilizer (0, 75, 150 and 225 kg K2O ha(-2) from potassium sulfate source) have been applied using a split factorial design with three replications. Nitrogen fertilizer have been applied in three stages (1/3 in transplanting stage, 1/3 in tillering stage and finally 1/3 in flowering initiation stage) and potassium fertilizer have been applied in two stages (1/2 in transplanting stage and 1/2 in shooting stage). Results showed that application of nitrogen increased gel consistency and decreased amylose content of rice kernel; however, had not significantly affected gelatinization temperature and grain protein content. Application of potassium increased gel consistency and grain protein content but had not significantly affected gelatinization temperature and kernel amylose content. Gel consistency and gelatinization temperature of Tarrom were higher than Neda; whilst, inversely, grain amylose and protein contents of Neda were higher than Tarrom. Simultaneous application of nitrogen and potassium has no significant effects on gel consistency, gelatinization temperature and grain protein content; But maximum amylose content was achieved using none of fertilizers in Neda and 75 kg K2O ha(-1) with no nitrogen fertilizer in Tarrom genotypes, respectively.