Effects of Potassium and Nitrogen Fertilizer Applications on Yield and Lodging of Rice (Oryza sativa L.) under Different Irrigation Regimes

To evaluate the effects of potassium and nitrogen fertilizers on yield and lodging characteristics of Gilaneh rice cultivar under two irrigation regimes (permanent flooding and irrigation with to 10 days interval) a field split split plot experiment based on complete randomized block design with 3 replications in Rasht. Nitrogen and potassium fertilizers used were at the 0, 60 and 120 kg.ha-1 and 0, 80 and 160 kg.ha-1 as sub and sub sub factor, respectively. The results showed that the highest seed yield obtained about 3713 kg.ha-1 from permanent flooding with the application of 120 kg.ha-1 of nitrogen fertilizer and 80 kg.ha-1 of potassium fertilizer and the lowest yield 634 kg.ha-1 from 10 days irrigation interval, without using of potassium and nitrogen fertilizers. The 10-day irrigation interval reduced the bending moment of the internode 4 by 40%. With increasing the rate of potassium fertilizer, the lodging index of intermediate 4 decreased, which was due to the increase of cellulose content by 60% in this intermediate. Increasing nitrogen and potassium fertilizers decreased the lodging index at internodes 3 and 4. Irrigation at 10 days intervals decreased plant height, internode bending moment, cellulose and hemicellulose and seed yield It increased lodging index of intermediate, butincreasing fertilizer levels in both irrigation regimes had adverse effect on the traits under study.