Introduction
Considering the conditions of Iran in terms of water resources, high consumption of nitrogen fertilizer and low consumption of potassium fertilizer, less water use in rice cultivation and balance in chemical fertilizer consumption will play very important role in saving and wasting water. Rice production should increase in the coming years due to population growth, and this is possible due to the use of improved cultivars and agricultural management. Water is the most important factor for sustainable production in many agricultural products. About 75% of the rice produced (50% of the total rice fields in the world) is irrigated. Mineral nutrition includes; Supply, absorption and consumption of nutrients are essential for the growth and yield of crops. Non-use of nitrogen in rice plant at the beginning of tillering reduces plant height and non-use of nitrogen in full clustering stage reduces 1000-seed weight.
Materials and Methods
The aim of this study was to investigate the effect of different irrigation methods and nitrogen and potassium fertilizers on yield, yield components, water use efficiency and nitrogen consumption efficiency of Gilaneh rice cultivar in 2016-2017 and 2017-2018 cropping years. The shredded load was performed based on a randomized complete block design with three replications in Rasht. The size of the experimental units was nine square meters (dimensions of the main plot were 3 × 3 m, the sub-plot was 3 × 1 m and the sub-plot was 1 × 1 m). Accordingly, experimental treatments include irrigation at two levels of permanent flooding and irrigation interval of once every 10 days as the main factor, nitrogen fertilizer at three levels of 0, 60 and 120 kg.ha^-1 as a secondary factor and potassium fertilizer at three levels. Zero, 80 and 160 kg.ha^-1 were sub-factors. To determine the grain yield by observing the margin effect (removal of two rows) in each plot in the physiological maturation stage was taken and grain yield was calculated based on 14% moisture.
Results and Discussion
The results of this study showed that the highest grain yield of 5198 kg.ha^-1 in flooding treatment, application of 120 kg.ha^-1 of nitrogen fertilizer and 80 kg.ha^-1 of potassium fertilizer and the lowest yield in 10 days irrigation cycle and no use of two types Potassium and nitrogen fertilizers equivalent to 887 kg.ha^-1 were obtained. Increasing the irrigation distance reduced the number of spikes per square meter, number of seeds per spike, 1000-seed weight and paddy yield. The highest nitrogen crop yield (45.8 kg.kg^-1) was recorded in both irrigation regimes at 160 kg.ha^-1 of potassium fertilizer with 60 kg.ha^-1 of nitrogen fertilizer. By increasing the irrigation cycle, treatments of 60 kg.ha^-1 nitrogen fertilizer along with 160 kg.ha^-1 of potassium fertilizer equivalent to 0.764 kg.m^-3 in the first year and equivalent to 0.775 kg.m^-3 in the second year increased water use efficiency. With increasing irrigation frequency, 1000-seed weight was reduced in all three levels of nitrogen fertilizer, which was significant only in one level of nitrogen fertilizer. The maximum weight of 1000 seeds per hectare with consumption of 80 kg.ha^-1 of potassium fertilizer and 60 kg.ha^-1 of nitrogen fertilizer was equal to 23.31 g. Increasing the irrigation cycle in all three levels of potassium fertilizer reduced the number of full grains in the panicle.
Conclusion
Nitrogen and potassium fertilizer application, in addition to optimizing fertilizer application, increased the yield and yield components of Gilaneh rice. Irrigation period of 10 days and non-application of two types of potassium and nitrogen fertilizers, the lowest grain yield and consumption of 80 kg.ha^-1 of potassium fertilizer and 120 kg.ha^-1 of nitrogen fertilizer in flooded conditions recorded the highest grain yield.