Effects Of Cultivation Methods On Agronomic And Physiological Traits And Nutrient Use Efficiency In Rice

The excessive input of chemical fertilizers and low use efficiency of nutrients in rice production in China are serious problems.Exploring the cultivation methods that can synergistically improve crop yield and use efficiency of nutrients is of great significance for developing green production of rice.This study used two rice cultivars,an indica/japonica hybrid rice cultivar Yongyou 2640 and a japonica inbred rice cultivar Wuyunjing 24,and conducted nine cultivation methods treatments.The treatments included no nitrogen fertilizer(ON),local conventional cultivation(control),nitrogen reduction,increase in plant density and reduction in nitrogen rates,precision irrigation,application of cake fertilizer,deep-plowing,application of silicon-zinc fertilizer,and application of manure.The objective of the study was to establish cultivation methods that can increase both grain yield and nutrient use efficiency by investigating grain yield and its components,agronomic and physiological traits,grain filling characteristics and nutrient absorption and utilization efficiency.The main results are as follows.1.Grain yield and its componentsCompared with local conventional cultivation(control),the improved cultivation methods,such as increase in plant density and reduction in nitrogen rates,precision irrigation,application of cake fertilizer,deep-plowing,application of silicon-zinc fertilizer,and application of manure,significantly increased grain yield by 7.42%,13.82%,19.76%,22.45%,27.74%,and 7.88%respectively,for Yongyou 2640,and by 3.59%,14.57%,18.59%,20%,28.37%,and 4.24%respectively,for Wuyunjing 24.Increase in the total number of spikelets contributed to the increase in grain yield under the improved cultivation methods.2.Agronomic and physiological traitsThe improved cultivation methods increased the percentage of productive tillers,grain-leaf ratio,effective and high-efficiency leaf area ratio,photosynthetic potential,post-anthesis accumulation and remobilization of nonstructural carbohydrates from the stems and sheaths compared with the control,suggesting that the improved cultivation methods improved the quality of rice population.3.Grain filling characteristicsCompared with local conventional cultivation(control),The improved cultivation methods,such as precision irrigation,application of cake fertilizer,and application of silicon-zinc fertilizer,increased grain-filling rate and grain weight,enhanced activities of the key enzymes involved in sucrose-to-starch metabolism,sucrose synthase,AGP pyrophosphorylase,starch synthase and starch branching enzyme,and increased contents of zeatin+zeatin riboside,indole-3-ethetic acid,abscisic acid and gibberellins in the grain.The results indicate that improved cultivation methods can improve grain filling through elevating activities of key enzymes involved in sucrose-to-starch metabolism and hormone levels in the grain of rice.4.Absorption and utilization of nutrientsIn relative to the local conventional cultivation,the improved cultivation methods significantly increased nitrogen use efficiency.For example,the partial factor productivity of nitrogen(grain yield/nitrogen rate)was increased by 19.37%,26.47%,33.06%,36.57%,6.46%and 19.87%for Yongyou 2640,and by 15.10%,27.29%,31.75%,33.32%,6.98%and 15.8%for Wuyunjing 24,respectively,under the increase in plant density and reduction in nitrogen rates,precision irrigation,application of cake fertilizer,deep-plowing,application of silicon-zinc fertilizer,and application of manure.The internal efficiency,absorption amount per unit grain yield,the amount and the percentage of remobilization of nitrogen,phosphorus and potassium were higher under the improved cultivation methods than the control for both tested cultivars.The results imply that the improved cultivation methods can increase both grain yield and nutrient use efficiency.In summary,both grain yield and nutrient use efficiency could be significantly increased if the cultivation methods were improved,especially under the improved methods of precision irrigation,application of cake fertilizer,deep-plowing,and application of silicon-zinc fertilizer.The improvement in the population quality,enhancement in the activities of enzymes involved in the sucrose-to-starch metabolism,and increases in the contents of hormones in rice grains are important agronomic and physiological basis for the increase in both grain yield and nutrient use efficiency under the improved cultivation methods in rice.