Effects Of Different Cultivation Patterns On Rice Yield And Their Physiological Bases

Rice is the foremost stable food crop in China. With the growth of population and economic development, it is necessary to increase more crop yield. Meanwhile, this increase needs to be accomplished under high input of water and fertilizer resources. It remains debates whether it is necessary to input more water and fertilizer resources for more food, and whether higher grain yield and higher nutrient use efficiency can be coordinately achieved? It is not only always focusing of attention at home and abroad, but also an important scientific proposition in academic circles. It is an essential way for sustainable development to increase crop yield and meanwhile increase resource use efficiency. In this study, Two rice cultivars, Yongyou 2640 (an japonica hybrid) and Wuyunjing 24 (a conventional japonica inbred), were field-grown with six cultivation patterns including no nitrogen application (ON), local routine cultivation (control), dense planting with less N fertilizer (DPLN), cultivation for precision irrigation (PI), cultivation for deep plowing (DP), dense planting with more N fertilizer (DPMN). The characteristics of grain yield and population growth and development, nutrient absorption and utilization efficiency, physiological characteristics, rice quality and the emission of greenhouse gases from paddy field were investigated. The main results are as follows:1. The characteristics of population growth and development of rice under different cultivation patternsThe average grain yield of the two cultivars under DPMN, DP, PI and DPLN was 12.49 t hm-2,11.76 t hm-2,11.48 t hm-2 and 10.4 t hm-2, respectively, and 9.5%-36.2% higher than that of control. Compared with control, DPMN, DP, PI and DPLN increased percentage of productive tillers, leaf area index (LAI) and efficient LAI, leaf area duration (LAD), crop growth rate (CGR), biomass from heading to maturity and grain-leaf ratio, indicating that the population quality of rice could be improved and higher yield could be achieved through the improvement of cultivation techniques.2. Nutrient absorption and utilization efficiency of rice under different cultivation patternsCompared with those of the control, nitrogen recovery efficiency (NRE) was increased by 36.6%,65.9%,53.4%,36.6%,65.9% and 53.4%, and nitrogen agronomic efficiency (NAE) was increased by 115.3%,147.9%,133.6% and 56.9%, respectively, under DPMN, DP, PI and DPLN. The percentage of nitrogen (N), phosphors (P), potassium (K) translocation from heading to maturity under PI and DP was also increased. The accumulation of N, P and K from panicle initiation to heading was very significantly and positively correlated with grain yield. The results suggest that higher yield and higher NUE can be achieved through integrating and optimizing cultivation techniques in rice production.3. Physiological traits of rice under different cultivation patternsThe DPMN, DP and PI increased SPAD values, photosynthetic rate (Pr) and activities of catalase (CAT) and peroxidase (POD) of the flag leaves, contents of zeatin (Z) and zeatin riboside (ZR) and indole-3-acetic acid (IAA) in grains, and the remobilization of non-structural carbohydrate (NSC) from the stem to the grain during grain filling when compared with the control. The results indicate that an enhanced physiological activities of shoot contributes to the increase in grain yield and nutrient use efficiency under the high-yielding and high nutrient use efficiency cultivation patterns.4. Emission of greenhouse gases from paddy field under different cultivation patternsWith the increase in grain yield, the emission of methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) was increased under DPMN, DP and PI, leading to an increase in global warming potential (GWP). However, GWP per unit grain yield (amount of GWP/grain yield) was significantly decreased under DP and PI, relative to that under the control. The results imply that higher grain yield, nutrient use efficiency and higher environmental efficiency would be achieved through integrating and optimizing cultivation techniques.5. The rice qualities under different cultivation patternsCompared with the control, DP significantly increased head rice rate, contents of protein in milled rice, gel consistency, breakdown and peak viscosity of rice, and reduced chalkiness, amylose and setback, indicating that the milling quality, appearance quality and nutrient quality could be improved under the deep plowing cultivation.In summary, a deep plowing cultivation pattern could increase not only grain yield but also nutrient use efficiency. A larger leaf area duration, more remobilization of pre-stored NSC from stems to grains, greater content of Z+ZR in leaves and grains during the grain filling period under the deep plowing cultivation pattern may have contributed to achieving the dual goal of increasing grain yield and resource use efficiency. An increase in planting density, a decrease in N rate, an increase in the proportion of N at latter growth stages and precise irrigation were key techniques in the high-yielding and nutrient use efficiency cultivation system of rice.