Studies On Rice Radiation Use And Nitrogen Use Efficiency In Different Cultivation Model Under Double-season Rice System

To ensure Food security and to reduce fertilizer rates for alleviating environment pollution are two key tasks in crop production in our country. Therefore it is urgent to achieve higher yield and higher use efficiency of resources in rice production in China. Early rice and late rice field experiments were conducted in Yong'an Town, Liuyang City in 2009 to investigate the mechanisms of high yield formation and high nitrogen use efficiency(NUE). Treatments included nitrogen omission plot (T1), local farmer's practice model(T2), high yield and high NUE model(T3), super-high yield model(T4), and super-high yield with high NUE model(T5). The cultivation models were respected to establish different yield and different NUE platforms. We analyzed the characteristics of canopy radiation utilization and NUE under different yield conditions.The major findings are as follows:(1) Rice yield of treatment T3,T4,T5 are significantly higher than that of treatment T2. The yield presented as T4>T5>T3>T2 and T4>T3>T5>T2 at transplanting and dibble-planting, respectively. T4 produced the highest yield of 8.62 t/ha and 9.24 t/ha, which were 30% and 26% higher over T2 in early rice and later rice, respectively. The difference was significant. It showed that the yield of double season rice could be increased differently by integrating and optimizing of cultivation technology and nutrient management approaches.(2) Significant differences in the amount of intercepted solar radiation (ISRA) and the radiation use efficiency (RUE) existed among tested treatments, and were closely related to rice yield. ISRA presented as T4>T5>T3>T2 in the experiments. RUE value at transplanting were 1.39-1.54g/MJ in early rice and 1.20-1.52g/MJ in late rice, while at dibble-planting were 1.43-1.68g/MJ in early rice and 1.39-1.70g/MJ in late rice. RUE in T3 and T4 are all significantly higher than that in R2. The result indicates that ISRA and RUE enhancement is the physiological foundation of rice yield increasing in different cultivation models in double season rice production.(3) There exist differences in the rice population growth characters such as tillering dynamics, leaf area index(LAI), dry matter accumulation and crop growth rate(CGR) among different cultivation models. T3, T4, and T5 had significantly higher effective tiller rate, dry matter accumulation, maximum LAI than T2. (4) Nitrogen recovery efficiency(RE), nitrogen agronomy efficiency(AE) and nitrogen partial factor productivity(PFP) were significant higher in T3,T4,and T5 than in T2 across two seasons and two transplanting types. T5 had the highest RE and AE except in transplanting type in later season, averaged from 38.1% and 30.8kg/kg in early rice, and 40.8% and 20.5kg/kg in later season across two transplanting types, respectively. Stable trend was observed for PFP in different cultivation models, i.e., T3>T5>T4>T2. PFP in T3 averaged 62.0 kg/kg, significantly higher than in any other cultivation models across two seasons and two transplanting types. Therefore, NUE in double season rice could also be significantly increased by integrating and optimizing of cultivation technology and nutrient management approaches under the same soil fertility condition.