The Grain Yield And Yield Formation Mechanism Under Different Cultivation Patterns And Varietiy Collocation In Double Rice-cropping Systems

A field experiment was laid out in a double-rice field at Yongan Town, Liuyang City, Hunan Province, China in2013, to improve the planting technology in double-rice system. The purposes of the present study were to better understand the physiological mechanism of high yield of rice to investigate how different varieties (Early indica rice-Late indica rice and Early indica rice-Late japonica rice) affects them.Five treatments and Nitrogen use efficiency were designed for the experiment, ie, Nitrogen blank cultivation (T1)、Local traditional cultivation (T2, CK),High-effciency-and-efficiency cultivation (T3)、Super-yield cultivation (T4)、High-effciency-and-super-yield cultivation (T5).Meanwhile, Dry weight、Leaf area index、Intercept active radiation、Radiation use efficiency、Grain yield and Yield components were measured in this study. The main results were showed as follows:(1) There was no significant difference of total rice yield between Early indica rice-Late indica rice and Early indica rice-Late japonica rice in double rice-cropping systems. Total rice yield from Early indica rice-Late indica rice and Early indica rice-Late japonica rice were17.0t/ha and16.8t/ha,respectively. Several explanations may be given for the almost total rice yield from two variety collocation. First, spikelet per panicle and1000-grain weight of late japonica was higher than that of late indica, however, the late indica had more panicle number in unit area than late japonica. Second, the Early indica rice-Late indica rice accumulate more dry weight than the Early indica rice-Late japonica rice in the every growth stage. Meanwhile, Early indica rice-Late indica rice had an lower harvest index compare to Early indica rice-Late japonica rice. Third, the Early indica rice-Late indica rice increased6.1%total Intercept active radiation compare the Early indica rice-Late japonica rice, total Intercept active radiation for Early indica rice-Late indica rice and Early indica rice-Late japonica rice were965.8MJ/m2and910.7MJ/m2, respectively. In addition, the Early indica rice-Late indica rice had a higher RUE than the Early indica rice-Late japonica rice.(2) Cultivation Models had significant effect on rice yield. The total grain yield was as follows:T4>T5>T3> T2>T1, T4produced the highest yield followed by T5and T3, whereas T1produced the lowest yield over other treatment, mainly driven by "zero" N application. The total grain yield in T4was20.2t/ha, which was23.2%higher than with the normal farmers’ practice (T2). Several suggested possible explanations are that i) in the early rice season, the spikelet number m-2、spikelet per panicle and grain filling percentage in T4was higher than that in T2. Meanwhile, in the late rice season, the Panicle number、spikelets、The grain plumpness and1000-grain weight in T4was higher than that in T2. ii) Total Dry weight in T4was higher than that in T2iii)T4had a higher total Intercept active radiation compare to T2(3) There was a significant interaction effects between variety collocation and cultivation models. The total grain yield for Early indica rice-Late indica rice was as follows: T4>T5>T3>T2>T1, T4produced the highest yield, the total grain yield in T4was20.1t/ha, which was20.3%higher than T2. The total grain yield for Early indica rice-Late japonica rice was as follows:T4>T5>T3>T2>T1, the total grain yield in T4was20.3t/ha, which was26.4%higher than T2.Several reasons may be given for the higher grain yield in T4, for Early indica rice-Late indica rice, Panicle number. Total dry weight. Leaf area index、IPAR and RUE in T4were higher than other cultivation models. For Early indica rice-Late japonica rice, Spikelet per panicle、1000-grain weight. Total dry weight、Leaf area index、IPAR and RUE in T4were higher than other cultivation models.Super-yield cultivation’s total grain yield of high nitrogen Fine management in the Early indica rice-Late japonica rice model is higher than the Early indica rice-Late indica rice model and increases the range of T4、T5、T3is more than T2, Implied by increasing nitrogen and the reasonable cultivation, the early rice-late japonica rice variety collocation will have greater yield potential in double rice-cropping systems..