Abstract:

Abstract: 【Objective】Our aim is to elucidate the effects of reduced urea application combined with slow-release urea on yield and photosynthetic characteristics of rice and to lay a theoretical basis for the application of mechanical transplanting. 【Method】A split-plot design was set with 16, 18 and 20 cm plant spacing at 30 cm row spacing and four reduced urea application levels combined with slow-release urea (96 kg/hm² of slow-release urea combined with 24 kg /hm² of conventional urea as basal fertilizer with no top-dressing; 96 kg/hm² of slow-release urea as basal fertilizer and 24 kg/hm² of conventional fertilizer as top-dressing; 96 kg/hm² of slow-release urea combined with 54 kg/hm² of conventional urea as basal fertilizer with no top-dressing; and 96 kg/hm² of slow-release urea combined with 30 kg/hm² of conventional urea as basal fertilizer and 24 kg/hm² of conventional urea as top-dressing) and Chuanguyou 7329 was used as material.【Result】 The plant spacing and reduced urea application level combined with slow-release urea showed significant or extreme significant regulating effect on leaf area index(LAI), photosynthetic characteristics and grain yield of mechanically transplanted rice in the main growing stages. The reduced urea application level combined with slow-release urea patterns played a more significant effect than the plant spacing. LAI, photosynthetic characteristics, dry matter accumulation, net photosynthetic rate and grain yield showed an increasing trend with the increase of conventional urea level combined with slow-release urea and the increase of postponed conventional urea application level under three plant spacing. At the plant space of 16 cm, the number of stem and tiller of the population increased significantly, resulting in more effective panicles, stronger competition for nutrients, weaker photosynthetic characteristics, and failure to form large panicles, although the seed setting rate was high, the grain number per panicle was low and the yield was low; Under 20 cm plant spacing, the plant density and the total number of tillers was significantly decreased, however, the lower panicle number resulted in the enhanced nutrition absorption, improved photosynthetic capability, large spike formation and increased grain number per panicle. Given the relatively low 1000-grain weight and seed setting rate, the grain yield was decreased; Under the plant spacing of 18 cm, more effective panicles were formed on the basis of sufficient tiller number of the population, which could effectively absorb nutrients in the later stage, with enhanced photosynthetic characteristics, significantly increased seed setting rate and 1000-grain weight, the correlation analysis showed that the population growth rate, photosynthetic potential and effective leaf area index at full heading stage had higher correlation with yield under reduced urea level combined with slow-release urea application and plant spacing. 【Conclusion】The treatment of 18 cm of plant spacing with 30 cm of row spacing at 96 kg/hm² of slow-release urea combined with 30 kg/hm² of conventional urea as basal fertilizer and 24 kg/hm² of conventional urea as top-dressing at 4-leaf stage, it could give full play to the high yield advantage of the machine-planted indica hybrid rice in this region and improve the photosynthetic material production, with the yield up to 11 681.56 kg/hm² was the best nitrogen application method for high yield in mechanically-transplanted rice.

Key words: mechanically-transplanted rice, plant spacing, yield, N fertilizer allocation and application, photosynthetic characteristic

摘要：

【目的】 研究不同机插株距下缓释氮肥与常规氮肥减量配施在水稻关键生育时期的运筹方式,为水稻机插秧配套技术的应用提供理论和实践依据。【方法】 以中迟熟杂交籼稻川谷优7329为试验材料,采用两因素裂区设计,在机插行距均为30 cm下,设株距16 cm、18 cm、20 cm;并设4种缓释氮肥与常规氮肥运筹模式：1)基肥为96 kg/hm²缓释氮肥和24 kg/hm²常规氮肥,不施追肥;2)基肥施96 kg/hm²缓释氮肥,追肥施24 kg/hm²常规氮肥;3)基肥施96 kg/hm²缓释氮肥和54 kg/hm²常规氮肥,不施追肥;4)基肥为96 kg/hm²缓释氮肥和24 kg/hm²常规氮肥,追肥为30 kg/hm²常规氮肥;以不施氮肥为对照。【结果】 缓释氮肥与常规氮肥减量配施运筹和株距对机插杂交籼稻叶面积指数(LAI)、拔节-齐穗期光合势及产量的影响均达显著或极显著水平,且缓释氮肥与常规氮肥减量配施运筹的效应明显高于机插株距。3种株距下,随缓释氮肥与常规氮肥配施量及常规氮肥后移量的增加,机插杂交籼稻的LAI、拔节-齐穗期光合势、干物质积累量、净光合速率及产量均呈增加的趋势。株距为16 cm时,群体茎蘖数显著增大,形成的有效穗多,对养分的竞争性增强,光合特性减弱,未能形成大穗,虽然结实率高但每穗粒数较少,产量较低;株距为20 cm,由于密度降低,群体茎蘖数显著减少,形成的有效穗少,后期对养分的吸收充足,光合特性增强,形成了足够的大穗,每穗实粒数显著增加,但结实率和千粒重较小,因此未能高产;而株距为18 cm时,在足够群体茎蘖数的基础上形成的有效穗较多,后期能有效吸收养分,光合特性增强,结实率和千粒重显著增大。相关分析表明,缓释氮肥与常规氮肥减量配施运筹和株距下,尤以齐穗-成熟期群体生长率、拔节-齐穗期光合势和齐穗期有效叶面积指数与产量相关性较高。【结论】 株距为18 cm,96 kg/hm²缓释氮肥和24 kg/hm²常规氮肥作为基肥施用,30 kg/hm²常规氮肥作为追肥在倒4叶期施用,能充分发挥本区域机插杂交籼稻的高产优势,提高光合物质生产,产量最高可达11 681.56 kg/hm²。

关键词: 机插稻, 株距, 产量, 氮肥配施运筹, 光合物质生产