施用有机无机肥与稻田氮素释放及水稻群体生长的关系

红壤丘陵区稻田氮素释放试验结果初步表明 :施用无机肥 ,早稻生长期间土壤NH4 -N释放量多 ,释放速度快 ,早稻生长发育快 ,构成单位面积的有效穗数多 ,产量高 ,且差异极显著。施用有机肥 ,晚稻生长期间土壤释放NH4 N量多 ,且时间长 ,这对促进晚稻生长 ,形成合理群体结构有利。而有机、无机肥配合施用 ,稻田氮素释放时间长 ,且较稳定 ,对构成合理的水稻群体结构更为有利 。

WRSIS系统中稻田田面水和地下排水中氮素的动态变化特征

在江苏高淳县WRSIS系统中进行田间试验,对不同氮肥施用量下稻田田面水和地下排水中氮素动态变化特性进行分析。结果表明：施肥1 d后田面水TN和NH4＋-N质量浓度值达到最大,随着时间推移,质量浓度迅速下降,施肥7 d后TN质量浓度下降70%~76%,NH4＋-N质量浓度下降83.5%~85.5%。田面水中ρ（NH4＋-N）/ρ（TN）和ρ（NO3--N）/ρ（TN）具有相似变化规律,先升后降,且ρ（NH4＋-N）/ρ（TN）显著大于ρ（NO3--N）/ρ（TN）。地下排水中氮素以NO3--N为主,施肥后NO3--N质量浓度在3.0~19.0 mg/L的范围内;NH4＋-N质量浓度较低,整个生育期质量浓度都在1.1 mg/L以下。田面水和地下排水中氮素质量浓度均随着施肥量的增加而增加。施肥7 d内是防止氮素大量流失的关键时期,需要控制排水;同时减少氮肥施用量能显著减少氮素地表流失和地下渗漏损失量。

Nitrogen recovery and nitrate leaching of controlled release nitrogen fertilizer in irrigated paddy soil

Ordinary high nitrogen fertilizer often results in nitrate (NO3--N) leaching and low recovery. Microplot and field plot experiments were conducted to determine the effect of controlled release nitrogen fertilizer (CRNF) on reco very and nitrate leaching on paddy soils. During two early rice cropping seasons (2002 and 2003), a single basal application of CRNF at 90 kg N ha-1 increased grain yields by 7.7%to 11.6%compared with two applications of urea. Estimated by the difference method fertilizer N recovery of CRNF (mean 76.3%) was 38.9 pe rcentage point higher than that of urea (mean 37.4%); estimated by 15N isotope method (mean 49.6%) CRNF (mean 67.1%) was 35.9 percentage point higher than ur ea (mean 31.2%). NO3--N leaching losses were 9.19 and 6.70 kg ha-1 for urea and CRNF, respectively. NO3--N leaching during the early rice cropping season was 27.1 %lower from CRNF than from two applications of urea. These losses repr esent 10.2%and 7.4%of applied urea-N and CRNF-N. Results from this study ind icate that CRNF improves N recovery and reduces NO3--N leaching and increases rice yield.

Effects of Green Manure Rotation on Rice Growth Dynamics and Nitrogen Uptake and Utilization

This study aimed to comprehensive evaluation of different winter green manure on characterization of nitrogen uptake and utilization, to provide the basis for N fertilizer reasonable operation and characteristics improvement of nitrogen nutrition in rice high-yield cultivation. This experiment was set to compare milk vetch, rapeseed,ryegrass and mixed of green manure on rice yield, rice growth dynamics and nitrogen uptake and utilization in rice. The results showed that among 4 different winter green manure, the treatment of MV-R-R（milk vetch-rice-rice） for the early rice yield was the most than others treatments. Compared with RG-R-R（ryegrass-rice-rice）, RPR-R（rapeseed-rice-rice）, MS-R-R（mixed green manure-rice-rice）, the treatment of MVR-R inceased by 6.61%, 3.29%, 0.78%, respectively. The treatment of MV-R-R in N content in plant of rice was maximized in the tillering, booting, heading and maturity periods, respectively higher than the average of other treatments 9.68%, 19.72%,6.23% and 8.66%. At tillering, booting, heading and maturity, the treatment of MV-R-R were the highest in N uptake, RP-R-R minimum. The N periodic accumulation for MV-R-R were higher than other treatments in the tillering to booting, booting to heading and heading to maturity periods. The rates respectively were 21.81%, 68.73% and286.5%. In addition, N periodic accumulation and its ratio to total in the heading to maturity was minimum, maximum before tillering under green manure rotation system.So the cropping system of milk vetch-rice-rice could increase nitrogen use efficiency and improve N cycling.

氮肥运筹对水稻氮代谢及稻田土壤氮素迁移转化的影响

稻田氮肥管理是水稻高产栽培的重要环节。解析氮肥运筹对水稻植株氮代谢生理生化特征及稻田氮素迁移转化特性的影响,对提高水稻氮肥利用效率及增加水稻种植效益有重要意义。本文综述了不同氮肥运筹模式对水稻植株氮代谢过程中相关转运蛋白的表达及氮同化关键酶活性的影响,分析了氮代谢与碳代谢相互影响的作用机制,并对施氮模式与施用方法影响稻田土壤各形态氮素的循环转化和稻田氮素损失的影响机制及可能的调控途径作了总结。我们认为,当前的研究对氮肥运筹对水稻氮代谢影响的生理层面已经有了较明确的认识,但在分子及基因层面的研究尚显缺乏;田间氮肥管理的改善对提高稻田氮素利用率起到了明显的促进作用,但在实际应用时仍存在较多问题,需进一步改进。未来的研究应着重于继续深入挖掘水稻的氮代谢潜力,采取更高效的田间氮肥管理措施,从而进一步提高稻田氮素利用效率。

Ammonia Volatilization and Nitrogen Utilization Efficiency in Response to Urea Application in Rice Fields of the Taihu Lake Region,China

Ammonia volatilization losses, nitrogen utilization efficiency, and rice yields in response to urea application to a rice field were investigated in Wangzhuang Town, Changshu City, Jiangsu Province, China. The N fertilizer treatments, applied in triplicate, were 0 （control）, 100, 200, 300, or 350 kg N ha^-1. After urea was applied to the surface water, a continuous airflow enclosure method was used to measure ammonia volatilization in the paddy field. Total N losses through ammonia volatilization generally increased with the N application rate, and the two higher N application rates （300 and 350 kg N ha^-1） showed a higher ratio of N lost through ammonia volatilization to applied N. Total ammonia loss by ammonia volatilization during the entire rice growth stage ranged from 9.0% to 16.7% of the applied N. Increasing the application rate generally decreased the ratio of N in the seed to N in the plant. For all N treatments, the nitrogen fertilizer utilization efficiency ranged from 30.9% to 45.9%. Surplus N with the highest N rate resulted in lodging of rice plants, a decreased rate of nitrogen fertilizer utilization, and reduced rice yields. Calculated from this experiment, the most economical N fertilizer application rate was 227 kg ha^-1 for the type of paddy soil in the Taihu Lake region. However, recommending an appropriate N fertilizer application rate such that the plant growth is enhanced and ammonia loss is reduced could improve the N utilization efficiency of rice.

Systematic Studies of Nitrogen Loss from Paddy Soils Through Leaching in the Dongting Lake Area of China

A two-year lysimeter study was conducted to study the effects of different fertilizers and soils on nitrogen leaching loss in a double rice cropping system by considering three major types of paddy soils from the Dongting Lake area. The results showed that N concentration in the leachate did not differ significantly among the treatments of urea, controlled release N fertilizer and pig manure and that all these fertilizers produced higher total nitrogen （TN） concentrations in the leachate compared to the case where no fertilizer was applied. The TN leaching loss following urea treatment accounted for 2.28%, 0.66%, and 1.50% of the amount of N applied in the alluvial sandy loamy paddy soil （ASL）, purple calcareous clayey paddy soil （PCC）, and reddish-yellow loamy paddy soil （RYL）, respectively. Higher TN loss was found to be correlated with the increased leachate volume in ASL compared with RYL, and the lowest TN loss was observed in the PCC, in which the lowest leachate volume and TN concentration were observed. Organic N and NH＋-N were the major forms of N depleted through leachate, accounting for 56.8% and 39.7% of TN losses, respectively. Accordingly, soil-specific fertilization regimens are recommended; in particular, the maximum amount of fertilizer should be optimized for sandy soils with a high infiltration rate. To avoid a high N leaching loss from rice fields, organic N fertilizers such as urea or coated urea should primarily be used for surface topdressing or shallow-layer application and not for deep-layer application.