Study On Nitrogen Application Regimes Of Double-cropping Rice Under The Mode Of Water-saving Simplified Cultivation

In order to clarify the suitable nitrogen fertilizer application mode for rice production under the condition of water-saving simplified cultivation in double-cropping rice area of Hunan.In this study,retain water in the late growth stage?heading stage?of early rice and the early growth period?Transplanting turning-green stage?of late rice as the premise,using early rice plowing and late rice no-tillage at mechanical planting and mechanical harvest combined with nitrogen application regimes technology.Study on the effect of water-saving simplified cultivation mode of"retain early and late irrigation"on rice yield and its components,growth characteristics,photosyntheticcharacteristics and nutritional characteristics.The effect of different nitrogen fertilizer ratio on late rice under the condition of water-saving simplified cultivation mode of"retain early and late irrigation"was studied.Explore the best fertilization program.To provide theoretical basis and technical guidance for saving-water simplified cultivation mode of"retain early and late irrigation".The main results are as follows:?1?Yuzhenxiang yield reached the highest 7.93t/hm² when the ratio of nitrogen at tillering stage:at booting stage,heading stage=4:3:3.Fengyuanyou299 yield reached the highest 7.98t/hm² when the ratio of nitrogen at tillering stage:at booting stage,heading stage=5:3:2.Nitrogen fertilizer to some extent conducive to increase rice yield,but excessive nitrogen fertilizer on rice yield is declining.Nitrogen fertilization was beneficial to the formation of effective panicle.There was a significant positive correlation between the effective panicle number and total grain number per plant.There was a significant positive correlation between the number of grains per plant and the effective panicle.?2?The leaf area index decreased gradually at the heading stage and reached the maximum at the heading stage.It increased 51.25%⁶4.46%from tillering to booting stage.The leaf area index and photosynthetic potential in the main growth stages of rice were the highest in single fertilization.Leaf area index and dry matter weight were positively correlated with yield at the late growth stage.The dry matter accumulation of rice at different growth stages increased first,then decreased and then increased.The dry matter accumulation of rice at booting to heading stage was the highest,which was as high as28.93%⁴4.63%,and were positively correlated with yield.The apparent output,material output rate and material conversion rate of rice leaves were the highest in single fertilization.The rice EPMSS was 14.75%⁴6.86%,and leaf material output rate was 13.99%³3.75%.?3?The higher the back shift ratio of nitrogen fertilizer,the lower the chlorophyll content?SPAD?of rice in the early growth stage,and the later growth stage showed the opposite trend and higher than the control treatment.There were a positive correlation among yield and chlorophyll content?SPAD value?,net photosynthetic rate,stomatal conductance,intercellular CO₂ concentration and transpiration rate at the later growth stage.?4?The nitrogen content of the leaves were higher than the stem-sheath,the panicle was higher than stem-sheath,but lower than leaves nitrogen content.There was a significant positive correlation between rice yield and leaf nitrogen content in milk and mature stage,and a significant positive correlation with the nitrogen content in the panicle stage of milk.The amount of nitrogen accumulation in rice tillering stage to heading stage was55.28%⁷9.85%,after heading nitrogen accumulation was only 5.72%²3.35%.The nitrogen fertilizer of rice was absorbed by the use of the utilization of the Yuzhenxiang at tillering stage:booting stage:heading stage=4:3:3,reached the highest,which was higher24.68%¹08.43%than other treatments;Fengyuanyou 299 nitrogen ratio at tillering stage:booting stage:heading stage=5:3:2,reached the highest,which was higher 10.53%⁹1.34%than other treatments;the highest rate was treated with compound fertilizer for soil nitrogen dependency rate and nitrogen physiological efficiency;the agronomic efficiency of nitrogen fertilizer,nitrogen fertilizer contribution rate and nitrogen partial productivity showed the same trend,but the performance was different,but the varieties were different.The rice yield and nitrogen uptake rate was positively correlated,with soil nitrogen dependency rate has a negative correlation,and agronomic efficiency of nitrogen fertilizer,the rate of nitrogen contribution and nitrogen partial productivity were very significant positive correlation.There was no significant correlation between nitrogen use efficiency and yield.