Response Of Rice Canopy Light And Temperature Characteristics And Yield Formation To Nitrogen Regulatio

In rice production,the influence of light,temperature,and humidity conditions within the population often limits the the yield potential,which poses a serious challenge to the safe production of rice.At present,the relationship between light-temperature characteristics and yield in rice population and its regulation technology need to be further studied.This study was conducted in two different ecological conditions in Xingyi City(XY)and Huangping County(HP),Kaili City,Guizhou Province in 2020 and 2021,using super hybrid rice Zhunliangyou 527(V1)and Xiangliangyou 900(V2)as the materials,and 4 different nitrogen application levels,namely N1(0kg/hm~2),N2(90kg/hm~2),N3(180kg/hm~2),and N4(270kg/hm~2)as the treatments.The canopy structure of different rice populations was constructed through ecological conditions and nitrogen fertilizer regulation to determine the effects of nitrogen fertilizer on temperature and humidity,light distribution characteristics within the rice population,rice growth and development,photosynthetic yield and yield formation,and to clarify the relationships between the light-temperature characteristics of canopy and yield formation,which is of great significance to rice yield formation and the cultivation of high-yield and stable yield.The main research results are as follows:(1)Nitrogen fertilizer and ecological conditions have a significant impact on the canopy structure and yield formation of rice.Among different nitrogen fertilizer levels,compared with no nitrogen fertilizer application,fertilization increased the leaf base angle,opening angle and leaf length of the upper three leaves,decreased the leaf direction value,and expanded the light receiving area of the upper three leaves.The total leaf area index increased with the application of nitrogen fertilizer,especially significantly increased leaf area index of the middle and upper layers(above 60 cm)and high-efficiency leaf area index,which ultimately led to a significant increase in dry matter accumulation and yield with increasing nitrogen application levels.Between the two ecological conditions,the yield in XY was significantly higher than that in HP.From the perspective of canopy structure,the main reason was that the base angle and opening angle of the upper three leaves of XY were significantly smaller than those of HP,while the leaf orientation value was higher than that of HP,which significantly increased the dry matter weight and the leaf area index of the middle and lower layers(0-60cm),indicating that the upper three leaves of XY are more erect than that of HP,which is beneficial to the accumulation of dry matter in the middle and lower layers and the expansion of the leaf area index in the middle and lower leaves,resulting in the total dry matter weight and leaf area index were significantly higher than those of HP,which were the main factors leading to the difference in yield under the two ecological conditions.From the perspective of yield factors,the number of panicles per unit area and grain weight increased synergistically in XY,especially the former were the main factors leading to the increase of rice yield.(2)LAI and total LAI in the upper and middle layers of rice significantly increased i PAR and intercepts in the upper middle layers and populations,while decreasing base angle,opening angle,and increasing leaf length of sword and inverted bilobes significantly increased i PAR in the upper middle layers and populations.Decreasing inverted trefoil base angle,opening angle at HP and properly increasing inverted trefoil base angle,opening angle,and leaf length at XY were able to significantly improve light intercept and i PAR of the population.The small RUE variation among cultivars,differences in i PAR at different canopy heights and populations are the main mechanisms responsible for the poor yield among cultivars.The light intercept and i PAR of rice in the middle and lower layers were not well regulated at the nitrogen fertilization level,and the length,base angle,total LAI,and LAI of all layers,functional leaves,and efficient LAI of the upper three leaves were improved with increasing N fertilization,which caused the light intercept and i PAR of the middle and upper layers and populations to increase with increasing N fertilization,combined with the fact that the total RUE was improved with increasing N fertilization.The i PAR and shoot yield of the upper and middle layers of rice and the population were significantly correlated with both rice yield and dry matter accumulation,and increasing the shoot yield and i PAR of the upper and middle layers of the middle and late reproductive stages could significantly increase the effective panicle,seed setting rate and 1000 grain weight,and then yield.The base angle,opening angle,and leaf length of the upper three lobes of HP were greater than XY,resulting in lower light intercept in the mid upper layers and lower light intercept in the population after XY anthesis than in the low producing regions,and the lower middle layers were greater than HP,but because the PAR of XY was greater than HP,resulting in significantly higher i PAR and higher RUE in the XY population and different canopy heights,and significantly higher RUE than HP,the synergistic enhancement of i PAR and rue was the main mechanism leading to high XY yield.(3)The maximum temperature and average temperature in rice canopy during each growth period decreased with the increase of nitrogen application rate,while the minimum humidity and average humidity increased with the increase of nitrogen application rate;both the maximum temperature and average temperature of HP were higher than those of XY,from the overall point of view,the minimum humidity and average humidity of HP are higher than that of XY.Rice yield and dry matter accumulation were significantly and negatively correlated with the highest temperature,lowest temperature and average temperature,and significantly positively correlated with humidity,indicating that low temperature and high humidity in the canopy during the key growth period were beneficial to the formation of rice panicle and the increased effective ear number and the expanded rice population,leading to the accumulation of dry matter and the yield formation.The maximum temperature and average temperature of PI-MA and FL-MA were significantly and negatively correlated with the leaf area index and total leaf area index of the middle and upper layers(greater than 60cm),and the maximum temperature in each period was negatively correlated with the base angle and opening angle of the upper three leaves.The average humidity and minimum humidity of PI-MA and FL-MA were significantly and positively correlated with the leaf area index,total leaf area index,and flag leaf length of the middle and upper layers(greater than 60 cm),indicating that decreasing the base angle,opening angle and increasing the leaf area index and the leaf area index of the middle and upper layers can form a low temperature and high humidity environment in the population,which were beneficial to the accumulation of dry matter and the formation of yield.To sum up:ecological environment,variety,nitrogen application rate and other factors will change the canopy structure,canopy light distribution,temperature and humidity.The key to further tap the yield potential of rice is to build a reasonable canopy structure to improve the interception rate and i PAR of the upper middle layer and population,improve the population quality,and improve RUE.