[Effects of planting methods on the utilization of temperature and sunshine resources and yield of rice under cabbage/rape-paddy cropping system.] / 青菜/æ²¹èœèŒ¬å£ä¸‹æ°´ç¨»æ ½æ¤æ–¹å¼å¯¹æ¸©å ‰èµ„æºåˆ©ç”¨å’Œäº§é‡çš„å½±å“.

Light simplified cultivation and high quality rice are the main directions of rice production in China. Meteorological factors are the most important environmental factors affecting rice growth and yield. Few studies examined the relationship between rice yield and microclimate under different light simplified cultivation modes. To explore the relationship between rice yield and climatic factors (temperature, sunshine and water) at different growth stages of hybrid rice under different forecrops in southwest China, we carried out a split-plot design experiment in 2019 and 2020, with two forecrops of green cabbage and rape as the main plot, and three planting methods, direct-seeding, blanket-transplanting, and artificial transplanting as the subplots, taking Yixiangyou 2115 as the experimental variety. Results showed that compared with rape-paddy cropping system, cabbage-paddy cropping system significantly improved the accumulated temperature and precipitation production efficiency and consequently improved the effective panicles, setting rate, and 1000-grain weight. The yield was increased by 12.7% and 8.3% under cabbage-paddy and rape-paddy cropping system, respectively. Compared with manual transplanting, mechanical transplanting improved effective panicles, production efficiency of radiation, accumulated temperature and precipitation, and the radiation use efficiency of grain during the whole growth period. The mean yield was increased by 4.6% in 2019 and 2020. However, the above parameters of direct-seeding significantly decreased, but the yield decreased by 8.7%. Compared with 2019, mechanical transplanting and artificial transplanting were sown one month earlier in 2020 under the same stubble, which shortened growth period, reduced air temperature, and increased precipitation after flowering, leading to a significant decrease in effective accumulated temperature and light radiation; production efficiency of accumulated temperature, light energy, and precipitation; and utilization efficiency of light energy of grain, spikelets per panicle, setting rate, and 1000-grain weight. However, the yield was significantly reduced. Partial least squares regression analysis was used to establish the production forecast equation of standardized regression coefficients of meteorological factors. There was a positive correlation between rice yield and effective accumulated temperature and total radiation during the growth stage or the whole growth period. In addition, there was a significant negative correlation between rice yield and precipitation during the whole growth period. In conclusion, mechanical transplanting under cabbage-paddy cropping system was a rice planting method that optimised the seasonal sunshine and temperature resources in southwest China. The method facilitated the full utilization of temperature and sunshine resources, resulting in high yield. However, it was not advisable to sow or transplant too early.

[Research advances on regulating soil nitrogen loss by the type of nitrogen fertilizer and its application strategy.] / æ°®è‚¥ç§ç±»åŠè¿ç­¹æŠ€æœ¯è°ƒæŽ§åœŸå£¤æ°®ç´ æŸå¤±çš„ç ”ç©¶è¿›å±•.

Unreasonable application of nitrogen fertilizer to cropland decreases nitrogen use efficiency of crop. A large amount of nitrogen loss to environment through runoff, leaching, ammonia volati-lization, nitrification-denitrification, etc., causes water and atmospheric pollution, poses serious environmental problems and threatens human health. The type of nitrogen fertilizer and its application rate, time, and method have significant effects on nitrogen loss. The primary reason for nitrogen loss is attributed to the supersaturated soil nitrogen concentration. Making full use of environmental nitrogen sources, reducing the application rate of chemical nitrogen fertilizers, applying deep placement fertilizing method, and applying organic fertilizers with chemical nitrogen fertilizers, are effective practices for reducing nitrogen loss and improving nitrogen use efficiency. It is suggested that deve-loping new high efficiency nitrogen fertilizers, enhancing nitrogen management, and strengthening the monitoring and use of environmental nitrogen sources are the powerful tools to decrease nitrogen application rate and increase efficiency of cropland.