Research On The Precise Absorption Model Of Rice Nutrients Based On Effective Accumulated Temperature

Rice is an important food crop in China and it plays a dominant role in the food consumption of Chinese residents.Precise fertilization can improve the efficiency of nutrient use,reduce environmental pollution,and increase grain production.Most of the existing research on precision agriculture in China is based on the spatial scale of 3S technology（Abbreviation of Global Positioning System,Geographic Information System and Remote Sensing）.For precision fertilization,the time scale of fertilization is still mostly based on the empirical judgment of the crop growth period.Therefore,precise timing and quantitative fertilization based on the characteristics of rice fertilizer demand is a new direction for the development of precision fertilization technology.The growth and development of crops and nutrient absorption are closely related to meteorological factors such as accumulated temperature.In this study,by analyzing the correlation between accumulated temperature and other meteorological factors and rice nutrient absorption,a precise model of accumulated temperature and rice nutrient absorption was established,and a rice recommended fertilization model and yield prediction model were designed and constructed,which provided the necessary theoretical basis for the realization of precision agriculture variable operations in the future.The main research results of this paper are as follows:1.Meteorological factors have an important impact on rice yield.This study shows that when the smoothing coefficient a=0.3,the increase of effective accumulated temperature,average temperature and average minimum temperature is helpful to increase yield.However,the trend of cumulative precipitation and cumulative sunshine hours is opposite,and the correlation is low.According to the above indicators,a regression equation related to rice meteorological yield is established:Y=1747.83-0.681x₁（x₁is the effective accumulated temperature）.The trend yield of rice was relatively stable under macro conditions,while the yield influenced by meteorological factors fluctuated to a certain extent with the fluctuations of meteorological factors.2.The results of the two-year field test showed that OPT（N2P2K2）,the optimal management plan for nitrogen,phosphorus and potassium,was able to achieve an average increase of 31.77%in rice yield compared with the CK treatment without fertilization.When nitrogen,phosphorus and potassium nutrient application was reduced,the effect on rice yield was most obvious when nitrogen nutrient was reduced alone and phosphorus and potassium were reduced at the same time.By analyzing the yield component factors,it can be seen that the OPT treatment（N2P2K2）had the highest two-year yield and nitrogen accumulation level,and the harvest index,nitrogen uptake by 100 kg grains,and nitrogen grain production efficiency showed opposite trends.The nitrogen fertilizer productivity of nitrogen reduction treatment was significantly higher than that of conventional nitrogen fertilizer treatment,and both OPT treatment（N2P2K2）and fertilizer reduction treatment N1P1K1 had higher nitrogen absorption rate.That is,under nutrient-deficient conditions,the nutrient accumulation in the crop is more inclined to transfer to the grain.3.It was determined that the optimal nutrient management method OPT（N2P2K2）treatment had the highest average yield and highest nutrient uptake.And taking this as a measure of high yield and good yield,a Gompertz model of rice dry matter accumulation based on the daily scale of relative effective accumulated temperature was established under the optimal nutrient management conditions:y=1.0390*exp（-exp（1.8955-4.1614x））.The results of the study confirmed that the treatment groups that could obtain higher nutrient accumulation generally entered the rapid growth period at the earliest and ended the rapid growth period at the latest,and had the highest accumulation in the rapid growth period.OPT（N2P2K2）entered the fast growth period at the earliest at 548.07°C·d,and ended at the latest at 1676.28°C·d.The accumulated dry matter weight in the fast growth period had a maximum value of14352.06kg/hm².4.The Gompertz model of plant height growth based on the daily scale of relative effective accumulated temperature under the optimal nutrient management method OPT（N2P2K2）was determined:y=0.9773*exp（-exp（0.9178-4.1010x））.The variation of the model of plant height growth rate has a certain monotonicity.The growth rate of plant height was higher in the early stage,and the growth rate of plant height was lower in the middle and late stage.The application of nitrogen and potassium fertilizers was beneficial to the increase of plant height;while the dynamic changes of rice tillers reached the peak at the accumulated temperature of 800-900℃·d,and the effective tiller number began to stabilize at about 15 tillers when the accumulated temperature was about 1600℃·d.Compared with other treatments,the optimal fertilization treatment N2P2K2 had the maximum tiller quantity at the accumulated temperature of 800℃·d and 2000℃·d.The nitrogen high treatment had a slightly higher overall tiller quantity than the nitrogen low treatment.Nitrogen application could promote the increase of the tiller number.5.Under different nutrient management conditions,nitrogen accumulation,phosphorus accumulation and potassium accumulation in rice experienced three stages of gradual increase,rapid increase and slow increase with the increase of effective accumulated temperature,and the overall trend was consistent.The growth rate gradually increased at first,reached a peak,and then gradually decreased until it approached zero.Under the reasonable conditions of nutrient management,the nutrient accumulation of rice is higher and reaches the peak faster.For the nutrient absorption simulation,a daily-scale nutrient accumulation Logistic model can be established based on the relative effective accumulated temperature.The nitrogen absorption model is:y=0.9116/（1+9387.5950*exp（-31.0385x））.The ratio of nitrogen uptake by various organs to the total nitrogen uptake at the mature stage of rice fertilization treatment was in the order of panicle>stem sheath>leaf.Compared with the rational nutrient management conditions,the nitrogen without fertilization treatment was more distributed to the grain.6.The dynamic changes of phosphorus and potassium nutrient accumulation showed certain volatility,but the overall trend can still be analyzed by the nutrient accumulation Logistic model based on the daily scale of relative effective accumulated temperature.The dynamic fluctuation of phosphorus is greatly affected by fertilization,and the dynamic fluctuation of potassium is greatly affected by the loss of potassium during the harvesting period.The key nodes can be simulated in stages.In the process of promoting the technology of soil testing and formula fertilization for actual farmers,the corresponding models can also be used as the basis to accurately increase the amount of fertilizer supply in the period of gradual increase in nutrient absorption and rapid increase based on the application of digital agriculture,so as to increase production and obtain greater economic benefits.