Study On The Characteristics Of Nutrient Absorption And Distribution And Greenhouse Gas Emission Of Ratton Rice

As a kind of resource-saving rice planting mode of provincial fertilizer,provincial medicine and ecological environmental protection,ratoon rice has the advantages of improving multiple cropping index,increasing harvest area,stable rice yield and better economic benefits.It has a good development prospect in Hunan province with more than two seasons.Explore the law of nutrient absorption and distribution and the characteristics of greenhouse gas emission in ratoon rice fields.The development of ratoon rice provides a research basis.From 2019 to 2020,double cropping rice（DR）and ratoon cropping rice（RR）were tested in Yanxi Town,Liuyang City,Hunan Province,The test materials are early rice（Zhongjiazao 17,ZJZ17;Liangyou 287,LY287）,late rice（Wuyou 103,WY103;Taiyou 390and TY390）and ratoon rice（Y Liangyou 911,YLY911;Liangyou 6326,LY6326）,combined into four treatments,namely ZJZ17+WY103（DR1）,LY287+TY390（DR2）,YLY911（RR1）,and LY6326（RR2）.The main research results are as follows:（1）Compared with DR,RR inhibited the accumulation of nitrogen and phosphorus in tillering and panicle initiation stage,promoted the accumulation of nitrogen and phosphorus in leaves and stem sheath from full heading to mature stage,as well as increased the nitrogen and phosphorus transport volume and transport rate of stem sheath and leaves.RR nitrogen accumulation decreased by 74.70%to 80.91%in the tillering stage,decreased by 50.27%to63.70%in panicle initiation stage,improved by 0.30%to 17.80%in full heading stage,and improved by 4.78%to 19.94%in the mature stage.RR compared with DR in phosphorus accumulation decreased by 77.54%to 82.04%in tillering stage,decreased by 51.60%to57.52%in panicle initiation stage,improved by 7.37%to 15.82%in full heading stage,and improved by 8.26%to 15.89%in the mature stage.Moreover,DR has certain advantages over RR in harvest index of nitrogen and phosphorus and harvest efficiency of rice production.Compared with RR,the nitrogen harvest index and rice production efficiency of DR increased by 23.60%to 28.12%and 7.54%to 24.34%,respectively;phosphorus harvest index and rice production efficiency of DR increased by 15.26%to 23.40%and 17.25%to24.10%,respectively.The accumulation of nitrogen and phosphorus and dry matter is concentrated in the stem sheath and leaves in the plant and dry material in the ear stage,and in the plant in the ear,followed by the stem sheath and finally the leaf.（2）The RR and DR anniversary yield were not significant.The total grain number per spike in two years was significant correlation with the yield;in the first season,RR1 was significantly higher than DR1,DR2 and RR2,with 58.92%,91.65%and 27.81%higher in2019 and 4.58%,45.08%and 34.48%higher in 2020.The total grain count per spike was highest with DR1,significantly higher than DR2,RR1 and RR2,with 50.86%,70.60%and82.08%higher in 2019 and 41.80%,65.61%and 85.16%higher in 2020.（3）Compared with DR,RR significantly increased soil nitrate nitrogen after the second season of each soil layer,increasing by 198.60%to 754.77%,reduced the soil ammonium nitrogen,decreasing by 9.28%to 68.85%;improved the soil catalase activity of the first season of each soil layer,the milk ripening stage increased by 34.71%to 55.59%and the maturity stage increased by 14.98%to 35.74%;improved the soil urease activity of each soil layer was,tillering stage increased by 2.77%to 12.87%,and full heading stage increased by1.01%to 17.72%;improved the soil urease activity in the second season,full heading stage increased by 8.54%to 23.34%,and milk ripe stage increased by 22.47%to 38.36%.（4）RR is 12.00%～27.03%less than the cumulative CH₄ emission from DR t;the difference of cumulative annual N₂O emission between treatments is not significant.The main contributor to the total warming potential（GWP）of each treatment is CH₄,accounting for more than 90%of the total GWP,among which the CO₂ equivalent of CH₄ is the highest with DR2 treatment,which is significantly higher than RR treatment,increased by 21.64%to 37.05%.In 2019,the cumulative CH₄emissions and N₂O emissions of each treatment were significantly correlated with yield,shoot biomass and soil catalase activity,and had a significant correlation with soil urease and shoot phosphate accumulation.Above,ratoon rice planting mode can be stable production,the cumulative increase of nitrogen and phosphorus is not significantly reduced,to a certain extent,improve the soil physical and chemical factors,and can effectively reduce annual CH₄ cumulative emissions,therefore,ratoon rice can be considered in rice producing areas with less than two seasons and more than one season.