Effect Of Wheat Straw Returning And Water Management On Soil Carbons Characteristic And Tiller Utilization And Earing And Quality Of Rice By Mechanical Transplanted Method

Wheat straw is the wheatgrass left in field after wheat harvests.It is one of the most valuable natural resources containing abundant mineral elements.Directly returning wheat straw to field has been the most direct,economic and sustainable technological approach,which has been extensively utilized to increase crop yield and soil fertility.However,it may cause some problems such as making plants of mechanical transplanted rice stunty and reducing effective spike numbers.Moderate water management plays an important role in improving the yield of the mechanical transplanted rice,and makes for the matter assimilating and accumulating,improving population quality,increasing effective spike numbers and finally boosting yields.Hence wheat straw recycle and water management are vital to promote high yield,good quality,high efficiency,ecological balance and safety of mechanical transplanted rice.Taking conventional rice Huaidao 5,Nanjing 9108 and hybrid rice Xuyou 401,Yongyou 2640 as materials,this study determined and analyzed yield components of different rice in the mature period,rice quality trait,characteristics of tillering positions and tillering productive,and dynamic changes of dry matter population,characteristics of N accumulation and physicochemical characters of soil as well as characteristics of wheat straw under different conditions of water management by wheat straw recycle and water management.The main research results of the experiment are listed as follows:1.The contents of total soil organic carbon and labile organic carbon decrease with the increasing of soil depth.Wheat straw recycle significantly improves the content of soil total organic carbon and labile organic carbon,which increases the content of soil total organiccarbon by 3.08%-19.74%,drying-wetting alternation irrigation also increases that by0.01%-10.09%.Wheat straw recycle increases the amount of bacteria,epiphyte and actinomycetes in soil and increased the microbial biomass organic nitrogen by 12.67%-46.22%,and drying-wetting alternation irrigation increases the amount of epiphyte in soil,decreases the amount of bacteria and actinomycetes and raises the microbial biomass organic N by 0.48%-7.84%.Both wheat straw recycle and drying-wetting alternation irrigation increase soil invertase and urease activity.The quick decomposing period of straw in soil is 0 to 60 days.Most C and N decompose within 60 days while P and K within 10 days.Drying,wetting alternation irrigation decreases the straw decomposing rate,and total decomposition in rice growth stages also decreases a little.2.Wheat straw recycle and drying-wetting alternation irrigation raise the critical effective period of tiller to the SPAD value of leaf in the mature period and the net photosynthetic rate of functional leaf in heading stage.After 30 days,it increases the critical leaf age of tiller to accumulated amount,ratio and rate of dry matter,accumulated amount,absorption ratio and rate of nitrogen in the mature period;and advance the apparent amount and rate of transfer and the rate of contributions to seeds of dry matter and nitrogen,and recovery utilization rate and agronomic N efficiency of nitrogen after rice heads.The recovery utilization rate of nitrogen in wheat straw recycle is 4.94%-10.55%higher than that in non-wheat-straw returned treatment,while that in alternative drying-wetting water treatment is 7.23%-14.72%higher than that in conventional water treatment.3.Under conventional irrigation condition,when there was no wheat straw returning treatment,the primary tiller position of mechanical transplanted conventional rice was 3/0 and the main tiller positions of tiller occurrence were 4/0,5/0,6/0,while when there was wheat straw returning treatment,the primary tiller position was 4/0 and the main tiller positions were 4/0,5/0,6/0.No matter whether there was wheat straw returning treatment or not,under dry-wet alternate irrigation,the primary position of mechanical transplanted conventional rice was 3/0,and the main tiller positions of tiller occurrence were 4/0,5/0,6/0,which meant wheat straw returning treatment restricted the tiller occurrence on tiller position 3/0,while the dry-wet alternate irrigation reversed the inhibition effects of wheat straw returning treatment.No matter whether there was wheat straw returning treatment or not,and no matter whether it was conventional irrigation or dry-wet alternate irrigation,when compared with mechanical transplanted conventional rice,both the primary and secondary tiller occurrences of mechanical transplanted hybrid rice had one tiller position advanced.Seen from the tiller-earing percentage,when the tiller positions were 4/0,5/0,6/0,the conventional mechanical transplanted rice had the highest tiller-earing percentage over 69.62%;while when the tiller positions were 3/0,4/0,5/0,6/0,the hybrid mechanical transplanted rice had the highest earing-tiller over 76.47%.At the same time,the tiller-earing percentage with wheat straw returning treatment was higher than that of non-wheat straw returning treatment,dry-wet alternate irrigation treatment was higher than that of conventional irrigation treatment,moreover,the enhancing effects of dry-wet alternate irrigation treatment was higher than that of wheat straw returning treatment.The mechanical transplanted conventional rice had the highest tiller-earing percentage on middle tiller position and lowest earing-tiller percentage on higher tiller position,while the mechanical transplanted hybrid rice had a quite high percentage on middle and lower tiller positions and the lowest on high tiller position.Wheat straw returning treatment decreased the tiller occurrence on low position and the total tiller-earing percentage,while the dry-wet alternate irrigation was the other way around.When it came to the contribution rate made by single stem to group panicle yield,the main stems had the highest contribution rate,and the main stems’ contribution rate of conventional rice was 25.44%～28.76%,while the hybrid rice’s was 20.32%～23.76%.And when it came to the tiller occurrence on different tiller positions,the primary tillering of all the tillers positions had the biggest contribution rate to group panicle yield.When the tiller positions were 5/0,6/0,the conventional rice had the highest panicle numbers and the yield contribution rate,and when tiller positions were 4/0,5/0,hybrid rice had the highest panicle numbers and yield contribution rate,at the same time,the panicle numbers and yield contribution rate of wheat straw returning treatment was higher than that of non-wheat straw returning treatment,and the dry-wet alternate irrigation was higher than that of conventional irrigation.Wheat straw returning treatment decreased the effective panicle numbers and increased the grain numbers at the rice’s mature stage while dry-wet alternate irrigation treatment increased the effective panicle numbers and grain numbers at mature stage.Wheat straw returning and dry-wet alternate treatments had an unobvious effect on rice’s thousand seed weight and seed setting rate.According to the essay experiment,wheat straw returning and dry-wet alternate treatments could lead to the maximized irrigation water use efficiency and the highest rice yield.4.Wheat straw recycle promotes the length of paddy caryopsis,but has little influence on width and thickness.Drying-wetting alternation irrigation can improve the length and thickness of caryopsis,but has little effects on width.Among all treatments,the size of caryopsis with wheat straw recycle and drying-wetting alternation irrigation is the biggest.Wheat straw recycle and drying-wetting alternation irrigation can raise the rate of brown,milled and head rice.And the effect of irrigation is greater than wheat straw recycle.The percentage of chalky rice quality with wheat straw recycle are 1.43%-19.17%lower than those with non-wheat-straw recycle.The percentage of chalky rice in drying-wetting alternation irrigation are 4.46%-25.66%lower than those in conventional water treatment.Wheat straw recycle increases contents of total protein and glutelin by 8.32%-19.76%and 7.26%-15.87%,respectively.Compared to non-wheat-straw returned treatment,it has no significant differences among contents of albumin,globulin and gliadin.Drying-wetting alternation irrigation also raises total protein and glutelin contents by 6.68%-15.50%and 4.67%-15.87%,respectively,compared with conventional water treatment.Wheat straw recycle increases amylose content and SBV and decreases amylopectin content,breakdown values and gel consistency,while drying-wetting alternation irrigation is on the contrary.Wheat straw recycle and drying-wetting alternation irrigation increases the crystallinity of rice starch and enhance crystal structure stability.