| To explore the effects of cultivation methods on soil physiochemical property,root growth,nitrogen uptake and utilization and straw decomposition and nitrogen release under different straw returning methods.The experiment was conducted in the paddy field of the Rice Research Institute of Sichuan Agriculture University in 2017-2018.The previous crop was wheat.A two-factor spilt-plot trail was conducted with hybrid rice cultivator F-you 498as material.The main plot was three different straw returning methods:no straw returning(M0),straw mulching(M1)and straw soil-returning(M2),the subplot was two rice planting ways:artificial transplanting(C1),precision hill direct seeding(C2)and mechanical transplanting(C3).The difference of rice yield,straw decomposition and nitrogen,soil physiochemical property,root morphology,root vigor,content of organic acids in root exudates,and rice nitrogen accumulation,transfer and utilization was studied,furthermore the relationship of root index and yield,and the contribution of soil basical nitrogen,wheat straw nitrogen and fertilizer nitrogen on rice plant nitrogen accumulation in muturing stage.The research result were as follows:1 The effects of planting methods on grain yield and its components of hybrid rice under different wheat straw returning methodsAfter the straw was returned to the field,the effective panicle of rice increased,and straw mulching>straw soil-returning,and straw mulching significantly increased total spikelets numbers,rice yieid increased by 3.30%?3.88%.Straw soil-returning significantly decreased total spikelets numbers or 1000-grain weight,the yield ranged by-0.8%?2.88%.Under each methods of straw returning,artificial transplanting owned the lowest effective panicle,and the highest total spikelets numbers,higher seed setting rate and highest yield(10.10?11.19 t/hm~2).As for mechanical transplanting rice,the total spikelets numbers were least,seed setting rate was higher than precision hill direct seeding,but the yield of mechanical transplanting rice(9.80?10.32 t/hm~2)was between artificial transplanting and mechanical transplanting.The total spikelets numbers of precision hill direct seeding were higher than mechanical transplanting,but the seed seeding rate and yield was lowest(9.13?10.04t/hm~2).Each planting methods was increased production stably under straw mulching,and straw mulching combined artificial transplanting has the highest yield(10.55?11.19 t/hm~2)2 The difference of wheat straw decomposition and nitrogen release under different way of wheat returning and rice planting.The amount of returning wheat straw was 5000 kg/hm~2(water content was 13.5%),the total nitrogen amount of returning wheat of 2017and 2018 was 27.69 kg/hm~2and26.97kg/hm~2.The decomposition rate and nitrogen release rate of straw in tillering stage were 30.89%?37.34%and 31.07%?48.39%,respectively,that were 56.68-64.01%and51.24%?58.39%in mature stage,respectively,it indicated that the decomposition of straw and nitrogen release were fast at first and then slow.The decomposition of straw and nitrogen of straw soil-returning was more and faster than straw mulching(except jointing stage).As for nitrogen release at maturing stage,the nitrogen release of wheat straw of three rice planting ways represented as soil-returning>straw mulching,and straw soil-returning combined with precision hill direct seeding owned highest amount of nitrogen release(16.03?16.37 kg/hm~2).3 The effect of different straw returning methods on soil physiochemical propertyCompared with no straw returning,straw returning reduced soil bulk density,increased soil porosity,and the effect of straw soil-returning was better than straw mulching,improved the 0?20 cm layer soil of soil organic matter content and soil total nitrogen content,the straw soil-returning was better at the tillering stage,the 0?10cm layer soil of soil organic matter and total nitrogen content is higher under straw mulching,at the same time,the effect of straw mulching on 10?20 layer soil was delayed by one stage than on 0?10cm layer.Straw returning could not increase the content of ammonia-nitrogen and nitrate-nitrogen in each soil layer of each period,and the content of ammonia-nitrogen and nitrate-nitrogen in soil 0-10cm under straw mulching was higher or equivalent to straw soil-returning,and its ammonia-nitrate ratio was smaller,and the difference of ammonia-nitrate ratio 10-20cm was not significant between two straw returning methods.It indicated that straw mulching was more benefit for soil fertilization than straw soil-returning.4 The difference of rice root growth under different way of wheat returning and rice planting.After straw returning the root morphology index was inhibited at first and the promoted,inhibited the root growth at active tillering stage,and from jointing stage the root growth and content of organic acids in root exudates was promoted,these indexs were biggest under straw soil-returning.Total content of organic acids in root exudates of heading,root bleeding indensity after heading stage,root number and length at maturing stage of soil mulching were bigger than straw soil-returning.It showed that straw soil-returning was benefit for early root growth,and straw mulching was more benefit for delay root senescence.Among different planting methods,artificial transplanting had the largest root diameter of each stage,and grown best at early stage,but the preponderance of artificial transplanting was decreased gradually after active tillering stage.At heading stage,the artificial transplanting owned minimum single stem root length and root number,and owned highest total organic acid content after straw returning,and its root senescence was slow.And it could maintain the advantage of single root index at maturing stage.Precision hill direct seeding had the smallest diameter,and grown worst at early stage,but then grown fast active tillering stage.At jointing and heading stage precision hill direct seeding owned maximum population root length and root number,but own the lowest total organic acid content of heading stage.5 The difference of the nitrogen uptake and utilization of rice under different way of wheat returning and rice plantingCompared with no straw returning,after straw returning the rice planting nitrogen accumulation of rice was inhibited at first and the promoted,inhibited the nitrogen accumulation of active tillering stage,and from jointing stage the rice planting nitrogen accumulation,root nitrogen accumulation of each stage,the nitrogen transfer of stem and leaf,N increase in panicle and N harvest index were promoted.The N harvest of straw soil-returning index was bigger,and other indexs were higher under straw mulching.In addition,straw mulching improved N agronomic efficiency(2.31?2.83kg/kg).Straw returning decreased N use efficiency for grain production.So straw mulching owned the highest nitrogen accumulation and transfer.Artificial transplanting had the higher or highest nitrogen accumulation of each stage and highest N increase in panicle.The nitrogen transfer of stem,translocation of leaf and N agronomic efficiency were highest in precision hill direct seeding,but N increase in panicle,N harvest index and N use efficiency for grain production were lowest.Under artificial transplanting treatment,the contribution rate of soil background nitrogen to nitrogen accumulation at maturing stage was the largest(57.72%?67.28%),that of nitrogen fertilizer was the smallest(28.14%?33.58%),and that of straw was different from year to year.Under circumstance of straw mulching,the straw contribution rate of all planting methods rice was higher than that under straw soil-returning.Above all,under circumstance of straw mulching,the nitrogen accumulation,root growth,the contribution rate of straw for maturing nitrogen accumulation,soil organic matter content and soil total nitrogen content of all planting methods rice was higher than that under straw soil-returning,artificial transplanting combined straw mulching was the highest. |
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