| In this article,experiments were carried out in winter fallow field.Paddy field tillage(tillage and no-tillage)and rice straw returning to paddy field with four treatments:conventional tillage/havest(CTH),conventional tillage/straw residue(CTR),no-till/havest(CTH),no-till/straw residue(CTR)were used to study the effects on rice yield,rice nutrient content,soils surface physical and Chemical properties,soil phosphorus accumulation and its morphology,the main results obtained are as follows:(1)After the second rice season,the grain yields of loam soil and clay loam soil showed NTR>NTH>CTR>CTH,NTR was significantly higher than that of CTH,loam soil and clay loam soil were 3.55%and 2.53%(p<0.05),respectively.and no significant difference between the other treatments.During the same period,the total nitrogen content of clay loam soil grain under no-till and straw-returning was higher than that of conventional tillage,the C:N of clay loam soil grain was lower than that of conventional tillage,but there was no significant difference for loam soil.After the second rice season,total nitrogen content of clay loam soil grain showed NTR>NTH>CTR>CTH,and NTR was significantly higher than that of CTH(15.75%,p<0.05),Grain C:N showed CTH>CTR>NTH>NTR,NTR was significantly lower than CTH,14.13%lower(p<0.05),no significant difference between other treatments.(2)After two years of experiment,the contents of total phosphorus in loam soil and clay loam soil were enrichment by 4.29%?8.80%and 1.97%?4.08%,respectively.After the second rice season for loam soil and after the first winter fallow for clay,the total phosphorus content of rice under no-till and straw-returning was higher than that of conventional tillage.For loam soil,after the second rice season,total phosphorus content of soil showed NTR>CTR>NTH>CTH,NTR was significantly higher than CTH,1.55%higher(p<0.05),and no significant difference was found among other treatments.After the second winter fallow,soil total phosphorus showed NTR>NTH>CTR>CTH,NTR was significantly higher than NTH,CTR and CTH(1.95%,2.70%and 2.71%,p<0.05),respectively.No significant difference between other treatments.For clay loam soil,total phosphorus in soil showed NTR>NTH>CTR>CTH after the first winter fallow.The NTR was significantly higher than CTH,0.77%higher(p<0.05),no significant difference was found among other treatments.After the second rice season,total phosphorus content in soil showed NTR>CTR and NTH>CTH,while NTR,CTR and NTH were significantly higher than those in CTH by 1.44%,0.89%and 0.89%(p<0.05),respectively.No significant difference between other treatments.After the second winter fallow,soil total phosphorus showed NTR>CTR>NTH>CTH,while NTR,CTR and NTH were significantly higher than CTH by 2.07%,1.25%and 1.12%(p<0.05),respectively.No significant difference between other treatments.(3)After two years of experiment,available phosphorus contents in loam soil and clay loam soil were enrichment by 8.21%?10.89%and 3.10%?4.61%,respectively.After the second rice season,under no-tillage and straw,available phosphorus content was higher than the conventional tillage.After the second rice season,soil available phosphorus showed NTR>CTR>CTH>NTH,For loam soil,NTR was significantly higher than that of CTH and NTH(2.35%and 2.64%,p<0.05),respectively.CTR was significantly higher than CTH and NTH,2.19%and 2.47%(p<0.05),respectively.For clay loam soil,NTR was significantly higher than CTH,1.10%higher(p<0.05),no significant difference between other treatments.After the second winter fallow,soil available phosphorus showed NTR>CTR>CTH>NTH.For loam soil,NTR was significantly higher than CTH and NTH,2.19%and 2.47%higher(p<0.05),respectively,CTR was significantly higher than CTH and NTH,1.37%and 1.65%higher(p<0.05),respectively.For clay loam soil,Soil available phosphorus showed NTR>CTR>NTH>CTH,NTR was significantly higher than CTH,1.12%higher(p<0.05),no significant difference between other treatments.(4)The results of NMR studies show that The highest content of all soil samples were orthophosphate and phosphatemonoester,while the contents of phospholipids,pyrophosphates and phosphates were low,and polyphosphates were almost undetectable.After two years of trial treatment,The proportion of orthophosphate in tillage soil is higher than that in tillage soil,while the proportion of phosphomonoester and phosphodiester in total phosphorus is higher than that in tillage.After two years of trial treatment,The proportion of orthophosphate in loam soil was 71.51%-72.29%,the proportion of phosphatemonoester was 19.79%?20.29%,the proportion of phosphodiester was 4.32%?4.42%.The proportion of orthophosphate in no-till soil ranged from 69.31%to 69.63%,the proportion of phosphatemonoester was from 21.65%to 22.18%,and the proportion of phosphodiester was from 3.33%to 3.44%.The proportion of orthophosphates in clay soil was 89.28%?89.36%,the proportion of phosphatemonoester was 8.03%?8.11%,the proportion of phosphodiester was 0.72%?0.75%?The proportion of orthophosphate in no-till soil ranged from 88.55%to 88.67%,the proportion of phosphatemonoester was from 8.49%to 8.61%,and the proportion of phosphodiester was from 0.75%to 0.78%.(5)The results of XANES showed that the forms of phosphorus in the loam soil and clay loam soil were AlPO4,Ca(H2PO4)2 and FePO4.On the whole,for loam soil,after two years of experiment,The proportion of Al-bound phosphorus decreased,with the lowest percentage(15.1%?36.5%)from the main form of phosphorus(46.8%?70.3%).The proportion of monocalcium phosphate increased from 21.3%?35.6%to 24.9%?35.0%.Iron oxide bound phosphorus increased significantly(8.5%?24.9%to 31.7%?48.4%),and it was the main form of phosphorus from the least proportion.The proportion of Al-bound phosphorus in clay loam soil decreased,and the dominant species(60.8%?74.7%)formed the dominant proportion(23.0%?53.4%)of phosphorus.The proportion of monocalcium phosphate increased from 2.3%?6.7%to 2.7%?10.2%.Iron oxide bound phosphorus increased from 19.6%?34.0%to 40.1%-69.3%,becoming the main form of phosphorus.Under different soil texture no-tillage Changes of different forms of soil phosphorus are different,For loam soil,Plowing reduces the proportion of aluminum oxide bound phosphorus,inCTReases the proportion of calcium dihydrogen phosphate and iron oxide bound phosphorus,No-till reduced the proportion of phosphorus bound to aluminum oxide and phosphorus monobasic,increased the ratio of iron oxide to bound phosphorus.For clay loam soil,Both no-tillage and straw returning reduced the proportion of aluminum oxide bound and increased the ratio of calcium phosphate monobasic and iron oxide bound phosphorus. |
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