| As a medium for plant growth,soil not only provides physical support for plant growth,but also provides water and necessary nutrients for plant growth.Rational ploughing is the result of the combined effects of soil physical,chemical and biological properties.Rice is one of the main food crops in China,and the high yield and stable yield of rice is related to the national security.The rationality of the paddy field is closely related to the high-yield cultivation of rice.Reasonable paddy field can make the rice get sufficient nutrients and water,and can promote the growth and development of rice,so as to obtain high yield.However,in recent years,due to many unreasonable farming methods and management methods,the plough layer of the paddy field has been destroyed,resulting in shallower plough layer,increased bulk density,and loss of effective nutrients,which seriously restricts the growth and development of rice,and thus affects the increase of yield.At present,there are many studies on reasonable ploughing layers,but most of them focus on the construction techniques of rational ploughing layers,and there are few studies on the evaluation of reasonable ploughing layers in paddy fields.Therefore,the scientific and reasonable evaluation of the rationality of paddy field can provide a theoretical basis for the high-yield cultivation of rice and the construction technology of fertile paddy fields,which is of great significance.This study is based on Guizhou rice production area,Jiuzhou Town of Anshun City,Puchang Town of Suiyang County,Zunyi City,Changji Town of Sansui County,southeastern of Guizhou,and Dewo Town of Xingyi City,and Yangba Town of Ceheng County,southwest of Guizhou,for the research object,the rationality of the paddy layer of different rice yields was evaluated.Principal component analysis,correlation analysis and variable Norm values were used to screen indicators and establish a reasonable tillage index system for paddy fields.The current widely used evaluation method in soil evaluation,namely fuzzy comprehensive evaluation method and improved Nemero synthesis The exponential method and principal component analysis method are used to evaluate the rationality of the paddy field in the study area,and the results of the three evaluation methods are tested in combination with the rice yield.The appropriate evaluation method is selected to evaluate the rationality of the plow layer in other test fields.Then according to the final evaluation comprehensive index,the rationality of the test layer is graded by cluster analysis.The main results of this study are as follows:(1)There is a significant correlation between the physical properties,chemical properties and biological properties of paddy fields(p<0.05).Organic matter is a more important indicator in the ploughed soil,and it has correlation with many other indicators,such as quick-acting with plough layer.The nutrient indexes such as potassium,alkali nitrogen and total nitrogen were significantly correlated,and were significantly correlated with physical indexes such as bulk density,porosity and microaggregates,and also correlated with the enzyme activities of enzymes(invertase,phosphatase and urease).There is a significant correlation between the activity of the plough layer enzyme and the physical and chemical properties.For example,urease,invertase and phosphatase are significantly or significantly correlated with the thickness of the tillage layer,bulk density,total porosity,capillary water holding capacity and microaggregates.Nitrogen and total nitrogen are significantly correlated.Correlation between physicochemical properties of tillage layer,total nitrogen,total phosphorus and CEC were significantly correlated with tillage bulk density,total porosity,capillary porosity and capillary water holding capacity,and available potassium and available phosphorus were significantly correlated with tillage microaggregates wait.(2)Using the principal component analysis method and the calculated variable Norm value,and then screening from the original 27 indicators according to the correlation between the tillage index.Finally,the indicators of tillage layer were organic matter,available potassium,available phosphorus,invertase,CEC,EC,microaggregates(0.25-0.05mm,0.05-0.01mm)and 9 soil indicators of tillage depth.,total phosphorus,bulk density,urease,active reducing substances,phosphatase,pH,total potassium and plow bottom depth 9 soil indicators,and then based on the selected indicators to establish a reasonable paddy field index system.(3)Using fuzzy comprehensive evaluation method,Nemero index method and principal component analysis method to analyze and evaluate the rationality of paddy soil layer.From the analysis results,it can be seen that the variation range of the Nemero index method is 0.14 of the tillage layer.0.55 and plow bottom layer0.15-0.38,the change range is small;fuzzy comprehensive evaluation method is0.22-0.78 for tillage layer and 0.23-0.65 for plow bottom layer,the change range is second;principal component analysis method is tillage layer-1.39-2.27 and plow bottom layer-0.62-1.81,the largest change.Correlation analysis between the evaluation index value and rice yield showed that the rice yield showed an increasing trend with the increase of the comprehensive index value calculated by the three evaluation methods.The correlation coefficient between the comprehensive index of paddy field and plow bottom layer calculated by fuzzy comprehensive evaluation method is R~2=0.4242 and R~2=0.2274,and the correlation coefficient of Nemero index method is R~2=0.3723 and R~2=0.1719,principal component analysis.The correlation coefficient of the method is R~2=0.3093 and R~2=0.161.Therefore,according to the variation range of the evaluation index value and the correlation with the rice yield,it is better to use the fuzzy comprehensive evaluation method to evaluate the rationality of the paddy layer.(4)Using the fuzzy comprehensive evaluation method and the constructed reasonable tillage index system to evaluate the rationality of the plough layer in the test plots of Changji Town and Puchang Town.The comprehensive evaluation results of Changji Town show that the comprehensive index of paddy field tillage layer is0.31-0.64,the bottom layer of plow is 0.38-0.67,and the average comprehensive index of tillage layer and plow bottom layer is 0.35-0.65;through the rice yield and paddy field,plow The correlation index of the bottom layer and the mean of the two were analyzed.The results showed that the correlation between the three indexes and the rice yield was significant.The correlation expressions were y=1.8449X+1.0576,R~2=0.9486,y=1.7716X+1.1802.,R~2=0.9015 and y=1.8772X+8.3175,R~2=0.9394.The comprehensive evaluation results of the experimental field in Puchang Town show that the comprehensive index of the paddy field is 0.25-0.53,the bottom layer of the plough is 0.21-0.55,and the average comprehensive index of the tillage layer and the plough bottom layer is 0.23-0.54.Through the rice yield and paddy farming layer,The correlation index of the bottom layer of the plow and the mean of the two were analyzed.The results showed that the correlation between the three indexes and the rice yield was significant.The correlation expressions were y=1.6692X+1.1286,R2=0.9413,y=1.4170X+1.8145,R~2=0.8995 and y=1.6860X+9.5736,R~2=0.9626.(5)Using the cluster analysis method to classify the rationality of the cultivated layer in the experimental field,from the results of the clustering analysis of the average comprehensive index of the paddy field and the plow bottom layer,for Changji Town,the rationality of the test field can be divided.It is 4 levels.There is one sampling point of the first-level plough layer,the comprehensive index is 0.54,the rationality of the paddy field is high;the sampling points of the secondary plough layer are 4,the comprehensive index is 0.44,0.42,0.41 and 0.48,and the rationality of the plough layer is medium and high;There are 5 sampling points in the three-level ploughing layer.The comprehensive index varies from 0.32 to 0.38,and the rationality of the ploughing layer is poor.The sampling point of the grading layer is four,and the comprehensive index is 0.23.The rationality of the ploughing layer is poor.For Puchang Town,the test field can also be divided into 4 grades.The first-level test field with high rationality is sample 7,the comprehensive index is0.32-0.38,and the samples with higher rationality are 1,4,5 and 6.The composite index is 0.45,0.49,0.51 and 0.46.The third grade with poor rationality is sample 2,the composite index is 0.40,and the poorest rationality of the tillage layer is sample No.3,and the comprehensive index is 0.35. |
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