| This study used in shaanxi province from 2017 to 2018 the cultivated land quality evaluation and hierarchy project soil survey data,using statistical and kriging interpolation method to study the topsoil in shaanxi main nutrients of SOM,TN,AP,AK and SAK content present situation and the contents and abundance of trace elements available iron,available manganese,available copper,available zinc,available boron and available molybdenum,which provide theoretical basis for high yield and accurate fertilization of cultivated soil crops in shaanxi province.The main results are as follows:1.At present,the average conten of OM,TN,AP,AK and SAK in the whole province is 15.4g/kg,0.9 g/kg,20.8mg/kg,171.9 mg/kg and 1051.6mg/kg,respectively.The largest proportion of organic matter is 40.8% in the range of 10-18 g/kg.The proportion of available phosphorus reached about 70% in the range of medium and below,the proportion of available potassium was mainly distributed in the range of 80-150mg/kg,accounting for 36.5%,and the proportion of available potassium was mainly 500-1000mg/kg,accounting for 40.8%.Compared with the soil survey of the province 40 years ago,the nutrient contents of OM,TN,AP and AK increased by 4.7g/kg(43.9%),0.17 g/kg(23.3%),14.1 mg/kg(210.4%)and 32.9 mg/kg(23.7%),respectively.The spatial distribution shows that the soil OM、TN are low from the north and high from the south-central,that is,southern Shaanxi > Guanzhong > Weibei >northern Shaanxi;available phosphorus is Guanzhong > southern Shaanxi > Weibei >northern Shaanxi;Soil AK and SAK generally showed a trend of high,south and low in the middle,that is,Guanzhong >Weibei >South Shaanxi>;Northern Shaanxi.2.In the past 40 years,the major trace elements in shaanxi soil have been significantly improved.Currently,the average contents of available iron,available manganese,available copper,available zinc,available boron and available molybdenum in shaanxi are respectively 25.5 mg/kg,13.4 mg/kg,1.3 mg/kg,0.5 mg/kg and 0.15 mg/kg.Soil available iron,available manganese,available copper,available zinc,and available boron increased by 16.7 mg/kg(215.3%),5.9 mg/kg(76.5%),0.334 mg/kg(35.4%),0.59 mg/kg(96.7%),and 0.234 mg/kg(87.9%),respectively,compared with the 1980 s.At present,in addition to the deficiency ratio of available zinc and available boron in the soil of the province,other trace elements are in an appropriate and abundant state on the whole,among which the effective copper content accounts for the largest proportion in the richness grade.At present,the soil trace elements in the province show a trend of increasing from south to north.3.Soil nutrients of wheat in Shaanxi Province have been greatly improved in the past 10 years,the average soil OM、TN、AP and AK content of wheat land are 15.5 g/kg、0.9g/kg、19.2mg/kg、218.6mg/kg,compared with 2005-2009,the SOM、AP、AK content has increased 1.2%)and 70.2% respectively The main distribution of soil organic matter in wheat field in the whole province is 10-20 g/kg,the proportion is 82.8%;the total nitrogen distribution in the whole province is 0.8-1.2 g/kg,the proportion is 53.9%;the proportion of AP in wheat field is the largest in 10-20 mg/kg,37.2%;the proportion of available potassium in >200mg/kg,is the largest 48.5%.In the three wheat planting areas,the soil nutrient content in southern Shaanxi was higher than that in the other two areas.4.At present,the average contents of OM,TN,AP and AK in maize fields in the province are 13.4g /kg,0.8g /kg,18.5mg/kg and 163.4mg/kg,respectively.Compared with that in 2005-2009,the soil organic matter and available phosphorus decreased by 1.8g/kg(11.8%),1.2mg /kg(6%),and available potassium increased by 10.5mg/kg(3.8%).The main organic matter subdivision in maize soil was 10-20 g/kg,the proportion was 46.0%,and the total nitrogen was in the proportion of 0.5 g/kg was the largest(30.6%),the proportion of available phosphorus was the largest(23.1%)at 5-15 mg/kg,and the proportion of available potassium was at >200 mg/kg is a large proportion.5.At present,the average contents of OM,TN,AP and AK in wheat and maize rotation fields in the province are 18.6g/kg,1.1 g/kg,29.0mg/kg and 259.3mg/kg,respectively.At 200 mg/kg,the soil nutrient content of wheat and corn rotation plots was significantly higher than that of wheat and corn monoculture.6.The content of soil OM、TN、AP and AK in apple land in the province is 13.0 g/kg、0.8g/kg、26.4mg/kg、238.3mg/kg,compared with 2005-2009,the content of organic matter,available phosphorus and available potassium increased 0.4 g/kg(3.0%)、8.4mg/kg(46.7%)、86.7mg/kg(57.2%).respectively The content of organic matter in apple soil in the whole province is mainly distributed in 10-15 g/kg,accounting for 35.5%,the total nitrogen content is mainly distributed in 0.5-0.8 g/kg,accounting for 38.9%,the available phosphorus content is the largest in <10mg/kg,and the available potassium content is mainly distributed at higher level(>250mg/kg),accounting for 37.9%.7.Soil fertility was evaluated by principal component analysis method for soil nutrients in Shaanxi Province.Three principal components were extracted by analysis and found that the three principal components could express 80% information of the original data.According to the final comprehensive score,the results showed that the soil fertility of four agro-ecological zones in the province was Guanzhong >southern Shaanxi> Weibei >northern Shaanxi. |
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