| In China,scientific management of soil nutrients and rational use of fertilizers are major issues for agricultural developmen.However,it is unclear whether the use of different mapping scale databases to assess the accuracy of soil nutrient estimation in the county,which may lead to the development of management measures that do not meet local conditions.So,in this paper,taking Changting County from Fujian Province as the study area.Soil nutrient(density and storage of organic carbon,total N,total P and total K,and available N,available P,available K)content of cultivated land(0-15 cm)at 1:10,000,1:50,000 and 1:250,000 mapping scale databases was estimated.Compare with the estimated result of 1:10,000 mapping scale database which was the most detailed mapping scale database at county scale,the influence of three mapping scale databases on the estimation accuracy of soil nutrient was evaluated,aimming to provide a theoretical basis for selecting the appropriate soil nutrient estimation scale for farmland soil.The main research conclusions were as follows:(1)At the 1:10,000 map scale,all of the cultivated land(0-15 cm)soil nutrients in Changting County were medium variation intensity.The order of coefficient of variation of soil nutrients was total kalium density(40.05%)>total phosphorus density(32.77%)>available kalium(19.72%)>total nitrogen density(15.81%)>available phosphorus(14.07%)>available nitrogen(13.55%)>organic carbon density(12.96%).With the decrease of the mapping scale,the coefficient of variation of soil nutrient(except available nutrient)decreased with the decrease of mapping scale,and the other nutrient was still moderate variation except that the organic carbon density decreased to weak variability.In addition,the cultivated area of soil nutrient in different interval was different under different mapping scales,and the difference increases with the reduction of the mapping scale.It was found that the mapping scale had a great influence on the spatial distribution of soil nutrients in Changting County.(2)Compare with the estimated result of 1:10,000 mapping scale database which was the most detailed mapping scale database,the relative deviation of the average value of soil nutrients in Changting County increased with the decrease of the mapping scale(except available nitrogen and total nitrogen density),which indicates that the error of soil nutrient estimating at 1:250,000 mapping scale was larger than 1:50,000 mapping scale.And the effect of mapping scale on organic carbon storage,total nitrogen storage,total phosphorus storage and total kalium storage which were affected by soil nutrient density and plaque area was greater than that of other nutrients.It can be seen that it was necessary to use a more detailed large-scale farmland soil database to estimate soil nutrient at the county level in the future.(3)At the 1:10,000 mapping scale,the soil organic carbon density and storage in Changting County were 2.93±0.38 kg·m-2 and 860,904.55 t.The organic carbon density and storage were 2.95±0.36 kg·m-2 and 831,120.52 t,2.79±0.24 kg·m-2 and 552,562.34 t,respectively,at the 1:50,000 and 1:250 000 mapping scale.From different types of cultivated land use,compared with 1:10,000 mapping scale,the relative deviation of organic carbon density and storage of irrigated land which was the most affected by mapping scale at the 1:50,000 and 1:250 000 mapping scale was 2.43%～4.89%and 0.97%～44.17%respectively.After irrigated land was paddy field which was the largest of all land uses,the relative deviation of organic carbon density and storage of paddy field was 0.60%～4.71%and 3.02%～36.06%respectively.The relative deviation of organic carbon density and storage of dry land which was the least affected by mapping scale was 0.30%-4.07%and 9.79%-32.08%respectively.From different soil types,the relative deviation of organic carbon density and storage of yellow soil which was the most affected by mapping scale was 3.94%～5.70%and 33.62%～90.71%respectively;the relative deviation of organic carbon density and storage of purple soil which was the least affected by mapping scale was 0.15%～2.70%and 5.89%～8.74%respectively.(4)At the 1:10,000 mapping scale,the soil total nitrogen density and storage in Changting County were 0.37±0.06 kg·m-2 and 107,514.99 t.The total nitrogen density and storage were 0.37±0.06 kg·m-2 and 103,538.48 t,0.37±0.04 kg·m-2 and 72,479.38 t,respectively,at the 1:50,000 and 1:250,000 mapping scale.From different types of cultivated land use,compared with 1:10,000 mapping scale,the relative deviation of total nitrogen density and storage of irrigated land which was the most affected by mapping scale at the 1:50,000 and 1:250,000 mapping scale was 0.63%～1.83%and 0.36%～40.93%respectively.The relative deviation of total nitrogen density of paddy fields which was the least affected by mapping scale was 0.18%～0.38%,and the relative deviation of total nitrogen storage of dry land which was the least affected by mapping scale was 10.33%～29.68%.From different soil types,the relative deviation of total nitrogen density and storage of yellow soil which was the most affected by mapping scale was 3.88%～6.29%and 34.03%～76.35%respectively.The relative deviation of total nitrogen density paddy soil which was the least affected by mapping scale was 0.13%～0.31%,and the relative deviation of total nitrogen storage of purple soil which was the least affected by mapping scale was 8.74%～12.87%.(5)At the 1:10,000 mapping scale,the soil total phosphorus density and storage in Changting County were 0.17±0.06 kg·m-2 and 49,754.15 t.The total phosphorus density and storage were 0.17±0.05 kg·m-2 and 47392.99 t,0.19±0.05 kg·m-2 and 37524.58 t,respectively,at the 1:50,000 and 1:250,000 mapping scale.From different types of cultivated land use,compared with 1:10,000 mapping scale,the relative deviation of total phosphorus density and storage of irrigated land which was the most affected by mapping scale at the 1:50,000 and 1:250,000 mapping scale was 0.65%～26.81%and 25.71%～41.69%respectively.The relative deviation of total phosphorus density of paddy fields which was the least affected by mapping scale was 0.61%～11.92%,and the relative deviation of total phosphorus storage of dry land which was the least affected by mapping scale was 11.83%～19.65%.From different soil types,the relative deviation of total phosphorus density of red soil which was the most affected by mapping scale was 3.42%～12.23%,and the relative deviation of ttotal phosphorus storage of yellow soil which was the most affected by mapping scale was 37.09%～84.72%.The relative deviation of total phosphorus density and storage of purple soil which was the least affected by mapping scale was 1.27%～6.75%and 9.76%～16.17%respectively.(6)At the 1:10,000 mapping scale,the soil total kalium density and storage in Changting County were 1.71±0.69 kg·m-2 and 503,760.33 t.The total kalium density and storage were 1.70±0.68 kg·m-2 and 480208.03 t,2.10±0.57 kg·m-2 and 414,715.55 t,respectively,at the 1:50,000 and 1:250,000 mapping scale.From different types of cultivated land use,compared with 1:10,000 mapping scale,the relative deviation of total kalium density of paddy fields which was the most affected by mapping scale at the 1:50,000 and 1:250,000 mapping scale was 0.86%～22.33%,and the relative deviation of total kalium storage of paddy fields which was the most affected by mapping scale was 12,88%～33.67%.The relative deviation of total kalium density of irrigated land which was the least affected by mapping scale was 13.01%～14.17%,and the relative deviation of total kalium storage of dry land which was the least affected by mapping scale was 8.01%～13.73%.From different soil types,the relative deviation of total kalium density and storage of yellow soil which was the most affected by mapping scale was 28.46%～67.95%and 18.24%～135.68%respectively.The relative deviation of total kalium density of fluvo-aquic soil which was the least affected by mapping scale was 1.60%～2.25%,and the relative deviation of total kalium storage of paddy soil which was the least affected by mapping scale was 5.00%^18.32%.(7)At the 1:10,000 mapping scale,the soil available nutrient(available nitrogen,available phosphorus and available kaliam)in Changting County were 135.05±18.30 mg·kg-1,42.89±6.04 mg·kg-1 and 54.76±10.80 mg·kg-1 respectively.The total kalium density were 135.78±17.39 mg·kg-1,42.86±6.65 mg·kg-1 and 54.94±10.22 mg·kg-1 respectively at the 1:50,000 mapping scale.The total kalium density were 134.32±20.39 mg·kg-1,43.64±12.30 mg-kg-1 and 82.53±24.21 mg·kg-1 respectively at the 1:250,000 mapping scale.From different types of cultivated land use,compared with 1:10,000 mapping scale,the relative deviation of available nitrogen,available phosphorus of irrigated land which was the most affected by mapping scale at the 1:50,000 and 1:250,000 mapping scale were 0.61%-9.67%and 4.00%～5.59%respectively.And the relative deviation of available kalium of paddy fields which was the most affected by mapping scale was 0.40%～51.33%.The relative deviation of available nitrogen of paddy fields which was the least affected by mapping scale was 0.49%～0.55%.And the relative deviation of available phosphorus of dry land which was the least affected by mapping scale was 0.75%～1.37%.And the relative deviation of available kalium of paddy field which was the least affected by mapping scale was 0.49%～23.54%.From different soil types,the relative deviation of available nitrogen,available phosphorus of yellow soil which was the most affected by mapping scale were 5.43%～8.34%and 6.18%～28.81%respectively.And the relative deviation of available kalium of purple soil which was the most affected by mapping scale was 0.08%～54.60%.The relative deviation of available nitrogen of paddy soil which was the least affected by mapping scale was 0.48%～0.55%.And the relative deviation of available phosphorus of purple soil which was the least affected by mapping scale was 0.03%～0.85%.And the relative deviation of available kalium of fluvo-aquic soil which was the least affected by mapping scale was1.18%～35.75%. |
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