| Climate,topography landform,parent material,time,cultivation and fertilization were the main factors affecting the soil-forming process.In the provincial scope,topography,landform and parent material factors were the main factors affecting soil mineral nutrient content,while cultivation and fertilization were main factors affecting SOM and Available-P evolution.It was of great significance to study the soil fertility evolution,especially the composition and evolution characteristics of soil potassium storage,for the sustainable utilization of soil nutrient resources.This study adopted the research method of combining the macro and micro by large area to determine the nutrient condition of different soil parent material development and compared with the second soil census results,systematically studied the soil fertility evolution and its relationship with soil material,rice planting time and fertilization in paddy area of the coastal plain,eastern Hebei,so as to provide a basis for scientific fertilization under the condition of continuous high yield of rice.The main results were as follows:(1)Soil nutrient and salinity changes in the paddy plains of Coastal Plain in Eastern Hebei: pH,SOM,total-N,available-P,total-K,slowly available-K,rapidly available-K,available-Zn were 7.46,17.02g/kg,1.09g/kg,18.38mg/kg,22.49g/kg,1743.3mg/kg,234.60mg/kg,1.93 mg/kg,respectively.Compared with the results of the second soil survey,the contents of SOM,total-N,available-P increased significantly,increasing by 2.13g/kg,0.14g/kg,13.20mg/kg,respectively.There was no significant change in soil total-K and rapidly available-K.The soil salinity content was 0.141%,which was 0.12 percentage points lower than that of the second soil survey.(2)The relationship between soil nutrients: Total-N,slowly available-K were significantly positively correlated with SOM;The relationship between soil available-P and SOM was not significant.The relationship between soil nutrients and soil salinity: available-P and salinity were significantly negatively correlated;slowly available-K,rapidly available-K,soluble-Ca and soluble-Mg were significantly logarithmic correlated with soil salinity.(3)The influence of soil parent material on soil fertility: Soil parent material mainly affected the rise and fall of various forms of potassium and soil salinity,while planting time mainly affected the change of SOM,available-P and soil salinity.Among them,with the increase of the distance from the coastline,the soil parent material was marine sediment,lagoon sediment,Luanhe river delta alluvium successively.Soil available-P was gradually increasing trend,SOM,soil salinity and various forms of potassium was gradually decreasing trend.That was,the SOM and available-P content developed by marine sediments were 17.98g/kg and 17.72mg/kg,respectively.The contents of SOM and available-P in lagoon sediments were 19.00g/kg and 18.28mg/kg,respectively.The content of soil organic matter and available phosphorus in Luanhe river delta alluvium were 14.09g/kg and 21.58mg/kg,respectively.Potassium status of soil forms: Total-K,slowly available-K and available-K contents in the soil developed by marine sediments were 23.46g/kg,1671.3mg/kg and 254.15mg/kg,respectively.Lagoon sediments were 23.14g/kg,1605.1mg/kg and 251.44mg/kg,respectively.Luanhe river delta alluvium deposits were 18.74g/kg,1085.9mg/kg and 173.22mg/kg,respectively.There was no significant difference in nutrient content between marine sediments and lagoon sediments.(4)The influence of rice planting time on soil fertility: With the growth of rice planting time,SOM,total-N and available-P presented an increasing trend,while soil salinity presented a gradually decreasing trend.There were no significant change in rapidly available-K and total-K,while slowly available-K presented a decreasing trend.The average annual increase of SOM,total-N and available-P was 0.07g/kg,0.01g/kg and 0.19mg/kg,respectively.The average annual decrease of slowly available-K was 20.19mg/kg,and the average l decrease of soil salinity was 0.03 percentage points per ten years.(5)Potassium potential of soil potassium pool: The potassium supply capacity of soils developed from Marine sediments and lagoon sediments was higher than that from alluvial sediments.The ratioes of slowly available-K and rapidly available-K in the soil potassium pool in marine sediments and lagoon sediments were higher than those in Luanhe river delta alluvium,and the difference between the two parent materials was not significant.At the same time,the relationship parameters of potassium capacity and potassium intensity(Q/I)of three parent soils indicated that the potassium activity ratio,active potassium,non-specific adsorption potassium and specific adsorption potassium of three parent soils were marine sediments > lagoon sediments > Luanhe river delta alluvium,and the soil potassium buffer capacity was represented by lagoon sediments > marine sediments > Luanhe river delta alluvium.The correlation between soil potassium Q/I parameters and soil chemical properties indicated that the soil's ability to supply potassium was affected by soil chemistry.In summary,from 1982 to 2018,different mother materials' soil fertility in paddy area of the coastal plain,eastern Hebei,evolved into: SOM,total-N and available-P increased to different degrees;The nutrient content showed an increasing trend with the growing time of rice.There was no significant change in soil available-K,but the slowly available-K was decreasing.Soil parent material was the main factor affecting the content of SOM,available-P,Various forms of potassium and soil salinity in paddy area of the coastal plain,eastern Hebei.The apparent balance of nitrogen,phosphorus and potassium in soil showed that soil nitrogen and phosphorus were in the accumulation state,while soil potassium was in the consumption state.The potassium supply potential of marine sediment and lagoon sediment were significantly higher than that of Luanhe river delta alluvium. |
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