Investigation and analysis on characteristics and grading of pH value and nutrients of paddy soil in Wenzhou City
Mastering the soil nutrient status of cultivated land is an important part of ensuring food production and the construction of cultivated land quality.This study collected 6 477 paddy soil samples from the topsoil layer in Wenzhou City from 2021 to 2022,analyzed soil pH value,organic matter,hydrolyzable nitrogen,available phosphorus,and available potassium content,and evaluated the soil nutrient classification based on the grading standards of the Second National Soil Census,providing a scientific basis for reasonable fertilizer application and cultivated land quality management in paddy fields.The results showed that the average soil pH value of paddy fields in Wenzhou City was 5.61,with 48.43％of the soil being acidic(pH 4.5-5.5),showing a significant acidification trend compared with the Second National Soil Census.The average contents of soil organic matter,hydrolyzable nitrogen,available phosphorus,and available potassium were 33.30 g·kg-1,123.49 mg·kg-1,67.93 mg·kg-1,and 162.36 mg·kg-1,respectively.Overall,the soil organic matter and hydrolyzable nitrogen were primarily in the very rich to intermediate levels;the proportions of the sum of the very rich to rich levels for available phosphorus and available potassium were 51.58％and 38.11％,respectively.However,there was still a significant proportion of soil with phosphorus and potassium deficiencies,with the combined proportion of the sum of lacking to lacking-extremely being 32.85％and 40.32％.Compared with the Second National Soil Census,the average content of organic matter in Wenzhou's paddy fields remained stable,and the contents of available phosphorus and available potassium significantly increased,with the average increasing by 430％and 68.25％,respectively.There were obvious differences in soil pH value,organic matter,hydrolyzable nitrogen,available phosphorus,available potassium content,and levels among different administrative regions.The analysis showed that the main obstacles to the fertility of paddy fields in Wenzhou City were soil acidification,coexistence of soil phosphorus enrichment and deficiency,and obvious soil potassium deficiency.Therefore,the application of fertilizer in paddy fields should achieve reduced nitrogen application and prevent soil acidification;balanced fertilization should be carried out according to the regional distribution of nutrients to maintain soil nutrient balance.
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