Status And Management Measures Of Soil Fertilities Of Cultivated Land In Zhejiang Province, China

To reveal the status and evolution of the cultivated soil in Zhejiang provience during the last 3 cecades, 35571 surface soil samples from 83 counties(cites and districts) are studied and the five nutrient index of soil OM(organic matter), pH, TN(total nitrogen), AP(available phosphorus) and AK(available potassium) are statistically analysed. The results show:1) The average content of soil OM of cultivated land (28.85 g·kg^-1) is lower than the weighted average of OM of paddy soils and Fluvo-aquic soils (29.97 g·kg^-1) of the Second National Soil Survey(SNSS). There is a trend that the accumulation of soil organic increases basically as the soil texture becomes heavier with the hydrographic net plain and the high hill area most and the littoral area least. The decline in soil OM is related to the expansion of dry land cropping, the decrease of green manuring, the reduction in dose of organic fertilizer, and so on.2) The soil pH ranging from 3.30 to 9.00 of the cultivated land of Zhejiang Province, most of which is acidic. Compared with SNSS, the acidification of soil is quite obvious, which is manifested by the facts that the percentage of the soil with pH between 4.5 and 5.5 significantly increases and that except that the soil of the coastal plain is mainly alkali, most of the soil of other areas is acidic with that of high hill area strongest and that of hydrographic net plain relatively weaker. The soil acidification has something to do with the long-term application of high dose of fertilizer, environmental pollution, dry land cropping in the paddy field, and so on.3) The average soil total N and available K decreased, and the average soil available P increased, as compared with SNSS. The cultivated soil samples with low levels of soil total N (<1 g·kg^-1), available P (<10 mg·kg^-1) and K (<80 mg·kg^-1) accounted for 13.90%, 44.80% and 48.17% of total soil samples, respectively. The proportion of soil samples with deficiency of one of N, P, and K was as high as 73.79%. There were imbalances among soil N, P and K. Great variations in concentrations of soil total N, available P and K were found. The variation coefficients of soil total N, available P and K decreased in the order of available P (192%) > available K (71%) > total N (39%). Soil total N was correlated positively with OM, and decreased in the order of clayey soil > clay-loamy soil > loamy soil >sandy soil, and in the order of hydrographic net plain > river plain > hilly area > coastal plain. Soil available P increased with decreasing pH, and decreased in the order of sandy soil > loamy soil > clay loamy soil, clayey soil, and in the order of high hilly area, coastal plain > river plain, low hilly area > hydrographic net plain. Soil available K was related to pH, texture, and geomorphic type, and decreased with decreasing pH. The available K decreased in the order of clayey soil > clay loamy soil > loamy soil > sandy soil, and in the order of coastal plain > hydrographic net plain > river plain > low hilly area > high hilly area.4) The rate of samples with one of the three nutrients, viz. TN, AP and AK, with low level is 73.79%, which illustrates the noticeable imbalance of soil nitrogen, phosphorus and potassium.5) In order to solve above problems, more attention should be paid to the combination of land utilization and land maintenance and the integration of fertility decline prevention and soil treatment during the quality management of the cultivated land. Other measures include enhancing the improvement and management of the acid soil, introducing new approach to the soil OM promotion of the cultivated land, the application of formula fertilizer, the remediation of soil continuous cropping obstacles in greenhouse, and so on.