Calcium Content Of Sichuan Basic And Crop Reponse To Calcium Fertilizer

Sichuan basin is the main agricultural area in Sichuan where paddy soils prevail. Owing to its high population density, very limited farmland area per capita, high cultivation index and serious water and soil losses, soil nutrient depletion by crop removal and leaching is a serious problem. In the past, study in plant nutrition was predominantly focused on macronutrients (N, P, K) and micronutrients, very little attention, if any, was drawn to calcium (Ca). Therefore, this study was conducted to better understand the status of calcium in soil and its impact on crops in Sichuan and make more precise fertilizer recommendations for crop production and sustainable agriculture.It is found that available calcium content ranged from 500mg/kg to 6212mg/kg and averaged 2956mg/kg in Sichuan basin. There are only 3.9% of soil samples deficient in calcium, 16.7% above the critical value, and the rest in adequate and sufficient ranges. Results reveal that soil available calcium was affected by soil pH, parent materials, land use patterns, fertilization, etc.The contents of total soil Ca and CaCO₃ were closely related to parent materials. The results indicate that the contents of total Ca were in an order of calcareous purple parent material > alluvial brown-grey material > alluvial grey material > neutral purple parent material > acidic purple parent material, and the contents of available Ca were in an order of carbonate calcareous purple parent material > neutral purple parent material > alluvial grey material > alluvial brown-grey material > acidic purple parent material.Application of Ca could enhance yields of Chinese cabbage and turnip, but overdosed Ca would decrease its yields. The critical value of soil Ca was affected by soil type, crop variety, calcium fertilizer variety and planting season. For example, the critical value of soil Ca was 920 mg/kg as CaCl₂ was applied to the winter Chinese cabbage in the brown-grey alluvial paddy soil and became 950 mg/kg in the grey alluvial paddy soil. The soil Ca critical value was tested for the summer Chinese cabbage as 700 mg/kg in the brown-grey alluvial paddy soil and 760 mg/kg in the grey alluvial paddy soil.