| Abundance of soil nutritional contents in controlled environmental agriculture is economically associated with the crop yield and quality. In this study, we conducted a series of experimental analysis of soil contents in controlled environmental agricultural greenhouses in Zichang, Yan'an, Shaanxi. Factorial design involving greenhouse initiate time and sampling depth (0-10, 10-20, 20-40 cm) for soil samples analysis was used, and that the open field soil samples were used as control. The soil nutritional contents were analyzed based on farm locations, years of farming, geological depth, and the results concluded:(1) In controlled environmental agricultural greenhouses, total nitrogen and soluble N content were positively correlated with years of farming whereas negatively correlated with soil sampling depth, with sharp drop in 20-40 cm depth. Years of farming with highly N fertilizer input increased the enrichment of total N.(2) Significant higher NON and ammonium N was found in controlled environmental agricultural greenhouses than open field farms, and concentration of both were positively correlated with years of farming whereas were negatively correlated with the sampling depth. Concentration of NON was found significantly higher than ammonium N in the same sampling site.(3) Concentration of total P and Olsen-P were found significantly higher than those in the open field farms. Due to shallow rooted crops were largely planted in controlled environmental agricultural greenhouses, fertilization was largely applied in 0-20 cm soil depth so total P and Olsen-P were found significantly higher in 0-20 cm soil depth than those in 20-40 cm. Concentration of P were found positively correlated with the years of farming in the past 11 years, whereas negatively correlated with the soil depth.(4) Concentration of fast-acting potassium was accumulated in the soil along with years of farming whereas the concentration was decreasing along with the soil depth. |
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