| Nutrient accumulations in soil under the vegetable cultivation in solar greenhouses have been investigated in Yangling,Shaanxi.It was found that the contents of organic matter in 020cm layer,available phosphorus and potassium in 040cm layer,and NO-3-N in 0~200 cm of soil profiles were significantly increased.The contents of NH+4-N in soil profiles remained stable during the growth of vegetable crops;however,the contents of NO-3-N in 0~200 cm soil profiles were significantly decreased due to the uptake of NO3——N by vegetables.After the harvesting,the residual NO-3-N in 0~200 cm soil profiles was in the range of 7071 161 kgN/hm2,with an average of 954 kgN/hm2,being notably higher than that in the crop field.The soil electric conductivities of greenhouses were higher than that of crop field,especially in the surface layer.There were close relationships between the soil electric conductivities and the contents of NO-3-N,available phosphorus and potassium,and the correlation coefficient between NO-3-N contents and soil electric conductivities was the highest,indicating that the excessive application of nitrogen fertilizer was the main reason to increase soil electric conductivities in greenhouses. |