TEMPORAL AND SPATIAL VARIABILITY IN TERMS OF PHYSICAL AND CHEMICAL ATTRIBUTES OF GREENHOUSE SOILS IN NINGXIA, CHINA

摘要

Greenhouse vegetable production is popular for extending the cropping season in China. Faulty cultivation, fertilization, and tillage practice lead to a decline in soil quality. Ningxia is a major base that supplies pollution-free vegetables to the north (in the winter) and the south (in the summer). We collected greenhouse soils that covered major vegetable production areas with different cultivation years to evaluate the temporal and spatial variability of the soil physical characters, pH, and EC in Ningxia. The soil solid volume fraction, bulk density, pH, EC, Na+content and Cl- content were significantly affected by the sampling sites (SS) and the interaction of cultivation years and sampling sites (CYxSS) in both soil layers. All the tested soils were alkaline. The soil EC was 0.18-1.16mS/cm in 0-30cm; showing an increase with the cultivation years, the pH and EC decreased and increased, respectively. Regarding the EC, specific gravity, and pH values were found to be at a higher level in the Yellow River Irrigation (YRI) region when compared to the other two regions. In general, soil bulk density, specific gravity, solid volume fraction, and pH values were lower in surface soil layer (0-30cm) than in the 30-60cm soil layer, while total porosity, EC, Na+ and Cl" were higher in surface soils. 99.0% of the soil5s plough layer thickness was higher than 20cm; out of which 88 % was 20-50cm depth. Overall, cultivation, fertilization, and tillage practice significantly affected the soil physical properties and caused the nutrients accumulation in the surface soil. Pengyang, Yuanzhou, Qingtongxia and Yanchi were significantly different from the other sampling sites.