Study On Variability Of Some Properties Of Sunlight Greenhouses Soils In Ningxia Province

Soil physical, chemical and some biological properties sampled from different layers (0 to 60cm), different types and different planting years (1 to 9 years) of sunlight greenhouses in irrigation and dryland regions in Ningxia province were measured. Soil fertility and its changing trends were analyzed by means of principal component and gray theory analysis. The main results as follow:1 Variability of soil properties in different soil types and different layers of sunlight greenhouses in NingxiaThere were significant differences at 1% or 5% level of soil bulk density, soil porosity, total salt, pH, content of organic matter, nitrogen, phosphorus, potassium, urease and catalase activities, and quantity of wireworm between different soil types and different depths. Soil bulk density of semiarid and irrigating silt soil was higher than that of Heilu soil from 0 to 60cm. The order of soil porosity, organic matter, total N, nitrate N, total P, available P, readily available K, slow-release K, wireworm from 0 to 60cm in three types soil were: Heilu soil > irrigating silt soil > semiarid; and for total salt was: irrigating silt soil > semiarid > Heilu soil; and pH was: Heilu soil, semiarid > irrigating silt soil; but for alkali-hydrolyzable N, urease activities, catalse activities were: irrigating silt soil equal Heilu soil> semiarid. The order of bacteria and fungi from 0 to 15cm in three soil types were: irrigating silt soil> semiarid > Heilu soil; and actinomycetes was: irrigating silt soil > Heilu soil > semiarid.2 Variability of soil properties in different planting years and different layers of sunlight greenhouses in NingxiaThe changing trends of soil properties (soil bulk density, soil porosity, total salt, pH, organic matter, nitrogen, phosphorus, potassium, urease activities, catalase activities, microorganism and wireworm) along with the planting years were assumed parabola as a whole. The highest soil fertility indexes increased with cultivation years can be modeled and calculated by quadratic equation. In this way, the optimized planting time for increasing soil fertility were focused on 6.5 to 9 years in irrigation region and 5.5 to 8 years in dryland region. There were significant differences at 1% or 5% level of pH, soil organic matter, nitrogen, phosphorus, potassium, catalase activities between different cropping years and different soil depths in irrigation region and dryland region, but no differences of urease activities and wireworm in different planting years in the two regions.The soil physical, chemical and some biological properties(except soil bulk density and pH) of 0-15cm were higher than that of 15-30cm and 30-60cm in different planting years and two regions. The order of annually increased ratio from one planting year to nine planting years in irrigation region was: nitrate N>available P> slow-release K>readily available K>urease activities>alkali-hydrolyzable N >total salt>total P>total N>organic matter>wireworm>catalse activities>soil porosity. But in dryland region the order was: total salt > available P> nitrate N> total P> urease activities > slow-release K> readily available K> wireworm > organic matter > alkali-hydrolyzable N> catalse activities>total N>soil porosity. The least annual increasing rate observed was soil porosity in both irrigation region and dryland region in Ningxia.3 The integrated evaluation of soil fertilityPrincipal component and gray theory analysis showed that soil fertility sampled form twenty-four sunlight greenhouses could plot four ranks. The first rank fertility was the soils rotated and cropped three years in greenhouses; the third grade was the soils continuous cultivated many years in greenhouses; the lowest grade was the soils planted one year in greenhouses. But there were no obvious difference between the first and the second grade: The first measure to increase soil fertility ingreenhouse is enhancing soil potassium level. The second way is integrated increasing organic matter, nitrogen, and phosphorus. Spade husbandry and correct management are well selections for soil fertility improving in sunlight greenhouses. 4 The relationships between soil fertility factorsSignificantly positive correlation between organic matter contents and total N, alkali-hydrolyzable N, nitrate N, total P, available P, readily available K, slow-release K contents were observed. Significantly negative correlation existed between pH and total salt.Significantly positive correlation between urease activity and total N, nitrate N were observed. Notable positive correlation between urease activity and organic matter, alkali-hydrolyzable N, total P, slow-release K contents were achieved. The relativities between catalase activities and organic matter, total N, alkali-hydrolyzable N, nitrate N, total P, available P, readily available K achieved significantly positive correlation.