Accumulation of Soil Soluble Salt in Vegetable Greenhouses Under Heavy Application of Fertilizers

摘要

Soil salt accumulation has been regarded as a key factor that limits vegetable production in greenhouses in China. The changes in soil salt ions, i.e., Ca2+, Mg2+, K+, Na+, HCO3?; Cl?, SO42?, and NO3?, and soil electrical conductivity (EC) in vegetable greenhouses were examined under heavy application of both chemical and organic fertilizers in Shenyang suburb, Liaoning province of China. Soil samples were collected at the depths of 0-10 cm, 10-20 cm, and 20-30 cm, respectively, form 1-, 4-, and 10-year greenhouses and their adjacent open vegetable field in October 2004. Both the soil total salt and EC were significantly higher in greenhouse than in open field (p < 0.01), and they were increased with the increasing age of greenhouses. Average soluble salt concentration in 1-, 4-, and 10-year greenhouses at the depth of 30 cm was 2.09, 2.31, and 3.69 times as much as in open field, respectively, and it was 77% and 60% higher in 10-year greenhouse than in 1- and 4-year greenhouses, respectively. Soil salt was positively correlated with soil organic carbon (p < 0.01), but negatively with soil pH (p < 0.01). In the 10-year greenhouse, the examined soil K+ and NO3- were the dominant cation and anion, respectively. The accumulation of soil salt in the surface soil layer of greenhouses may be due to (a) the heavy applications of both chemical fertilizer and organic manure that exceed crop requirements, and (b) the upward movement of soil ions with water evapotranspiration. The accumulation of soil NO3- and K+ in greenhouse is regarded as the results of heavy N and K fertilizer applications, while those of the other ions the movement of water under the greenhouse conditions. Application of chicken manure has the potential to prolong the process of salinization in soils of vegetable greenhouse, according to the results of this study.