Effect Of Potassium Chloride On Yield And Quality Of Watermelon And Soil Chloride Content

The soil potassium deficiency is becoming more severe with the development of the intensive agriculture in Ningxia Hui Autonomous region. Watermelon production has been a principal industry in the arid and semi-arid areas in Ningxia. While watermelon has been reported to be a crop with negative response to chloride, watermelon is a high potassium demanding crop. Considering the lower price of potassium chloride, there is a necessity to clarify the feasibility and the application technology of potassium chloride on watermelon in Ningxia. In order to explore the effects of potassium chloride application on the yield and quality of watermelon and the chloride content of soils, a series of field experiments, combined with lab analysis, were carried out with various watermelon varieties on different locations for several years. The main results conclude as follows:1. The watermelon yields were significant increased by rational application rates of potassium chloride. The results from a four year filed trial demonstrated that water melon yields could be increased by 19.5%-36.4% at the application rate of 150 kg K₂O /ha, indicating the significant yield increasing effect of potassium chloride. A regression analysis indicated the optimal application rates should be in the range of 138 -172 kg K₂O /ha. As watermelon had similar yiled responses to potassium chloride and potassium sulfate at the same application rate of K₂O, application of potassium chloride on watermelon could get a higher economic return due to its cheaper price for farmers.2. Watermelon were improved in sugar content and did not negative affected in other nutritional indice with rational application rate of potassium chloride. The total sugar content of watermelon were increased with the increasing rates of potassium application. The total sugar content was increased to 9.2% at the rate of 225 kg K₂O /ha compared with 8.3% at zero application of potassium chloride. With the increasing rates of potassium application, the reductive sugar contents of watermelon did not vary significantly amoung treatments while the non-reductive sugar contents increased significantly. Application of potassium chloride did not result in significant difference of Vitamin C contents and crude fibre contents of watermelon amoung treatments neither.3. The Cl" were not significantly accumulated in melon of watermelon with rational application of potassium chloride. The Cl^- contents in the watermelon plants showed a decreasing order of bottm leave(1.11%) > vine(0.59%) > top leave (0.36%) > melon(0.012%) without potassium chloride application. With KCl application, the Cl^- content of bottm leave, vine, top leave and melon changed to 1.09%, 0.59%, 0.31% and 0.013% respectively, indicating the unsignificant difference between treatments of no KCl application and ones with KC1 application and the lowest Cl^- content in the melon amoung the plant organs.4. The Cl^- accumulation in soils was not significant with application of the potassium chloride. It was observed that Cl^- was mainly located in soil plow layer and Cl^- content in 0⁶0 cm soil depth increased with the increase of potassium chloride application. The soil Cl" contents with applicationof 150 kg K2O/ha in potassium chloride was not significantly different from the soil without applying potassium chloride. However, compared with soils with no KC1 application, significantly higher soil Cl" contents could be observed on the soils with KC1 application rate up to 225 kg K2O /ha in form of potassium chloride.It is concluded that potassium chloride could be used as a high quality fertilizer on watermelon in arid and semi-arid areas in Ningxia. The rational application of potassium chloride can increase the watermelon yield, improve the fruit quality, not significantly affect the melon Cl- content and soil Cl-content. The optimal application rate of potassium chloride in the study area should be 150 kg K2O/ha.