| Soil available calcium, including water-soluble calcium and exchangeable calcium, the two maintain a dynamic balance. When the water-soluble calcium is absorbed or leaching, the exchangeable calcium can be exchanged by other high content cationic(H+, NH4+, K+ etc.) in the soil to convert it into water-soluble calcium. At present, the application of N, P and K fertilizers in the process of vegetable cultivation is very common, and we have all focused on the phenomenon of soil compaction, acidification and salinization. but the research that impact on the soil of calcitonin behavior and the effectiveness is not enough in-depth, systematical. In this paper, the changes of water soluble calcium and exchangeable calcium in brown soil were studied in different levels of nitrogen and potassium fertilizers during 0-40 days. The results can provide theoretical support for revealing problems such as the change of calcium in vegetable soil, the occurrence of physiological deficiency of calcium deficiency in vegetables and the rational use of chemical fertilizers.The conclusions are as follows:(1)Through the study that availability of different levels of nitrogen fertilizer on the availability of calcium, we found that the soil ammonium nitrogen commutativity NH4+ content accumulation is most in 15 days, nitrate nitrogen content in the 30th day it becomes stable. With the increment of the N fertilizer, and gradually reduce the content of exchangeable calcium in the soil, water soluble calcium increase gradually. Ammonium nitrogen in the soil in 3-15 days to most effectively the influence of calcium. Nitrate in the 30th day after began to enhance effectively the influence of calcium. Commutativity NH4+ is the increase of soil exchangeable calcium to reduce the direct factors and water soluble calcium increased.(2) Through the study that availability of different levels of potassium fertilizer on the availability of calcium found with the prolongation of culture time, the content of available K in the soil began to decline, but the decline was smoothly. The content of exchangeable K in the treatments showed a trend of increasing.Exchangeable calcium content and available potassium content showed a negative positive correlation, exchangeable calcium content decreased with the increase of available potassium content in soil, while the reduction effect was not obvious. The content of water-soluble calcium in soil increased with the increase of potash fertilizer. Exchangeable potassium was negatively correlated with exchangeable calcium, and had a positive correlation with soluble calcium.In the latitude of time, the effect of potassium fertilizer on exchangeable calcium content and water-soluble calcium content in soil was gradually weakened.(3) The study of different levels of nitrogen and potassium fertilizers on soil calcium showed that with the increase of nitrogen and potash fertilizer concentration, the content of exchangeable calcium in soil could be obviously reduced. With the prolongation of culture time, the content of exchangeable calcium in each treatment continued to decline, but the decrease was small. The content of water-soluble calcium in soil increased with the increase of nitrogen and potassium concentration in different levels.The contents of ammonium nitrogen and nitrate nitrogen and exchangeable NH4+ were positive negatively correlated with soil water calcium content, and there was a negatively correlation between exchangeable calcium. While, the pH value was negatively correlated with the exchangeable calcium content before the 5th day, and it was positively correlated with the soluble calcium content. There was a positive correlation between available phosphorus content and soluble calcium content at each stage, In the later period, pH value was positively correlated with exchangeable calcium content, and negatively correlated with water soluble calcium content.(4) The study on the availability of N, P and K fertilizers to soils shows that N, P and K fertilizers could obviously decrease the content of exchangeable calcium and increase the content of soluble calcium.With the prolongation of culture time, the content of exchangeable calcium decreased and the content of soluble calcium gradually increased.With the extension of incubation time, the exchangeable calcium content in each processing gradually reduce, the content of water soluble calcium increased. Due to root on soil water soluble calcium phosphate fixation, high phosphate treatment of water soluble calcium content in the late fall.Due to the effect of fixed of phosphate on soil water soluble calcium, high phosphate treatment of water soluble ealcium content fall in the late.(5) The different levels of nitrogen and potassium fertilizers single or mixed application had all effected the availability of soil calcium. The effect of nitrogen fertilizer on the availability of calcium was greater than that of potassium fertilizer, and the effect of nitrogen and potassium combination could exacerbate the effect on calcium availability. The effect of nitrogen fertilizer on the availability of calcium was greater than that of potassium fertilizer. The effect of N and K combined application could exacerbate the effect on the availability of calcium. When the total nitrogen, phosphorus and potassium application, in reducing the exchange of calcium content at the same time, it will reduce the water-soluble calcium content. |
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