The Fixation Character Of Potassium In Grey Desert Cotton Soil And Potassium Activation Of Humic Acids

The grey desert soil is primary soil type of northern Xinjiang, also is important agricultural soil. With the cotton yield increasing, potassium fertilizer was regarded gradually. The available potassium of grey desert soil is very high, average content is about 300 mg/Kg, but increasing production of potassium fertilizer was reported. The purpose of study was found out the potassium fixation characteris of grey desert soil; dynamic of different form potassium with different. On the basis, the effect of dynamic of potassium using different method and rate of humic acids was studied. These would provide proof for reasonable application of potassium fertilizer and humic acids.Laboratory incubation, pot and field experiment was used. Soil samples were from basis of long-term located fertilization in the grey desert soil and typical grey desert cotton soil in Manasi. The results were following:1. The potassium fixation character in grey desert cotton soilThe potassium fixation character in grey desert soil was studied using laboratory-simulating methods. Results showed that: the correlation of K fixation capacities and added K were linear, while the correlation of K fixation rates and added K was quadratic equation. When added K was 195.58mg/Kg, K fixation rate was highest, 89.92%. The result verified the existence of wedge zone. Therefore potassium fertilizer filled in wedge zone firstly, then it was absorbed by cotton. Rate of potassium fertilizer application should exceed the highest K fixation rate.2.The effect of different fertility soil on application of potassium fertilizerThe effect of soil available K, slowly available K and plant total K on application of potassium fertilizer in fertile soil and lean soil was studied by pot experiments. Results showed that: whether fertile soil or lean soil, the change of soil readily available K and slowly available K was similar. The correlation of plant K and soil readily available K was significant, but that of soil slowly available K was not significant. Under same management, the potassium supply intensity of fertile soil was stronger than that of lean soil; K p.d accumulation rates were higher. That was mainly reason for difference of cotton yield.3.The effect of soil available potassium on application method of humic acidsBecause the cation exchange capacity of humic was bigger, K fixation rates should be reduced due to adsorption of humic acids. But the effect of humic acids and potassium fertilizer method on K fixation rates was great. Laboratory-simulating results showed that: the K fixation rates were reduced when humic acids were applicated before K fertilizer. If they were applied together, the absorbability of soil would be enhanced. It led to the increasing of K fixation rates in soil. And we should apply humic acid firstly, and then K fertilizer in 10 days4. The effect of dynamic of forms K on application humic acidsUnder experiment condition, it did not accelerate releasing of soil water-soluble K, ordinary adsorption K and extraordinary adsorption K by using humic acids. So much as, the K content of using humic acids was less than that of CK. Combined with pot and laboratory-simulating results showed that soil available potassium was not increased until quantity of humic acids and potassium fertilizer should be enough. That of application methods should be correct.Humic acids could improve soil slowly available potassium especially in cotton florescence. It was potential potassium source. Compared with CK, the potassium intensity was decreased after using humic acids, but the effect of potassium efficiency in soil was not significant.