Nutrient Slow-release Mechanism Of Humic Acid Fertilizer Extracted From Brown Coal And Its Effects

Now, low N use efficiency and high environmental risk of chemical N fertilizer are worldwide concerned, which may be overcomed by using new slow-release fertilizers. So, the study on slow release fertilizer has very important practice meanings to the production in agriculture and forestry, etc. The brown coal is a kind of important raw material of the fertilizer and its reserve in our country is up to more than 130 billion tons. Simulative experiments, potted experiments and field experiments are used to study the effects of N,P,K concentration, equilibrium time and pH value on the adsorption of humic acid extracted from Shanxi brown coal. Humic acid fertilizer was manufactured through the adsorption characteristic. At the same time, release characteristic of N,P,K and the effect of this humic acid fertilizer on spinach and poplar were studied. The purpose of this research was to offer basic data for the production of humic acid slow-release fertilizers, the main results are as follows:1. The effects of various kinds of inorganic acid on the content, cation exchange capacity and optics nature of humic acid in brown coal were studied .The results showed that the content and the optics nature were not affected by Phosphoric acid and Hydrochloric acid treatment ,but the cation exchange capacity can be increased to some extent .The content of humic acid can be increased by 25 per by suitable for intensity Nitric acid, The cation exchange capacity can be greatly increased and the optics characteristic was greatly changed too. The best conditions would be different to different brown coal.2. With the increase of NH4+ concentration, adsorption capacity of NH4+ increased. The adsorption of NH4+ on humic acid could be well described by Freundlich equation and its kinetics adsorption fit Elovich equations best. Under the condition of pH lower than 7.04, pH increase of medium was great of advantage of NH4+ adsorption and could improve the velocity of adsorption reaction. Under the condition of pH lower than 4.03, physical adsorption was the dominant. However, under the condition of 4.03