| Humic acid,which comes from the soil and fed back to the soil,is a kind of environment-friendly fertilizer.It can improve the soil environment and increase the fertilizer utilization ratio.Convenient transportation and use make people more inclined to use humic acid to improve soil environment to achieve the purpose of increasing production.The goal of this paper is to find suitable additives to increase the hardness of humic acid particles and to coat the ammonium sulfate particles with humic acid to achieve the sustained release of fertilizer.The effects of different liquid binders and solid additives on the hardness of humic acid particles were studied in the first chapter.It was found that the hardness of humic acid particles is the best when water is used as binder,ammonium sulfate and urea as solid additives.The optimum ratio of humic acid: ammonium sulfate: urea is 94: 5: 1.The average hardness of granulated particles with this formula can reach more than 10 N.Ammonium sulfate is the key to increase the hardness of humic acid particles.The greater the amount of ammonium sulfate,the greater the hardness.The results showed that the increase of the hardness of humic acid particles is due to the reaction between ammonium sulfate,urea and humic acid.Moreover,the acicular crystals of ammonium sulfate and urea will grow in the intercalation of humic acid and lamellar space in wet environment,which could increase the stability of the structure by hindering the slide between the layers.Some laboratory parameters of coating ammonium sulfate with humic acid as coating material were studied in the second chapter,and the slow-release effect of humic acid coated fertilizer was determined.It was found that the fertilizer had a better wear resistance when the ammonium sulfate particles were coated for several times.The coating effect was better when the particle size was 2-4mm and the film content was 22-42% of the weight of the particles.Soaking experiment and soil culture method showed that humic acid had slow release effect on ammonium sulfate coating.The slow-release properties of fertilizer increased with the increase of the fine density of coating layer and the decrease of soil temperature.After water vapor enters into the core of fertilizer for a period of time,some of the dissolved fertilizers release nutrients through the membrane gap,and some slowly crystallize into bulk crystals to delay the swelling time which prolongs the fertilizer efficiency period by 2-5 weeks compared with the uncoated fertilizer.The third chapter mainly focuses on the conversion of laboratory results to scale production.The process conditions of humic acid granulation and ammonium sulphate particle encapsulation with disc pelletizer under the conditions of the factory were studied.Fertilizer treatment on the lawn was used to observe the coating effect of fertilizer on turfgrass growth.It was found that the optimum technological conditions for granulation of humic acid in discs were 60 degrees inclination and 34 r/min,and water consumption was5 mL per 100 g which was obviously less than the water consumption under laboratory conditions.The more water is used,the longer the particle sieving time and the lower the hardness.The optimum technological conditions of ammonium sulfate coating were 60 degrees inclination and 30 r/min.The results showed that the treatment of turfgrass grown with the coating fertilizer was the best.The lack of nitrogen supply in the non-fertilized soil resulted in slower growth of the grass and bad color.The turf which had not been coated with fertilizer had just started to grow well,and the late supply of nitrogen was insufficient for growth. |
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