Preparation Of Nitrogen And Phosphorus Slow-release Fertilizer With Bentonite And Studies On It’s Release Property

From the point of promoting clean and green production methods,management of agriculturalnon-point source pollution and analyzingapplication of bentonite in The Twelfth Five-Year Plan of National Economicand Social Development, the paper selects bentonite with the character ofwater feature,wide variety of sources, low-cost and slow-release ascontrolled-release carrier material to research the preparation of slow releasefertilizer bentonite and the characteristics of its nutrient release.In this paper, after the low grade calcium base bentonite supplied byHubei Zhongfei Bentonite Co., LTD being preliminary broken, then beingsieved over20mesh screen, and then being sieved over200mesh screen afterbeing crushing by roll crusher, we purifies it. This paper discusses theadvantages and disadvantages of calcium base bentonite, calcium purificationsoil, and sodium based soil in the bentonite carrier SRFS. The experimentalresults show that the carrier SRFS prepared by the calcium base purificationsoil under the optimum condition has better slow-release effect. Meanwhile,this paper researched3factors influencing the slow-release effect during thepreparation of bentonite through orthogonal experiments. It is concluded thatthe main factor of SRFS preparation is the soil/（soil+fertilizer） ratio, thesecond factor is the addition amount of urea-formaldehyde resin and theaddition amount of magnesium salt. And it’s concluded that the best ratio ofpreparing bentonite SRFS is A3B3C3, namely70%of the bentonite SRFS issoil/（soil+fertilizer）, the addition amount of urea-formaldehyde is20%, theaddition amount of magnesium salt is25%.This paper prepared some slow release fertilizer in the optimizedconditions, using water carrier SRFS baptized, sand column leaching andsoil column leaching method for the determination of homemade SRFS instatic water, sand column and soil column, the nutrient cumulative release rate of soil explores the influence of nitrogen, phosphor elements.Experimental results found: Early dissolution rate of SRFS total nitrogenand P₂O₅in static water were lower, respectively is6%and7%, the effectivenutrient nitrogen and phosphorus in28days of total nutrient content wereonly70%and74%become small molecules spread to solution.Because ofslow speed hydrolysis,most of the material did not dissolve out.17dayslater, bentonite SRFS nutrient release slow, rate of failure to form betweenlayers of small molecule has slow-release, when total nitrogen and P₂O₅content in60%and50%or so, then bentonite SRFS structure are basicallystruvite grain, has more effective slow-release performance.The preliminarydissolution rates of total nitrogen and P₂O₅in SRFS were very low,respectively was5%and6%. The efficient nutrients of nitrogen andphosphorus hydrolyzed only about65percent and75%respectively within28days. In former11days they hydrolyzed slow relatively and thecumulative dissolution rate is about14%and19%. Then there was a smallrise, mainly because bentonite SRFS particle extruded by the upper sandcolumn. At last, the dissolution rate increased slowly for the formation ofbentonite SRFS structure. Meanwhile the waterproof performance ofbentonite played a role.The total nitrogen and P₂O₅in MAP has beendissolved out in the same time.Total nitrogen and P₂O₅in slow-releasefertilizer in the soil column early dissolution rate increased compared forsand column respectively by5%and6%rise to8%and9%.Total nitrogendissolution rate curve is a gentle bullish power exponent function, thedissloution speed increasing in12days. The first15days or so bentoniteand soil on NH₄⁺and PO₄^3- adsorption reached with a relative balance,bentonite SRFS slow release due to negative pressure and nutrients to thesoil drench solution In the same period, the cumulative dissolution rate ofTN in MAP showed a proportional rising trend with the gradual increasingof leaching time. It is mainly because that the soils in the experiments were slightly alkaline and it promoted the hydrolysis of MAP to the right. PO₄^3-formed insoluble compounds with magnesium. As the hydrolysis went onstep by step, P₂O₅was released gradually in soil. After12days, thedissolution speed began to increase, and slowed down slightly on the18thday. But with the increase of leaching time, TN in soil was washed outgradually. And due to nutrients adsorption by soil, nutrients in MAPreleased fast. Till the18th day, they were all released, and MAP lostmanurial effect in the22ed day basically.This study continues to investigating the curve of N、P in soil aftertreated with sustained-release fertilizer and MAP on Tomato. This experimentinvestigates the variation curve of the nitrogen in the soil after dealing RedTomato with sustained-release fertilizer and MAP. In the fifth days, themaximum accumulation of nitrogen in the soil dealed with MAP comes to128mg/Kg, then reduced gradually; The maximum accumulation of nitrogenin the soil dealed with bentointes sustained-release fertilizer is only55.4mg/Kg, so the initial release rate is significantly lower than MAP. Thepeaks of its release are about in the25th day and the65th day, about84.7mg/Kg and78.4mg/Kg respectively. Thus it can be seen that bentonitessustained-release fertilizer has a good slow release effectAccumulation ofavailable P of MAP became the largest in five days, and the number is48.5mg/kg. And that of bentonite sustained-release fertilizer accumulate up tothe most of34.2mg/kg in20days. On the whole, MAP’s content of availablephosphorus in soil showed a downward trend：accumulates largely in a shortterm, then decreases rapidly. The curve of bentonite slow-release fertilizer isrelatively flat while the phosphorus release increases in the growing season.Finally, this paper compared the MAP in the same conditions andinvestigated homemade bentonite carrier in exploiting the release offertilizer effect of pot.Slow-release fertilizer plants results show that:thissection discusses the influence of different fertilizer treatments on growth status of potted tomato. Compared with those treated with MAP，plantstreated with sustained-release fertilizer have more obvious advantages inplant height and leaf number. The tomato yield is increased by33.9%andthe fluctuation is smaller. The nitrate content on the fruit differs not verymuch. All the tomatoes can reach the first level of limits of nitrates infood-level standards.