Study On The Role Of Magnesium Ion In Sustained-release Nitrogen And Phosphorus Compound Fertilizer With Carrier Of Bentonite

With natural, cheap and porous mineral bentonite as the carrier ofsustained-release nitrogen and phosphorus compound fertilizer, the researchthen add some ammonium dihydrogen phosphate, magnesium salt andurea-formaldehyde according to a certain to bond and mix them. With thehelp of electric pressure machine, the slow release fertilizer was well made.Through the method of water dissolution rate and the sand column leachingsolution, the paper then gave a preliminary study on the sustained releaseeffect in the type and the amount of magnesium salt of the above self-madeslow release fertilizer. The main conclusions were as follows:General conclusion：The dosage of magnesium chloride, magnesiumsulfate, magnesium nitrate, magnesium carbonate and magnesium oxide ismore, the effect of the nutrient release of the prepared slow release fertilizertablets is better; the utilization rate of effective nutrient is higher. Slow-releaseeffect is not significant when the dosage of that increase to a certain extent.Personality conclusion：(1) When slow release fertilizer tablets culturedin calm water and sand column, a small number of water molecules willthrough the resin pore diffusion into the matrix of the slow release fertilizerinside, to dissolve fraction of ammonium dihydrogen phosphate andmagnesium chloride. As magnesium chloride is soluble salts and its solubilityin water is big, it will release a small amount of magnesium ion, reaction withammonium ion and phosphate of the matrix of the slow release fertilizer toform a small amount of struvite which have a good slow-release effect. Withthe extension of culture time, the cured resin will gradually be dissolved, poresize increased, more water molecules enter into the cured resin film,ammonium dihydrogen phosphate and magnesium chloride dissolved moremagnesium ion, ammonium ion and phosphate from the matrix of the slowrelease fertilizer, they reacted with each other to form much more slow release struvite, which against N, P effective release when it is too much.Consideration of various factors comprehensively, the slow-release effect ofsustained release tablets is best when the dosage of magnesium chloride is4%(2) The content of magnesium ion in magnesium sulfate is in the middle,compared with magnesium chloride and magnesium nitrate which also issoluble salt under the same culture condition and the adding proportion, therelease of magnesium ion in magnesium sulfate is less than magnesiumchloride, but more than magnesium nitrate. The calcium which is high in thecarrier of calcium base bentonite will react with sulfate into calcium sulfate topromote the release of magnesium ion. But struvite will produce too muchthat against N, P effective release when the dosage of magnesium sulfate istoo large. Consideration of various factors comprehensively, the slow-releaseeffect of sustained release tablets is best when the dosage of magnesiumchloride is4%.(3) Compared with magnesium chloride and magnesium sulfate whichalso is soluble salt under the same culture condition and the adding proportion,the content of magnesium ion in magnesium nitrate is least. Magnesium ionreacts with ammonium ion and phosphate which release from the matrix ofthe slow release fertilizer to form slow release struvite which is effective forN, P release. Consideration of various factors comprehensively, theslow-release effect of sustained release tablets is best when the dosage ofmagnesium nitrate is5%.(4) Magnesium carbonate is slightly soluble in water, release the sameamount of magnesium ion under the same culture condition, compared withsoluble salt, the dosage of magnesium carbonate must to be large, comparedto magnesium oxide which is insoluble in water, the dosage of magnesiumcarbonate should be relatively large. Therefore, when the content ofmagnesium carbonate is more, can release a considerable amount ofmagnesium ion which reacts with ammonium ion and phosphate that release from the matrix of the slow release fertilizer to form much more slow releasestruvite which against N, P effective release. Consideration of various factorscomprehensively, the slow-release effect of sustained release tablets is bestwhen the dosage of magnesium carbonate is15%.(5) Magnesium oxide is insoluble in water, release the same amount ofmagnesium ion under the same culture condition, compared with soluble salt,the dosage of magnesium oxide must to be large, compared to magnesiumcarbonate which is insoluble in water, the dosage of magnesium oxide shouldbe relatively small. Therefore, when the content of magnesium oxide is more,can release a considerable amount of magnesium ion which reacts withammonium ion and phosphate that release from the matrix of the slow releasefertilizer to form much more slow release struvite. Consideration of variousfactors comprehensively, the slow-release effect of sustained release tablets isbest when the dosage of magnesium oxide is20%.