Study On The Materials For The Water-retention And Slow-release Fertilizer

Agriculture has an essential effect in China.Mostly,we need spend much money on fertilizer which leads the fertilizer to stay at a significant place in farming.So far,the utilization of fertilizer in our country faces some challenges:1,an amount of fertilizer is applied but the utilization rate is so low,and the release rate of nitrogen is just 30%-35%;2,lots of fertilizer is washed away and causes the economic loss and polluts the environment.To solve these problems above and improve the utilization of fertilizer,our study chose tamarind gum,xanthan and guar gum,respectively,mixed with diatomite and urea,which were named TUD,XUD and GUD,respectively,as the inner fertilizer.And then the inner cores coated several times by tamarind gum and diatomite in turn.We named the slow-release fertilizer as TUD,XUD and GUD slow-release fertilizer and determined their properties to find an adaptable preparation process,such as water-retention and slow-release ability.Because the natural polymer is easy to degrade,which directly influences the slow-release ability of the coated fertilizer.To improve the water-holding ability and the slow-release ability,firstly we found super absorbed polymer(PMMA)to coat the TUD,XUD or GUD fertilizer to determine the water-holding ability and decide whether the PMMA was a suitable material for the fertilizer.And then the film of polyvinyl alcohol and polyacrylate were prepared as the last layer to coat fertilizers which improved the slow-release ability.We determined the properties of the slow-release to find the suitable materials and prepared factors.The results as followed:1.The appropriate technological parameters of preparing slow-release fertilizer:xanthan gum:diatomite:fertilizer =1:8:2 coated with tamarind gum and diatomite in turn.the suitable crosslink was epichlorohydrin;the condition of dry temperature was T=50?;the best rotating time in rotary drum was t=2h.Under this condition the release ratio of nitrogen was 74%in 24 hour and was 88%in 28days.2.Our study found that xanthan gum was better than tamarind gum or guar gum in our experiment.Firstly,xanthan gum had a better water-retention and slow-release ability compared with the tamarind gum and guar gum;then xanthan gum could adhere diatomite and urea more tightly than other two,which coated fertilizer was much more stable;last,we added less mass of xanthan gum than the other two,which cut cost.3.Polyvinyl alcohol film and polyacrylate film coated the TUD,XUD and GUD slow-release fertilizers,respectively.These coatings improved the slow-release ability and the release ratio of nitrogen in 24 hour was 59.3%and 28 days was 85.1%of polyvinyl alcohol film coated fertilizer and the polyacrylate's results in 24 hour was 43%and 28 days was 81.5%.