Effect of Additives on Stability Immersed in Water of Biochar Based Long-acting Fertilizer
Biochar based long-term fertilizer can be prepared by extrusion granulation process with cow dung biochar,digestate,chemical fertilizer and ferric oxide as main materials and quicklime,portland cement and pregelatinize starch as auxiliary materials.In order to study the influence of addition of excipients on the stability of biochar based long-acting fertilizer in water immersion,8 treatments according to the differences in the addition of excipients were set up.By analyzing the compressive strength,soaking resistance,soaking quality loss,soaking nutrient release rate,pH,electrical conductivity(EC)and other indexes of fertilizers in different treatments,the influence of different excipients on the stability of fertilizers in water immersion was comprehensively evaluated.The results showed that the addition of portland cement and quicklime could reduce the compressive strength of fertilizer particles,but could significantly improve the stability of fertilizer particles in water immersion.The addition of pregelatinize starch not only significantly reduced the compressive strength of fertilizer particles,but also was not conducive to improving the stability of fertilizer particles in water immersion.compared with no excipients,the soaking resistance of adding quicklime only,adding portland cement only and without adding pregelatinized starch increased by 24.00%,19.20%and 45.60%,respectively,and the soaking quality loss decreased by 8.61%,6.96%and 12.04%,respectively;within 56 d,the cumulative release of nutrients was reduced by 16.20%,11.87%and 21.34%,respectively.Compared with adding 3 excipients,the nitrogen accumulation rate of without adding quicklime,without adding portland cement and without adding pregelatinized starch increased by 2.11%,1.27%and-8.66%,respectively,and the phosphorus cumulative release rate increased by 19.66%,15.30%and-8.93%,respectively,during 56 d of immersion;the cumulative potassium release rate decreased by 1.95%,0.92%and-5.15%,the mass loss increased by 2.32%,1.29%and-8.86%,and the soaking resistance decreased by 10.07%,5.04%and-30.94%,respectively.Therefore,when using this technology to produce biochar based fertilizer,portland cement and quicklime could be recommended as auxiliary materials to improve the water stability of fertilizer,and it was not recommended to add pregelatinized starch.
biochar based fertilizersexcipientsimmersion stability in water