In agricultural production, the characteristics of water absorption and release of super absorbent polymers (SAP) are generally affected by soil solution and nutrient icons. The study on SAP of absorption and release of water and nutrients was mainly focused on through laboratory tests. These tests were used to investigate the kinetics of repeated absorption and release of water and nutrients in three particle sizes of SAP (0.8~1.6 mm, 1.6~3.5 mm and 3.5~5.0 mm) at different NH4H2PO4 concentrations (0.02 mol/L, 0.04 mol/L and 0.08 mol/L). The results indicated that the water absorption rate of SAP reached the maximum value initially, and then decreased gradually and finally tended to reach the swelling equilibrium state. The water absorbency was decreased with the increase of solution concentration while water absorbency under different particle sizes of SAP ranked as follows: 1.6~3.5 mm, 3.5~5.0 mm and 0.8~1.6 mm. Meanwhile, the water absorbency was decreased with the increase of water absorption times. The ability of SAP to absorb water and the amount of water released per hour were decreased with the increase of rotational speed (soil suction). The water retention rate was decreased with the increase of solution concentration when releasing water, while the water retention rate under different particle sizes of SAP ranked as follows: 0.8~1.6 mm, 3.5~5.0 mm and 1.6~3.5 mm. However, the influence of centrifugation times on water retention rate was not significant. The concentrations of NH4+-N and PO43--P of the released solution were decreased with the increase of rotational speed (soil suction). The cumulative amounts of NH4+-N and PO43--P were increased with the increase of concentration of solution, while the cumulative amounts of NH4+-N and PO43--P under different particle sizes of SAP ranked as follows: 1.6~3.5 mm, 3.5~5.0 mm and 0.8~1.6 mm. The cumulative amounts of NH4+-N and PO43--P were decreased with the increase of centrifugation times. It can be concluded that the amount of water absorbing, releasing and nutrient releasing at particle size of 1.6~3.5 mm for SAP were much more than the other treatments. © 2019, Chinese Society of Agricultural Machinery. All right reserved.
