The application of super absorbent polymer(SAP )in agriculture

Super absorbent polymer(SAP)is not only widely used in sanitary materials, industrial dewatering materials, sludge solidifying materials, anti-condensation materials, etc., but also has begun to be used in the agricultural field, and achieved obvious effect. Of course, water retention agent is not omnipotent, can not think that the use of water retention agent does not need to irrigate, or increase the amount of water retention agent can save a lot of water.

1) Characteristics of SAP

With high water absorption ratio and small particle size, especially micro-powder super absorbent polymer, it is easy to be affected by wind when applied in the field, so it is difficult to spread evenly and the effect is not good. With low water absorption ratio and small particle size, the granule super absorbent polymer is easy to use, easy to achieve uniformity and good response of crops.

The pH value of the super absorbent polymer was in the range of slightly acidic to slightly alkaline, and had no adverse effect on crops. The water absorption ratio of super absorbent polymer is the main characteristic in agricultural application. The water absorption ratio is significantly affected by the salt concentration in soil and irrigation water, and the water absorption ratio is greatly reduced when the salt concentration is high. There is no proportional relationship between water absorption ratio and crop growth, and crop growth is mainly determined by the mixing ratio of super absorbent polymer, irrigation amount and soil characteristics.

The effects of super absorbent polymers on soil physical properties are shown in the following aspects:

1) Influence on the "three phase" distribution of soil

The test results of Takenuchi et al. (1983) proved that the liquid phase in the soil increased significantly after irrigation with super absorbent polymer. But at the same time, the gas and solid phases in the soil decreased (see figure below). This is caused by water - retaining agent swelling. However, excessive reduction of gas phase will bring different side effects to crop growth, so the mixing amount of super absorbent polymer should be determined according to soil properties and different crops. The experiment indicated that the mixing ratio of super absorbent polymer and sand soil is about 0.5%, which is the most advantageous to the growth of spinach and so on.

2) Effects on soil temperature

The application of super absorbent polymer not only increased the water content in the soil, but also reduced the diurnal temperature range. The experiments conducted by Bamboo et al on sandy loam showed that within 6 days, the highest ground temperature of super absorbent polymer treatment was 3℃ lower than that of the control, while the lowest ground temperature was 1.5℃ higher, and the daily ground temperature range was reduced by nearly 5℃ than that of the control.

3) Effects on soil water evaporation

The general trend is that the lower the water absorption ratio of super absorbent polymer is, the greater the cumulative evaporation is; conversely, the smaller the cumulative evaporation is.

2) Application of super absorbent polymer in agriculture

A. Application of super absorbent polymer in vegetable cultivation

Vegetables are very sensitive to super absorbent polymers. Therefore, Japan to live in order to identify the effect of water - retaining agent. On the whole, the water-retaining agent has obvious effect on increasing vegetable yield, but its effect varies with the type of water-retaining agent, the amount of soil mixture and the amount of irrigation.

Under the condition of a small amount of irrigation, the large amount of water absorbed by superabsorbent super absorbent polymer weakened the water supply of soil to rape. Compared with the conventional method, the irrigation times and irrigation amount of cucumber seedlings with super absorbent polymer can be reduced by two thirds, and the seedlings can be strong and full, and the ratio of high-quality seedlings can be increased.

B.Application of super absorbent polymer in crop cultivation in dry field

The water-retaining agent also has the effect of increasing the yield of crops in the dry field. In order to improve soil moisture status during midsummer drought, a super absorbent polymer of 140 g/m 2 was applied during summer soybean cultivation. The results showed that the 100-grain weight of soybean increased by more than 2 grams compared with the control area, and the yield increased by more than 14 kg per mu, or about 10%. The soil bulk density and solid phase ratio in the super absorbent polymer application area were significantly lower than those in the control area, and the liquid phase ratio was higher than that in the control area. The results indicated that the super absorbent polymer could not only preserve soil water but also improve its physical properties under dry farming.

C. the application of super absorbent polymer and plastic film covering

With the use of super absorbent polymer, combined with plastic film covering to inhibit evaporation on the ground, can accumulate the potential of both, more suitable for crop cultivation in dry field. Taking uchi et al. planted azalea kushima in sandy land, and the survival rate of the plant was investigated 9 months after planting. The survival rate of the plant was 45% without the application of super absorbent polymer, and 90% with the treatment of super absorbent polymer plus mulch film.