Effects Of Sand-gravel Mulching On Soil Water And Growth And Development Of Field Crop

Mulching is an important measure of agricultural production in arid areas. It can effectively suppress soil water evaporation, hold soil moisture, and improve agricultural water use efficiency. Sand-gravel mulching can be applied to arid and semi-arid areas under different conditions of climate, geography, soil and etc. to effectively maintain soil moisture,improve the soil environment, increase crop yields, and improve crop quality in agriculture production.In this paper, laboratory simulation experiments of different amounts of sand-gravel mulching and field experiments of winter wheat and summer maize were conducted. The laboratory experiments had five coverage levels of 0, 25%, 50%, 75%, 100% and two size levels of 0.5 cm, 1 cm. The field experiment of winter wheat had five coverage levels as CK(0), 0.25, 0.5, 0.75, 1.0 and two irrigation levels 0, 50 mm, which resulted in five no-irrigation-mulching treatments(CK, S0.25, S0.5, S0.75, S1.0) and five irrigation-mulching treatments(WCK, W0.25, WS0.5, WS0.75, WS1.0). The field experiment of summer maize had five levels of cover thickness(CK or 0 cm, 1, 2, 3, and 4 cm), two irrigation level(0,50mm), which consequently resulted in five no-irrigation-mulching treatments(CK, S1, S2,S3, S4) and five irrigation-mulching treatments(WCK, W1, WS2, WS3, WS4). The study compared and analyzed the effects of different treatments on soil evaporation and crop growth and development. Some main conclusions have been drawn as follows:(1) Compared with bare soil, sand-gravel mulching can suppress soil evaporation. The results of suppressing were closely related to sand-gravel mulching degrees and sizes.Gravel-sand mulching efficiently suppressed the cumulative soil water evaporation, which was more obvious when the mulching degree was bigger and grain size was smaller. The dynamics of cumulative evaporation met the Gardner’s theory for different mulching degrees. The cumulative evaporation and evaporation rate could be expressed as functions of evaporation time and mulching degree. Gravel-sand mulching can suppress the evaporation of soil moisture capacity. When the mulching degree was greater, the ratio between soil evaporation and atmospheric evaporation capacity(E / E0) was smaller, namely coverage of gravel and soil evaporation capacity were significantly positively correlated. Gravel-sand mulching wasmore effective on suppression of sandy soil evaporation for the same grain size.(2) Compared with the control, mulch treatments increased the 0-100 cm soil water storage of wheat field. With the increasing coverage of the gravel, sufficient water supply created the conditions for more accumulation of wheat biomass. Plant height and biomass accumulation of mulching treatments were significantly greater than the control and increased with the increasing of mulching degrees. Mulch treatments could effectively improve the water consumption and water use efficiency(WUE) of growth stages and wheat growth period, effectively suppress invalid wheat moisture evaporation, and promote the efficient use of water. Under mulching conditions, wheat yield and grain weight were higher than the control and increased with the increasing of mulching degrees. The number of grain per panicle and panicles of wheat had a certain degree of randomness. The crop coefficient(Kc)in the whole growth season were: WS1.0 > WS0.75 > WS0.5 > WS0.25 > WCK. And the values of Kc may be fitted as polynomials of days after sowing and cumulative temperature above 0℃. The greater the mulching degree, the greater the crop coefficient will be for given typical growth stages.(3) Mulching treatments increased the 0-100 cm soil water storage in maize field. With the increasing coverage of gravel, sufficient water supply created the conditions for more accumulation of maize biomass. Accumulations of maize biomass of mulch treatments were significantly greater than the control and increased with the increasing of thickness.Compared with the control, plant height and leaf area index of mulch treatment was higher and increased with the increasing of thickness. Compared to the control, mulch treatment can improve WUE of maize during the whole growth period. Gravel-sand mulching can effectively suppress invalid evaporation and promote efficient use of soil moisture. Under mulching conditions, maize yield, ear length, ear diameter, grain number, and grain weight per panicle were greater than CK, and increased with the increasing of cover thickness. Crop coefficients(Kc) during the whole growth season were: WS4 > WS2 > WS3 = WCK >WS1. Kc could be fitted as polynomials of days after sowing and cumulative temperature above 10℃ and. The greater the mulching degree, the greater the value of crop coefficient will be for given typical growth stages.(4) Wheat growth period, yield, and biomass of CK treatment had better simulation results with the RZWQM(Root Zone Water Quality Model) model, but the simulation results of wheat biomass and yield of gravel-sand mulching treatments were relatively poor. It was because the simulation ability for sand-gravel mulching of the model was limited, which made it less applicable in mulching simulation. Maize yield of CK treatment had better simulation results with the RZWQM, but the simulation results of growth period and biomassof mulching treatments were poor. It was because the model did not consider serious drought in the earlier growth stage. Similarly, yield and biomass of maize of CK treatment also had poor simulation results with the RZWQM model.