Regulation Mechanism Of Soil Water,temperature And Ecological Performance In Maize As Affected By Mulching Method In A Semiarid Region In Northwest China

In the semi-arid rain-fed area of the Northwest Loess Plateau,there is insufficient water and heat.Dryland spring maize is mainly cultivated in double ridges and furrows mulching.The residual film pollution caused by plastic film mulching has attracted increasing attention,and the straw strip mulching can significantly increase the yield of wheat and potatoes,but the application effect on corn has not yet been systematically studied.Under the background of the hydrothermal environment in the dry farming and spring maize production area in Northwest China,a comparative experiment was carried out in 2017-2019 between the straw strip mulch and two full-film double ridge and furrow models,and the soil moisture and soil temperature between the mulching methods were systematically measured,growth indicators,ecological and physiological indicators,yield structural factors and yield differences,and analyzed the formation mechanism of soil water and heat changes and yield differences caused by mulching.The experiment included 3 kinds of mulching treatments: white film mulching(WP),black film mulching(BP),straw strip mulch(SSM,coverage 42%,planting belt sowing 2 rows,covering belt width 50 cm,planting belt width 70 cm),with WP commonly used in production as a control.The main results are as follows:1.The water use efficiency of the grain yield and biological yield of the straw strip mulching was significantly lower than that of the white film and black film mulching,but there was no significant difference between the white film and the black film mulching,straw strip mulching the grain yield was reduced by 16% and 13% compared with white film and black film mulching,respectively.From the perspective of vegetative growth and reproductive growth,the reason for the lower yield of straw strip mulching than that of white film and black film mulching is firstly that it significantly reduces the amount of vegetative growth,and secondly,it reduces the harvest index.Although the grain yield of straw strip mulching is lower than that of white and black film mulching,due to the reduced input,the average net income is similar to that of the two types of mulching,and even higher than that of black film mulching(BP)in abundant water years;if it is used for silage corn production,the average net income is significantly higher than the two types of film mulching 21 to26%.2.Although straw strip mulching is a partial ground mulching,it does not reduce the water supply capacity of the soil.Straw strip mulching the average soil water storage capacity of 0-200 cm during the whole growth period was similar to or even higher that of white film and black film mulching(P>0.05).The main reasons for the straw strip mulching and the two types of film mulching to maintain a similar or higher water supply capacity are that they increase the precipitation infiltration rate and reduce the intensity of water consumption through cooling temperature.Compared with white film mulching,the moisture-increasing effect of straw strip mulching is mainly in the bell-mouth stage to grain filling stage and 0-90 cm soil layer.Compared with the two kinds of film mulching,straw strip mulching weakens the difference in water gradient of different soil layers in the 0-200 cm soil profile.Although the average water consumption(or evapotranspiration)during the whole growth period between treatments is similar to the treatments,there are phased water consumption differences.Increasing water consumption in the bell mouth stage to silking stage is beneficial to increase the accumulation of dry matter,but excessive soil moisture and water consumption of 0-40 cm after the silking stage will cause greediness and late maturity and decrease in grain weight.In the semi-arid area of the Loess Plateau,the water consumption of spring maize mainly depends on the precipitation during the growth period.When the precipitation during the growth period exceeds 400 mm,the precipitation can not only fully meet the water consumption requirements of various treatments,but even a surplus of soil moisture will be supplemented.However,in a flat water year,soil water storage(bottom moisture)before planting contributes as much as 11% to 15% of soil water consumption,and bottom moisture plays an important role in mitigating seasonal drought hazards.The water consumption of spring maize mainly depends on the precipitation during the growth period.The precipitation during the growth period is higher than 400 mm in rainy years.The precipitation during the growth period can not only meet the water consumption needs of each treatment,but may even have a surplus.However,in a normal water year when the precipitation during the growth period is less than 400 mm,soil water storage before planting still has a large contribution to water consumption(11%-15%).3.Mulching materials and methods significantly affect the soil temperature of 0-25 cm cultivated layer.Compared with white film mulching,straw strip mulching and black film mulching significantly reduced the soil temperature in each period and each soil layer,and the cooling effect of strip mulching was the most prominent.In three-year average,the average temperature of 0-25 cm straw strip mulching and black film mulching in the whole growth period are 2.03 ℃ and 0.55 ℃ lower than that of white film mulching,respectively.The cooling rate is the largest from the seedling stage to jointing stage,and the cooling effect in rainy years is greater than that in normal water years.The cooling effect of the straw strip mulch will delay the growth and development process and delay the maturity by about one week.The soil water temperature interacts significantly,and the increase in ground temperature will cause the soil moisture to decrease.The mulching method also affects the soil heat conduction,which in turn affects the movement,consumption,and temporal and spatial distribution of soil moisture.Compared with white film mulching,straw strip mulching can significantly smooth the violent fluctuations of soil temperature,and this temperature smoothing effect is more obvious in rainy years.In the spring maize area with insufficient heat,higher soil temperature under film mulching is beneficial to the formation of high yield and promoting vegetative growth,and the significant cooling effect of straw strip mulching is also the main reason that inhibits vegetative growth,decreases grain weight and reduces yield.The effect of soil temperature on grain weight was significantly greater than that of grain number per spike and spike number.In particular,the temperature of each soil layer of 0-25 cm during the grouting period is positively correlated with the height of the grain.4.Compared with white film mulching,straw strip mulching can significantly increase leaf catalase activity,soluble protein content,and net photosynthetic rate,but reduce the content of malondialdehyde.Although the soluble sugar content(WSC)increase and the proline content(Pro)decrease of the straw strip mulching are relatively smaller than that of the leaves covered with white film mulch,WSC and Pro are more sensitive to changes in soil water temperature and increase soil moisture and temperature.Conducive to the accumulation of WSC,while maintaining a high leaf water content,soil moisture and temperature will reduce the leaf Pro content.The differences in the above physiological indicators prove that the straw strip mulching can improve the anti-oxidation ability,osmotic adjustment ability and plant vitality of plants in the later stage,delay senescence and prolong the duration of photosynthesis,and enhance the photosynthetic production capacity in the later stage.However,in the later stage,the enhancement of photosynthetic capacity and anti-aging ability of straw strips can not make up for the yield loss caused by insufficient growth and decreased grain weight.5.Under the environmental background of drought and cold in the northwest,the coupling degree of spring maize growth period and precipitation season is relatively high,and water consumption mainly depends on precipitation during growth period.Soil temperature is the dominant environmental factor that affects the vegetative growth and yield differences of spring maize in this area.6.Straw strip mulching is a green and sustainable production technology.It can not only avoid residual film pollution and smog pollution caused by straw burning,but also can increase fertility and improve soil after returning straw to the field,and realize the recycling and reuse of rich straw resources.It has obvious advantages in ecological and economic benefits,and has high Application prospects.