| Wheat,corn and potato are three major crops in northwestern China,and the mulching cultivation is becoming the main way to maintain high and stable yield production and efficient water-use.Film mulching and straw mulching are two important mulching methods utilized in this region.Compared with the film mulching,straw mulching is a sustainable production technology,which is more economical and environment-friendly than that of film mulching.The traditional straw mulching uses crushed straw to cover farmland,but this method will affect the emergence and delay the growth due to excessive reduction of soil temperature,especially in vast heat deficient area,which causes severe loss of wheat and corn yield.In order to address the conflict between the soil moisture conservation and cooling by straw mulching,we invented the technology of partial strip mulching with corn stalk.With the technology,the dryland winter wheat soil moisture has increased significantly,but whether the technology can yield the same effect on potato and corn soil moisture conservation still remains unknown and no experimental research has been carried out in this regard.There are great differences between winter wheat and two autumn crops in their moisture and temperature environment in their growing season and their characteristics of the demand for and response to moisture and temperature are also different.However,under the same environment and mulching cultivation condition in Northwest China,no systematic comparative study has been carried out on the difference in soil moisture and temperature response between three crops.This study will provide a basis for revealing the yield-increase mechanism by mulching cultivation and for improving the mulching cultivation technology.The study was conducted in normal rainfall and wet years.There are five treatments,namely,straw strip mulching,all film mulching,film partial mulching,film mulching with different film materials(black opaque and white film),and traditional uncovered field planting.The traditional uncovered field planting was used for winter wheat and potato as control(CK);all-film double-furrow(white film)was used for corn as control.Under the same coverage,three straw strip mulching modes(SM1,SM2 and SM3)were adopted for winter wheat according to the mulching width and the number of rows.The main conclusions are as follows:1.Under the condition of dry farming in Northwest China,different mulching cultivation patterns had significant effects on yield,yield structure factors,growth and development,and other important agronomic indicators(P<0.05).The yield of winter wheat and potato with film mulching and straw strip mulching significantly increased compared with that of uncovered land(CK)(P<0.05).The winter wheat and potato yield with straw strip mulching reached the yield level with all film mulching,but there was no remarkable difference in potato and corn yield between all film mulching(PMF)and partial film mulching(PMP).However,the latter was cost-efficient.However,with straw strip mulching,the corn yield significantly decreased compared with that with the above two mulching film mulching(PMF and PMP).The yield reduction was mainly because the corn was a temperature-sensitive crop and the straw strip mulching reduced soil temperature,which,in turn,reduced kernel weight.2.The analysis of the yield difference mechanism from the perspective of yield components revealed the following results: The winter wheat yield increase with the mulching was mainly contributed to spike number increase,the potato yield increase was mainly due to single tuber weight increase,the wheat kernel weight and potato tuber number were less affected by different cultivation ways.The single potato tuber weight had a strong compensation effect on the under-tuberization in early potato tuberization stage,which is also an important mechanism for stale potato yield and yield increase in soil moisture-unstable area in Northwest China.The sufficient nutrition was the foundation for high yield of the three crops.For the same crop,the harvest index was stable among different cultivation ways.The further analysis of the nutrition showed that the sufficient nutrition could significantly increase wheat spike number,corn and wheat spike number,corn kernel weight,and single potato tuber weight,but it had little effect on wheat kernel weight and the number of potato tubers.3.The mulching could significantly increase soil moisture in different years.The soil moisture with straw strip mulching in 0-200 cm layer soil during the whole growth period effects was higher than that with film mulching and the soil moisture for winter wheat and potato was higher than that for corn.Compared with film mulching,the straw mulching could conserve more water for soil.This is because,in addition to conserving soil moisture,it could also increase rainfall infiltration,lower temperature and restrain evaporation,and thus postponing the growth period to rainy season.Although in general the soil moisture was significantly higher with both film and straw mulching treatments than that with the non-mulching treatment,with the different growth stages and the soil layers,there were double effects of increasing and decreasing soil moisture.In general,the effect of increasing soil moisture with both mulching was bigger than that with non-mulching treatment for the three crops.But as far as the effect for each crop is concerned,the effect for winter wheat was bigger than that for potato and corn,the effect in wet years than that in normal rainfall years,the effect in the early stage and midstage was bigger than that in late stage.The film mulching would remarkably aggravate the fluctuation of soil moisture in different periods.The improvement of soil water supply could increase crop growth and yield component factors,which was the main reason why mulching could increase the yield.There were significantly positive correlations between the yield of the three crops and the average moisture content in the 0-200 cm soil layer during whole growth period.The water content in most of the growth period and soil layer.There was also a positive correlation between the yield structure factors and water content during the corresponding formation period.The relevant response trend of yield and nutrition growth indicator to soil moisture was consistent.In addition,it was found that deep water supply could remarkably increase wheat kernel weight single potato tuber weight.The yield and kernel weight of corn were positively correlated with soil moisture in 0-20 cm soil layer,but the kernel number per spike,kernel weight and yield of corn were not sensitive to soil moisture in 0-200 cm soil layer.The high yield and nutrition growth of winter wheat and potato must depend on high water consumption,but for corn the correlation between water consumption and the nutrition growth was weak.For the same crop,there was big difference in water consumption proportion in different stages between different cultivation ways.As straw mulching reduced soil temperature,it could remarkably reduce water consumption proportion in the early and mid stage while increasing the water consumption proportion in late stage.For potato and corn,on the contrary,it could increase water consumption proportion in the mid stage,which is an important mechanism for straw mulching to increase the yield.The correlation analysis showed that the difference in stage water consumption affected the yield by significantly affecting the nutrition growth and the yield component factors.The difference in stage water consumption was consistent with the development of the yield component factor in the corresponding stage,nutrition growth and the yield.Drought could increase harvest index of the three crops.Three crops had obvious consumption of soil moisture in 0-200 cm soil layer,but the water consumption mainly took place within the range of 0-120 cm.The mulching and drought would increase the consumption ratio of deep water storage under 120 cm,and the effect of mulching for wheat on deep water consumption was bigger than that for the two autumn crops.4.The mulching remarkably affected the soil temperature of the three crops.Compared with the CK,the straw mulching could yield cooling effect in general while film mulching could yield a warming effect in general.However,in different stages and soil layers,the mulching had double effects of both warming and cooling for the three crops.The cooling effect of straw mulching was bigger than its warming effect while the effects were reverse for film mulching.The straw mulching had bigger cooling effect and the film mulching had bigger warning effect for potato than for winter wheat.In winter stage,the warming effect of straw mulching on winter wheat mainly took place in winter.The cooling effect of straw mulching on potato and corn was bigger in early growth stage than that in late period.The monitoring of diurnal soil temperature change showed that there was a lag effect in soil temperature fluctuating with air temperature.Mulching could reduce the daily soil temperature difference for winter wheat and potato,but increase that for corn.The soil temperature significantly affected the yield development and growth.The mulching could increase winter temperature for winter wheat,which made it safe it to survive through winter and eventually increasing the yield.The increase in soil temperature at jointing stage could help increase the number of spikes,while reducing soil temperature at filling stage could significantly increase kernel weight.Straw mulching could decrease the soil temperature for potato from seedling stage to starch accumulation period from,which could increase single potato weight.But the soil temperature had no significant effect on the number of tubers.Straw mulching could decrease soil temperature especially the soil temperature in filling stage,which led to reduced kernel weight and eventually low corn yield.5.There was an remarkable interaction between soil temperature and soil moisture.The conduction of soil temperature in tilth layer could significantly affect the migration and consumption of layer below 25 cm.For winter wheat,the straw mulching reduced soil temperature in 0-25 cm soil layer,which was conducive to reducing the evaporation and transpiration of soil,and improve pondage in 0-200 cm soil layer.However,this was just the other way round for potato.There was a positive correlation between soil temperature and water content in 0-25 cm deep soil layer,but it was negatively correlated with water content in 0-200 cm deep soil layer,indicating that high water content at the upper level maintained at the cost of deep water supplement.This was related to the fact that corn has large root plant body,and big capacity for transpiration and transferring water.The degree and direction of the interaction between water and temperature were different in different periods.There is not so much precipitation for winter wheat during the growth period,so the effect of cooling and inhibiting evaporation on soil moisture was remarkable,while the temperature in the tilth layer for the two autumn(potato and corn)was negatively related to soil moisture.This was because for autumn crops rain season and hot season took place at the same time and the effect of soil moisture conservation and infiltration was far greater than the effect of cooling and inhibiting evaporation.6.Film mulching and straw mulching could remarkably increase the growth rate of wheat and potato,but the growth rate of corn with film mulching was bigger than that with straw mulching.The straw mulching could remarkably increase the contribution rate of beforeanthesis accumulation to kernel,stimulate absorption of nitrogen and phosphorous and reduce the loss of potassium accumulation in the post-anthesis stage.The straw strip mulching is environment-friendly,and the whole wheat and potato farmland can be mulched with straw.The straw mulching can also be used for growing forage corn,which can retain the leaf green of stem to improve forage quality and alleviate the labor tension during harvest and processing season.So it can be seen the straw mulching is of great potential value for extension and application. |
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