| Lessing the accumulated temperature, shoting of natural rainfall and serious dislocation in wheat growth stage, so wheat production was low and unstable in arid and semi-arid rainfed region of Northwest China. Mulch and straw return had been widely recognized to be effective cultivation measures, and were used to regulating soil temperature and protecting soil moisture, stabling crop yield. The study determined effects of straw return,mulch materials, mulch modes, mulch seasons, on soil water, soil temperature, grain yield and important agronomic parameters of wheat. Straw return treatments included maize straw or wheat straw return, and combined mulching plastic film or not; mulch materials included straw, white plastic film, black plastic film; mulch modes included flatten culture and whole mulched, micro-ridge and whole mulched, large ridge and half mulched; and mulch season included mulching in summer, autumn and spring, compared with non-tillage treatment as control(CK). Analyzed the effects on soil water and temperature environment and the mechanism of yield and growth of wheat under cultivation measures such as straw return and mulch treatments, explored suitable straw return and mulch measures, with a view to set up some theoretical and technical support for sustainable production system of wheat in the rainfed farming areas in the Northwest China. Main conclusions as followed:1.Mulch and Straw return had outstanding functions on increasing grain yield(GY)and water useefficiency(WUE),the positive effect on GY was more prominent in drought year. The Spikes per unit area(SPUA) was the main factor caused difference of GY.Both in the normal rainfall year and drought year, treatments of straw return increased grain yield(GY) of winter wheat with average increasing ratio of 19.2% and 40.5% compared to CK, and improved water use efficiency(WUE) by 22.1%, 19.0%.The average increase rates of GY and WUE of treatments of maize straw return was higher than wheat straw return, while mulch higher than non-mulch. The maximum rate was that of maize straw return combined mulching film(MRP), in the normal rainfall year, increase rate of GY and WUE were32.8%?41.6%, while 69.4%?38.1% in the drought year. The Spikes per unit area(SPUA) was the main factor caused difference of GY. There was significantly correlation between GYand SPUA(r =0.903**), GY and grains per spike(r =0.810**). Treatments of straw return promoted the growth of aerial parts of winter wheat, especially under mulching film condition, significantly increased plant height, Spike length, Spike weight and dry weight per plant, regulated vegetative growth of the wheat effectively, stored enough dry matter for reproductive growth and built a good nutritional base, so as to achieved high yields.Mulch film significantly increased GY and WUE of spring wheat compared with no mulching(CK), the SPUA and grain number per spike(GPS) were the two main factors caused difference of GY. Increase ranges of GY among mulching methods as follows: whole mulching film> semi mulching film, micro-ridge and whole mulching film>flatten culture and whole mulching film, mulching white film> mulching black film, mulching film in autumn > in summer > in spring. Yield of straw mulch showed in the order such as mulching maize straw> mulching wheat straw >CK, while mulching whole wheat straw decreased the production due to reduce of SPUA. Among three elements of GY, CV value of SPUA was largest, followed by GPS, and 1000-grain weight(TKW) was most stable, so the change of SPUA was main reason caused GY change under mulch condition.2. Mulch and straw return had double functions of increasing or decreasing soil moisture, warming and cooling on soil temperature. Overall, positive effects on soil moisture and temperature environment were more prominent.2.1 Straw return had effective function to increase soil water storage and soil moisture of winter wheat, and increasing effect was more prominent in the drought year. Straw return combined mulch film increased storage efficiency of rainfall in fallow period, the maximum storage efficiency of rainfall in fallow was that of MRP, higher than CK with 26.0 percentage point, and more soil water storage with 56.8 mm. Straw return combined mulching improved soil moisture, the increased humidity of maize straw return was better than that of wheat straw return. In the two growth seasons, MRP increased soil moisture in various growth stages and soil layers significantly, and increased average soil moisture during whole growth stages by 0.8~1.7; in 2011-2012 growth season, MRP increased soil moisture with 0.1~1.5 percentage point compared to CK, and higher increasing rate appeared in seeding ~ jointing period and upper soil layer(0~90 cm); in 2012-2013 growth season, increased soil moisture with 0.1~1.5 percentage point, and higher increasing rate appeared in booting ~ harvest period and lower soil layer(90~200 cm). In two growth seasons, Wheat straw return combine mulch(WRP) had significant effect on soil moisture in sowing ~ jointing stage, and little effect after jointing stage, and increased average soil moisture during whole growth stages by 0.5~0.6 percentage points; among soil layers, characteristics of soil moisture of WRP was similar to the MRP.2.2 Straw return had the double function of warming and cooling on soil temperature of winter wheat. Straw return combined mulch had a warming effect on soil temperature in seeding ~ reviving stage, and cooling effect in booting ~ filling stage, both warming and cooling performance for maize straw return were notable than that of wheat straw return; while mulching film or not had not significant effect on soil temperature. Processing, MRP effectively regulated soil temperature in the critical period of growth and yield of wheat. In seeding ~ reviving stage, MRP warmed soil temperature by 0.7~0.8?, promoted the formation of the early seedings, against the winter safely and ahead to revive 4-6 days in spring, shorten the growth period 2~3 days than CK.There was difference of the influence on soil temperatures ondifferent soil layers of straw return between years. In 2011-2012 growth season, straw return cooled the soil temperature on 5~10 cm layer, warmed the soil temperature on 15~25 cm layer, while in 2012-2013 growth season, straw return only warmed the temperature on 15 cm soil layer, and cooled the other layers. The difference of soil temperature fluctuations in different soil layers were not obvious among the treatments.2.3 Mulch had obvious effect on increasing and retaining soil moisture of spring wheat. Analyzed the average soil moisture during whole growth period, soil moisture of mulch film was better than mulch straw; mulch maize straw better than wheat straw, and mulchwhole wheat straw better than broken wheat straw, while similar between the black and white film. Among mulch methods, increasing range of soil moisture showed the order such as micro-ridge and whole mulched film> flatten culture and whole mulched film>large ridge and half mulched film; among mulching season,the soil moisture of mulch in summer was significantly better than that of CK,while those of mulch in autumn and spring were less than CK.Mulch decreased the soil moisture in booting stage, while effect in the other stages was notable different because of different mulch season. Mulch in summer had actively function on soil moisture in each growth stage, and increasing ranges in sowing ~jointing stage were higher than in flowering ~ maturity stage. The soil moistures of mulch in autumn and spring were less than CK in sowing ~ jointing and filling stage.Mulch increased the soil moisture on 0-40 cm soil layer, however, the effect on each layer dipper than 40 cmwere obvious different due to different mulch martials, mulchmethods and mulch seasons. The treatments as maize straw return combined mulch film in summer, flatten culture and whole mulched film,micro-ridge and whole mulched white film,large ridge and half mulched black film obviously increased soil moisture on soil layers which dipper than 40 cm, and those of mulching in summer, autumn, spring were similar to CK. Mulch reduced water consumption in sowing~jointing and jointing ~ flowering stage, raised that of flowering ~ maturity stage, meantime, intensified the consumption of the water in 0-90 cm soil layer.2.4 Mulch had the double function of warming and cooling on soil temperature, overall, the warming effect of mulch film was greater than that of mulch straw, while cooling effect of mulch straw was more prominent.But there were some specific differences among treatments: flatten culture and whole mulched white film increased soil temperature in each growth stage and soil layer; cooling effect of mulch maize straw and large ridge and half mulched black film were more obviously than warming effect; under the conditions of poor moisture and temperature of climate, warming effect of mulch wheat straw was more obviously than cooling effect, and under good conditions was preferably opposite. Mulch obviously affected soil temperature in sowing ~ tillering stage with CV of 7.5%~11.9%, and un-obviously affected soil temperature in jointing ~ maturity stage. There was notable difference of effect on soil layers among treatments due to environment condition. Under high altitude and drought condition, the least difference among treatments appeared on 5 cm soil layer, while the maximum difference among treatments appeared on 5 cm soil layer under low altitude and normal rainfall condition.2.5 There were differences of regulation to soil moisture and temperature of mulching broken wheat straw and mulching film in spring between two ecological conditions. Under poor soil moisture and temperature condition, mulching in spring could improve spring wheat growth microenvironment, promoted wheat tillering, increased panicle, GPS and TKW, while lessed soil moisture and temperature than CK under better soil moisture and temperature condition. Mulching broken wheat straw had limited increasing effect on soil moisture, and cooled soil temperature obviously, especially cooled soil temperature in sowing ~ tillering stage more significantly, it caused reducing emergence rate and spike rate.MRP improved soil moisture and temperature of winter wheat in the early growth stage, conductive to the growth of wheat plants, group construction; decreased soil temperature and increased soil moisture in the later growth stage, made wheat defering organs senescence, avoiding high temperature, hasening wheat to maturity. The regulated effect on soil temperature and moisture condition of MRP, significantly improved the SPUA,GPS and TKW, made coordinated development of three elements of GY, further increased GY. MRP was the one of more suitable straw return measures for rain fed farming areas in the Northwest China.Mulching method of micro-ridge and whole mulched film could significantly improve soil moisture and temperature environment in sowing ~ tillering stage of spring wheat, increasing SPUA of spring wheat, establishing reasonable population for increasing GY. Considering rainfall distribution in Northwest arid region, mulching in autumn was more conducive to improving the utilization of rainfall in last year. In all, micro-ridge and whole mulched film in autumn should be even more suitable for planting of spring wheat in arid and semi-arid region in Northwest China. |
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