| Mulching is a major drought resistance cultivation technique in the dry farming areas of Northwest China. The previous research and development on mulching cultivation techniques laid more emphasis on the effect of mulching on preserving soil moisture, but failed to pay enough attention to the interactions between water and temperature under mulching. This study presents a new mulching technique for preserving soil moisture—bundled straw covering, which can regulate moisture with temperature and reduce evaporation by lowering the temperature while highlighting the moisture preserving effect of mulching. This study was carried out to determine the differences and difference mechanism of soil moisture, soil temperature, yield, yield structure factors and other important agronomic indexes for winter wheat in a semiarid rain-fed region of Loess Plateau, Northwest China during 2012-2013 and 2013-2014 growing seasons. Winter wheat was grown under four cultivation patterns: bundled straw covering that is mean covering spaces mulched with whole maize straws and bunch-seeding in planting spaces(T1), whole field plastic mulching with soil covering on the top of the plastic mulch and bunch-seeding(T2), whole field mulching with the 5 cm wheat straw and bunch-seeding(T3), and un-mulched with bunch-seeding as control(CK). Main results were concluded as follows:1. Compared to CK, T1, T2 and T3 increased winter wheat grain yield by 37.1%~51.8%, 41.1%~60.5% and 19.3%~30.2%, respectively. T1 and T3 both had the same potential yield. Grain yield of the three mulching methods increased was mainly caused by spike numbers increased more than 20%. Meanwhile, 1000-grain weight and kernels per spike increased to the extent. Among the three mulching methods, T1 could accelerate synergistically spike numbers, 1000-grain weight and kernels per spike. In addition, the tiller number, finally panicles and dry matter accumulation of population, single plant weight, and grain weight per ear were increased with three mulching methods, so as the dry matter accumulation and relative growth rates at post-anthesis, thus promoted the dry matter at maturity translocation from vegetative organs to grain. T1 achieved the highest dry matter accumulation and relative growth rates at post-anthesis, as the same time, T1 had the highest grain dry matter partitioning at maturity.2. Compared to CK, both plastic mulching(T3) and straw mulching(T1, T2) increased soil temperatures before the jointing stage of winter wheat but decreased soil temperatures after the jointing stage. The increasing magnitude of soil temperature plastic film mulching was greater than straw mulching, whereas the decreasing magnitude of soil temperature was just contrary. Among the mulching treatments evaluated in the study, T3 increased soil temperatures most and higher than CK 0.86~0.94℃before the jointing stage, whereas T1 decreased most and lower than CK 1.8~2.7 ℃in 0~25 cm soil layer from jointing to maturity. In addition, it suggested that soil thermal conductivity of the three mulching methods were stronger at lower soil temperature condition, weaker at higher soil temperature stage, the three mulching methods adjust the characteristics of soil thermal conductivity, keep the relative stable soil temperature. T1 had the least fluctuation of soil temperature with different growth stages.3. In T1, the soil moisture in different layers at different winter wheat growth stages was all higher than that in CK. In both T2 and T3, the soil moisture in 0~200 cm layer before heading stage was obviously higher, but that after flowering stage was little by little lower than that in CK. T1 improved 34.8~49.6 mm more soil water storage in the 0~200 cm soil profile than the CK during the whole growth period. Winter wheat with both T1 and T3 consumed 13.0~51.2 mm and 19.2~63.0 mm more water than the CK in the whole growth period. Meanwhile, the three mulching methods were found to able to increase water consumption amount from jointing to maturity, promoted deep soil water usage, and then enhanced the biomass and grain yield at maturity. The three mulching methods led to a higher soil water consumption over the whole growing season, but the water use efficiency was also increased due to much more increase of grain yield. Compared with CK, T1, T2 and T3 enhanced water use efficiency by 25.2%~31.9%, 19.4%~25.7% and 27.2%~33.6%, respectively. There was a significant positive correlation between the crop productivity and the soil water consumption during the growth period(r=0.954*~0.975*). Though the high grain yield of mulching was based on high water consumption, the soil storage in the 0~200 cm depth with the three mulching methods was restored rapidly from postharvest to the autumn seeding of the next crop to the level equivalent to the soil moisture in open field. Among all methods, T1 had the best per-sowing soil water, CK was lowest.4. In the three mulching methods, the plant water content from wintering to mid-filling stage was obviously higher than that in CK, as well as T1 had the best plant water content. The plant water content was significantly correlation with the soil water content from wintering to mid-filling stage, as well as the plant water content variation was influenced by the 90~200 cm soil water content. But the plant water content was not significantly correlation with the 0~25 cm soil temperature. In both T2 and T3, the average soil respiration rates were 56.9% and 217.3% higher than that in CK respectively, and the carbon dioxide emissions were 69.5% and 248.3% more than that in CK respectively. Whereas, T1 was not significantly correlation with CK. Soil temperature and moisture could explain 50.2%~77.1%, 3.2%~36.4% of the seasonal variations in the soil respiration, respectively. Soil respiration was significantly sensitive to soil moisture, whereas not significantly sensitive to soil temperature. The sensitivity of soil respiration to soil temperature(Q10) was 3.24~6.04 and was CK>T1>T2>T3. It was suggested that soil respiration under different mulching methods was mainly controlled by soil temperature in this area. T1 could inhibit soil respiration, and helped agriculture sustainable development.5. Both plastic mulching and straw mulching are an effective way to improve water use efficiency in dry winter wheat field, as well as WUEET?B. Compared to CK, both T1 and T3 could improved WUEET?B from jointing to maturity, as well as T2 could improved WUEET?B after the flowering stage. T1, T2 and T3 were 5.4%~33.5%, 20.2%~28.9% and 34.3%~51.9% more WUEET?B than that in CK, respectively. The three mulching methods obtained higher WUEET?Y than that in CK. In all treatments, T3 achieved the highest WUEET?Y, as well as T1 was not significantly correlation with T3. There was a significantly positive correlation between WUEET?Y and WUEET?B during flowering to maturity. In contrast, there existed significantly negative correlation between WUEET?B and corresponding water consumption during sowing to reviving, and flowering to maturity, respectively. Moreover, there were positive correlations among WUEET?B and WUEET?Y and the soil moisture in 0~20 cm layer, but both WUEET?B and WUEET?Y were not correlations with the soil temperature in 0~25 cm layer.Generally, Bundled Straw Covering firstly kept soil average temperature in 0~25 cm soil profile during sowing–jointing stage, increased Gra and 0~200 cm soil water before jointing stage of winter wheat, promoted seeding establishment and benefited to winter wheat safe over-wintering, increased winter wheat populations for increase grain yield. Secondly, Bundled Straw Covering decreased soil temperature in 0~25 cm soil profile, increased 0~200 cm soil water after jointing stage, and improved dry matter accumulation and relative growth rates at post-anthesis, especially filling stage, promoted the transferring of energy to grain, improved filling, benefit to the using of light, heat and water. Thus, yield components of winter wheat improved significantly, spike numbers, 1000-grain weight and kernels per spike of winter wheat increased significantly. In conclusion, Bundled Straw Covering had the same potential of yield and WUE with plastic mulching. Though the high grain yield of Bundled Straw Covering was based on high water consumption, the soil storage in the 0~200 cm depth with Bundled Straw Covering was restored rapidly from postharvest to the autumn seeding of the next crop to the level equivalent to the soil moisture in open field, as well as it had the higher soil water than CK at maturity. In addition, Bundled Straw Covering could inhibit soil respiration, and reduced the carbon dioxide emissions. We conclude that the Bundled Straw Covering is a highly-efficient cultivation pattern for increasing crop productivity, enhancing water use efficiency, and improving agriculture sustainable development in the semiarid rainfed Loess Plateau area of Northwest China. |
PDF Full Text Request