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To evaluate the effects of straw belt-covering on soil temperature and yield of winter wheat in rain-fed semiarid region in Northwest China, five mulching modes, including flat field planting without any mulching (CK), whole plastic film mulching (PM), straw mulching by 30 cm covering belt with an interval of 30 cm planting belt with three-row sowing (SM1), straw mulching by 40 cm covering belt with an interval of 40 cm planting belt with four-row sowing (SM2), and straw mulching by 50 cm covering belt with an interval of 50 cm planting belt with five-row sowing (SM3), were set by two-year fixed-site trails in 2013-2015. The results showed that soil temperature significantly varied among different growth stages and soil layers in all treatments. SM1, SM2 and SM3 significantly decreased soil temperature by 1.0-1.3 ℃, 0.7-0.9 ℃ and 0.7-1.1 ℃ in the 0-25 cm soil layer, respectively. The mulching had double effects with increasing and decreasing soil temperatures. The straw mulching significantly increased soil temperature in the duration of seedling to overwintering stage, but greatly decreased soil temperature in the duration of reviving to mature stage. The temperature-increasing effect of film mulching was stronger than that of straw mulching, which was opposite to the temperature-decreasing effect. Straw mulching significantly reduced in the effective accumulated temperature and the daily temperature variations during the whole growth stages. The effective accumulated temperature under straw mulching decreased by 3.4-33.5 ℃·d, and the soil temperature difference decreased by 0.6-2.0 ℃. During over-wintering stage, the straw mulching showed a higher average soil temperature (0.2-0.3 ℃) and negative accumulated temperature (0.4-17.0 ℃·d) than those under the CK. The straw mulching significantly increased grain yield by 11.9%-19.5%. The variations of spikes per unit area were the main factor responsible for yield difference. The findings indicated that that straw mulching method is suitable for winter wheat production in rain-fed region of Northwest China.

Regulatory effects of bundled straw covering on winter wheat yield and soil thermal-moisture utilization in dryland.

Bundled straw covering (BSC), using corn whole straw for partial coverage planting, is a novel dryland cultivation technique. To examine the effects of BSC on the thermal-moisture status and winter wheat yield under typical arid and semiarid conditions in the Loess Plateau of Northwest China, soil temperature, soil water content and consumption, grain yield and water-use efficiency were compared for four treatments, including no-tillage with straw mulch (NTS), whole field plastic mulching with soil covering on the top of the plastic mulch and bunch-seeding (PFM), open field cultivation (CK) and BSC during three growing seasons from 2013 to 2016. The results showed that PFM significantly increased soil temperature of 5-20 cm depth before jointing stage, while the warming effect of BSC and NTS was mainly in the wintering period. The three kinds of coverage methods after jointing stage had significant cooling effects. Both BSC and PFM significantly improved soil water storage effect during the fallow period. BSC significantly elevated soil moisture in the depth of 0 to 200 cm in the whole growing season. The improvement of soil moisture by PFM and NTS mainly occurred before the heading stage, and soil moisture in PFM treatment gradually decreased after heading stage. BSC and PFM significantly increased water consumption in the whole growth period and increased that during the jointing stage to the flowering stage, and promoted the utilization of soil moisture below 120 cm. Compared with CK, BSC, NTS and PFM significantly increased the number of panicles per unit area and biomass at maturity. In those three treatments, grain yield was increased by 19%-52%, 14%-30% and 15%-60%, respectively, and the annual water use efficiency was increased by 19%-61%, 14%-31% and 15%-58%, respectively. BSC had the same potential for increasing yield and water use efficiency as PFM. Based on factors such as winter wheat yield, soil thermal-moisture utilization and annual water consumption, BSC is a high-yield and efficient cultivation method that is conducive to the sustainable development of dryland agriculture in Northwest China.

[Effects of mulching on soil moisture in a dryland winter wheat field, Northwest China].

This paper studied the effects of different mulching modes on the soil moisture in a semi-arid rainfed area of Loess Plateau, Northwest China. Seven treatments were installed, i. e., mulching plastic film in summer (T1), mulching plastic film in autumn (T2), mulching 5 cm long wheat straw in summer (T3), mulching whole wheat straw in summer (T4), mulching plastic film in summer plus wheat straw (T5), mulching used plastic film after harvest (T6), and un-mulching (CK). In T6, the soil moisture in different layers at different crop growth stages was all higher than that in CK. In the other five mulching treatments, the soil moisture in 0-90 cm layer before flowering stage was obviously higher, but that in 0-90 cm layer after flowering stage and in 90-200 cm layer during the whole growth season was lower than that of CK. The soil moisture in 0-200 cm layer in T6 during the whole growth period was significantly higher than that in CK, with a difference of 0.9%, but the soil moisture in 0-200 cm layer in other mulching treatments was lower. As compared with plastic film mulching, straw mulching increased the soil moisture in 0-200 cm layer. The soil moisture under mulching with used plastic film after harvest was higher than that under mulching with new plastic film. As compared to CK, the grain yield of winter wheat with plastic film mulching was increased by 20.3%-29.0%, and that With straw mulching was increased by 5.0%-16.7%. There was a significant positive correlation between the crop productivity and the soil water consumption during the growth period (r = 0.77*).

[Experiment precision and comprehensive environmental evaluation of regional wheat trials in rainfed regions of China].

Based on the grain yield data of regional trials with 233 winter- and spring wheat cultivars (lines) in rainfed farmlands at 82 locations in four subregions of China in 2003-2009, this paper studied the experiment precision (EP), variety comparison precision (VCP), and testing-site discrimination ability and representativeness of national regional trials, and comprehensively evaluated the trial environment. The results showed that in one-location-one-year experiments, the average coefficient of variation (CV) and the relative least significant difference (RLSD) were 6.1% and 10.5%, respectively, and in multi-location-one-year experiments, the CV was all within 8.2%, and the CV and RLSD were mostly well controlled, indicating that the trials had a high precision. The testing-site discrimination ability was the highest in the northwest spring wheat subregion, but showed less difference in the other subregions. The testing-site representativeness was the best in the northeast spring wheat subregion, and the worst in the northwest spring wheat subregion. On the basis of the comprehensive consideration of the testing-site discrimination ability and representativeness, and by using the parameters of the environmental comprehensive assessment (r(g)h) of GGE model, it was shown that the proportion of the ideal trial locations for wheat in our rainfed farmlands was only 32.4%. Among the wheat production regions, the proportions of the ideal trial locations were in the order of northwest spring wheat subregion (40.9%) > northeast spring wheat subregion (33.3%) > Huang-Huai winter wheat subregion (30.4%) > north winter wheat subregion