控释尿素与普通尿素(CRUNU)混合可作为一种高效氮肥类型，但其对小麦茎秆抗倒伏、产量及产量稳定性的影响尚不清楚。在2017-2021年4年的田间试验中，研究了氮肥类型(CRUNU和普通尿素(NU))和施氮量(低水平(L): 135 kg hm ^-1、中水平(M): 180 kg hm ^-1、高水平(H): 225 kg hm ^-1)对小麦群体抗倒伏性、基部节间强度、木质素含量及其合成酶活性、茎秆抗倒伏力、籽粒产量及其稳定性的影响。结果表明，两种氮肥类型在高施氮水平下小麦倒伏率均最高，其中CRUNU结合中等氮施用水平倒伏率最低。与NU相比，CRUNU在3种施氮水平下均提高了小麦群体的抗倒伏能力，这主要与小麦群体特性和第二基节间断裂强度改善有关。相关分析进一步表明，基部第二节间断裂强度与节间的物理特性、化学成分和微观结构有关。低、中和高施氮水平下，CRUNU分别使小麦籽粒产量提高4.47、14.62和3.12%。此外，在中和高施氮水平下，CRUNU的产量差异不显著，但同时中施氮水平下产量稳定性最高。综上所述，CRUNU与中氮施用量相结合可作为一种适宜小麦生产的农艺管理策略。

    Drought is a multifaceted stress condition that inhibits crop growth. Seed germination is one of the critical and sensitive stages of plants, and its process is inhibited or even entirely prevented by drought. Polyamines (PAs) are closely associated with plant resistance to drought stress and seed germination. However, little is known about the effect of PA on the seed germination of wheat under drought stress. This study investigated the involvement of PAs in regulating wheat seed germination under drought stress. Six wheat genotypes differing in drought resistance were used, and endogenous PA levels were measured during seed germination under different water treatments. In addition, external PA was used for seed soaking and the variation of hormones, total soluble sugar and starch were measured during the seed germination under different water treatments. These results indicated that the free spermidine (Spd) accumulation in seeds during the seed germination period favored wheat seed germination under drought stress; however, the free putrescine (Put) accumulation in seeds during the seed germination period may work against wheat seed germination under drought stress. In addition, seed soaking in Spd and spermine (Spm) significantly relieved the inhibition of seed germination by drought stress; however, soaking seeds in Put had no significant effect on seed germination under drought. External Spd and Spm significantly increased the endogenous indole-3-acetic acid (IAA), zeatin (Z)+zeatin riboside (ZR), abscisic acid (ABA), and gibberellins (GA) contents in seeds and accelerated the seed starch degradation and increased the concentration of soluble sugars in seeds during seed germination. This may promote wheat seed germination under drought stress. In conclusion, free Spd and Put are key factors for regulating wheat seed germination under drought stress and the effects of Spd and Put on seed germination under drought notably related to hormones and starch metabolism.

Although plastic-covered ridge and furrow planting (RF) has been reported to produce substantial increases in the grain weight of winter wheat, the underlying mechanism is not yet understood. The present study used two cultivars, Xinong 538 and Zhoumai 18, and RF and traditional flatten planting (TF, control) with the objective of investigating the effect of RF on wheat grain filling and the possible relationship of hormonal changes in the wheat grains under RF to grain filling. The results indicated that RF significantly increased the grain weight, although the effects on grain filling were different: RF significantly increased the grain-filling rate and grain weight of inferior grains, whereas RF had no significant effect on grainfilling rate and grain weight of superior grains. The ?nal grain weight of inferior grains under RF was 39.1 and 50.7 mg for Xinong 538 and Zhoumai 18, respectively, 3.6 and 3.4 mg higher than the values under TF. However, the final grain weight of superior grains under RF was only 0.6 and 0.8 mg higher than under TF for Xinong 538 and Zhoumai 18, respectively. RF significantly decreased the ethylene and gibberellic acid content in the inferior grains and increased the indole-3-acetic acid, abscisic acid and zeatin + zeatin riboside content in the inferior grains; however, no significant difference between RF and TF was observed for the hormonal content in the superior grains. Based on these results, we concluded that RF significantly modulated hormonal changes in the inferior grains and, thus, affected the grain filling and grain weight of the inferior grains; in contrast, RF had no significant effect on grain filling, grain weight and hormonal changes in the superior wheat grains.

To accurately evaluate the carbon sequestration potential and better elucidate the relationship between the carbon cycle and regional climate change, using eddy covariance system, we conducted a long-term measurement of CO2 fluxes in the rain-fed winter wheat field of the Chinese Loess Plateau. The results showed that the annual net ecosystem CO2 exchange (NEE) was (-71.6±5.7) and (-65.3±5.3) g C m-2 y-1 for 2008-2009 and 2009-2010 crop years, respectively, suggesting that the agro-ecosystem was a carbon sink (117.4-126.2 g C m-2 yr-1). However, after considering the harvested grain, the agroecosystem turned into a moderate carbon source. The variations in NEE and ecosystem respiration (Reco) were sensitive to changes in soil water content (SWC). When SWC ranged form 0.15 to 0.21 m3 m-3, we found a highly significant relationship between NEE and photosynthetically active radiation (PAR), and a highly significant relationship between Reco and soil temperature (Ts). However, the highly significant relationships were not observed when SWC was outside the range of 0.15-0.21 m3 m-3. Further, in spring, the Reco instantly responded to a rapid increase in SWC after effective rainfall events, which could induce 2 to 4-fold increase in daily Reco, whereas the Reco was also inhibited by heavy summer rainfall when soils were saturated. Accumulated Reco in summer fallow period decreased carbon fixed in growing season by 16- 25%, indicating that the period imposed negative impacts on annual carbon sequestration.

Field experiments were conducted in 2003 and 2004 to study the effects of plastic ridges and furrow film mulching (plastic film on sowing, as well as plastic film on flat soil and hole sowing) and chemicals (a drought resistant agent and a waterretaining agent) on growth, photosynthetic rate, yield, and water use efficiency (WUE) of spring millet (Setaria italica L.). The experimental results showed that water-collecting and -retaining techniques can effectively increase soil moisture content, the leaf photosynthetic rate and crop growth. Due to increased soil moisture under the plastic-covered ridge and furrow water-collecting in July and August, dry matter and plant height had a increase at the booting stage (late growth advantage). However, the plastic-covered flat soil and hole sowing reduced soil evaporation during early growth, the increase of dry matter and plant height appeared at the seedling stage (early growth advantage). Plastic-covered ridge and furrow sowing supplemented with chemical reagents had significant positive effects on water collection and soil moisture retention. Improvement of soil moisture resulted into the increase of the photosynthetic rate, dry matter accumulation yield and WUE. The water-collecting and -retaining techniques can improve WUE and enhance crop yield. Correlation analysis demonstrated that the photosynthetic rate under the water-collecting and -retaining techniques was significantly associated with the soil moisture, but had no significant relationship with leaf chlorophyll content. Plasticcovered ridge and furrow sowing supplemented with chemical reagents increased the yield and WUE by 114% and 8.16 kg ha-1 mm-1, respectively, compared with the control; while without the chemical reagents the yield and WUE were 95% and 7.42 kg ha-1 mm-1 higher, respectively, than those of the control.