宁夏黄灌区退水过程中氮污染特征模拟

宁夏黄灌区是我国商品粮生产基地之一,农业高强度和化肥高投入对灌区水环境和黄河水安全造成了严重威胁。农田退水中氮素迁移流失的网室土柱模拟实验表明:1每次施肥1~2d后(穗肥是1周后),田面水中全氮量均出现峰值,不断下降后逐渐趋于稳定,全氮量随时间的变化符合对数衰减规律;23次施肥后,种植水稻的土柱各土层渗漏水中的全氮量高于未种植水稻的土柱,水稻根系的发育,一定程度上促进了氮素向下迁移,加剧了氮素流失的风险,水稻收获前控制氮的渗漏损失尤为重要。     

基于HYDRUS-2D的地下滴灌下水分运移数值模拟研究

利用HYDRUS-2D软件模拟了地下滴灌条件下滴头周围黏壤土的土壤水分动态,并与田间观测进行对比;通过分析不同滴头流量对试验地土壤湿润模式的影响,明确了最佳灌水技术参数。结果表明,HYDRUS-2D软件模拟结果与观测值一致,体积含水率均方根误差为1.2%~4.5%,湿润范围均方根误差变化范围为2.1~3.87cm。     

Water Relations, Abscisic Acid and Yield of Wheat Plants in Relation to the Interactive Effect of Seawater and Growth Bioregulators

Irrigation of wheat plants with seawater (10 and 25 %) led to significant increases in free and bound abscisic acid (ABA) in leaves, especially at 25 %. The relative water content (RWC) and water use efficiency (calculated from grain yield, WUE_G, or from biomass yield, WUE_B) of the seawater-irrigated plants were lower than those of the control. Grain pre-soaking in gibberellic acid (GA₃), indole-3-acetic acid (IAA) or ABA reduced the levels of accumulated ABA (free and bound) produced by seawater irrigation. The stress imposed by seawater generally reduced yield and yield components of wheat plants and the effect was more pronounced at the higher level of seawater irrigation (25 %). Furthermore, seawater treatments decreased the carbohydrate content and increased the protein content of the developing grains. The effect of seawater treatments on ion concentrations in the developing grains was not consistent. The application of growth bioregulators appeared to mitigate the effect of seawater salinity stress on wheat productivity. GA₃ was the most effective hormone in this regard. The economic yield (grain yield) had a strong positive correlation with RWC, WUE_G, WUE_B, plant height, shoot fresh and dry weight, grain number/main spike, kernel weight and harvest index.     

Compensatory Growth Responses During Reproductive Phase of Cowpea after Relief of Water Stress

Unpredictable drought affects growth and yield of dryland cowpea ( Vigna unguiculata [L.] Walp.) during rainy season. With the objective of identifying compensatory growth responses after relief of water stress, pot-grown plants (cv. C-752) were water-stressed at flowering, and physiological responses, short term dry matter partitioning upon relief of water stress, and productivity at maturity were studied. Water stress decreased, to varying degrees, leaf water potential, stomatal conductance, photosynthesis rate and transpiration rate. Recovery in assimilation lagged behind that in water relations. Assimilate supply seemed to be limiting early pod growth upon relief of water stress due to low photosynthesis rate, reduced leaf area per pod, and increased partitioning to leaf expansion. However, later pod growth was not limited by assimilate supply and final dry matter per pod was similar in both non-stressed and stress-affected plant. Cowpea exhibited the following growth responses during pod-fill stage upon relief of water stress: 1. increase in leaf area, 2. shift in dry matter partitioning in favour of leaf expansion, 3. extended green leaf duration, and 4. increase in pod number. These partially compensating physiological responses probably ensure reasonable productivity of dryland cowpea during rainy season.     

Comparison of selection indices to screen lowland rice for drought resistance

Summary Although many selection indices have been used to screen rices (Oryza sativa L.) for drought resistance, there has been little comparison of the relative merits of these indices. Research was conducted to compare drought resistance as estimated from grain yields, canopy-temperature-based stress indices, visual scoring, and uprooting force for 30 rice genotypes grown in the field with a puddled Maahas clay (Typic Tropaquept) and to evaluate traits related to drought resistance from nonstressed plants grown in the field and in aeroponic culture. Water deficit was imposed in the field by withholding irrigation from 45 to 75 days after transplanting compared to a continuously flooded control. Grain yields in the stress treatment were most strongly correlated with visual assessment of drought stress symptoms according to a standard evaluation system (r = 0.66). Canopy-temperature-based indices were also significantly correlated with grain yields of the stress treatment (r from –0.55 to –0.63). No trait of aeroponically grown plants was correlated with traits of stressed plants in the field. We conclude that visual scoring of stressed plants was the best method of screening for drought resistance, but if controlled water deficit cannot be imposed, then drought resistance may be estimated by measuring both uprooting force and grain yield.     

Effect of Water Status on Leaf Angle and Leaf Movement in Wheat

Water stress was imposed by watering withholding or application of PEG during the period following ligule emergence of Hag leaves or fifth leaves. Treatment reduced markedly the downward rotation of these youngest fully expanded leaves, and the angle finally reached. Leaf angle changes appear to be sensitive indicators of water shortage in wheat.     

旱地谷子集水保水技术的生理生态效应

将地膜覆盖与保水剂两种集水保水技术集成应用，观测了抽穗期不同处理谷子光合作用日变化，分析了不同集水保水技术对产量和水分状况的影响。结果表明，各处理光合速率日变化存在“午休现象”，两种覆膜方式结合使用保水剂的处理使这种趋势有所减轻；蒸腾速率日变化为“单峰曲线”，气孔导度以上午8:00最高。地膜覆盖与保水剂处理表现出一定的增产和提高水分利用效率的效果，平膜方式与垄沟方式分别较露地栽培增产78.98％、60.12％，保水剂使用较不使用平均增产7.66％，季末垄膜沟植有较好的水分效应，收获后2 m土层贮水量平均较对照增加59.9 mm。     

浅圆仓仓顶自动喷水降温试验

为了缓解夏季高温对仓温及粮温的影响,对浅圆仓仓顶进行自动喷水降温试验,利用水的蒸发带走仓顶热量,以减少外热向仓内热传递,减缓仓温和粮温上升,从而延缓粮食陈化速度,保持粮食原有品质,确保储粮安全度夏,为最终实现绿色储粮创造有利条件。     

拱板仓屋面喷水储粮安全度夏效果研究

针对拱板仓储粮度夏粮温偏高、分层明显和温差较大的特点，利用自来水自动循环装置对仓顶屋面进行喷水降温，最大限度地减少了盛夏仓顶曝晒后的积热，缩小了仓顶与粮堆之间的温差，延缓了粮温的上升速度，从而有效地改善了储粮在盛夏的高温环境，抑制了害虫的生长繁殖和粮食品质的陈化，是拱板仓储粮安全度夏的有效方法。