为了明确昆明地区小麦生育期需水量和缺水状况，根据田间实际观测的资料，采用FAO推荐的Penman Monteith公式，以小麦各生育期为单位，分析了昆明1972-2007年小麦出苗至成熟各生育期的需水量和缺水率。结果表明，在小麦生长期，平均降雨量为142.1 mm，平均需水量为284.1 mm，小麦生长期的降雨量明显不足。在小麦拔节和孕穗期，降水亏缺率为73.0%和72.4%；抽穗和开花期，降水亏缺率达到83.5%和78.0%。在拔节至成熟期，重度和特重度水分亏缺出现频率＞0.8，尤其是在抽穗、开花、乳熟期，重度和特重度水分亏缺出现的频率分别为0.86、0.95、0.89，对小麦年际生长发育和产量形成影响严重。

Four treatments, including ridge tillage with plastic mulch (RP), ridge tillage without mulch (RB), flat tillage with plastic mulch (FP) and flat tillage without mulch (FB), were carried out to examine the tillage type and mulch on the effects of soil moisture and temperature, yield and water use efficiency (WUE) of dry land spring maize in the North China. Results showed that the average soil temperature was increased by 1-3 °C and the accumulated soil temperature was increased by 155.2-280.9 °C from sowing to tasseling by plastic mulch, and the growing duration was extended by 5.9-10.7 d. The water conservation effect of plastic mulch was significant from sowing to the seedling establishment, with WUE being increased by 81.6%-136.4% under mulch as compared with that without mulch. From the seedling to jointing stage, which coincided with the dry period in the region, soil water utilization by the maize under mulch could reach the depth of 80-100 cm, and its WUE was about 17.0%-21.6% lower than the maize without mulch, since the latter was affected by dry stress. With the coming of rainy season around the trumpeting stage, soil water in each treatment was replenished and maintained at relative high level up to harvest. Yield of maize was increased by 9.5% under RP as compared with RB. However, yield was reduced by 5.0% under FP, due to the plastic film under flat tillage prevented the infiltration of rainfall and waterlogging occurred. No significant difference in yield was found between RB and FB. Higher yield of spring maize was limited because of the mismatching in water supply and demand characterized by soil water shortage before the rainy season and abundant soil water storage after the rainy season.

Humic acid (HA) is a relatively stable product of organic matter decomposition and thus accumulates in environmental systems. Humic acid might benefit plant growth by chelating unavailable nutrients and buffering pH. We examined the effect of HA on growth and micronutrient uptake in wheat (Triticum aestivum L.) grown hydroponically. Four root-zone treatments were compared: (i) 25 micromoles synthetic chelate N-(4-hydroxyethyl)ethylenediaminetriacetic acid (C10H18N2O7) (HEDTA at 0.25 mM C); (ii) 25 micromoles synthetic chelate with 4-morpholineethanesulfonic acid (C6H13N4S) (MES at 5 mM C) pH buffer; (iii) HA at 1 mM C without synthetic chelate or buffer; and (iv) no synthetic chelate or buffer. Ample inorganic Fe (35 micromoles Fe3+) was supplied in all treatments. There was no statistically significant difference in total biomass or seed yield among treatments, but HA was effective at ameliorating the leaf interveinal chlorosis that occurred during early growth of the nonchelated treatment. Leaf-tissue Cu and Zn concentrations were lower in the HEDTA treatment relative to no chelate (NC), indicating HEDTA strongly complexed these nutrients, thus reducing their free ion activities and hence, bioavailability. Humic acid did not complex Zn as strongly and chemical equilibrium modeling supported these results. Titration tests indicated that HA was not an effective pH buffer at 1 mM C, and higher levels resulted in HA-Ca and HA-Mg flocculation in the nutrient solution.

与传统水肥相比,优化水肥、秸秆还田优化水肥处理冬小麦主茎上第四叶叶面积和厚度略微减少,叶倾角、消光系数、各层透光率与传统水肥处理差异很小,株形尚好.优化水肥和秸秆还田优化水肥处理冬小麦籽粒产量略高于传统水肥处理.与优化水肥处理相比,秸秆还田优化水肥处理有利于增加光合面积,提高叶片质量,改善冠层结构和光分布状况,增加单位面积籽粒产量.