日光温室内反光膜补光的实践与理论探析

试验结果表明 ,温室后墙悬挂反光膜进行补光后 ,对温室内测定点处最大光照度值无影响 ,但平均提高测定点处水平光照度值 15 4 8% ;温室内凌晨时气温、地温、墙温和被反光膜遮掩处墙温分别比对照温室低 1 1℃、1 5℃、0 9℃和 1 8℃ ,但正午时分别比对照温室高 1 6℃、1 4℃、0 3℃和低 11 4℃。温室经济产量增加 7 4 % ,当期经济效益增加 2 1元 /m2 。     

Two-year development of southern pine seedlings and associated vegetation following spray-and-burn site preparation with imazapyr alone or in mixture with other herbicides

Eight herbicide combinations containing imazapyr alone or in mixture with glyphosate, triclopyr, or picloram+2,4-D were applied July–August 1991 at each of three upland sites in the southeastern U.S., with or without a subsequent broadcast burn in September. Seedlings of loblolly (Pinus taeda L.) or slash (P. elliottii Engelm. var. elliottii) pine were planted that winter. Second-year (August 1993) vegetation responses indicate that broadcast burning, in combination with herbicides, was associated with increased abundances of grasses, forbs, and shrubs and decreased abundances of vines and hardwood trees. In the presence of burning, imazapyr-in-mixture treatments were associated with a high abundance of grass (53% cover) and a mean size of pines less than that of seedlings growing in imazapyr-alone treatments. In the absence of burning, imazapyr-alone treatments were associated with a high abundance of blackberry (21% cover), an average height of hardwoods (131 cm) exceeding that of pines (71 cm), and a mean size of pines less than that of trees growing in imazapyr-in-mixture treatments. Hardwood height in the absence of burning was less when imazapyr was combined with glyphosate (75 cm) than with triclopyr (102 cm). Regardless of the presence or absence of burning, size of pines and abundance of shrubs and hardwoods did not differ between imazapyr rates of 0.56 and 0.84 kg acid equivalent/ha or among herbicides applied in mixture with imazapyr.     

不同栽培模式及施氮量对半旱地冬小麦氮素累积及分配的影响

【目的】研究不同栽培模式和施氮量对半旱地栽培条件下冬小麦-夏玉米轮作体系中冬小麦地上部氮素累积、分配及利用效率的影响。【方法】在陕西关中地区进行了田间试验,以常规栽培为对照,比较了补灌、覆草和垄沟等栽培模式及0,120,240 kg/hm2施氮水平,对冬小麦连续2年(2004和2005年)不同生长期各部位氮素累积量的影响。【结果】在补灌模式下,2004和2005年成熟期冬小麦叶片和茎秆的氮素累积量较其他模式低,氮素分配率也较低,而籽粒的氮素分配率较高;施用氮肥显著增加了各生长时期冬小麦叶片、茎秆、颖壳和穗轴以及籽粒的氮素累积量,当氮肥施用量由120增加到240 kg/hm2时,除籽粒外,成熟期冬小麦叶片、茎秆、颖壳和穗轴的氮素残留量均随之明显增加。与不同栽培模式相比,施用氮肥对冬小麦不同器官中氮素分配的影响较小。随着氮肥施用量的增加,氮肥利用效率、氮肥农学效率和氮肥生理效率均呈降低趋势。在不同栽培模式中,连续2年补灌栽培模式下冬小麦的氮肥利用效率、氮肥农学效率以及氮肥生理效率均较高,而其他栽培模式下这3个指标年际间的变化较大。【结论】施用氮肥可显著增加冬小麦各生长时期不同器官的氮素累积量,但对氮素在不同器官中分配比例的影响较小;与施用氮肥相比,不同栽培模式对冬小麦氮素的累积、分布无明显影响;冬季补灌有利于提高冬小麦的氮素效率。