土下覆膜与适宜灌水提高冬小麦水分利用率

为缓解河北平原区水资源匮乏与小麦生产水分高耗的特征性矛盾,该文采用大田试验方法,设置土下微膜覆盖结合拔节期灌水75 mm、抽穗期灌水75 mm、灌浆期灌水75 mm、雨养,露地条件下雨养和常规生产(CK)共6个处理,定位研究了连续3个生长季的土下微膜覆盖与不同时期灌水对冬小麦用水与产量形成的效果。结果表明,采用土下微膜覆盖种植小麦,基本苗数和有效穗数较CK分别降低了8.6%~12.0%和7.4%~11.7%,拔节至抽穗期75 mm灌水保证了覆盖下小麦生物产量形成及穗粒数、粒重的提高。土下微膜覆盖并适时灌水75 mm,开花后营养器官干物质向籽粒转运量比CK提高37.2%~57.3%,对籽粒贡献率提高4.7%~10.1%。土下微膜覆盖结合抽穗前一次灌水,全生育期田间耗水减少99.9~118.9 mm,用占CK 3/4的耗水量生产了与其相当的籽粒产量,水分利用效率提高26.1%~34.5%。回归分析表明,土下微膜覆盖下拔节-抽穗田间耗水118 mm可获得最高的生物产量,抽穗-灌浆耗水78 mm可获得15个以上的结实小穗数和灌浆期不小于5的叶面积指数,从而籽粒产量得以有效维持。2 m土体贮水随小麦生育进程和种植年限的推进而呈现亏损态势,而且趋近地表土壤水分亏损就越多。从第2季开始,持续干旱导致覆盖下灌浆期灌水对提高产量已不具有作用,反而增加耗水,灌溉时间前移可增加产量并提高水分利用效率。播种时土壤贮水较上季小麦收获时大幅增加,播种-拔节期间土壤贮水保蓄是小麦节水生产的关键,土下微膜覆盖则可实现麦田土壤贮水的秋冬保蓄、春季供应的跨季节调用。在河北省小麦产区,土下微膜覆盖结合春季适时少量灌水是有效降低小麦耗水、提高水分利用效率和维持小麦产量的新型种植方法。

Soil-coated ultrathin plastic-film mulching and suitable irrigation improve water use efficiency of winter wheat

More than 70% of water is used for agriculture, excessive water consumption for conventional winter wheat production is aggravating the groundwater crisis in Hebei Plain. In order to mitigate the water supply and demand conflict, a field experiment was conducted from 2011 to 2014 (October-June) in Shenzhou County, where more than 90% of the agricultural fields are used for the winter wheat-summer maize double-cropping. A randomized block design was employed with six treatments and four replicates, the treatments included: 1) soil-coated ultrathin plastic-film mulching (SUPM) with 75 mm irrigation at jointing stage, 2) SUPM with 75-mm irrigation at heading stage, 3) SUPM with 75 mm irrigation at filling stage, 4) rainfed under SUPM, 5) rainfed, 6) conventional farmers’ practice with 225 mm irrigation splitted into three applications (control). The study examined the effects of SUPM with different irrigation management on WUE, yield formation of winter wheat. The fieldwork procedure of SUPM was as follows:the straw of the previous crop was removed, and after base dressing with chemical fertilizer the field was plowed twice, the field surface was leveled, and wheat seeds were sown. The whole plot was mulched using ultrathin 0.004-mm-thick plastic film without separation between adjacent strips of film. The film was tensioned and its surface kept flat without folding, then 1-2 cm of soil was manually placed on it;consequently, the film was completely covered with soil. A wheat plumule could pierce the film and emerge. So relative seamless coverage of field was achieved to control soil water evaporation. After the wheat was harvested, summer maize was manually dibbled without plowing, only 60 mm irrigation applied after sowing during its whole season. The result showed that under SUPM the seedlings and spike number decreased by 8.6%-12.0% and 7.4%-11.7%, respectively, compared with the control, but the 75 mm irrigation at jointing or heading stage ensured the biomass formation and increased grain number per spike and kernel weight. The timely 75 mm irrigation under SUPM promoted the dry matter transfer to grain from vegetative organs, the transfer amount was 37.2%-57.3%higher than the control, and the contribution rate of transfered matter to grain increased by 4.7-10.1 percentage points. Also, the field water consumption decreased by 99.9-118.9 mm, and the water-use efficiency increased by 26.1%-34.5%. Regression analysis showed, under SUPM with 118 mm filed water consumption from jointing to heading, wheat could obtain the most biomass, and with 78 mm from heading to filling could achieve more than 15 fertile spikelets per spike and a higher leaf area index with the value of 5 at filling stage. This was why the wheat whose field water consumption was only 3/4 of the control could achieve an equivalent grain yield to the control. In the study, as wheat growing process and the cropping years continued, the soil water in 2 m soil body tended to decrease, and greater water deficit occurred as the soil layer was closer to the surface. Furthermore, the layer of soil water extracted by the rainfed wheat was deeper than that irrigated. From the second growth season, the continuous soil drought resulted in the yield reduction of the wheat which was irrigated until filling stage, the irrigation at filling stage was unhelpful for yield and increased the field water consumption. As the soil water decreased continuously, it was very necessary that the irrigation was earlier applied to increase yield and WUE. The soil water content at wheat sowing in autumn was significantly higher than that at harvest of previous wheat in summer, decreasing soil water consumption from sowing to jointing was crucial for water-saving of wheat production. SUPM could conserve soil water in autumn and winter,and to supply across seasons for wheat growing in the following spring. Overall, in Hebei Plain SUPM in combination with timely 75 mm irrigation could be considered a new method to decrease the water consumption, improve WUE and maintain grain yield of wheat production effectively.