涂蜡沙子可使干旱区土壤保湿时间更长，提高作物产量

诸平

Paraffin wax-coated sand is an extremely water-repellant material, which keeps soil wet and increases crop yields in arid environments. Credit: ACS Agricultural and Science Technology (2022). DOI: 10.1021/acsagscitech.1c00148

据美国化学会（American Chemical Society）2022年3月16日提供的消息，在干旱地区，涂蜡的沙子可以使土壤保持更长时间的湿润，提高作物产量（Wax-coated sand keeps soil wet longer, improves crop yields in arid regions）。

干燥、炎热的地区很难种植植物，因为那里的土壤干得很快。因此，干旱和半干旱地区的农民用埋在地下的灌溉管网灌溉农田，并用塑料薄膜覆盖地面。但是塑料薄膜很贵，而且会造成浪费。现在，研究人员在《美国化学会农业与科技》（ACS Agricultural & Science  Technology ）杂志上报告说，已经开发出一种简单的、生物可降解的、涂蜡的地面覆盖物，它可以保持土壤湿润并增加作物产量。详见：Adair Gallo Jr., Kennedy Odokonyero, Magdi A. A. Mousa, Joel Reihmer, Samir Al-Mashharawi, Ramona Marasco, Edelberto Manalastas, Mitchell J. L. Morton, Daniele Daffonchio, Matthew F. McCabe, Mark Tester, Himanshu Mishra. Nature-Inspired Superhydrophobic Sand Mulches Increase Agricultural Productivity and Water-Use Efficiency in Arid Regions. ACS Agricultural and Science Technology, Publication Date:February 24, 2022. DOI: 10.1021/acsagscitech.1c00148. https://doi.org/10.1021/acsagscitech.1c00148

参与此项研究的有来自沙特阿拉伯阿卜杜拉国王科技大学（King Abdullah University of Science and Technology (KAUST), Saudi Arabia）、阿卜杜勒阿齐兹国王大学（King Abdulaziz University）以及埃及艾斯尤特大学（Assiut University, Egyp）的研究人员。阿卜杜拉国王科学技术大学(KAUST)通过奖学金对于此项研究给予了支持。

为了灌溉庄稼，农民通常从附近的水道或地下蓄水层取水。当植物在干旱地区（arid regions）生长时，这些供给会迅速耗尽，因为那里的土壤大部分是沙子，不能很好地保持水分。提高灌溉用水效率的一种方法是确保灌溉水在土壤中停留的时间足够长，以便植物的根系能够吸收它。以前的研究表明，诸如塑料薄膜和工程纳米材料等地表覆盖屏障可以减缓蒸发，并提高植物生长和作物产量。然而，这两种方法都可能将有害的化合物滤入土壤，造成未知的长期影响。一些植物和动物自然产生蜡状物质，从雾或凝结物中捕获和聚集水，以便它们能够获得这些湿气源。希曼舒·米什拉(Himanshu Mishra)和他的同事从自然中获得灵感，想看看他们是否可以在沙子上涂上蜡，创造一种环境友好的地面覆盖物，以控制土壤蒸发。研究人员选择了纯化的石蜡，一种可大量使用的可生物降解物质，用于他们的实验。他们把蜡溶解在己烷中，然后把硅砂倒进混合物中。随着溶剂蒸发，颗粒上留下了一层20 mm厚的蜡层。当该团队将涂有蜡的沙子涂在沙特阿拉伯的一块空地上时，土壤水分的流失减少了50%~80%。田间试验表明，用这种新材料覆盖的西红柿、大麦和小麦植株比在没有覆盖的土壤中种植的植株产出更多的西红柿和谷物。此外，植物根部和土壤中的微生物群落并没有受到蜡质覆盖物的负面影响，这些覆盖物可能是一些微生物的食物来源。研究人员说，这种简单的自然启发技术可以使干旱地区的用水效率更高。

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Benefits of cover crops extend to dry areas

Abstract

Excessive evaporative loss of water from the topsoil in arid-land agriculture is compensated via irrigation that exploits massive freshwater resources. The cumulative effects of decades of unsustainable freshwater withdrawals in many arid regions are now threatening food–water security. While plastic mulches can reduce evaporation from the topsoil, their cost and nonbiodegradability limit their utility. In response, we report on biodegradable superhydrophobic sand (SHS), a bioinspired enhancement of common sand with a nanoscale wax coating. When SHS was applied as a 5–10 mm-thick mulch over the soil, evaporation was reduced by 56–78% and soil moisture increased by 25–45%, which benefited the development of crops. Multiyear field trials with tomato (Solanum lycopersicum), barley (Hordeum vulgare), and wheat (Triticum aestivum) under normal irrigation demonstrated that SHS mulch application enhanced yields by 17–73%. Under brackish water irrigation (5500 ppm NaCl), SHS mulching produced 53–208% higher fruit and grain yields for tomato and barley crops, respectively. SHS application did not affect the soil–root–rhizosphere microbial communities as evidenced by 16S rRNA gene analysis. The rhizospheric environments were dominated by an assemblage of diverse bacterial communities, such as Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes, followed by Firmicutes, Gemmatimonadetes, and Actinobacteria, which could be responsible for the degradation of paraffin wax on the SHS. Thus, SHS technology should benefit irrigated agriculture and city-greening efforts in arid regions under the constraint of high water-use efficiency.