稻田露水对水稻生长的影响研究

Effect of paddy dew on rice growth

  • 摘要: 露水凝结是水田生态系统普遍发生的气象现象, 露水作为水田生态系统重要的环境因子具有多方面的生态效应, 露水易于被作物叶片吸收, 在夜间调节补充叶片水分, 保持冠层叶面湿度, 减少作物蒸腾作用, 也可补充必要的氮、磷等营养元素。为揭示露水在水稻生长中的作用及意义, 于2013年水稻生长期对三江平原水田露水凝结量及有效态营养元素含量进行监测和分析。结果表明, 试验区作物生长期露水凝结量为28 mm, 试验期露水占同期降水量的8.3%, 露水中NO3--N含量显著高于NH4+-N和 PO43--P含量(P<0.05), 水田露水中氮、磷营养物质的浓度均高于雨水(P<0.05)。试验区未出现酸露现象, 水田露水呈偏酸性, pH均值为6.37, 露水不会腐蚀作物叶片。经监测计算, 7-10月水田露水中NH4+-N、NO3--N和 PO43--P的输入量分别为0.11 kg hm-2、0.22 kg hm-2、0.04 kg hm-2, 生长期露水量明显高于叶面肥的喷施量, 露水中NH4+-N、NO3--N和 PO43--P的输入量是叶面肥的近百倍。露水可有效地被水稻吸收, 促进作物生长, 是高效潜在肥料来源。露水是水田生态系统水分循环和养分循环不可缺少的输入项。

     

    Abstract: Dew, a crucial element of water cycle in farmland ecosystems, plays an important role in water and nutrient balance in paddy field. As a form of wet deposition, dew is a major pathway for the flow of acidic pollutants from the atmosphere to the biosphere. Acidic dew can damage protective surfaces of leaves, interfere with guard cells and poison plant cells. With dew as a surfactant by nutrient adherence to leaves, recognition of dew as an important factor of nutrient uptake is particularly significant. Dew, as a nutrient input, has always been ignored. Identifying the nutrients in dew is necessary to determine the significance of leaf dew in agricultural practices. The goals of this study were to investigate pH and essential nutrients ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3--N) and phosphate (PO43--P) in paddy dew and to explore the role of dew in nutrition availability to rice. To this end, in situ dew samples in paddy field were collected from the early July to early October of 2013 at the Sanjiang Plain Paddy Experimental Station (47°35′N, 133°31′E) of Chinese Academy of Sciences. The leaf dew samples were collected 30 min before sunrise on heavy dew days and a total of 22 dew samples were collected directly on rice leaves. A conservative unit area of actual dewfall estimated by LAI in paddy field was 28 mm in 2013. Dew was accounted for 8.3% of total rainfall during the period of study. NO3--N concentration in dew was significantly (P< 0.05) greater than NH4+-N and PO43--P concentrations. Based on statistical analysis, pH affected PO43 -P and NH4+-N concentrations of dew in paddy field. Dew contained more NH4+-N, NO3--N and PO43--P than rain. pH of dew was in the range of 5.34 7.10 with a mean of 6.37, which was not strong enough to cause damage to rice leaves in paddy field. The higher concentrations of N and P in dew were attributed to dry deposition on wet surfaces and variations in composition at high-altitude (cloud level) and low-altitude (ground level) aerosols and gases, to which the dew and rain were exposed. The contribution of leaf dew to rice growth was limited because of its limited condensation time. The deposition amounts of NH4+-N, NO3--N and PO43--P in the 28 mm dewfall from July to October in the paddy field were respectively 0.11 kg·hm-2, 0.22 kg·hm-2 and 0.04 kg·hm-2. Although nutrients were in low concentration in the dew, dew-nutrient supply was long-term. Leaf dew was not temporal, while the foliar fertilizer was evaporative. Thus leaf dew contributed more nutrients to paddy field that subsequently enhanced significant rice growth. The deposition amount of NH4+-N, NO3--N and PO43--P of dew were about 100 times as much as that of foliar fertilization. In addition, dew condensation on both sides of the leaf enhanced more effective uptake of nutrients. Therefore N and P in dews in paddy fields were other significant source nutrients. Dew was an important pathway for the nutrient transfer in paddy fields.

     

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