滴灌紫花苜蓿根层水分稳定同位素特征分析

Distribution of Stable Hydrogen and Oxygen Isotopes in the Root Zone of Alfalfa under Drip Irrigation

为了明确滴灌紫花苜蓿根层水分运移,进一步阐明滴灌节水机理,采用液态水稳定氢氧同位素技术,分析了滴灌紫花苜蓿根层水分稳定氢氧同位素分布特征。结果表明,紫花苜蓿根层水分稳定氢氧同位素在下层富集,且随土壤剖面深度的增加同位素富集量有增加的趋势。滴灌条件下,紫花苜蓿根层发育有较多细根,可迅速而高效地利用灌溉水,灌溉后紫花苜蓿对灌溉水的利用不明确偏向于某一深度土层,根层内各土层土壤水均有利用。灌溉前土壤干旱时,滴灌紫花苜蓿以30 cm上下土层土壤水作为主要水分来源的概率较高。

To understand moisture movement in the root zone of alfalfa and the mechanism of water use efficien- cy under drip irrigation, we analyzed the stable isotopes of hydrogen and oxygen in water within the root zone of alfalfa. The results showed that the stable hydrogen and oxygen isotopes were enriched in the lower part of the root zone, and the enrichment increased with soil depth. Drip irrigation promoted root development, thereby in- creasing water uptake. After irrigation, it is not clear where the roots take water, while when the soil was dry prio- ri to irrigation, the alfalfa roots appeared to have taken water from soil at the depth of approximately 30 cm.