水分胁迫对紫花苜蓿产量、品质和微量元素的影响

干旱严重影响牧草生长和生产,是黄土高原地区畜牧业发展的重要限制因素之一,深入理解牧草对水分供应的响应有助于优化管理、提高草地生产力。在温室控水条件下,探究了田间饱和含水量(FWC)的35%、50%、65%和80%,共4个水分水平下紫花苜蓿的生产性能差异,阐明水分胁迫对黄土高原牧草的影响。结果表明:1) 随水分胁迫的增强,紫花苜蓿株高和单株干鲜重均显著降低(P<0.05),但在65%FWC和80%FWC处理间干鲜重差异不显著。2) 50%FWC处理下紫花苜蓿中性洗涤纤维显著低于65%FWC处理(P<0.05),但与其他处理均无显著差异;35%FWC和80%FWC处理下粗蛋白含量显著高于50%FWC和65%FWC处理;可消化干物质、可消化养分总量、可消化干物质摄取量和相对饲喂价值在各水分水平下无显著变化。3) 随水分胁迫的增强,Cu和Fe浓度呈先升后降的趋势,而Mg和Mn则呈相反的趋势,Zn呈升高的趋势。5种微量元素的积累量在各水分水平下均差异不大,仅在80%FWC处理下Mg和Mn显著高于35%FWC和50%FWC处理。因此,轻度水分胁迫有利于紫花苜蓿产量和品质的提高,在50%FWC处理下,紫花苜蓿纤维含量低,营养价值高;在65%FWC处理下,紫花苜蓿产量较高。微量元素Mn、Mg、Cu和Fe在一定程度上可反映紫花苜蓿的品质特征。

Effects of water stress on yield,quality and trace element composition of alfalfa

Drought seriously affects the growth and production of forage crops and has long been one of the most important limiting factors for animal husbandry in the Loess Plateau of China. Understanding of forage response to water deficit can help to optimize grassland management and improve productivity. This study was carried out in a greenhouse with alfalfa (Medicago sativa) under four water levels of 35%, 50%, 65% and 80% field saturated water capacity (FWC) to clarify the influence of water deficit on forage yield and quality. It was found that: 1) With increasing water stress, the height and fresh and dry weight per plant of alfalfa decreased significantly (P<0.05), although fresh and dry weight per plant did not differ between 65% FWC and 80% FWC. 2) The neutral detergent fiber content (NDF) of alfalfa at 50% FWC was significantly lower than that under 65% FWC (P<0.05), but did not differ from NDF at other water levels. The crude protein content at 35% FWC and 80% FWC were significantly higher than those at 50% FWC and 65% FWC. There was no significant difference in digestible dry matter, total digestible nutrient, digestible dry matter intake and relative feeding value among various levels of water deficit. 3) Copper and Fe concentrations initially increased and then decreased with increasing water stress, while Mg and Mn concentrations showed an opposite trend and Zn concentration increased. The accumulations of five trace elements tested differed little among the different levels of water stress, except that Mg and Mn accumulations were significantly higher at 80% FWC than at 35% FWC and 50% FWC. In summary, mild water stress was conducive to the improved yield and quality. At 50% FWC, alfalfa forage showed lower fiber content and higher nutritional value, while at 65% FWC, alfalfa showed higher yield. Trace elements Mn, Mg, Cu and Fe can reflect the quality characteristics of alfalfa to a certain extent.