外源Ca2+和水杨酸对苜蓿幼苗盐害的缓解效应

通过盆栽试验,研究了NaCl胁迫下外源Ca2+与水杨酸(SA)对3种苜蓿(甘农3号、金皇后和新疆大叶)幼苗盐害的缓解效应.结果表明,外源Ca2+和SA对苜蓿幼苗的NaCl胁迫都有一定的缓解作用,能够显著(P<0.05)增加供试苜蓿植株的株高,提高植株叶绿素和根、叶K+含量,降低植株根、叶Na+含量和Na+/ K+.Ca2+和SA分别单独处理和二者复配处理对供试3个苜蓿品种的缓解效果不同,其中以Ca2+和SA复配组合处理效果最好.与对照相比,Ca2+和SA复配组合处理后甘农3号、金皇后和新疆大叶苜蓿幼苗的株高分别增加了46.1%、45.7%和45.2%,叶绿素含量依次为对照的3.71、2.84和1.61倍;甘农3号和金皇后苜蓿根部Na+含量分别降低了94.9%和89.4%;金皇后苜蓿叶部Na+含量降低了78.6%.Ca2+和SA复配组合处理对盐害的缓解效应大于单一Ca2+、SA处理;SA的缓解作用大于Ca2+.     

NaCl胁迫对苜蓿幼苗生长及不同器官中盐离子分布的影响

研究了不同浓度NaCl胁迫下(盐浓度处理为0,0.1%,0.3%,0.5%,0.7%,0.9%)苜蓿不同器官的生长情况(存活率、根长、茎长、叶片数),以及不同器官中Na⁺、K⁺、Ca²⁺、Mg²⁺的含量,并分析了K/Na、Ca/Na、Mg/Na值的变化。结果表明,存活率、根长、茎长与盐浓度呈负相关,且当NaCl≤0.1%时,有利于苜蓿的生长。除根茎叶中Na⁺含量、根中Ca²⁺与盐浓度呈正相关,茎叶中的Ca²⁺与盐浓度相关性不明显外,根茎叶中K⁺、Mg²⁺、K/Na、Ca/Na、Mg/Na均随盐浓度增加而显著下降,且盐处理与对照差异显著(P＜0.05)。另外从离子角度讨论了盐对苜蓿的毒害以及耐盐的原因。     

Concentrations of macro- and micro-elements in the milk of pasture-fed thoroughbred mares

OBJECTIVE: To determine the changes in Ca, P, Mg, Na, K, S, Cu, Fe and Zn concentrations of milk during the lactation in pasture-fed Thoroughbred mares and then calculate the dietary mineral requirements of the sucking foal and the lactating mare. PROCEDURE: Milk was sampled on days 1, 3, 7, 14, 21, 28 and at various times between 55 to 65, 85 to 95 and 135 to 150 days after parturition from 21 pasture-fed mares. The concentrations of macro- and micro-elements in the milk were determined by inductively coupled plasma emission spectrometry. RESULTS: Concentrations (mg/L) of these elements were highest in colostrum (Mg 302, Na 561, K 955, S 1035, Cu 0.76, Fe 0.79 and Zn 5.5) except for Ca (1245) and P (895), which where highest on day 7. The mean milk mineral element concentrations (mg/L) over days 55 to 150 were Ca 843, P 543, Mg 47, Na 120, K 590, S 219, Cu 0.19, Fe 0.34 and Zn 2.1. The mean plasma element concentrations (mg/L) over the same period were Ca 120, P 77.1, Mg 17.0, Na 3110, K 168, S 983, Cu 1.1, Fe 1.5 and Zn 0.49. Concentration gradients between plasma and milk were observed and, in the case of Ca, P, Mg, K and Zn, their concentrations in milk were greater than those in plasma, while a reverse situation was observed for Na, S, Cu and Fe. CONCLUSION: With the exception of Ca and P, the highest concentrations of mineral elements were observed in the colostrum. The nursing foal should have access to good pasture or creep feed, because the intakes of Ca, P and Cu from milk may be less than optimum to meet the daily mineral element requirements.     

Movement of nutrient and non-nutrient elements in the liquid phase in sheep rumen

Changes in the concentrations of B, Ca, Fe, K, Mg, Mn, Na, P, S, Sr and Zn in the liquid phase in sheep rumen were determined to obtain information on their rate of disappearance from the soluble pool after feeding. Sheep were fed alfalfa (Medicago sativa) hay hourly. The concentration of infused Cr(III)-EDTA into the rumen (over a period of 4 d) was used to establish steady-state conditions, after which feeding was stopped and the rapidly changing elemental concentrations in 30,000 x g ruminal supernatant fluid were determined by plasma emission spectrometry. The concentrations of all elements, apart from Fe, Na and P, decreased in a first-order manner over 5 h after feeding. For one sheep, these concentrations (microM) were: B, 199 to 126; Cr, 184 to 111; Ca, 4,150 to 1,130; K, 51,000 to 28,800; Mn, 11 to 4.2; Mg, 4,190 to 1,810 and Zn, 14 to 7.8. For S, first-order decay was observed over only the 0- to 2-h period (2230 microM to 865 microM). Phosphorus increased from 10.4 to 13.1 mM over the 5-h period, whereas Na remained constant (85 mM); this was attributed to saliva input. Mean half-lives for B (8.8 h), K (7.5 h) and Zn (5.3 h) were similar to those of Cr (6.3 +/- .3 h), the water flow marker. Mean half-lives of Ca (2.6 h), Mg (4.0 h), Mn (3.3 h), Sr (3.3 h) and S (1.8 h) were shorter (P less than .01) than that of the Cr marker.(ABSTRACT TRUNCATED AT 250 WORDS)     

外源2，4-表油菜素内酯对NaCl胁迫下紫花苜蓿幼苗光合特性及离子吸收、运输和分配的影响

为明确外源2,4-表油菜素内酯(2,4-epibrassinolide,EBR)诱导紫花苜蓿幼苗抗盐性的效果及其可能的生理调节机制,采用营养液水培法,以紫花苜蓿品种‘中苜3号’和‘陇中苜蓿’为材料,研究NaCl胁迫下施用外源EBR对紫花苜蓿幼苗光合色素含量、气体交换参数及离子吸收、运输和分配的影响。结果表明,1)150mmol/L NaCl胁迫下,苜蓿幼苗叶片的光合色素含量显著降低,光合能力及地上、地下生物量显著下降,苜蓿幼苗体内无机离子的吸收、运输和分配等代谢过程失调。2)NaCl胁迫下,施用0.1μmol/L外源EBR后,苜蓿幼苗叶片的Chla、Chlb、Chla+b、Chlx·c含量及Chla/Chlb显著提高,Chl/Car显著降低,Pn、Tr、Gs、WUE均显著提高,光合能力增强,促进了地上、地下生物量的积累。苜蓿幼苗不同器官(叶片、茎秆、根系)中的Na~+、Cl~-含量及Cl~-/Na~+显著下降,K~+、Ca~(2+)、Mg~(2+)含量及K~+/Na~+、Ca~(2+)/Na~+、Mg~(2+)/Na~+显著升高,体内无机离子的运输比及阳离子的运输选择性比率得到有效调控。3)说明外源EBR能够有效缓解盐胁迫对苜蓿幼苗造成的光抑制,增强有机物的合成和积累,促进对无机离子的选择性吸收和运输,维持体内的离子代谢平衡,提高苜蓿幼苗的耐盐性。     

Plant contents of magnesium, calcium and potassium in relation to ruminant nutrition

Grass tetany and wheat pasture poisoning are metabolic diseases of mature, lactating beef cattle. In some other countries, similar problems occur with dairy cattle. In grass tetany, the animals generally are grazing cool-season forages in which Mg concentration or bioavailability of plant Mg is low. Levels of Mg in the blood serum also generally are low. Grass tetany can occur in beef cattle fed hay made from grass, small grains or alfalfa Medicago sativa L.). In wheat pasture poisoning where animals are grazing small grains forages, blood levels of Ca often are low, and blood Mg also may be low. Both grass tetany and wheat pasture poisoning occur when plants are growing rapidly in the spring, at the time of heavy lactation demand by ruminants for Mg and Ca. When the temperature increases and plants start to grow rapidly in the spring, concentrations of K, N, organic acids, and the ratio of K/(Ca + Mg) all increase, and the percent dry matter decreases. Much research remains to be done to understand all the soil, plant, and animal aspects of grass tetany and wheat pasture poisoning.     

西藏那曲地区高寒草地牧草矿物元素动态变化及盈缺分析

测定了那曲地区尼玛县高寒草地不同月份围栏内和围栏外牧草矿物元素（Ca、P、Na、K、Mg、Cu和Zn）含量，并根据元素的吸收率及藏山羊矿物元素需要量，对放牧藏山羊采食牧草中矿物元素的盈缺进行了分析。结果表明：同月份围栏内与围栏外的矿物元素含量差异不显著（P〉0．05），但不同季节的变异很大。夏秋季牧草Ca、P、Na、K、Mg、Cu、Zn的含量（Ca1．25％DM，P0．1419％DM，Na0．06％DM，K1．51％DM，Mg0．28％DM，Cu8．70mg／kg，Zn27．35mg／kg）高于冬春季（Ca0．72％DM，P0．0005％DM，Na0．02％DM，K0．43％DM，Mg0．10％DM，Cu3．02mg／kg，Zn8．49mg／kg）。除Mg和青草期的K能满足藏山羊的需要外，其余元素不能满足藏山羊生长、繁殖和泌乳对矿物元素的需要量。     

锌、铁、钼肥对紫花苜蓿草产量和品质的影响

为了满足紫花苜蓿Medicaco sativa对微量元素的需求,提高其产量和品质,采用田间试验方法,在比较贫瘠的土壤条件下,研究了锌、铁、钼肥单独施用及组合施用对紫花苜蓿草产量及品质影响。结果表明：施用微量元素锌、铁、钼肥均能显著提高紫花苜蓿的草产量,其中铁单施（15 kg/hm2）和锌钼配施（12 kg/hm2,0.5 kg/hm2）处理效果最好,分别增产15.9%和5.9%。微肥对粗蛋白含量没有明显影响,但铁单施、钼单施、锌钼配合施用能显著提高苜蓿粗蛋白产量。微肥能降低粗脂肪含量和产量;对粗纤维含量没有影响,但能提高其产量;对粗灰分和无氮浸出物含量的影响不显著,但能提高其产量;显著降低钙含量,对钙产量无显著影响;能提高磷含量和产量。     

Extent and site of mineral release from six forage species incubated in mobile dacron bags

A study was conducted to measure the extent of DM disappearance and mineral release from six forage species within the rumen, abomasum and intestines of the adult bovine using the mobile bag technique. Three nonlactating Holstein cows, fitted with ruminal and duodenal cannulas, were given ad libitum access to alfalfa hay. One gram (DM) of alfalfa, rhizoma peanut, dwarf elephantgrass, bahiagrass, bermudagrass, and limpograss was individually weighed into 8-cm x 3-cm dacron bags. After ruminal incubation for 24 h, bags were incubated in an acid-pepsin solution (a simulated abomasal environment) for 1 h, inserted into the duodenum via cannula, and collected in the feces upon excretion. Ruminal incubation accounted for 86% to 100% of total DM disappearance. Release of Ca from all forages was at least 65%, with the majority having extents of release of over 70%. Most Ca was released in the rumen, but acid-pepsin incubation and washing increased Ca release an additional 17 to 272%. Forages with the highest NDF concentration (bermuda, bahia, and limpograss) sequestered Ca in the intestines. Total tract P release ranged from 84 to 98%, with an average of 7.5 percentage units occurring postabomasally. Grasses released more P in the intestines than legumes. Eighty-eight to 98% of total Mg was released in the rumen. Acid-pepsin incubation increased Mg release only slightly, with some Mg being sequestered in the intestines. Potassium release was complete in the rumen. Ranking of minerals based on maximal extent of release was K greater than Mg greater than P greater than Ca. With the exception of K, legumes released more of their minerals than grasses.     

异龄苜蓿土壤浸提液对3种植物种子萌发的影响

采用自甘肃庆阳和定西地区不同年龄紫花苜蓿(Medicago sativa L.)土壤制备浸提液,应用纸上发芽法检测其对苜蓿、萝卜(Raphanus sativus L.)和小麦(Triticum aestivum L.)种子萌发的影响.结果表明:不同生长年龄苜蓿土壤浸提液对苜蓿种子萌发以及胚根和胚芽的抑制程度为年>3年>9年,在庆阳龄苜蓿土壤浸提液(00 g干土/L)中苜蓿发芽率下降18%,其胚芽和胚根显著受抑(P<0.0),比对照分别降低69%和80%.在平均降水391mm的定西,4年以下苜蓿土壤无明显自毒性;苜蓿秋季翻耕休闲有利于3个供试种的萌发及胚根和胚芽的生长,有效解除了年龄以上苜蓿土壤的自毒效应,苜蓿-小麦轮作系统中,苜蓿后茬小麦建植不受苜蓿毒性的影响.     

Content and distribution of macro- and micro-elements in the body of pasture-fed young horses

OBJECTIVE: To determine the content and distribution of Na, K, Ca, P, Mg, S, Cu, Mn, Fe and Zn in the body of pasture-fed young horses and then use a factorial model to calculate the dietary mineral requirements for growth. PROCEDURE: Twenty-one foals were killed at about 150 days of age and the organs, soft tissues, skin and bones and a sample of muscle were dissected out and weighted. The mineral concentrations of elements in all soft tissues and bones were measured by inductively coupled emission spectrometry. The total mineral element composition associated with a tissue was determined from the weight of tissue and its mineral element concentration. RESULTS: Expressed as a percent of total body mineral elements, muscle contained 20% Na, 78% K, 32% Mg, 62% Cu, 36% Mn and 57% Zn, bone contained 47% Na, 99% Ca, 81% P, 62% Mg, 30% Mn and 28% Zn while the organs accounted for a smaller percentage ranging from 0.06% for Ca to 26% for Fe. In liver Cu accounted for 9.2% of total body Cu. Each kilogram of empty body weight was associated with 1.0 g Na, 2.5 g K, 17.1 g Ca, 10.1 g P, 0.4 g Mg, 1.1 mg Cu, 0.39 mg Mn, 52.5 mg Fe and 21.4 mg Zn. CONCLUSION: The mineral element content of body weight gain is a component used in the factorial model to determine dietary mineral element requirements for growth. The calculated dietary mineral requirements, expressed per kg dry matter, for a 200 kg horse gaining 1.0 kg/day were 1.0 g Na, 2.1 g K, 4.6 g Ca, 3.5 g P, 0.7 g Mg, 4.5 mg Cu and 25 mg Zn.     

轻度盐碱地和半干旱地区苜蓿种植技术

通过对轻度盐碱地和半干旱地区苜蓿种植技术的研究摸索,提出了该类地区苜蓿种植的技术要点。对敖汉苜蓿、中苜1号、阿尔冈金和金皇后4个品种的出芽率、出苗率、返青情况及产草量进行了测定。苜蓿种植技术的进一步推广应用,可望有效缓解"粮草矛盾",并对开发新的饲草生产资源具有重要意义。     

不同秋眠性苜蓿SRAP体系优化及遗传多样性分析

用改良CTAB(十六烷基三甲基溴化铵)法提取苜蓿基因组DNA,用L₁₆(4⁵)正交设计,研究了模板DNA、dNTPs、Mg²⁺、Taq酶和引物的浓度对扩增迁移率重现性的影响,结果表明,在20 μL体系中含有50 ng DNA、1.4 mmol/L Mg²⁺、1.2 U Taq酶、0.4 mmol/L dNTPs和0.25 μmol/L浓度的引物最为稳定,重现率达到100%。利用最佳体系从100对引物中筛选出8对在34个苜蓿上扩增效果好的引物,共扩增出87个SRAP标记,有84个多态性位点。聚类分析结果表明,来自安徽和江苏两地的野生南苜蓿和其他栽培苜蓿的遗传差异最大,单独聚为一类;其他32个苜蓿品种在相似系数0.68附近聚为3个亚群,秋眠型苜蓿品种主要分布在第2个亚群中,半秋眠和非秋眠型苜蓿品种分布散乱,并不表现出成族分布,表明秋眠性与苜蓿的亲缘关系不完全一致。     

Ruminal in situ disappearance kinetics of dry matter and fiber in growing steers for common crabgrass forages sampled on seven dates in northern Arkansas

Southern crabgrass (Digitaria ciliaris [Retz.] Koel.) is often viewed as an undesirable weed, largely because it encroaches upon field and forage crops, gardens, and lawns. However, visual observations of livestock grazing mixed-species pastures suggest that cattle seem to prefer crabgrass to many other summer forages. The objectives of this study were to assess the nutritive value of crabgrass sampled weekly between July 11, and August 22, 2001, and then to determine ruminal in situ disappearance kinetics of DM and NDF for these crabgrass forages. A secondary objective was to compare these kinetic estimates with those of alfalfa (Medicago sativa L.), bermudagrass (Cynodon dactylon [L.] Pers.), and orchardgrass (Dactylis glomerata L.) control hays. All forages were evaluated in situ using five (383 +/- 22.7 kg) ruminally cannulated crossbred (Gelbvieh x Angus x Brangus) steers. Whole-plant crabgrass exhibited more rapid (P < or = 0.002) ruminal disappearance rates of DM (overall range = 0.069 to 0.084 h(-1)) than did bermudagrass (0.054 h(-1)) and orchardgrass (0.060 h(-1)) hays, but disappearance rates were slower (P < 0.001) for crabgrass than for alfalfa hay (0.143 h(-1)). Effective ruminal disappearance of DM was greater (P < 0.001) for crabgrass (overall range = 69.3 to 75.4%) than for all the control hays. Similarly, disappearance rates of NDF for crabgrass (overall range = 0.069 to 0.086 h(-1)) were more rapid (P < 0.001) than observed for bermudagrass and orchardgrass hays; however, NDF in alfalfa disappeared at a faster (P < 0.001) rate (0.107 h(-1)) than crabgrass. These results indicate that crabgrass offers greater effective ruminal degradability of DM and NDF than orchardgrass or alfalfa of moderate quality. More importantly, it potentially offers faster and more extensive ruminal disappearance than perennial warm-season grasses typically found throughout the southeastern United States, and it should likely support improved performance by ruminant livestock in this region.     

陕西省3种北极狐饲料中矿物质元素的含量分析

随机抽取陕西境内 3家养狐场哺乳期北极狐饲料 ,对其中的Ca、P、K、Mg、Fe、Cu、Zn、Mn、Co、Se 1 0种矿物质元素的含量进行了检测。结果表明 ,在 3种饲料样品中Ca、Mg、Mn、Co、Se的含量都明显偏高 ,Cu、Zn基本符合要求。另外 ,P在A样中含量较高 ,C样中基本符合要求 ,而B样中略低 ;但部分元素如Ca与P、Cu与Zn、Zn与Ca、P与Cu等之间的比例严重失调。     

Determination of undegradable intake protein digestibility of forages using the mobile nylon bag technique

Two experiments were conducted using 2 ruminally and duodenally fistulated steers to determine the digestibility of undegradable intake protein (UIP) of smooth bromegrass (Bromis inermis), birdsfoot trefoil (Lotus coniculatus L.), and heat-treated alfalfa (Medicago sativa) using the mobile nylon bag technique. Undegradable intake protein was determined using neutral detergent insoluble CP at a single in situ incubation time point based on 75% of the total mean retention time estimated from IVDMD plus a 10-h passage lag. In Exp. 1, UIP (% DM) of smooth bromegrass in June and July were 1.82 and 1.71, respectively (P = 0.11). Undegradable intake protein (% DM) of birdsfoot trefoil increased from 1.30 in June to 1.94 in July (P < 0.01). Total tract indigestible protein of smooth brome-grass and birdsfoot trefoil increased in July (P < 0.05). Digestibility of UIP decreased in July for smooth brome-grass (P < 0.01) but tended to increase for birdsfoot trefoil (P = 0.07). In Exp. 2, alfalfa from plots fertilized with low (66 kg of N/ha) or high (200 kg of N/ha) amounts of N were dried to simulate 3 preservation methods: dehydrated (100 degrees C, 10 h), sun-cured (50 degrees C, 15 h), and lyophilized (-50 degrees C, 72 h) alfalfa. Undegradable intake protein (% DM) was estimated as in Exp. 1 and was 3.13, 2.10, and 1.84 for dehydrated, sun-cured, and lyophilized alfalfa, respectively. Total tract indigestible protein (% DM) was increased (P < 0.05) for dehydrated alfalfa (1.66) compared with sun-cured (1.54) or lyophilized (1.57) alfalfa. As a result of greater UIP flow to the lower tract, digestibility (%) of UIP was greater (P < 0.01) for dehydrated (46.4) than for sun-cured (25.6) or lyophilized (14.7) alfalfa. Heat-treated alfalfa samples increased net UIP absorption in the lower tract because 1.47, 0.56, and 0.27 percentage units of UIP (% DM) of dehydrated, sun-cured, and lyophilized alfalfa, respectively, disappeared. Overall, the digestibility of the UIP of these forages was low in the lower tract.     

豆科牧草对多花黑麦草化感作用的种间差异

实验室砂培法检测了红三叶、白三叶、杂三叶、黄花草木樨、紫花苜蓿、红豆草和毛苕子等7种豆科牧草茎叶及根的10%水浸提液处理对多花黑麦草种子萌发和幼苗生长的化感作用,结果表明:供试豆科牧草茎叶和根的水浸提液处理对多花黑麦草种子发芽势和幼苗根的生长均有显著(p<0.05)的化感抑制作用;10%水浸提液处理对多花黑麦草幼叶伸长无显著(p>0.05)影响,但对幼叶的干物质积累具有抑制作用;豆科牧草对多花黑麦草幼苗生长的化感作用在作用强度和作用机制两方面存在显著的种间差异。     

有机肥与化肥配施对低产田苜蓿产量、品质和经济效益的影响

采用田间试验,研究不同有机肥水平及配施化肥对低产田苜蓿的产量、营养品质及经济效益的影响。结果表明,施肥对低产田苜蓿草产量具有显著影响(P0.05),不论单施有机肥还是配施磷钾肥,苜蓿产量均得到提高,有机肥配施磷钾肥的3个处理显著提高苜蓿产量,第1、2茬苜蓿产量均以处理OF3PK增产最高,与对照相比分别增加了278.16%、276.54%,与其余各处理间差异显著(P0.05)。有机肥与磷钾肥配施能明显改善苜蓿营养品质,其中,粗蛋白含量得到显著提高,中性洗涤纤维和酸性洗涤纤维含量显著降低,综合分析,处理OF3PK苜蓿营养品质最佳。产投比以处理OF2PK最高,OF3PK次之,均有较好的经济效益。通过对苜蓿产量、营养品质及经济效益的综合全面的分析,处理OF3PK在实际大田生产中更适合进行推广。     

陇东野生紫花苜蓿的遗传特异性分析

为初步判定陇东野生紫花苜蓿(Native Medicago sativa L. cv. Longdong)的遗传特异性,及与其他苜蓿材料的亲缘关系,借助垂直板聚丙烯酰胺凝胶电泳技术,对包括该材料在内的41个紫花苜蓿材料进行POD同工酶酶谱特征分析。结果表明:供试材料共出现22条酶带,最多9条,最少5条;陇东野生紫花苜蓿出现6条酶带,其特征谱带为Rf0.26;将0,1二态性矩阵转化为遗传距离矩阵进行聚类,陇东野生紫花苜蓿单独聚为一类。聚类分析的结果表明,陇东野生紫花苜蓿与其他40个材料存在较大的遗传差异,为其在形态学上与其他苜蓿的差异提供了有利支持。     

紫花苜蓿根系生物量

本文综述了紫花苜蓿(Medicagosativa L.)根系生物量的影响因子和若干自然区域内的紫花苜蓿根系生物量。影响紫花苜蓿根系生物量的影响因子包括土层厚度、地下水位、土壤特性、淹水、耕作、施肥、灌溉、刈割、生长调节剂、混播、植株密度、品种和生长年限。土壤障碍(酸、碱、盐、粘重和紧实)越重、土层越薄、地下水位越高,紫花苜蓿根系生物量越小。淹水降低紫花苜蓿根系生物量。深耕可增加紫花苜蓿根系生物量,播种当年效果尤为明显。施肥可增加紫花苜蓿根系生物量。灌溉可增加紫花苜蓿根系生物量,灌溉模式及灌溉量适当时可获得相对较大的根系生物量。刈割频率越高,紫花苜蓿根系生物量越低。添加生长调节剂可增加紫花苜蓿根系生物量。混播降低紫花苜蓿根系生物量。在一定范围内,紫花苜蓿根系生物量随着植株密度的增加而增加。不同品种(材料)的根系生物量存在一定差异。生长年限越长,紫花苜蓿根系生物量越大。在每个生长季内紫花苜蓿根系生物量呈逐渐提高趋势,但在返青之初和每次刈割之后出现降低,3～4周后恢复至刈割前水平,其后则继续增加。不同自然区域紫花苜蓿的根系生物量差异较大。在相对正常的栽培管理条件下,生长1年紫花苜蓿的根系生物量约在2～7t.hm-2之间,生长2年者约为3～9 t.hm-2,生长3～5年者约为4～21 t.hm-2。