不同氮用量下小麦/玉米/大豆周年体系的干物质积累和产量变化简

 通过２０１１,２０１２连续两年田间定位试验,研究了“小麦／玉米／大豆”套作体系在不同氮用量下（小麦,０,６０,１２０,１８０,２４０ｋｇＮ／ｈｍ^２,记为ＷＮ_１、ＷＮ_２、ＷＮ_３、ＷＮ_４、ＷＮ_５;玉米,０,９７．５,１９５,２９２．５,３９０ｋｇＮ／ｈｍ^２,记为ＭＮ_１、ＭＮ_２、ＭＮ_３、ＭＮ_４、ＭＮ_５;大豆ＳＮ_１、ＳＮ_２、ＳＮ_３、ＳＮ_４、ＳＮ_５）的干物质积累和产量变化。结果表明,施氮显著提高了作物地上部干物质积累量和籽粒产量（P＜０．０１）。小麦各时期的干物质积累量和籽粒产量都随氮用量增加而呈增大趋势,收获期干物质积累量以ＷＮ_４处理最高,为２０６１０ｋｇ／ｈｍ^２,产量以ＷＮ_５ 处理最高,为８１７６ｋｇ／ｈｍ^２,但ＷＮ_３、ＷＮ_４、ＷＮ_５ 间无显著差异。玉米拔节期、喇叭口期和吐丝期的干物质积累量随氮用量增加而先增大后减小,在ＭＮ_３时达最大;玉米成熟期干物质积累量和产量随氮用量增加而增大,在ＭＮ_５ 处理最高,分别为１３１４３ｋｇ／ｈｍ^２和６９７６ｋｇ／ｈｍ^２,但ＭＮ_４、ＭＮ_５ 间差异不显著。大豆在盛花期、收获期的干物质积累和籽粒产量随氮用量增加而呈先减少再增大的变化趋势,收获期干物质积累和籽粒产量以ＳＮ_４ 处理最高,分别为５４５７ｋｇ／ｈｍ^２ 和１９７７ｋｇ／ｈｍ^２,但ＭＮ_４、ＭＮ_５ 间差异不显著。小麦／玉米／大豆周年体系的总籽粒产量和产值随氮用量增加而增大,在Ｎ_５处理最高,分别为１１９５９ｋｇ／ｈｍ^２ 和２７２８８ 元／ｈｍ^２,但总产值减去氮投入的产值效益在Ｎ_４ 时最高,为２５１９６元／ｈｍ^２,Ｎ_３、Ｎ_４、Ｎ_５ 间无显著差异。小麦、玉米、大豆的产值占体系周年总产值的比重分别为３２％,５５％,１３％,因此,小麦／玉米／大豆周年体系中玉米为主要作物,其次是小麦,再次是大豆。适宜施氮量小麦为１２０ｋｇ／ｈｍ^２,玉米为１９５～２９２．５ｋｇ／ｈｍ^２,大豆可据苗情不施或适当追施氮肥,周年体系氮肥用量应为２５５～３８２．５ｋｇ／ｈｍ^２。     

磷与海南柱花草生产

对热带地区柱花草生产的主要限制因子——磷进行了盆栽和田间试验研究，以探索柱花草的营养诊断适宜值和海南地区缺磷土壤的磷肥用量。试验表明，施用磷肥能提高产量、改善品质，随磷肥用量的增加，柱花草含磷量和粗蛋白含量提高；柱花草营养诊断的适宜磷含量为０．１４％～０．３４％，磷含量与采样时间无明显差异；根据磷肥试验建立的回归模型Ｙ＝５３２４．８５＋７４５．０５Ｘ－５０．５５Ｘ２，海南缺磷土壤推茬施磷（Ｐ２Ｏ５）量为：５２．５～９７．５ｋｇ／ｈｍ２（过磷酸钙３２９～６０９ｋｇ／ｈｍ２），最大施磷（Ｐ２Ｏ５）量应低于１１０ｋｇ／ｈｍ２。     

不同缓控释氮肥对高羊茅草坪生长及氮素挥发的影响

 通过田间试验,研究了氮释放期为３０和６０ｄ的树脂包膜尿素（ＰＣＵ３０、ＰＣＵ６０）,硫包衣尿素（ＳＣＵ）,抑制剂型缓释尿素（ＵＩ）和普通尿素（Ｕ）对高羊茅草坪生长、氮素吸收及氮素挥发的影响。结果表明,在全年施氮量２６０ｋｇ／ｈｍ^２ 的情况下,ＰＣＵ３０、ＰＣＵ６０和ＳＣＵ 一年分春秋２次施用可以满足高羊茅草坪正常生长需要,其草屑累积量和氮素吸收量显著高于普通尿素一年４ 次施用处理;氮素气态损失方面,ＵＩ处理的氨挥发损失氮量高达４４．４２ｋｇ／ｈｍ^２,显著高于其他施氮处理,其Ｎ_２Ｏ 排放氮量为６．４６ｋｇ／ｈｍ^２,显著低于其他施氮处理;ＰＣＵ３０、ＰＣＵ６０、ＳＣＵ 处理的氨挥发量和Ｎ_２Ｏ 排放氮量分别为１７．６７,１３．５９,１８．５４ｋｇ／ｈｍ^２ 和８．１４,６．９２ ,９．９１ｋｇ／ｈｍ^２,显著低于Ｕ处 理。综合考虑各种因素,建议高羊茅草坪一年分春秋２次施用树脂包膜尿素ＰＣＵ６０较为适宜,可有效提高肥料利用率、降低氮素挥发损失,环境效益明显。     

黄河口潮滩湿地土壤 CH4氧化潜力及其对有机物输入的响应简

 ２０１０年１１月，采集了黄河口北部滨岸高潮滩、中潮滩、低潮滩和光滩表层土壤样品，基于短期培养实验，研究了不同潮滩土壤CH₄ 氧化潜力及其对有机物输入的响应。结果表明，尽管４种湿地土壤的CH₄ 氧化潜力存在一定差异（P＞０．０５），但整体变化规律相似。１２～６０ｈ，CH₄ 氧化潜力均呈先增加后降低变化；６０～１３２ｈ，CH₄  氧化潜力均呈迅速增加趋势。４种湿地土壤CH₄  氧化潜力整体表现为光滩（２．３７μｇ／ｇ·ｄ）＞低潮滩（２．２９μｇ／ｇ·ｄ）＞中潮滩（１．７０μｇ／ｇ·ｄ）＞高潮滩（１．４７μｇ／ｇ·ｄ）。甲醇输入整体抑制了湿地土壤的CH₄  氧化潜力，抑制程度表现为光滩＞中潮滩＞低潮滩＞高潮滩。４种湿地土壤的CH₄  氧化潜力分别为１．２７，０．４９，０．６７和０．３８μｇ／（ｇ·ｄ），较对照组降低１３．５６％，７０．９８％，７０．６５％和８３．８３％；酵母膏输入对高潮滩、中潮滩和光滩土壤的CH₄  氧化潜力表现为促进作用，促进程度表现为中潮滩＞ 高潮滩＞ 光滩。３种湿地土壤的CH₄  氧化潜力分别为２．８９，２．４１ 和２．９６μｇ／（ｇ·ｄ），较对照组增加６９．３８％，６４．０１％和２４．７６％。与之相比，酵母膏对低潮滩土壤的CH₄  氧化潜力表现为弱抑制作用，其氧化潜力为２．１４μｇ／（ｇ·ｄ），较对照组降低６．６７％。可见，不同有机物对潮滩湿地土壤CH₄  氧化潜力的影响差异较大，在当前外源有机物为黄河入海主要污染物情况下，潮滩湿地CH₄  的源／汇功能将会发生明显变化，这就使得在估算黄河口潮滩CH₄  排放清单时应特别关注不同有机物输入对CH₄  释放的影响。     

不同磷素水平对紫花苜蓿磷累积动态和种子产量构成因子的影响

为研究晋北轻度盐碱地区紫花苜蓿（Medicago sativa）种子生产过程中磷素（Phosphorus,P）吸收规律,并探索适宜的施磷水平,本试验以苜蓿品种‘巨能2号’、‘3010’和‘WL366HQ’为材料,进行不同磷素水平（100,160,220,280 kg·hm^-2）对不同生长时期的苜蓿干物质累积、磷素累积量、繁殖器官磷素累积及收获指数的动态变化以及对种子产量构成因子的相关研究。结果表明：3个苜蓿品种的干物质累积量、磷素累积量、磷素分配率、磷素收获指数的动态变化规律不一致,‘巨能2号’在盛花期的P₁₀₀处理下（即施磷量为100 kg·hm^-2）,植株和繁殖器官的磷素累积量最大,而在P₂₂₀处理下（即施磷量为220 kg·hm^-2）表现出最高的磷素收获指数;‘3010’和‘WL366HQ’均在结荚期的P₁₆₀处理下（即施磷量为160 kg·hm^-2）植株和繁殖器官的磷素累积量和磷素收获指数最大。综合分析认为,适宜施磷量可有效提高种子荚果数、结荚率和种子产量,在晋北地区较合理的施肥时期和适量为：‘巨能2号’宜在返青期施磷肥220 kg·hm^-2;‘3010’和‘WL366HQ’宜在返青期施磷肥160 kg·hm^-2。     

四川凉山州光叶紫花苕良种选育及推广研究

通过对凉山光叶紫花苕良种选育及应用研究，系统分析了该草种在不同生态条件下（海拔１５００～３２００ｍ）的生物学和生态学特性。主要经济性状是：分枝期全草干物质中粗蛋白含量为３０．６９％，粗脂肪８．７０％，粗纤维２２．８０％，无氮浸出物为２８．０３％，粗灰分８．７２％，钙１．４８％，磷０．２３％，还含有１７种必需氨基酸。平均鲜草产量４５０００～７５０００ｋｇ／ｈｍ２，种子产量６００～１２００ｋｇ／ｈｍ２。１９９６～１９９８年全州种植面积达８．５万ｈｍ２，鲜草总产２６．２６８亿ｋｇ，产值２．６２６８亿元，推动了全州畜牧业生产的发展。     

浇施沼液对狼尾草植株硝酸盐累积及其氮素利用效率研究

 采用土柱栽培法,通过不同氮素水平的沼液浇灌（设Ｎ０～Ｎ６共７个氮素水平,即每次浇灌折纯氮０,５,１０,２０,４０,８０,１６０ｋｇ／ｈｍ^２,每４５ｄ刈割周期浇灌９次）,研究浇施沼液对狼尾草植株硝酸盐累积及其氮素利用效率的影响。结果表明,狼尾草植株的硝酸盐含量受沼液中氮素水平的影响较大,二者之间呈正相关。但在高氮肥水平下,牧草各个刈割期的硝酸盐含量均低于硝酸盐有毒限量指标０．２５％。另外,随着沼液中氮素水平的提高,牧草蛋 白质含量和蛋白质产量逐渐上升,蛋白质含量和蛋白质产量最高值分别达到２１．３５％和４４．０９ｇ／盆。对全年牧草生产的氮肥利用率、蛋白质生产效率、氮素生理利用率、氮素农学生产效率和氮肥偏生产力等５个氮素利用效率指标分别表明,随着沼液中氮素水平的提高,氮素利用效率也越低,损失率也越大。从土柱淋溶的氮量分析也表明,氮素淋溶的量随着氮素水平呈明显的加大趋势,其中Ｎ５和Ｎ６处理全年淋溶的氮量分别达到８０．６９和３１２．３ｍｇ。此外,Ｎ５和Ｎ６处理土柱４０ｃｍ 以下土层全氮含量也显著高于Ｎ０～Ｎ３处理（P＜０．０５）。综合考虑认为,在１个刈割周期,狼尾草草地消纳的沼液中氮量应低于纯氮３６０ｋｇ／ｈｍ^２ 较为合理。     

氮素运筹对皖草２号和墨西哥玉米吸收Ca、Mg、S 的影响

 为明确氮素运筹对皖草２号和墨西哥玉米植株吸收矿质元素的影响,本研究分析了皖草２号和墨西哥玉米植株各器官中的矿质元素含量、累积量以及产量变化情况。结果表明,底肥一次性施入３００ｋｇ／ｈｍ^２（即Ｎ１）处理的皖草２号和墨西哥玉米Ｃａ、Ｍｇ、Ｓ含量最高,叶片Ｃａ和Ｓ含量高于茎,茎Ｍｇ含量高于叶片,皖草２号头茬草３种矿质元素含量高于墨西哥玉米;墨西哥玉米单株Ｃａ、Ｍｇ、Ｓ累积速率和累积量显著高于皖草２ 号,再生草Ｃａ、Ｍｇ、Ｓ矿质元素累积速率均呈逐渐下降趋势;皖草２号矿质元素产量显著高于墨西哥玉米,前者分次施肥处理各矿质元素产量高于一次性施肥处理。回归分析表明,皖草２号植株中３种矿质元素对生物量的作用顺序为Ｃａ＞Ｓ＞Ｍｇ,墨西哥玉米为Ｓ＞Ｍｇ＞Ｃａ,随着Ｃａ、Ｍｇ、Ｓ三种矿质元素含量升高,２种牧草单株生物量有增加趋势。生产上可以采取一次性施入氮肥３００ｋｇ／ｈｍ^２ 的管理措施,来获取矿质营养较高的牧草。     

重金属离子对２种草坪草荧光特性及根系形态的影响

 以高羊茅和多年生黑麦草为试验材料,分别设置Ｃｄ^２＋ 、Ｃｕ^２＋ 、Ｚｎ^２＋ 、Ｐｂ^２＋ 不同浓度处理,研究４种重金属离子对其荧光特性及根系形态的影响。结果表明,高羊茅在４种重金属离子处理下,其最大量子产量（F_ｖ／F_ｍ）值均低于对照,说明高羊茅在受到重金属离子胁迫后,其ＰＳⅡ 活性受到伤害;多年生黑麦草在Ｃｄ^２＋ 不同浓度处理下,其F_ｖ／F_ｍ 值均略高于对照,但差异不显著,说明Ｃｄ^２＋ 胁迫对多年生黑麦草的ＰＳⅡ系统的活性影响不大;但是Ｃｕ^２＋ 和Ｚｎ^２＋ 浓度分别达到５００ｍｇ／ｋｇ及以上时,对多年生黑麦草F_ｖ／F_ｍ 值影响较大,均显著低于对照;同时,多年生黑麦草还表现出低浓度Ｚｎ^２＋ 促进ＰＳⅡ系统活性的作用,但随着浓度升高,表现出对ＰＳⅡ系统越来越强的抑制作用;在４种重金属离子不同浓度处理下,２种草坪草的光化学淬灭系数（qP）和电子传递速率（ＥＴＲ）值均低于对照,说明其光合活性和电子传递效率均受到影响;经过４种重金属离子处理后,除部分离子低浓度处理外,高羊茅总根长、根表面积、总分叉数和总根尖数均显著低于对照,并且有随着离子处理浓度升高而逐渐降低的趋势;多年生黑麦草根系则表现出对低浓度重金属离子抗性较强,对高浓度重离子抗性较差,并且也有随浓度升高而不断降低的趋势。     

热带优良牧草落花生营养需求的初步研究

用亚热带湿热地区思茅曼中田耕作层赤红壤土,盆载优良热带豆科牧草栽培品种落花生阿玛瑞罗（Ａｒａｃｈｉｓ ｐｉｎｔｏｉ Ｌ．ｃｖ．Ａｍａｒｉｌｌｏ）,研究其正常生长所需各营养元素,结果表明：磷为影响落花生生物产量的主要肥力因子,且施磷量与落花生的干物质产量间呈有显著线性正相关（Ｙ＝１．６５＋１．２Ｘ,ｒ＝０．９０５２＾＊＊）,当施磷量为５６ｋｇ／ｈｍ＾２时,落花生的干物质产量达２６１９ｋｇ／ｈｍ＾２的最高水平。此外,硫、铜、锰、锌等微量元素也对其产量有一定影响。     

饲料中无机磷和有机磷的测定方法

用分光光度法测定了饲料中的总磷、无机磷、有机磷的含量,将饲料样品处理成溶液,在酸性条件下,磷酸根离子与矾钼酸铵试剂形成黄色配合物,在420nm处测定吸光度,方法操作简便、快速、准确,回收率为97.4%～101.8%。     

The course of phosphorus excretion in growing pigs fed continuously increasing phosphorus concentrations after a phosphorus depletion.

A balance study was performed in order to quantify the effect of continuously increased phosphorus (P) intake on faecal and urinary P excretion. The aim was to quantify the level of intake where regulatory P excretion becomes relevant for comparative digestibility measurements on P, and when the pig adapts its urinary P excretion to increased P intake. Phosphorus intake of growing pigs was continuously increased on a daily basis starting at a marginal level and P excretion via faeces and urine was continuously followed for 92 days. Two semi-synthetic diets were prepared with different proportions of Na2HPO4 resulting in 2.4 (diet 1) and 6.3 (diet 2) g P/kg DM. Concentration of Ca was adapted to achieve a Ca supply approximately 3.1 fold the digestible P supply. Six castrated male crossbred pigs (31 kg BW) were kept individually in metabolism crates after they had undergone a 14 d P depletion period during which they were fed diet 1 solely. Pigs received 1.04kg of diet 1 per day throughout the experiment, and each day the amount of feed and P supplied to pigs from diet 2 was increased by 12 g and 69 mg, respectively. ME supply was approximately 2.4 fold maintenance and average daily BW gain of pigs during the entire experiment was 690 +/- 30 g. While intake increased linearly, faecal excretion of P and Ca increased non-linearly and could be best described by third order polynomial functions. The proportion of ingested P not excreted via faeces followed a quadratic type of curve with a maximum of 81% at 25 days on experiment and P intake of 4.0 g/d. Thereafter, the proportion decreased continuously. The digestibility of P from diet 2, determined by the slope ratio technique, was constant and not affected by P intake up to a P intake of 5 g/d. Renal P excretion did not exceed inevitable losses until day 60 and increased exponentially thereafter when body P reserves were restored. It is concluded, that an adaptation to surplus P supply occurred earlier on the intestinal than on the renal level. While faecal P excretion appeared regulated depending on the actual requirement for P retention, the regulation via urine depended on the P status of the pig. Once the renal P excretion of growing pigs exceeds a level of 25 mg/d, intake of digestible P cannot be regarded sufficiently low to measure P digestibility as a capacity of the feedstuff.     

低磷土壤条件对不同苜蓿品种的生长和磷效率的影响

为探究不同苜蓿品种对低磷土壤条件的适应性,以甘农3号、甘农5号、甘农9号、甘农10号、WL358HQ、WL343HQ、WL363HQ、WL354HQ、金皇后9个苜蓿品种为研究对象,采用盆栽试验方法,对不同苜蓿品种的株高、生物量、磷含量、磷吸收和利用效率进行了研究,并采用灰色关联度对不同品种苜蓿的表现进行综合评价.结果表明:低磷条件下,结合鲜重和干重,WL343HQ品种生长速度较其他品种快;9个苜蓿品种的磷含量排序为:甘农10号>WL354HQ>WL343HQ>WL358HQ>WL363HQ>金皇后>甘农3号>甘农5号>甘农9号;WL343HQ磷吸收效率最高,为1.32 mg/pot,金皇后最低,为0.58 mg/pot,总体表现为WL343HQ>WL358HQ>甘农5号>甘农9号>WL363HQ>甘农10号>甘农3号>WL354HQ>金皇后;甘农3号磷利用效率最高,为0.84 g/mg,甘农10号最低,为0.53 g/mg.灰色关联度综合评价得出WL343HQ、WL358HQ、WL354HQ和甘农5号为低磷土壤条件下表现较好的4个品种,适宜在土壤有效磷含量较低的土壤上种植.     

Relative bioavailability of phosphorus in inorganic phosphorus sources fed to growing pigs

The relative bioavailability of P in 5 sources of inorganic P was determined using growing pigs. The 5 sources of inorganic P were dicalcium phosphate (DCP), monocalcium phosphate (MCP) containing 50% MCP (MCP50), MCP containing 70% MCP (MCP70), MCP containing 100% MCP (MCP100), and monosodium phosphate (MSP). A total of 11 diets were formulated. The basal diet was formulated to contain 0.10% P, and 10 additional diets were formulated by adding 0.07 or 0.14% P from each of the 5 P sources to the basal diet. Growing pigs (n = 44; initial BW: 16.8 ± 4.3 kg) were individually housed and randomly allotted to the 11 experimental diets. Feed was provided on an ad libitum basis throughout the 28-d experimental period. At the conclusion of the experiment, all pigs were killed, and 4 bones (i.e., the third and fourth metacarpals on both front feet) were harvested. Bone-breaking strength, bone ash, and Ca and P concentrations were determined. The concentration of bone ash increased (P < 0.05) as MCP50, MCP70, MCP100, or MSP were added to the basal diet, and the concentration of bone P also increased (P < 0.05) as MCP70, MCP100, or MSP were added to the basal diet. The relative bioavailability of P in each of the feed phosphates was determined using slope ratio methodologies based on breaking strength, and expressed relative to MSP. The slope of the regression line for diets containing MSP or MCP100 was steeper (P < 0.05) than the slope for pigs fed the diet containing DCP, but not different (P > 0.05) from that of pigs fed diets supplemented with MCP50 or MCP70. In conclusion, P in MSP and MCP100 is more bioavailable than P in DCP, but there were no differences within MCP sources.     

内源磷和磷的真消化率评定方法

磷(P)是动物体内必需的矿物质元素,具有重要的生物学功能。但是,磷的过多又会造成浪费和环境污染。只有磷的真消化率才能够更准确、真实地反映动物对磷的消化吸收情况。因此准确测定内源磷的排泄量和准确测定磷真消化率已经变得至关重要。本文介绍了几种测定内源磷和磷真消化率评定方法。     

Effect of dietary phosphorus content on milk production and phosphorus excretion in dairy cows

Background：Phosphorus（P） supplementation is costly and can result in excess P excretion.This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation.Method：Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield,and assigned randomly to one of the three dietary treatments：0.37,0.47,and 0.57%P（DM basis）;these P levels represent the NRC recommendations,Chinese recommendations,and the amount of dietary P commonly fed by Chinese dairy farmers,respectively.Average daily feed intake was calculated from monthly data on feed offered and refused.Milk yields of individual cows were recorded weekly,and milk samples were taken for analysis of protein,fat,solids-not-fat,lactose,and somatic cell count.Blood samples were collected on days-6,-3,0,3,6 relative to calving,and then monthly throughout lactation,and analyzed for P and Ca concentrations.Spot samples of feces and urine were collected for 3 consecutive d during weeks 12,24,and 36,and P concentrations were analyzed.Reproduction and health data were recorded.Results：Dietary P did not affect dry matter intake or milk yield（P〉 0.10）.Milk fat content was slightly higher in cows fed 0.37%P than in cows fed 0.47%P（P = 0.05）.Serum concentrations of P and Ca did not reflect dietary P content（P〉 0.10）.Fecal and urinary P both declined linearly（P〈 0.05） as dietary P decreased from 0.57 to0.37%.Fecal P content was 25%less when dietary P was 0.37%compared to 0.57%.Health events and reproductive performance were not associated with dietary P content（P〉 0.05）.Conclusions：Lowering dietary P from 0.57 to 0.37%did not negatively affect milk production,but did significantly reduce P excretion into environment.     

Effect of dietary phosphorus content on milk production and phosphorus excretion in dairy cows

Background

Phosphorus (P) supplementation is costly and can result in excess P excretion. This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation.

Method

Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield, and assigned randomly to one of the three dietary treatments: 0.37, 0.47, and 0.57% P (DM basis); these P levels represent the NRC recommendations, Chinese recommendations, and the amount of dietary P commonly fed by Chinese dairy farmers, respectively. Average daily feed intake was calculated from monthly data on feed offered and refused. Milk yields of individual cows were recorded weekly, and milk samples were taken for analysis of protein, fat, solids-not-fat, lactose, and somatic cell count. Blood samples were collected on days −6, −3, 0, 3, 6 relative to calving, and then monthly throughout lactation, and analyzed for P and Ca concentrations. Spot samples of feces and urine were collected for 3 consecutive d during weeks 12, 24, and 36, and P concentrations were analyzed. Reproduction and health data were recorded.

Results

Dietary P did not affect dry matter intake or milk yield (P > 0.10). Milk fat content was slightly higher in cows fed 0.37% P than in cows fed 0.47% P (P = 0.05). Serum concentrations of P and Ca did not reflect dietary P content (P > 0.10). Fecal and urinary P both declined linearly (P < 0.05) as dietary P decreased from 0.57 to 0.37%. Fecal P content was 25% less when dietary P was 0.37% compared to 0.57%. Health events and reproductive performance were not associated with dietary P content (P > 0.05).

Conclusions

Lowering dietary P from 0.57 to 0.37% did not negatively affect milk production, but did significantly reduce P excretion into environment.     

施磷对滴灌苜蓿干草产量及磷素含量的影响

为探讨不同施磷量对滴灌苜蓿干草产量、吸磷量及苜蓿磷素利用效率的影响,明确不同磷素水平下土壤全磷和速效磷的含量分布特征。试验设4种施磷梯度,分别为施P₂O₅ 0 kg·hm^-2(CK)、50 kg·hm^-2(P₁)、100 kg·hm^-2(P₂)、150 kg·hm^-2(P₃),采用滴灌水肥一体化施肥方式,平均分4次分别在返青后的分枝期、第1茬、第2茬、第3茬刈割后3~5 d施入。结果表明,各茬次苜蓿植株叶片、茎秆磷含量在P₂处理下达到最大值,其中叶片磷含量数值分别为0.223%,0.275%,0.292%和0.218%;茎秆磷含量数值分别为0.202%,0.223%,0.201%和0.146%。苜蓿叶片磷含量大于茎秆磷含量。滴灌苜蓿植株的干草产量、吸磷量随着施磷量的增加呈先增加后降低的趋势,在第1茬P₂处理达到最大值,数值分别为6.54 t·hm^-2和13.78 kg·hm^-2。土壤全磷含量、速效磷含量随着施磷量的增加呈逐渐增大的趋势,且各施磷处理显著大于未施磷处理(P<0.05),滴灌苜蓿总干草产量在P₂处理条件下达到最大,达21.24 t·hm^-2。苜蓿的磷素利用效率为随施磷量的增加呈逐渐降低的趋势,P₁处理苜蓿的磷素利用效率在第1茬达到最大值为28.37%。滴灌苜蓿植株吸磷量与干草产量呈极显著正相关(P<0.01)。当施P₂O₅为100 kg·hm^-2(P₂)时,能够有效促进苜蓿根系对土壤速效磷的吸收,提高苜蓿磷素利用效率,进而提高滴灌苜蓿干草产量。