【作者】 温洋；

【导师】 金继运；

【作者基本信息】 中国农业科学院 ， 植物营养学， 2005， 博士

【摘要】 紫花苜蓿（Medicago sativa L.）是具有良好品质和生态、经济效益的优质牧草。随着我国畜牧业的快速发展和农业产业结构的调整,苜蓿草生产越来越受到人们的重视。氮、磷、钾营养作为植物正常生长所必需的大量营养元素,也是评价牧草品质高低的重要指标,对提高紫花苜蓿草产量和品质有重要的影响。但迄今为止,有关磷、钾营养对紫花苜蓿草产量及其产量构成、苜蓿草品质的研究不全面,而有关磷、钾营养对紫花苜蓿草产量、品质等产生影响的生理机制尚缺乏深入系统的研究。 本文针对上述问题,于2003年分别在山东省陵县设田间磷肥用量试验;在甘肃省景泰县,青海省乐都县、湟中县和西宁市郊区分别安排了磷钾配比试验。研究磷、钾用量及其配比对苜蓿草产量、品质及养分吸收特性的影响。2004年在重复上述田间试验的同时,在中国农业科学院土壤肥料研究所采用盆栽试验系统研究了磷、钾用量及其配比对紫花苜蓿草产量、品质、养分吸收及碳氮代谢的影响。主要研究结果如下: 一、盆栽条件下,在适宜用量范围内,随磷、钾施用量的增加苜蓿植株高度、侧枝数以及产量均相应增加,但磷、钾施用量过高并不利于苜蓿植株的生长和产量的提高,磷钾配比有一定的交互作用。获得最大年产草量、年平均最高植株高度和最多侧枝数的磷、钾用量分别为P₂O₅1.06g/10kg土(P₂₄₀处理)、K₂O 0.7g/10kg土(K₉₀处理),磷钾配比为P₂O₅ 0.53-1.07g/10kg土和K₂O 0.4g-0.8g/10kg土(P_120-240K_90-180处理)。在此最适施肥处理下,植株平均高度增加3.3-4.3cm,侧枝数增加3-3.8个/株,产量提高了10.4-23.3%。 山东陵县田间连续两年的磷肥用量试验结果表明,增施磷肥能显著增加苜蓿植株的高度和侧枝数,提高苜蓿草产量。在该地区第一年获得最佳经济效益磷肥用量为85.2kg/hm²,其产量为19875.1kg/hm²。第二年苜蓿草产量随磷肥用量的增加而增加,最大磷用量120kg/hm²时产量最高,达88333.3kg/hm²。 在我国西部4个试验点连续进行两年的田间磷钾肥配比试验中,磷钾肥交互作用明显,在适宜用量范围内,随磷钾肥用量的增加苜蓿年平均植株高度、侧枝数和年总产量增加。应用Logistic方程y=k/(1+ae^bx)和二元二次回归方程对苜蓿草植株高度、侧枝数和生物产量进行了分析,得到了不同磷钾配比下的苜蓿草产量、植株的最大增长速率,最大增长速率出现的天数和平均增长速率。结果表明,不同试验地获得最高苜蓿草产量、植株最大增长速率出现的天数最短、植株最大增长速率和平均增长速率最大的适宜磷钾配比处理分别为甘肃景泰第一年P₆₀K₉₀,第二年P₁₂₀K₀;青海乐都第一年P₆₀K₉₀,第二年P₆₀K₉₀;青海西宁第一年P₆₀K₉₀,第二年P₁₂₀K₉₀;青海湟中第一年P₆₀K₉₀,第二年P₁₂₀K₉₀。 二、在适宜用量范围内,随着磷、钾施用量的增加苜蓿草粗蛋白、粗脂肪、钙含量等营养成分含量不同程度增加,过量施用会降低牧草营养成分的含量。磷、钾用量对苜蓿草灰分和无氮浸出物含量影响无明显规律。 苜蓿产草田增施磷钾肥可促进苜蓿对N、P、K、Cu、Fe、Mn、Mg等矿质养分的吸收,使苜蓿更多还原

【Abstract】 Alfalfa （Medicago sativa L.） is an important high quality forage crop with ecological and economic benefits. With rapid development of animal husbandry and re-adjustment of cropping systems in China, alfalfa is receiving more and more attention. Nitrogen, phosphorus （P） and potassium （K） are not only essential nutrients for normal plant growth, but also important components in alfalfa forage quality evaluation. Therefore, the status of P and K nutrition has significant effects on alfalfa yield and quality. Although there are research results reported in the literature on effects of P and K use on yield and quality of alfalfa, little work has been done to study the effects of P and K nutrition on physiological processes of yield formation and related mechanisms.In 2003, one field experiment with 5 different P application rates was established in Lingxian County of Shandong province to study the effect of P application rate on yield and quality of alfalfa; and 4 field experiments with 3 levels of P and 3 levels of K combinations were established in Jingtai County of Gansu province, Ledu County and Huangzhong County and Xining of Qinghai Province to study P and K application and their interaction on yield, quality and mineral nutrients absorption. In 2004, the above 5 field experiment were continued, and additional three pot experiments were conducted in Beijing to study the influences of P, K fertilizer application and their interactions on yield and quality of alfalfa, on mineral nutrients absorption and related mechanism. The results and main findings are as following:I. Results from pot experiments indicated that average plant height, the number of lateral branches and forage yield were increased with increase of application rates of P and K, until to an optimal level, over which, further increase of P and K application rate resulted in negative effects on plant growth and yield. Significant interactive effects of P and K on alfalfa plant growth and yield were also found. The optimum rates of P₂O₅, K₂O and proper combination were P₂O₅ 1.06g/10kg soil, K₂O 0.7g/10 kg soil, and P₂O₅ 0.53-1.07g/10 kg combined with K₂O 0.4g - 0.8 g/10 kg soil, respectively. These treatments with optimum rates of P, K or their combination resulted in maximum yield, maximum plant height, and largest number of lateral branches. Compared with CK treatment, the optimum treatments increased plant height by 3.3-4.3 cm. increased number of lateral branches by 3-3.8/plant, increased yield by 10.4-23.3%.The two years results from the field experiment in Lingxian County of Shandong province with 5 different P levels indicated that application of P fertilizer significantly increased average plant height, the number of lateral branches and the forage yield. The optimum application rate of P fertilizer in 同 the first year was 85.2 kg P₅O₂/hm² with yield of 19875.1 kg/ hm². In the 2^nd year, alfalfa yield increased with increase of P rate with the highest rate of 120 kg P₅O₂/ hm² resulted the highest yield of 88333.3 kg/hm².The two years results from the 4 field experiments of P and K combination in Gansu and Qinghai Province indicated that P and K application and their combined use significantly increased yield andimproved quality, and significant interaction was found. Within the proper range of application rates, P and K application increased average plant height, the number of lateral branches and the yield. By using the Logistic equation, y=k/（l+aebx） and binary quadratic equation, the maximum yield, the highest increased rate （HIR） of plant growth （plant height）, appearance time of HIR （days after planting when the HIR of plant height was observed）, and the average growth rate were estimated for different P and K combinations. Results indicated that the optimum rate of P and K to obtain the highest yield, the highest increase rate of plant growth and its earlier appearance, and highest average growth rate were P60K90 in year one and P120K0 in year two in Jingtai of Gansu; P6oK9oin year one and PW)K9o in year two in Ludu of Qinghai; P60K90 in year one and P120K.90 in year two in Xining of Qinghai; and P60K90 in year one and P120K90 in year two in Huangzhong of Qinghai.II. The contents of crude protein, crude fat and Ca were increased with increase of P and K fertilizer application rates till an optimum level. Further increase of P and K rates reduced the contents of crude protein, crude fat and Ca. No significant differences among various P and K treatments were observed for ash and non-nitrogenous extract contents. Absorption ofN,P>K> Cu -. Fe ?, Mn -. Mg by alfalfa plants increased by P and K fertilizer application, with average increase ranged from 4.5 tolO.1%. Application of K fertilizer resulted in increased absorption of Zn. Proper use of P and K improved alfalfa quality, but over-application of P and K had negative influence on alfalfa forage quality. In all experiments, the highest alfalfa yield and the best quality were observed from the same treatment, indicating that proper use of P and K can increased alfalfa yield and at the same time to improve the forage quality.III. Proper use of P and K increased absorption of N, P and K by alfalfa plant, increased photosynthesis rate, improved activity of NR, GS, GOGAT, GDH, GOT and GPT, which were enzymes involved in carbin and nitrogen metabolism.IV. Phosphate and K fertilizer use increased absorption of Mg* Fe^ Mn> Cu, increased chlorophyll and carotenoid of alfalfa leaves and improved photosynthetic rate. These processes would stimulate photosyn thesis, improve C metabolisms, and then improve yield and quality.V. Compared the results from experiment sites located at different altitudes with different annual average temperature, but with same soil type and similar soil nutrition level, it was found that altitude and annual average temperature has significant effect on alfalfa forage yield and quality. Compared with the result from Ledu site with relatively low altitude of 1920 m and higher average annual temperature of 6 °C, alfalfa in Huangzhong site at an altitude of 2630 m and average temperature of 3.7 °C showed slower growth rate, lower forage yield, lower crude protein and N, P, K contents, but higher crude fiber. According to the current world alfalfa forage quality standard, the forage produced from the higher altitude site can only meet the standard of 2nd grade with total yield of 12424 kg/ha in two years, 28.4% increase than CK treatment, and average content of crude protein in two years,3.13更多还原