《苜蓿用钾肥》PPT课件.ppt

,苜蓿钾养分,苜蓿钾养分,概要: 植物发育Plant development 诊断Diagnosis 产量与质量Yield and quality 经济Economics 灌溉与记录收成Irrigation and record yields 阳离子竞争Cation competition 平衡营养Balanced nutrition,苜蓿生产,另外,加拿大苜蓿11百万英亩，1.4 ton/A U.S. $70亿/年, 2000-2003,USDA-NASS; Statistics Canada,苜蓿根系发育,多数侧根第一年贴近于土壤表面，但随着作物的生长，会发育更多、更深的侧根 苜蓿根际较深、根密度较低 养分应用提高根系生长，确保根系获取水分和养分的土壤范围更大。,苜蓿根系形态（种植后约2月）,旱地Dryland 渗透更深Deeper penetration 少而长侧根 更多的二级分支 灌溉地Irrigated 较浅Shallower 多而短侧根More but shorter laterals 较少的二级分支,Weaver, 1926 (NE),旱地,灌溉地,苜蓿根系形态（种植后约3月）,旱地Dryland 根系更多丰富的分支 分支达到与主根相同深度 较浅的根系 灌溉地Irrigated 较少的分支 更大的根深度 主根占优势,旱地,灌溉地,Weaver, 1926 (NE),苜蓿根系形态（第一年结束）,旱地Dryland 土壤中更多分支超过1英尺 最深达 5 英尺 根向下延伸 灌溉地Irrigated 土壤中更少的分支超过1英尺 最深达 6 英尺多 根系有更多的侧根,旱地,灌溉地,Weaver, 1926 (NE),苜蓿根系形态（第二年七月十日）,旱地Dryland 深度超过9英尺. 根向下延伸 横向延伸少 灌溉地Irrigated 深度近10英尺. 横向延伸多,灌溉地,Weaver, 1926 (NE),旱地,限制根系生长的因素降低养分吸收,病害,虫害,温度,酸度,低氧,排水不畅,过量盐或钠,营养不足,根瘤少,土壤压实,不同土壤深度的K回收率,Recovery at the end of the growing season with K placed in the Spring at various depths in an established alfalfa stand,Peterson and Smith, 1973,养分缺乏诊断,目测 测土 组织分析,苜蓿缺钾症状：小白点或黄点首先出现在老叶子外缘,缺钾苜蓿,中度缺钾苜蓿,严重缺钾苜蓿,Typical K Concentrations (at optimum fertility),植株近顶部茎秆含钾高 上下部叶子钾浓度相似 根系含钾较少 含2.5%钾的牧草相当于每收获吨重干物质除掉60英镑K2O,Lanyon and Smith, 1985,随着苜蓿成熟钾浓度降低,Barton and Reid, 1977 (WV),Soil Testing and Plant Analysis,Soil Testing Verify that K levels are being maintained Soil pH 6.5 or higher for efficient N fixation Plant Analysis Usually sample the top 6 in. at harvest Indication of adequate K fertility: 2% indicates insufficient K for winter hardiness Optimum yields usually contain around 2.5% K Record yield of 10 tons/A (non-irrigated), K content of 3%,K Deficiency Hurts More Than Yield,Adequate K Improves: Plant persistence Number of shoots per plant Shoot yield Deficient K: Reduces root starch storage Reduces protein concentration in root Results in poor survival and slow shoot growth,Li et al., 1997 (IN),K2O added, lb/A,Grewal and Williams, 2002 (Australia),K Fertilization Increases Nodule Activity,K2O added, lb/A,K Fertilization Improves Hay Quality,Grewal and Williams, 2002 (Australia),Plant counts taken in May as % of those previous September,Bailey, 1983 (MB),K Helps Reduce Winterkill in Alfalfa,Alfalfa Responses to K in Mixed Stands,Largest where soil K fertility levels are low Increases over the life of the stand Includes quality as well as yield Increased proportion of legume to grass more protein Increases in irrigated production,Hay yield, tons/A,Fertilizer K2O, lb/A,Initial soil test K was 35 ppm (low),4-yr total,1989 1992 1990 1991,Most Economic Rate,Klausner and Goyette, 1993 (NY),Response to K Increases Over Life of Stand,Rock Springs,Landisville,Yield, tons/A,Forage K, %,Fertilizer K2O, lb/A,Alfalfa response to K at two sites,Most Economic Rate,Beegle, 1992 (PA),Initial soil test K ranged from 130 to 170 ppm,Response to K Increases Over Life of Stand,Berg et al., 2003 (IN),Response to K Increases Over Life of Stand,Yield, tons/A,Fertilizer K2O, lb/A,Forage K, %,Most Economic Rate,1985,1986,Sheard et al., 1988 (ON),1985,1986,Response increases after intensive management,Alfalfa response to K under intensive 5-cut management Initial soil test K of 170 ppm in 1984, declined to 80 ppm in the unfertilized treatment by spring 1987,Soil K Levels: Turn K Fertilization into Profit,Example: Annual economic return to K fertilizer use: Assuming $90 per ton of hay and K2O at $0.15 per pound (price ratio of 3 lb hay per lb of K2O),Economics of K Fertilization,The most economic rate of K fertilization changes as the ratio of K prices to hay prices changes,Profitability: Short vs. Long-Term,The yield increase in response to K application gets larger as the alfalfa stand ages,Burmester et al., 1991 (AL),K Fertilization According to Soil Test Recommendation Maintains Alfalfa Stands,Follet and Wilkinson, 1995,苜蓿产量受土壤PH影响,Walworth and Sumner, 1990 (GA),石灰中和酸性土壤改善苜蓿生长并提高营养恢复,1公顷=15亩 1英亩=6亩 1公顷=2.5英亩 1英镑=0.45公斤 1b/A=0.45kg/6mu=0.075推导出下表中系数为0.075 21001b/A=157.5kg/mu 34001b/A=255 kg/mu,Liming Acid Soil Improves Alfalfa Growth and Nutrient Recovery,Walworth and Sumner, 1990 (GA),苜蓿发芽组成 Alfalfa shoot composition,How Does this Change with Irrigation?,Record Yield: Researchers at University of Arizona (Yuma) set record for alfalfa yield in a year: 24.1 tons/A alfalfa hay in 10 cuttings,Optimal and uniform irrigation Chopped hay removed immediately after cutting N fertilizer regularly added was it needed? 460 lb P2O5/A added before planting K management unknown,Optimum K Rate in Irrigated Alfalfa: An Example,Koenig, 2002 (UT),Best economic return,Too much in one application,Placement and Application Options,Establishment Broadcast to build up soil test K before seeding Banded starters should contain mostly P Maintenance Apply following harvest to replace removal High rates: split over several cuts to avoid salt injury To boost winter hardiness, apply before critical fall growth period (before last 6 weeks of growth) When soil K levels are high, spring applications can lead to higher K levels than desired, and may be unnecessary,Yield response to K found in last harvest of 2000 For first harvest of 2001, no response to K fertilization was observed Reason: K can be released from soil minerals during winter and spring,Volenec, 2002 (IN),K Impacts Fall Harvest more than Spring,Manure Management,Manure supplies many nutrients but usually not in the ratio required for alfalfa! Physical problems compaction, crown damage, leaf burn, salinity Nutritional problems N can stimulate weeds excessive K can cause cation imbalance in dairy feed rations,Luxury Uptake of K for Dairy Feed,K in alfalfa varies from 3% Luxury uptake when soil K is very high K levels above 3% unnecessary Liquid manure systems efficiently recycle K High K forage: A concern for dry dairy cows Leads to milk fever, retained placentas after calving For the transition period (2 to 4 weeks before calving) forage with 2% K desired; dietary K should be 1.2% Corn silage, grains, distillers grains are low K feeds Anionic salts (chlorides or sulfates of NH4+, Mg, or Ca) can help correct the problem,Burmester et al., 1991 (AL),K Competes with Other Cations for Plant Uptake: Mg,K Competes with Other Cations for Plant Uptake: Ca,Burmester et al., 1991 (AL),K Fertilization Reduces Uptake of Other Soil Cations: NA,James, 1988 (UT),Alfal