苜蓿用钾肥.ppt

International Plant Nutrition Institute * Dryland alfalfa production in Australia, potassium chloride (KCl) used as K source. Error bar indicates LSD at 5% level. Number of nodules and dry weight of nodules per 10 plants. Source: Grewal, H.S. and R. Williams. 2002. Influence of potassium fertilization on leaf to stem ratio, nodulation, herbage yield, leaf drop, and common leaf spot disease of alfalfa. J. Plant Nutr. 25:781-795. International Plant Nutrition Institute * Units: Leaf Drop is % of total leaves Leaf Spot Rating is % of leaves infected by common leaf spot. Leaf drop is one of the major problems associated with dryland alfalfa production, typically associated with water stress. Potassium fertilization has some effect on this problem, perhaps associated with hormonal regulation or water stress tolerance. The effect of K addition on improving the ability of other plants to withstand water stress has been frequently observed. Source: Grewal, H.S. and R. Williams. 2002. Influence of potassium fertilization on leaf to stem ratio, nodulation, herbage yield, leaf drop, and common leaf spot disease of alfalfa. J. Plant Nutr. 25:781-795. International Plant Nutrition Institute * Winter injury can be severe when alfalfa is grown on soils low in K. Potassium increases the carbohydrate accumulation in the crown root during the fall enhancing winter hardiness and early spring growth. This figure shows the effect of K fertilization on preventing winterkill of alfalfa on a sandy loam soil over an 8-year period in Manitoba. Initial soil K concentration was 232 lb K/A in the 0 to 6 in. depth. Source: Bailey, L.D. 1983. Fertilizing alfalfa forage. Manitoba Agriculture Agdex 541. International Plant Nutrition Institute * When grown in mixtures, forage grasses compete with legumes for K, and usually are more successful. When K is limiting, the stand will shift toward a greater proportion of grasses. To maintain more alfalfa in a mixed stand, it is especia