Relationship Between Some Nutrient Uptake and Early Abscission of Fruits in Ash (Fraxinus excelsiorL. )

Ash (Fraxinus excelsior) has a distribution from Astara in Guilan to Gildaghi in Golestan province in North part of Iran. This species is used widely in reforestation programs because of its suitable growth, production and resistance against cold and drought. Investigation on metabolic evaluation of seeds has shown that most of them were hollow and early abscission. In this investigation, the effect of plant nutrition was studied during 2 years in Gisoum region in Guilan province. The amount of potassium, calcium, natrium, magnesium and phosphorus was measured by atomic absorption and spectrophotometer in leaves. Samplings were done in four months (June, July, August and September). Sampling from soil was done and the chemical and physical properties were determined. The amount of elements showed that the amount of Mg was optimum but phosphorus was more and calcium was much more than required. In spite of optimum amount of potassium in soil, measurement of K in leaves showed a severely deficient. Results indicated that pH of soil has changed about 1- 2 unit from neutral to acidic (5-5.2) reaction during past 30 years. In acidic soils, the absorption of K by roots is limited but the absorption of Ca is increased .This caused disorder in Ca/K ratio. This situation along with climatical changes caused reduction in production and remaining of seeds in ash