Effect of Different levels of Irrigation Water and Potassium Fertilizer on Root and Shoot Growth of Forage Sorghum

In order to study the effects of irrigation water (50، 75 and 100%) and potassium fertilizer (50 and 100% Potassium fertilizer required) on the growth of roots and shoots of sorghum varieties (Pegah، Karaj and Speedfeed)، a pot experiment was conducted in Agricultural Research Center of Semnan province (shahrood). The experimental treatments were arranged as split plots based on a randomized complete block design with three replications. Factors in this study were including irrigation water، potassium fertilizers and varieties of forage sorghum. To measure the characteristics of shoot plant، at first they were removed and leaf area، leaf dry weight، stem dry weight and shoot weight were measured. Then the roots were completely removed and washed. The root volume was determined by immersion in water and weighed. Root length and root volume was calculated by the method of Atkinson. The results showed that the effects of irrigation water and potassium fertilizer on the root morphological characteristics (length، volume، area and dry weight) and plant shoot (leaf dry weight، leaf area، shoot dry weight and shoot to root ratio) were significant. The maximum length، volume، area and root dry weight، dry weight of leaf، stem dry weight and leaf area were obtained from the water level of 100 percent. The maximum length، volume، area and root dry weight، leaf dry weight، stem dry weight were obtained from the fertilizer level of 100 percent. Speedfeed variety had maximum length، volume، leaf area and root dry weight. Speedfeed variety was the most sensitive to the amount of irrigation water. The amount of irrigation water affected on the growth characteristics both shoots and roots severely.