BALANCED NITROGEN AND POTASSIUM FERTILIZATION MANAGEMENT FOR IMPROVING THE NUTRITIONAL STATUS AND MAXIMIZING SUGAR QUALITY AND YIELD OF SUGAR BEET

摘要

Two field experiments were conducted at the Experimental Farm at El-Ghorieb, Faculty of Agriculture, Assiut University during 2001/2002 and 2002/ 2003 seasons to study the effect of three ratios of N:K2O fertilization (80 kg N : 48 kg K_2 O, 80 kg N :72 kg K_2 O and 120 kg N : 48 kg K_2 O/fed.) and three application times of K fertilizer (before sowing, at thinning and post-thinning) as well as their interactions on yield and quality of sugar beet (Hipoly cuitivar). A split plot design with three replications was used in both seasons. The results indicated that the N/K ratio and the application time of K fertilizer exhibit significant effects on all productivity traits, i.e. root, top and recoverable sugar yields (ton/fed) as well as technologicalquality characteristics, i.e. sucrose %, sugar loss %, sugar recovery % and quality index of sugar beet in both growing seasons. Data indicated that the best N/K_2 O fertilization ratio for attaining the highest sugar yield and quality of sugar beet was120 kg N : 48 kg K_2 O. The highest values of yield and quality traits (the highest sucrose % and the lowest impurities) were obtained mainly with early K application at thinning with the first dose of N or pre-sowing compared with those of the post-thinning (one month after thinning). Top and root dry matter yields as well as concentrations of Fe and Mn in tops, N, K and Mn in roots were affected significantly with N/K fertilization ratio in both seasons. Interaction effect of N:K_2 O fertilization andK application time showed significant effects in dry matter yield of tops and concentrations of P, K and Mn in tops in both seasons as well as the dry matter yield of roots, concentrations of N, K and Mn in roots in the first season, N, P and Mn concentration of roots in the second season. The N:K_2 O fertilization ratio of 120 kg N:48 kg K_2 O/fed and K application time at thinning stage lead to arise both fresh and dry yields as well as total uptake of N, P, K, Fe and Mn in both tops and roots of sugar beet. Adding nitrogen and K fertilizer at 120 kg N to 48 kg K_2 O ratio with the addition time of K fertilizer at thinning stage increased yield and quality of sugar beet through improving the plant nutritional status which affects the physiological performance of the plants. Therefore, N/K ratio and the time of K application must be considered to achieve the maximum values of sucrose %, root and recoverable sugar yield of sugar beet as well as to minimize impurities and sugar losses to molasses.