SUGAR BEET RESPONSE TO BALANCED NITROGEN FERTILIZATION WITH PHOSPHORUS AND POTASSIUM. PART II. DYNAMICS OF BEET QUALITY

摘要

The key objective of the study was to evaluate the seasonal course of quality characteristics of storage root of sugar beet to imbalanced fertilization. The field trial arranged as one-factorial design was consisted of eight treatments: N_0P_0K_0; N_0P_0K_0; N|PpK,; N_0P_0K_0; N_0P_0K_0 and N_1P_1K+Ca; where 1 is recommended level of NPK fertilization and Ca means that phosphorus applied as partially acidulated phosphate rock, (PAPR). The consecutive sampling of sugar beet was conducted at followingdays after sowing: 92, 113, 134, 155 and 175. At each sampling date concentration of sucrose (SC) and molassigenic compounds such as a-amino-N, K and Na were determined. The course of SC during vegetation was best described by the Tangh regression model.Based on it, the optimum day after sowing for the maximum SC concentration was fixed at 172 and at 18.6%, respectively. Beet concentration of K showed a linear trend. The in-season courses of a-amino-N and Na were highly specific, being optimal for thefully balanced treatment, i.e., N_0P_0K_0. The in-season assessed relationships between SC and a-amino N, and K underwent at 155 DAS a change from positive to negative. This period of sugar beet growth can be, therefore, considered as the borderline between the phase sucrose accumulation sink build-up and its fill-up. The lowest white (extractable) sugar concentration of 0.8% was noted for the N_1P_1K_0 as compared to the N_0P_0K_0 treatment. This dependency implicitly indicates on importance of K current fertilizing for sucrose accumulation. The slightly lower effect of N_1P_1K_1 treatment (-0.3%), indirectly indicates on non-suitable conditions for sugar beet growth, limiting sucrose accumulation in the late-season. The main reason was drought in twoof tree years of study, reducing the yield forming effect of P.