Influence of Straw Application Rates, Plowing Dates, and Nitrogen Applications on Yield and Chemical Composition of Sugarbeets

Fertilizer N applied at ever-increasing rates sometimes accumulates in the soil. The practice of fertilizing grain straw with N to stimulate decomposition is questionable, but decomposition of straw immobilizes N that must be compensated for in fertilizing the succeeding crop. Too much N decreases the sucrose content of sugarbeets and decreases sucrose recovery. Experiments were conducted to determine the relative value of early and late straw applications, plowing with N applied in the fall or spring, and the amount of N needed to compensate for straw applications in obtaining optimum beet and sucrose yields with maximum quality. Sugarbeets (Beta vulgaris L.) were grown following winter wheat (Triticum aestivum L., var. ‘Nugaines’) in 1970 and I971 on a Pormeuf silt loam soil near Kimberly, Idaho. Straw was applied to the beet plots at rates of 6.7, and 13.4 metric tons/ha, and the plots were plowed either in early September or mid-November. Nitrogen was applied at 67 kg N/ha in the fall and at 67 and 134 kg N/ha in the spring. The treatments were arranged in a split-split plot design with 4 replications. Control plots were used with all experiments. N fertilization increased beet, top, and sucrose yields, as well as amino N, Na, K concentrations, and impurity index. It decreased the sucrose percentages of the beets. Straw applications decreased beet, top, and sucrose yields, Na and amino N concentrations, and impurity index, but they did not influence K content of the beets. Early plowing increased sucrose percentage and yield and decreased Na, K, and impurity index. Interactions between straw applications and plowing dates were significant for sugarbeet and beet top yields. Approximately 7.5 kg N fertilizer per metric ton of straw were required to compensate for the deleterious effects of the straw.