COMPARISON OF THE EFFICIENCY OF SINGLE APPLICATIONS WITH REPEATED TOP DRESSINGS OF NITROGENOUS FERTILIZERS IN INCREASING THE YIELD OF DRY MATTER, NITROGEN, AND VITAMIN C (ASCORBIC ACID) OF SUDAN GRASS

Abstract

Sudan grass was grown on Brennan Fine Sandy Loam. The 1st cutting was made 25 days after planting. A 2d cutting was made 11 days later. The relative efficiencies of (NH4)2SO4 and of ammonium phosphate were studied when a given amt. was added at the time of seeding and when pai''t was added at seeding and the remainder as a later top dressing. The greater efficiency per unit of added N in increasing the total yield of dry matter was found when the entire amt. of fertilizer was added at seeding time. Ammonium phosphate was significantly more efficient per unit of added N than was (NH4)2SO4. The greater efficiency per unit of added N in increasing the recovery of N by the 2 cuttings also was obtained when the entire amt. of fertilizer was added at seeding time. Ammonium phosphate was more efficient per unit of N added than was (NH4)2SO4. The total yield of vitamin C per acre varied inversely as the yield of dry matter and the recovery of N by the crop. The greater efficiency per unit of N added was found when part of the fertilizer was added at the time of seeding and part just following the 1st cutting. (NH4)2SO4 was more efficient per unit of N than ammonium phosphate. A tentative explanation is offered of the comparative efficiency of nitrogenous fertilizer based on its distribution throughout the soil profile and on the depth of the root system of the plant.