Economic Optimum Fertilization Rates for Subirrigated Meadow Hay Production, Including Values for Hay Quality

Abstract

The Sandhills of Nebraska support over 1 million head of range cattle (Bos spp.). Hay production from subirrigated meadows is the primary source of winter forage. Increasing hay production by meadow fertilization could be an important practice if economically feasible. Study objectives were: (i) determine economic optimum levels of N fertilization and (ii) evaluate the economic efficiency of applying S and phosphate (P2O5). Data on vegetation responses to N, P2O5, and S were from a 4-yr research study near Whitman, NE. Four levels of N (0, 40, 80, and 120 lb N/acre), two levels of P2O5 (0 and 40 lb/acre) and two levels of S (0 and 20 lb/acre) were applied each year to the same plot areas. Soils of the study area were Gannett-Loup fine sandy loam (Typic Haplaquoll). Forage responses to two levels of P2O5 and S were evaluated for several combinations of dollar values for hay, and costs for P2O5 and S. A forage response function was developed to estimate economic optimum levels of N. The vegetation responded significantly to all three fertilizers with no significant interactions, thus forage response to each nutrient was analyzed independently. Crude protein (CP) and in vitro dry matter digestibility (IVDMD) were evaluated as quality measures of the hay. The first 40-lb increment of N decreased CP by 0.7%. When applied N was priced at $0.35/lb and hay at $50/ton, about 70 lb N/acre was the optimum fertilizer rate, if the value of the decreased protein was considered zero. When the decreased protein was valued at a replacement cost of $230/ton of 32% supplement or about $4.44/ ton hay, then hay must be valued at approximately $65/ton before fertilization was profitable with N at $0.35/lb. At these prices about 78 lb N/acre was optimum. At hay values exceeding $51/ton, 40 lb P2O5/acre at $0.25/lb P2O5 was economically feasible. When hay values exceeded $34/ton, applying 20 lb S/acre was economically feasible when S was priced at $0.17/lb.