Effect of Topdressed Nitrogen and Potassium on the Feeding Value of Orchardgrass Hay for Lactating Dairy Cows¹

Abstract

Twenty lactating Guernsey cows were used to compare the feeding value of four orchardgrass (Dactylis glomerata) hays from established fields which received different combinations of topdressed nitrogen and potassium fertilizer. A 4 ✕ 4 Latin square changeover design was used. Grain and beet pulp consumption was held constant and hay was fed ad libitum throughout this trial. The average daily dry hay intake was 1.10, 1.06, 1.14, and 1.00 kg per 100 kg body weight for the treatments P, PK, NP, and NPK, respectively. Consumption of hay NPK was significantly less than the consumption of the other hays at the 5% level of significance. The average daily production of fat corrected milk was 11.45, 10.84, 11.14, and 11.19 kg for the hays from treatments P, PK, NP, and NPK, respectively. There were no significant differences in milk production from any of the hays. Top dressing with a complete fertilizer mixture containing 120 kg N and 186 kg K per hectare nearly tripled the hay yield and quadrupled the crude protein yield over top dressing with phosphorus alone.