Effect of Potassium Application Rate on Dry Matter Yield and Forage Nutritive Value in Alfalfa

Abstract

The United States is the largest producer of alfalfa (Medicago sativa L.) however there is still a wide variation in yield among states. Potassium (K) is one of the key plant macronutrients that affect alfalfa yield and stand persistence. To the best of our knowledge, the evaluation of K rates on alfalfa forage yield and quality attributes has not been done in the United States. Thus, the main objective of this study was to evaluate the effect of K rates along with harvesting intervals (HI) and varieties on alfalfa dry matter yield (DMY), forage nutritive value, and soil K content. The experiment was carried out in a split-split plot with two HI (28 and 35-day after the first cut), two varieties (Hi–Gest 360: reduced-lignin and AFX 457: conventional), and four K application rates (0, 56, 112, and 168 kg K2O ha-1) in a randomized complete block with four replications. The results indicated that harvesting alfalfa at a shorter interval (28-day) resulted in higher dry matter yield and forage nutritive value than a longer harvest interval (35-day). Yield, nutritive values, and soil K content were, however, not significantly influenced by alfalfa variety and K rates. Further research is essential to quantify the actual trade-off between applied K and soil and plant K content in alfalfa production.