Relationship between Alkaline Mineral Concentration and Rate of pH Decline in Ensiled Greenhouse‐Grown Alfalfa1

Abstract

AbstractAlkaline minerals present in forage may form salts with fermentation end products during the ensiling process, thus slowing the rate of pH decline. For legumes, which have high concentrations of alkaline minerals, excessive degradation of plant protein might occur because of extended duration of proteolytic enzyme activity. This hypothesis was examined by fertilizing greenhouse‐grown alfalfa (Medicago sativa L.) so that the concentrations of the alkaline minerals, K, Mg, and Ca, varied. Stepwise regression techniques were used on data from 11 cuttings to relate mineral composition, lactic acid buffering capacity, initial pH, and percentage dry matter of green herbage to the rate of pH decline of the resulting silage. Results indicated that the rate of pH decline of alfalfa was significantly, but weakly, correlated to its alkaline mineral concentration. Unexpectedly, higher concentration of water soluble K and water soluble Ca resulted in increased rate of pH decline. The cause for this response is not known but may be related to specific effects of mineral concentration or content on microbial activity or mineral induced changes in levels of carbohydrates, soluble N, or other plant components that may strongly affect microbial activity and fermentation rate.