FIBER COMPOSITION AND IN-VITRO DIGESTIBILITY OF CORN STOVER FRACTIONSIN RESPONSE TO AMMONIA TREATMENT

The composition and digestibility of corn stover leaves and stems afte r prolonged NH3 treatment was compared with that after isonitrogenous NH3 addition (NH3 control), represented by samples immediately frozen after initial NH3 application. Ammonia treatment decreased concentrati on of hemicellulose in leaves, particularly arabinose residues. Concen tration of saponifiable hydroxycinnamic acids was reduced by NH3 treat ment in upper stems only. Ammonia addition, compared to a H2O control, increased the extent of in vitro fiber degradation of all plant fract ions but the rate of fiber degradation for leaves only. Ammonia treatm ent increased the extent of fiber degradation over NH3 addition in lea ves but not in stems. The variable response to NH3 treatment among sto ver fractions of drought-stressed corn may be related to the high conc entration of water-soluble carbohydrates in the stalks and immobilizat ion of NH3-N with lignin.