GROWTH OF NEW ALFALFA AND COCKSFOOT SHOOTS DURING WATER-DEFICIT AND IRRIGATION .2. MODELING

Eight regrowths of alfalfa and thirteen of cocksfoot were compared with and without irrigation and with two levels of nitrogen supply (cocksfoot). Aerial biomass was modellized according to PARa. Following a water shortage, the efficiency of radiation intercepted decreased more frequently than the efficiency of the conversion of radiation in biomass for cocksfoot, but the contrary was observed for alfalfa. The decrease in PARa resulted from the direct effect of water shortage, but also from indirect (low value of herbage nitrogen level) and deferred (after-effect as residual leaf area index effects).