Growth and ignitability of annual pastures in a Mediterranean environment. 1. Effect of length of season and of defoliation on the growth, water content and desiccation of annual pastures

Abstract

The growth and water content of annual swards were examined in a Mediterranean environment under three lengths of season (attained by extension of the natural season by irrigation), and under two defoliation treatments. Swards attained their maximum percentage water (about 800-950 per cent of the dry matter) in late July or early August. Maximum dry matter yields were attained two months later, when the percentage water had fallen to 150-400 per cent. The swards were dead and dry about 50 days after maximum yield. Earlier commencement of the growing season (18 days) doubled the winter production, delayed desiccation, in the spring and gave heavier dry herbage in the following summer. Extension of the season in the spring gave little response by undefoliated swards, but a considerable response by defoliated swards ; it failed to prevent the maturation and desiccation of these annual pasture plants. Autumn irrigation gave a greater return of dry matter per inch of water than did spring irrigation. The influence of these practices on pasture growth and summer fuel production is discussed.