Studies on Growth and Development in Lolium: I. Relation of the Annual Habit to Head Production Under Various Systems of Cutting

Abstract

The effect of 4 intensities of cutting on head production and seasonal productivity was studied in L. rigidum, L. italicum, and 4 strains of L. perenne. All show an initial peak of head production associated with ear emergence. In the annual and biennial types, heading continues through the summer, even under a fortnightly cut. In the perennials, heading rapidly decreases as cutting continues. In all cases the total yield decreases as intensity of cutting increases. The biennial L. italicum is superior for all initial cuts, but its recovery after cutting is lower than the perennials. The annual L. rigidum gives low initial yields and poor recovery. Inflorescence development in Lolium under field conditions and the agronomic differences between strains as related to the pattern of bud development on the shoot apex are described. In the field, all strains become "ripe-to-flower" during winter, and spikelet buds are formed in the spring. Cutting at a low level removes the young elongating spikes. In the annual and biennial the remaining axillary tillers become "ripe-to-flower" quickly and head before the next cut. In the perennials, this condition is reached more slowly, and little heading occurs. The main shoot can influence the "ripeness-to-flower" of its axillary tillers. Seasonal productivity and recovery after cutting are related to depletion of stored root reserves. A fortnightly cut gives too small an interval for re-storage of reserves, but a monthly interval is adequate. Good recovery is associated with lack of heading after cutting, possibly because of an inhibitory effect of head production on tillering.