Tobosa tiller defoliation patterns under rotational and continuous stocking

Abstract

Continuous low animal density grazing of tobosa [Hilaria mutica (Buckl.) Benth.] in the northern Chihuahuan desert results in nonuniform forage utilization. Stocking smaller tobosa rangeland paddocks with high numbers of cattle for short periods of time may facilitate more uniform forage utilization. Two grazing periods in each of 2 consecutive years were monitored to investigate the frequency with which tobosa tillers were defoliated and the intensity of defoliation (change in height) in relation to grazing pressure under high-density seasonal rotational and low-density seasonal continuous grazing. Approximately 40% of tiller height, including leaves, was removed at each defoliation in the rotational treatment, while intensity of defoliation per grazing event remained consistent. In the continuous treatment, amount of tiller removed varied widely and was not consistent among the 4 periods. Percentage of tillers defoliated in the rotational treatment was always greater than 75%, and always less than 30% in the continuous treatment. The probability that a tiller would be grazed at least once in the rotational treatment was more than twice as great as in the continuous treatment. However, within the rotational treatment, the probability of multiple grazing events (greater than or equal to 2) on an individual tiller was less than the probability of a tiller being grazed just once. In general, high-density rotation grazing promoted more uniform. forage utilization of tobosa than low-density continuous grazing.