Volume 27, 349

Tropical Grasslands (1993) Volume 27, 349–358

Tropical pasture establishment.
9. Establishing new pastures in difficult tropical environments — do we expect too much?

R.G. SILCOCK¹ and P.W. JOHNSTON²

¹Queensland Department of Primary Industries, Toowoomba, and
²Charleville, Queensland, Australia

Abstract

Sowing pastures in marginal environments is essentially shifting the pasture composition, rapidly from one state to another. State and transition ecological theory says such large changes generally occur only when a combination of extreme events coincide. A combination of light soil disturbance, small amounts of new seed plus establishment rains (a common scenario for tropical pasture sowing) is hardly an extreme event for an existing perennial pasture. Hence, the transition needs reinforcement with astute grazing management to achieve this desired leap.
Pasture improvement schemes can be very costly. Therefore, the effort must be concentrated on a limited area to ensure the desired new pasture is achieved. Often large areas are attempted and desirable management can not be achieved, resulting in serious timber regrowth for decades and high cost/benefit ratios. If the pasture is well adapted, it will compete strongly against rivals via its soil seed supplies and control of nutrient balance. If adequate rains do not fall, the cost ecologically and economically to the pastoral enterprise must be absorbed and the exercise repeated later in the hope of a better establishment season.
Often the cost is over-emphasised to disguise a poorly conceived pasture improvement project. If a sown pasture is required, the economics are of equivalent importance to choice of species and post-emergence management.