Pasture and the theory of diversification

Abstract

Diversifying farm activities can reduce the business risk of agricultural production. The aim of the present study was to investigate the effect of diversifying the types of dairy pastures sown on (1) the average seasonal growth rate (kg DM/ha/day) of pasture and (2) the variability of seasonal growth rate of pasture over time by diversifying the types of pastures grown on a dairy farm. This approach is similar to the approach used to assess the diversification of annual cropping activities, although repeated harvest of pasture by grazing animals and the seasonality of pasture DM production complicates the question. The question investigated was ‘How does substituting chicory (Cichorium intybus L.) or tall fescue (Festuca arundinaceae Schreb.) monocultures for a perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.) pasture in increasing proportions affect (1) the average growth rate (kg DM/ha.day) of pasture and (2) the variability of growth rate of pasture in each season?’. The biophysical model DairyMod was used to simulate 30 years growth of a mixed sward of perennial ryegrass and white clover and monocultures of chicory and tall fescue for two rain-fed locations in the high-rainfall zone of southern Australia. Including chicory in the pasture base had the potential to increase pasture growth rate during the summer–early autumn period compared with growing perennial ryegrass–white clover alone. This increase in pasture growth rate increased variability, and reduced growth rates in late autumn–winter and spring. The simulated growth rates of tall fescue and perennial ryegrass were strongly correlated in all seasons; hence, tall fescue did not reduce the variability of total DM. Further analysis would include price correlations and variability and consider the whole-farm implications. The analysis presented here for the high-rainfall zone showed that introducing alternative forages may have benefits in terms of increasing pasture growth rates at critical times of the production year, but the variability of the growth rate was not reduced.