Optimising pasture and grazing management decisions on the Cicerone Project farmlets over variable time horizons

Abstract

Abstract. This study addresses the problem of balancing the trade-offs between the need for animal production, profit, and the goal of achieving persistence of desirable species within grazing systems. The bioeconomic framework applied in this study takes into account the impact of climate risk and the management of pastures and grazing rules on the botanical composition of the pasture resource, a factor that impacts on livestock production and economic returns over time. The framework establishes the links between inputs, the state of the pasture resource and outputs, to identify optimal pasture development strategies. The analysis is based on the application of a dynamic pasture resource development simulation model within a seasonal stochastic dynamic programming framework. This enables the derivation of optimum decisions within complex grazing enterprises, over both short-term tactical (such as grazing rest) and long-term strategic (such as pasture renovation) time frames and under climatic uncertainty. The simulation model is parameterised using data and systems from the Cicerone Project farmlet experiment. Results indicate that the strategic decision of pasture renovation should only be considered when pastures are in a severely degraded state, whereas the tactical use of grazing rest or low stocking rates should be considered as the most profitable means of maintaining adequate proportions of desirable species within a pasture sward. The optimal stocking rates identified reflected a pattern which may best be described as a seasonal saving and consumption cycle. The optimal tactical and strategic decisions at different pasture states, based on biomass and species composition, varies both between seasons and in response to the imposed soil fertility regime. Implications of these findings at the whole-farm level are discussed in the context of the Cicerone Project farmlets.

Comparing the climate experienced during the Cicerone farmlet experiment against the climatic record

“…The variability of the response in the grazing system under both drier and wetter years is required to more fully understand the interactions between climate and the management strategies studied in the farmlet experiment, namely pasture renovation, fertiliser application and grazing management. The management of the farmlets in response to climatic uncertainty has been conceptually described as a complex decision problem that is familiar to graziers who commonly have to make decisions in spite of imperfect knowledge of the state of a farm's resources and an uncertain climate (Behrendt et al 2013a). Rational responses to these climatic constraints include employing deep-rooted perennial species that permit some growth over dry periods (Boschma and Scott 2000) and ensuring the retention of sufficient temperate C 3 species, which, especially when adequate soil nitrogen is available, are capable of some modest growth under cold winter temperatures (Newman et al 1962).…”

“…To overcome this constraint and provide insight into the effect of climate on the results of the Cicerone farmlet experiment, daily available soil water was estimated using a modelling approach as part of investigations into optimising grazing management and pasture renovation (Behrendt et al 2013a), as well as soil fertility .…”

Reflections on the concept, conduct and findings of the producer-led Cicerone Project

“…This made the calculations of the longer-term returns from pasture investments at a whole-farm scale by Scott et al (2013a) and Behrendt et al (2013a) all the more important.…”

“…Another facet that impressed producers was the accumulation of so much data, that they considered valuable and trustworthy, on soils, pastures, animals, worm egg counts and economics that allowed for valid conclusions to be drawn . Also of great value, were the economic analyses of investments in soil fertility, pasture renovation and intensive rotational grazing, which allowed for realistic comparisons at a whole-farm scale as well as exploring issues of risk over variable time frames (Behrendt et al 2013a(Behrendt et al , 2013bScott et al 2013aScott et al , 2013b.…”

“…Also of great interest to them were the importance of maintaining the legume component of pastures (Shakhane et al 2013a) as a source of protein needed for meat ) and wool products (Cottle et al 2013); the significant differences observed between farmlets, in spite of the years being relatively dry; and the challenges of getting sown pastures to persist long enough to be worthwhile investments (Behrendt et al 2013a).…”