A stochastic model to study the control of grazing systems

Abstract

<jats:p>Most modelling research into grazing management has focused on planning. However, if target outcomes for pastures, animals and profit are to be realised, planning and control must be closely linked. Control is required if actual outcomes are likely to deviate from those planned. This may be because of: variability in uncontrollable variables (e.g., the weather); imprecision in implementation (including timeliness); inaccurate measurement of outcomes (i.e., sensor errors); and errors in prediction during the planning process. A dynamic grazing system model was used with a genetic optimising algorithm to simulate the outcomes for different control strategies for a sheep farmlet. The optimum control sequencing for pasture allowance, nitrogen application, lamb drafting weight and supplementation was investigated. Optimum pasture cover levels were similar to those recommended to farmers, except for winter when higher allowances were suggested. Sensor errors for pasture measurement were shown not to have a significant financial cost to farmers if recommended measurement techniques are closely followed. Keywords: grazing control, grazing management, grazing system model, pasture measurement, system optimisation</jats:p>

75 years of scientific and technological advances in pastoral agriculture - what will it take to continue to deliver?

“…• The use of satellites to measure pasture growth appeared in the 1970s (Cochrane 1976; Ellis 1977) • The knowledge wave was heralded under the guise of information to continue to improve New Zealand's competitiveness by Trim (1980) • The development of a large range of models for understanding farm systems and to assist with decision making on-farm began to occur in the 1980s (e.g. McCall et al 1986;Baars 1990;Marshall et al 1991;Lewis & Garrity 1993;Barker & Baars 1993;Rollo et al 1996;Metherell et al 1997;Barioni et al 1997;Martins da Silva et al 1997;Wheeler & Thorrold 1997;Davis et al 1998;Barker et al 1998;Ledgard et al 1999;Woodward et al 2000;Ogle et al 2000;Ogle & Tither 2000;Ridler et al 2001;Fiorelli et al 2001;Webby 2002;Wheeler et al 2003;Thorrold et al 2004;Monaghan et al 2004;Zhang et al 2004;Beukes et al 2005). • The potential impact of plant genomic technologies on pastoral agriculture has been discussed since the 1980s (e.g.…”