Economic contribution of French serradella (Ornithopus sativus Brot.) pasture to integrated weed management in Western Australian mixed-farming systems: an application of compressed annealing

Sowing phases of French serradella (Ornithopus sativusBrot.) pasture betweenextended cropping sequences in the Western Australian wheatbelt can sustain grainproduction through restoring soil fertility and reducing selective herbicide use. Theobjective of this article is to investigate the profitability of rotations involving thispasture under a variety of weed management scenarios to obtain greater insight intoits value for mixed farming systems in this region. A stochastic search procedure,compressed annealing, is used to identify profitable sets of weed management strategiesin a simulation model representing a large number of potential combinations of chemicaland non-chemical forms of weed control. In contrast to a continuous-cropping sequence,the inclusion of a serradella phase in a rotation is profitable at high weed densities andwith increasing levels of herbicide resistance. A single year of pasture in the rotationis optimal if resistance to Group A selective herbicides is present at the beginning ofthe planning horizon, but a three-year phase is required if resistance to multiple herbicidegroups is observed. Sowing a serradella pasture twice over a two-year phase is alsoshown to be economically attractive given benefits of successive high weed kills.