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Lincoln University (2011)

Managing climatic variability in high performance dryland sheep production systems

Gicheha, Mathew G.

Titre : Managing climatic variability in high performance dryland sheep production systems

Auteur : Gicheha, Mathew G.

Université de soutenance : Lincoln University

Grade : Doctor of Philosophy (PhD) 2011

Résumé
This research investigated the physical and economic impact of incorporating tactical responses in risk management strategies in high performance dryland sheep production systems. An existing grazing sheep simulation model was used in the study. The model was extended by incorporating additional pasture, animal and management modules required in line with the objectives. Seven strategies (S) which differed in the pasture mixes utilised (either grass- or legume-based) and stock class utilised as flexibility options (cattle ; grass-based system or old ewes ; legume-based system), were evaluated at different stocking rates (SR ; stock units (SU) per ha (SU ha 1)), with and without tactical adjustments to trigger soil moisture level (SML) in the top 25 cm soil. Strategy 1 simulated a conventional sheep farm with 13 paddocks of perennial grass:clover mix, 2 paddocks in forage crop (kale) and one paddock into lucerne ; strategy 2 was similar to 1 but with 25.0% of the ewes replaced with equivalent cattle stock units ; strategy 3 was similar 1 but with introduction of a 1st cycle ewe policy ; strategy 4 was a combination of strategies 2 and 3 ; strategy 5 was similar to 3 but with introduction of 2 paddocks of switch pasture and 3 of lucerne ; strategy 6 was similar to 4 but with introduction of 2 paddocks of switch pasture and 3 of lucerne ; and strategy 7 was similar to 5 but with 5 paddocks of switch pasture and 4 of lucerne. Initially, each of the seven strategies was run at 10, 12, 14 and 16 SR resulting in a 2 factors (7S x 4SR) experiment but without incorporation of tactical adjustments to drop in target SML. In the subsequent analysis, each strategy was re-run with tactical adjustments to the SML target set at 10.0, 12.5 or 15.0% resulting in a 3 factors (7S x 4SR x 3SML) experiment. In general, lambing percentage was consistently higher in strategy 5 for all the SR considered when the opportunities of incorporating tactical responses in risk management strategies were ignored. However, following inclusion of tactical adjustments to climatic variability, the lambing percentage averaged 137.07% across all strategies and SR. Strategy 4 resulted in the highest meat yield and gross margin (GM) but trailed in wool yield. Results obtained in this study show that coefficients of variability (CV) for lambing percentage increased with increase in SR translating to increased risk with increase in SR in high performance dryland sheep systems. All strategies incorporating tactical responses were economically superior to those which did not. In some instances, the difference in GM between corresponding strategies with and without including tactical adjustment to climatic variability was as high as 39.65%. In all cases, corresponding risk management strategies incorporating tactical responses to climatic variability resulted in higher GM (P < 0.05) and lower risk (P < 0.05). The extra income derived from including tactical responses can be viewed as the cost to the farmer of basing choice regarding a management strategy on analysis that neglects the tactical advantages afforded by such a strategy

Sujet : embedded risk ; climatic variability ; tactical adjustments ; dryland grazing systems ; risk management strategies ; risk efficient frontier ; cost of climatic variability

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Page publiée le 20 septembre 2018