Abstract

Dexcel`s Whole Farm Model (WFM) is a computer model of a dairy farm that simulates individual cows and paddocks, with pasture growth driven by observed climate data and with management policies guiding decisions on a daily basis. The aim of the study was to design a farm system to produce 1750 kg milksolids (MS)/ha/yr from feed grown on-farm. An average predicted pasture growth curve was derived by initialising the WFM for a typical all-pasture Waikato farm (3 cows/ha) with "best practice" management policies and running the simulation for 29 years of Ruakura climate data. The model was then used with this average growth curve to design the high producing system. Pasture growth alone (17.3 t DM/ha) did not fulfil the feed requirement for the 1750 kg MS/ha scenario, with an overall feed deficit of 3.1 t DM pasture/ha. Improvements in ryegrass cultivars and N-fertilisers could be expected to increase pasture production by around 10%, reducing the overall feed deficit to 1.6 t DM pasture/ha. These improvements together with irrigation at 2 mm/day over the three summer months (Dec - Feb) reduced the feed deficit to zero. Irrigation could be replaced by cropping between 11% and 20% of the farm in a rotation of annual ryegrass yielding 7 t DM/ha and maize yielding 22 to 28 t DM/ha respectively.

PC, Beukes, CEF Clark, ME Wastney, CC Palliser, G Levy, C Folkers, JAS Lancaster, C Leydon-Davis, and BS Thorrold

Proceedings of the New Zealand Society of Animal Production, Volume 66, Napier, 29-34, 2006