Modelling the impact of surplus pasture management techniques on production and profit in a pasture-based dairy system

Abstract

Three options for controlling surplus pasture on Northland dairy farms were modelled to determine the impact of each on production and operating profit. The three options were a) Light cut, fixed break size (LCFB): Paddock cut for silage as soon as surplus was identified. No effect on rotation length. b) Bulk cut, fixed break size (BCFB): Paddock closed until cover of 4000 kg dry matter (DM)/ha was reached then cut for silage. Rotation length was shortened. c) Bulk cut, variable break size (BCVB): Paddock closed until cover of 4000 kg DM/ha was reached then cut for silage. Rotation length was maintained thus reducing available grazing area. The hypothesis was that LCFB would translate into the most profitable option as pasture is being cut as soon as a genuine surplus is realised, optimising silage feed quality. Results showed LCFB to be $100/ha more profitable (operating profit) compared with BCFB and BCVB at only one of the three sites investigated (P<0.05). The LCFB option resulted in a significantly higher (P<0.05) pasture yield at both the Northland Agricultural Research Farm and Whangarei sites, however, there was no effect of silage-making option on milk production at any of the sites. This modelling exercise showed that LFCB was not consistently more profitable across sites, that it is a simplification to assume that "one size fits all" and that the same pasture conservation rules can be applied across different sites and pasture types. This suggests that farmers can be flexible in choosing pasture conservation practices to help balance competing demands on labour and other resources without risking a loss in profit. Key words: dairy farm, pasture surplus, production, profit, whole farm model