West Coast DairyNZ Monitor Farms

For the past three years the West Coast has had four dairy monitoring farms spread from Westport in the north to Hokitika in the south because there are significant differences in pasture growth rates and milk production between farms along the coast. This story looks at the highest performing farm in the four monitor farms, the Mirfin farm at Ikamatua, and the lowest, which is the Landcorp Kotuku farm.

Westland has some unique challenges such as high rainfall which is variable across the region. There is debate on how pasture growth rates and annual production on dairy farms throughout Westland compares to that collected from three years of monitoring on the Landcorp Kotuku Focus Farm. Additionally there is a lack of good data on pasture quality and its variation throughout the season. Westland lacks reliable pasture growth and consumption information against which farmers can benchmark themselves and set targets to achieve. This project funded by the Development West Coast, Westland Milk Products, MAF Sustainable Farming Fund, and ARL-Ravensdown, aims to generate reliable pasture growth and quality and soil temperature information, over the full 12 months, on four commercial dairy farms in Westland.

The Landcorp Kotuku dairy farm is 410 ha effective, milking 1050 cows, stocked at 2.6 crossbreds/ha, classified as system 3, producing 332kg/cow MS, using 0.8 tonnes/ha imported feed and 300kgN/ha. Last season’s production was 362,000kgs. The Kotuku dairy farm has undergone significant development and re-contouring since being converted from sheep 10 years ago. All of the land, with the exception of remnant indigenous vegetation, has been turned upside down and sown in to highly producing pasture grasses. The entire property is under a Queen Elizabeth II conservation covenant and is currently planting up along stream edges and in wetland areas. Shane Kelly is the farm manager and has overseen the farm’s development since the early stages of its conversion.

The Mirfin family Ikamatua dairy farm is 250 ha effective, with peak milk 650 cows, stocked at 2.6 Holstein Friesians/ha, classified as system 4, producing 514kg/cow MS (2010-11 season) with the addition of 2.7t/ha of imported feed and nitrogen use of 280 kg/ha/year. Included in the imported feed totals are wintering off for 90% of the herd at a nearby property with break-feeding of a brassica crop, plus feed wheat and baleage fed to the milking cows all year round. Last season the cows had between 700 and 800kg each of wheat, at a peak of 3kg/day, milled and fed through the farm dairy at milking. Total production was 362,000kgs MS.

The Mirfins have further developed the farm during the past 12 months with the addition of a 750m centre-pivot irrigator which draws water from the nearby river. It covers 75ha or 30% of the effective area, plus some room for extension with K-Line pods or similar. It was commissioned in March and Andrew expects it to be used for irrigation January to March.

NZ dairying System 3 – Feed imported to extend lactation (typically autumn feed) and for dry cows. Approx 10-20% of total feed is imported. Feed to extend lactation may be imported in spring rather than autumn.

System 4 – Feed imported and used at both ends of lactation and for dry cows. Approx 20-30% of total feed is imported onto the farm.

The trends in pasture growth have been similar across all four monitor farms but actual pasture growth rates varied substantially between farms. Ikamatua achieved the highest average monthly growth rates of more than 70 kgDM/ha/day October to December and at the same time Kotuku was achieving 40-45kgDM/ha/day. Pasture growth rates drops on both farms over the summer months and from January to April the Ikamatua rate is around 50kg/ha/day, while the Kotuku rates are 30-35kg/ha/day.

Growth rates in June and July drop below 10 kgDM/ha/day.

Out of the four monitor farms Kotuku had the lowest growth rates for much

of the season, and Ikamatua, the highest.

This past season Kotuku had a slow start in spring and only reached 40kg/ha/day growth rate in November, when Ikamatua was at 70kg/ha/day. Ikamatua then had a very growthy autumn with a peak over 80kg/ha/day in March, when Kotuku was around 50kg/ha/day.

Interestingly, the measured soil temperatures throughout the year have been close on all four farms despite differences in latitude and altitude. Also both Ikamatua and Kotuku produced the same milk last season – 362,000kgs – but by different methods.

DairyNZ scientist Dawn Dalley says this information highlights the impact of local climate, soils, and individual farm management practices on pasture growth rates. Soil type, soil temperature, soil moisture and solar radiation are key environmental factors affecting pasture growth, with rotation length, residual height, and fertiliser use (particularly nitrogen) being under managerial control. Soil temperature data partially explains some of the trends in pasture growth on these farms, particularly during winter and early spring when low soil temperatures strongly inhibit pasture growth in all districts. However, the different management systems employed on these farms are also likely to be having a major influence on pasture growth rates. The large variation in growth rates recorded on the monitor farms confirms the need for multiple monitor farms which are representative of the range of farming conditions and microclimates in the West Coast region. In recent years, West Coast dairy farmers not monitoring their own pasture growth rates, have had to rely on pasture growth rates generated from Landcorp’s Kotuku farm to support their decision making. The monitoring carried out for this project has highlighted the inadequacy of this information for most of these farmers as growth rates on Kotuku are not representative of the wider West Coast region.

The real value in this project is its ability to generate opportunities for the extension

of pasture management principles to West Coast dairy farmers. The project has already highlighted the variation in pasture growth and quality between farms which is a direct message to farmers that they need to be monitoring their own pasture if they want to manage it efficiently. As West Coast dairy farmers become more aware of the monitor farms and the information they are generating there is enormous potential to create some of the tension required to create change on farms with regard to pasture monitoring and management. Knowledge of differences in pasture growth trends across the region will allow farmers to make more informed decisions about the stocking rate and calving date that will best match the feed supply curve.