Pastoral 21 - Reducing Dairy Farm Run-off

December 2014

Massey University's No. 4 Dairy Farm is host to a Pastoral 21 collaborative project

The Pastoral 21 project is all about how to implement duration controlled grazing on a commercial farm scale to lift profit and lower nitrate leaching and phosphorus runoff.

Pastoral 21 Next Generation Dairy Systems is a five year farm programme that aims to provide a system that lifts production and reduces nutrient loss.  It’s a collaborative venture among DairyNZ, Fonterra, Dairy Companies Association of New Zealand, Beef+Lamb NZ and the Ministry of Business, Innovation and Employment, and managed by AgResearch.

The Pastoral 21 programme has been set up in four regions to address issues relevant to each area.

The research project looks at two dairy systems. Cows housed part-time in the barn (2.8 cows/ha) are compared to a more typical management system with a herd grazed-off in winter and a feed pad used on wet days in spring and winter.

The barn cost $1.4 million to build and houses more than 200 cows in stalls, with room for 300. The ends are open to allow feed to be brought in and effluent is deposited in aisles which have automatic scrapers.

Previous research has shown it only takes cows three to four hours to eat their allocated feed. The rest of the time they’re sitting, standing or excreting. The premise is that (1) treading damage on winter and spring wet soils reduces dairy farm productivity in the lower North Island and (2) urine patches are the main source of N loss to water so a reduction in the number of urine patches per hectare of pasture grazed is required. Duration controlled grazing provides a solution to both limitations. Longer term standoff in wet periods in winter requires housing that deals with large slurry volumes easily and economically which can then be distributed back onto 80% of the farm area.

The cows aren’t being housed fulltime, rather the research is exploring how the barn might best be used as a management tool to increase the amount of pasture grown and harvested by the cows, and to reduce the environmental footprint by better timing the collected effluent being redistributed onto paddocks.

The idea is that cows will stay indoors particularly in winter and spring, when pasture is vulnerable to pugging and through the autumn months for reducing urine patch deposition and consequently nitrate leaching.

The housed cows are sent out after milking for around four hours. At night they are brought in between 8 and 9 and stay in overnight.

Research officer Christine Christensen said 200 cows go into the barn for part of the day.

Relative to the control herd on pasture, a 52% reduction in leaching has been recorded by duration controlled grazing. Duration controlled grazing during autumn and summer only still has a major impact on reducing N leaching.

No 4 dairy unit is a commercial farm and an objective of the research was to recoup the money spent on the barn through less treading on wet pasture with its loss of feed, combined with more even and carefully timed applications of effluent.

Autumn grazing has had the greatest impact on amount of N.

The housed cows’ effluent is gravity fed into a pond alongside the barn. Spreading of slurry on 80% of the farm area is by tanker. Tanker traffic, slurry application depth and timing is controlled by soil moisture and temperature and N concentration. Slurry N application rules are similar to best practice for urea application.

They have measured the effluent coming out of the barn and estimate it will accumulate on average 167 kg N/ha/yr in dung and urine, which needs to be reapplied to the farm as slurry.  The nutrient content of the slurry varies with the type of standoff, the cows diet and whether the standoff slurry and farm dairy effluent are combined or stored separately.

Part of the research on the cow barn was to look at the rate of accumulation and nutrient concentration of slurry generated in the barn.  They looked at how much slurry storage was needed.   They also looked at the growth response caused by slurry reapplication in pastures where cows had restricted or controlled grazing

The cows were trialed on a range of bedding – sand, canvas covered foam, and rubber to see which the cows felt most at home on. 54% liked sand, 26% foam and 6% rubber.  The addition of sawdust increased the use of the foam mats. Although the sand was the most popular there was a problem with sand loss.

There was also the phenomena of stubborn cows who didn’t want to use the beds, so they stood in the alley or lay in the alley. This raises the issue of training cows for the barns which has already been noted in housed cows in Southland.