Dedicated cropping block a solution for the future?

At the recent Australasian Dairy Science Symposium, Dr Pierre Beukes from DairyNZ presented a paper which I, alongside Tai Chikazhe (a modeller with DairyNZ), helped co-author. It investigated the profitability and sustainability of feeding maize silage which was grown on a dedicated cropping block within a dairy farm.

Pierre showed a great cartoon where a married couple in bed were fighting over a duvet that was obviously too small to cover both of them. He made the point that, at a systems level, there will always be compromise as we seek to maximise profit and milk production while at the same time minimising nitrogen loss. The paper showed that using a dedicated cropping block to grow maize silage in summer and grass silage in winter, dairy farmers could potentially meet their nitrogen loss goals without too much reduction in profit.

The study simulated three different scenarios over five consecutive seasons (2013/14 to 2017/18), using DairyNZ’s Whole Farm Model (WFM), Agricultural Production Systems sIMulator (APSIM) and the Urine Patch Framework (UPF). The scenarios were:

1) A typical Waikato dairy farm (P21 Base farm (CF) - 3.2 cows/ha, 125kg N/ha fertiliser on pasture 25% replacement, harvesting grass silage for use during periods of feed deficits, no standoff pad.

2) The P21 Future Farm (FF) (2.6 cows/ ha, applying 85kg N/ha fertiliser, high genetic merit cows, imported maize grain as low-N feed, with a standoff pad.

3) The maize silageblock farm (Future Farm Plus (FFP) 3.2 cows/ha, high genetic merit cows, 85kg N/ha to pasture, feed pad, maize silage grown on a dedicated block occupying 15% of the effective farm area followed by annual ryegrass).

Each scenario considered the production, profit and N leached implications, with profit calculations also including depreciation on the feed pad.

The results of the modelling exercise are shown in Table 1.

The results show that by adding a dedicated cropping block to a dairy farm and using a range of mitigation strategies, farmers can reduce N leaching by 26% with a relatively small (4%) reduction in profit. The reasons why this system worked were numerous:

- Maize silage is a high N demand, high yielding, low protein crop.

- Effluent captured from the milking shed and feed pad is an excellent fertiliser source to grow maize.

- Annual ryegrass is an effective winter catch crop.

- The extra feed grown on the cropping block meant the farm didn’t need to reduce the stocking rate and the farm produced more milksolids per cow and per hectare.

Any change in farm system nearly always requires compromise of one metric compared to another. I started this article with the statement, “You can’t have it both ways”. This modelling exercise hints that maybe you can.

While the FF had the largest reduction in N leaching per hectare, it also had the largest reduction in profit when compared to the CF. The FFP farm still had a very significant drop in N loss, but the profit was close to breaking even when compared to the CF.

Many regional councils are requiring farmers to make significant reductions in the N loss from their farms. The FFP farm gives the industry some hope that, by including a dedicated cropping block on the farm, farmers may be able to meet these targets with very little reduction in profitability.

Ian Williams is a Pioneer forage specialist. Contact him at This email address is being protected from spambots. You need JavaScript enabled to view it.