Back Maize builds profitable and sustainable dairy systems

Date: 14 April 2016

While Pioneer® brand maize hybrids have been available in New Zealand for the last 40 years, maize silage really only started to rise in popularity as a dairy cow supplement in the early 1990’s. At this time a number of top farmers had hit a feed barrier with pasture availability limiting milk production and profit. They were searching for a high quality supplement. The solution was maize silage.

More cows, higher feed demand

In the 1985-86 season there were 2.3 million dairy cows in 15,753 herds. The average herd was 147 cows producing around 275 kg milksolids per cow. Over the next 30 years the national dairy herd more than doubled while the number of herds decreased by 24%. Average farm size increased by 128% and herd size by 185%. The result has been a significant increase in stocking rate.1

Table 1: Changes in NZ dairy farm systems in the last 40 years1

National herd size (cows) 2,321,012 5,018,333
Number of dairy herds 15,753 11,970
Average farm size (ha) 64 146
Average herd size (cows) 147 419
Stocking rate (cows/ha) 2.30 2.87
Average milksolids production per cow (kg) 275* 377

*Estimated from milk fat production levels

While ryegrass-clover pasture remains the backbone of New Zealand dairy farm systems, the increased feed demand outstripped the genetic gain in ryegrass (estimated to be an average of 0.5% per year2). Higher breeding worth (BW) cows were programmed to produce milk at the expense of body condition. As a consequence, lactation lengths were short with cows being dried off early in the autumn so farmers could build up pasture cover and increase cow condition score prior to calving.

Maize silage delivers more drymatter

Maize was the answer to the problem. Advances in maize hybrid genetics, coupled with improvements in crop management methods, meant silage yields were increasing at more than 300 kgDM/ha per year. Maize silage followed
by annual ryegrass could produce more than double the yield of perennial ryegrass pasture.

Figure 1: New Zealand maize silage yield trend 1961 - 2015.3


Waimate West Demonstration Farm trial

By the late 1990’s many leading farmers had started to feed maize silage to increase days in milk, either by calving early or milking longer in the autumn, or to fill feed deficits. A trial conducted at Waimate West Demonstration Farm (now known as the Westpac Taranaki Agricultural Research Station) showed high increases in production and profit were possible when maize silage was fed strategically.

Table 2: Waimate West Demonstration Farm production and financial results of the 1997-98 season.4

Cows/ha 3.8 3.8 3.8 3.8
Maize silage (kgDM/cow) 0 300 293 290
Milksolids per cow 285 332 309 337
Milksolids per ha 1,083 1,262 1,174 1,281
Days in milk 228 268 256 259
Economic Farm Surplus (EFS) ($/ha) 1,489 1,824 1,532 1,904
EFS % Increase - 23% 3% 28%
Milksolids response to maize silage (g MS/kgDM maize silage fed) - 157 82 179

Farm systems evolve over time

By 2001-02 the majority of New Zealand dairy farms were still highly reliant on pasture production with imported feed, including purchased supplements and dairy grazing, comprising less than 10% of total feed input on 70% of all
dairy farms. By the 2013-14 season there were more higher (more than 25% of feed bought in) and medium (10 - 25% of feed bought in) input farms than lower input farms (See Figure 2).5

A number of factors had driven the substantial shift in farm systems including escalating dairy land prices, which made it more cost-effective to intensify than purchase another property, higher milk prices and a series of record-breaking droughts in key dairy districts.

Figure 2: Percentage of lower, medium & higher input farms in New Zealand.5

Stabilising on-farm feed supply

The “100 year” Waikato drought in 2007-08 reinforced the benefit of growing and feeding maize silage. The deep rooting structure and improved water use efficiency of maize allowed it to continue growing long after ryegrass
had stopped. Farmers who had a stack on hand were not exposed to feed shortages and sky rocketing prices.

Maize and the environment

In the last decade it has become evident that while it has contributed significantly to the New Zealand economy, the expansion and intensification of dairy farm systems is having an impact on the environment. As cows graze protein-rich pasture, they produce nitrogen-rich urine patches. Surplus nitrogen quickly drops out of the rootzone of shallow rooted pasture species eventually ending up in lakes, rivers and streams. Feeding maize silage - a relatively low crude protein feedstuff - reduces the amount of nitrogen in urine and can sharply reduce leaching losses.

Growing maize is beneficial too. High yielding maize crops can be grown on high fertility dairy paddocks, including those with a history of dairy shed effluent application, without the need for additional fertiliser. The gains are two-fold, farmers get high yields of low cost drymatter, while at the same time maize strips excess soil nutrients including nitrogen.

Farming for the future

The challenge for today’s farmers is to build systems which will deliver stable returns across a range of climatic conditions and milksolids payouts. The farmer stories here show how a number of top farmers are using maize
silage to help them build resilient farm systems which will stand the test of time.


1New Zealand Dairy Statistics 2014-15.
2Lee et al 2012. Perennial ryegrass breeding in New Zealand: a dairy industry perspective. Crop and Pasture Science 63: 107-127.
3Pioneer® brand products maize hybrid evaluation program.
4Deane, 1999. Proceedings of the Ruakura Farmers Conference 51:64-77.
5DairyNZ Economic Farm Survey 2013-14.