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You are here: Agriculture » About Agriculture » Newsletters and Updates » Ag in Focus » Ag in Focus - Winter 2011 » Nutrient research saves farmers and environment

Nutrient research saves farmers and environment

Accounting for Nutrients on-farm project team

At a glance

• DPI-led national project monitoring 44 contrasting dairy farms across Australia.
• The efficiency of nutrient use on dairy farms generally low and nutrient surpluses often high.
• On average 14 grams of nitrogen is lost to the environment for every litre of milk produced.
• Substantial opportunities for farmers to increase nutrient use efficiency and increase profitability.

Smarter nutrient use could increase profitability on the average dairy property by $26,000 each year and $70 million annually across the industry, a new DPI-led study has shown.

Project leader Cameron Gourley said the national study funded by DPI, Dairy Australia and other industry partners, revealed significant opportunities to increase the efficiency of nutrient use on dairy farms.

Through better management of fertilisers, cow diets and the management of excreta, he said Australian dairy farmers could better use nutrients within their businesses to save money, improve productivity and benefit the environment along the way.

A national project

DPI technical officer Donna Gibson

The DPI-led project studied 44 farms over two-years, involving eight detailed farm visits and sampling periods. Farms were chosen to represent the range of dairy businesses across Australia, in terms of location, rainfall, soil type, irrigation and productivity per hectare. Four of the farms are accredited organic operations.

Dr Gourley said DPI was delighted to lead such an important study that incorporated expertise from key players across the country. All up, 16 regionally-based teams across the country collected more than 2000 feed, milk and manure samples, 3000 soil samples and it included more than 25,000 laboratory analyses.

The project was in response to the trend of increased intensification in the Australian dairy industry.

"We have seen internationally that as dairy farms increase their overall productivity and intensity per hectare, nutrient surpluses tend to increase. This poses a greater challenge for the dairy industry to increase the efficiency of nutrient use and minimise environmental impacts," Dr Gourley explained.

He said surplus nutrients could negatively affect air and water quality and were a waste of farmers' money, particularly as fertiliser prices are on the rise.

Dr Gourley estimated that in the next few years, fertiliser costs could increase anywhere from $10,000 to $100,000 per farm, depending on the farming system.

Although the study considered all the major nutrients which contribute to dairy farm productivity, a special focus was given to nitrogen and phosphorus due to their potential environmental impacts.

But Dr Gourley said any fertiliser should be used efficiently.

"From a farmers' perspective, any expenditure on fertiliser that's not providing production gains is a waste of money.

"It's a classic win-win. There's a great environmental benefit and farmers can increase their overall production per hectare."

The project found that whole-farm nitrogen use efficiency ranged from 14–50 per cent, with an average of 26 per cent.

The opportunities to improve nutrient use on-farm focussed on three primary areas, including fertilisers, cow diet and excreta.

Better managing fertiliser applications

More than three quarters of the 2200 dairy paddocks sampled had surplus phosphorus, potassium and sulphur levels.

"At these levels most pastures and crops are unlikely to produce additional dry matter from additional fertiliser inputs," Dr Gourley said.

Nutrient levels were particularly high in paddocks close to the dairy shed and where animals are held for extended periods.

Dr Gourley said farmers should soil test and target fertiliser applications each year. Since fodder conservation and milk production can remove substantial amounts of nutrients, soil testing needs to target paddocks with different uses across the property.

Delivering on diet

Dr Gourley said when considering nutrients, it was important to take into account the diet fed to cows, especially given the increase in dairy supplements over the past thirty years.

The study examined 75 types of feed and found that mineral composition and metabolisable energy varied significantly between and, at times, within types of feeds as shown in Table 1.

Researchers estimated that a typical 300 cow dairy farm, which consumed 450 tonnes of wheat grain and 150 tonnes of lucerne hay, would be importing in feed the equivalent of 33 tonnes of urea, 23 tonnes of single superphosphate and 10 tonnes of potash fertiliser.

Although some nutrients go directly into milk, the bulk is excreted in urine and dung (see Table 2). By using feed analysis to better match the nutrients and minerals supplied in the diet with the cow's requirements, farmers can improve animal performance and also reduce excreted nutrients and environmental impacts.

Table 1: Nutrient characteristics of three common supplementary feeds and ryegrass pasture

# The values in brackets represent the range
	Nitrogen (N) (%)	Phosphorus (P) (%)	Potassium (K) (%)	Sulphur (S) (%)	Calcium (%)	Magnesium (%)	Metabolisable energy (MJ ME/kg DM)
Wheat grain	2.2 (1.5–3.1)	0.3 (0.2–0.4)	0.4 (0.3–0.5)	0.16 (0.1–0.2)	0.05 (0.01–0.08)	0.13 (0.10–0.15)	12.9 (12.4–13.3)
Cereal hay	1.6 (0.3–2.5)	0.2 (0.05–0.4)	1.7 (0.6–3)	0.16 (0.1–0.3)	0.2 (0.1–0.5)	0.14 (0.08–0.2)	8.5 (5.3–9.7)
Lucerne hay	3.4 (2.3–4.8)	0.4 (0.15–0.7)	2.0 (0.8–3.2)	0.3 (0.1–0.4)	1.2 (0.2–2.2)	0.4 (0.1–0.7)	9.6 (7.8–11.2)
Ryegrass pasture	3.7 (1–5.6)	0.4 (0.1–0.8)	2.8 (0.5–4.9)	0.3 (0.1–0.6)	0.6 (0.1–1.1)	0.3 (0.1–0.5)	10.5 (6.7–12.4)

Table 2: Daily nutrient excretion by lactating cows on the farms surveyed (grams per cow per day)

	Nitrogen (N)	Phosphorus (P)	Potassium (K)	Sulphur (S)	Calcium (Ca)	Magnesium (Mg)
Average	432	61	340	44	91	52
Range	199 to 792	20 to 132	120 to 671	19 to 102	10 to 210	21 to 274

Managing manure

Project leader Cameron Gourley

Dr Gourley said cows were the forgotten fertiliser spreader.

"Across the 44 herds we studied, only 20 per cent of the nitrogen consumed ended up in milk. That means 80 per cent was excreted in urine and dung."

Dairy cows also excrete large amounts of phosphorus, potassium, sulphur, calcium and magnesium each day, depending on their dietary intake and milk production.

"It is important to ensure that excreted nutrients are effectively redistributed to the productive parts of the farm," Dr Gourley said.

"When dung and urine are not deposited on pasture or crop land, this places a substantial limitation on production," Dr Gourley said. "The concentration in non-productive areas also presents a significant environmental problem."

Where cattle are kept in feeding and holding areas for any length of time, Dr Gourley recommended setting up effective systems for collecting and reusing excreted nutrients.

He said regularly rotating cows through paddocks, even in dry weather, would ensure that feed nutrients were more evenly distributed.

The recommendation

The results of this national study demonstrate that most dairy farms could improve the efficiency of nutrient use, meaning more go into production and less are lost to the environment.

Dr Gourley said better understanding the amount of nutrients which come and go out the farm gate, helps to define nutrient needs. Within the farm, cows play a major part in redistributing large amounts of nutrient.

"In today's dairy farms, a more targeted approach should be undertaken," he said.

Dr Gourley recommended farmers soil test across at least 6–10 different areas of their property, reducing phosphorus, potassium and sulphur applications on those parts that have excess nutrient levels.

"The relatively small costs with undertaking a strategic and on-going soil sampling program are likely to be returned many times through the potential savings in unnecessary fertiliser expenditure."

Managing nitrogen also required a more refined and targeted approach. In particular, he recommended better distribution of cow manure and applications of nitrogen fertiliser when soil and climate conditions are right.