Excessive urea pollutes, scientist warns

23:12, Feb 14 2013
Arden Anderson
MORE PROFIT: Adopt a biological approach, Arden Anderson advises.

Many farmers are neglecting their soil health and putting too much urea on paddocks,  says American soil scientist and physician Dr Arden Anderson.

Anderson, who maintains urea is ''the cocaine of agriculture'', doubted  that many dairy farmers were taking care of their soil.

''I really don't think so and the statistics show that as well. When we look at the urea issue we have problems with water run-off in streams and lakes.''

He said it was possible to operate more productively and profitably through biological farming and without chemicals detrimental to the environment and human health.

The dairy industry was saying advances were being made in this direction, but fertiliser run-off was poor and the results were mastitis and calving problems which were reducing total milk production, he said.

Biological agriculture focuses on re-setting the balance of minerals and raising microbiology in the soil. The approach uses conventional and organic farming methods with a focus on making calcium and trace elements available and supporting microbial diversity to increase  humus and reduce the use of petrochemical products.


Anderson said research by the Ministry of Primary Industries showed levels of dry matter a hectare had declined even though urea use was increasing and this was causing environmental pollution.

''The latest thing is the DCD issue. They are trying to soft peddle that it's not a problem  ... but it's an antibiotic. We don't want antibiotics in our milk.''

He said DCD may not be toxic, but as an antibiotic it wiped out bacteria.

Fertiliser manufacturers have voluntarily withdrawn DCD (dicyandiamide) from their product ranges after traces were found in Fonterra milk. DCD is a nitrogen inhibitor and is applied to pastures to reduce the harmful environmental effects of urea use and run-off from cow effluent.

Andersen is a biological soils consultant to farmers around New Zealand and is leading a round of biological farming and human health courses including in Ashburton yesterday.

He said farmers needed to get more efficient with  converting nitrogen to protein and extract more energy from grass.

''The bottom line is we have to get appropriate nutrition in the soil and particularly include getting calcium back into the equation instead of all nitrogen and phosphorous.''

He said more benefits could come from converting manure into humus rather than have nitrogen running into waterways.

Farmers could not keep doing the same thing they had for the last 10 to 15 years by loading more urea into soils, Anderson said.

He said some farmers were taking the biological approach to reduce nitrogen and were getting better dry matter rates for healthier cows.

The approach was not unique to the United States and was about basic nutrition applied to soils and crops and understanding their biology.

The focus by Fonterra on nutrient density in the milk was all about the soil, he said.

An estimated 200,000 hectares of land is farmed under biological principles in New Zealand.

The Press