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Published: 2004-08-16 00:00:00

Soil compaction under dairy pasture and excessive nutrients on dairy, drystock and cropping land are increasing the risk to surrounding water, last week’s Environment Waikato Environment Committee meeting heard.

Environment Waikato and Landcare Research staff have been working on developing ‘early warning’ indicators for the Waikato’s soils - internationally recognised research which identifies changes in soil quality in time to take action to avoid long-term damage.

Environment Waikato soil scientist Dr Reece Hill said in the Waikato most soil issues related to soil degradation – a decrease in the biological, physical and chemical condition of the soil and excessive addition of nutrients. Maintaining soil quality was essential for sustainable land use to benefit the Regional economy and maintain water quality.

Developing long-term soil quality monitoring provided information for state of the environment reporting, future land use decisions and policy development as well as greater understanding of the interaction between land and water for different soil-land use combinations, he said.

The soil quality research had helped develop on-farm assessment tools and empowered land users to reduce their environmental impact and maintain production capacity.

Seven indicators were measured. In the Waikato 100 sites had been established for long-term monitoring representing dominant soil and land use types, and those which captured the effects of land use change and practices. More than 600 sites are monitored nationally.

Landcare Research scientist Dr Graham Sparling said all land uses had some indicators that did not meet requirements. Dairy land generally had problems with low macroporosity – large pores were destroyed – the result of high compaction rates and high phosphorous levels. Compaction levels were now worse than in 1998/99.

The main concerns were that now more than 50 percent of dairy pasture had moderate soil compaction, leading to lost production and more runoff.

About a third of farms had excessive phosphorous levels above those needed by pasture. At the May meeting of the Environment Committee Dr Doug Edmeades said Dexcel research showed $70-$80 million of nutrient applied by farmers may not be necessary.

“The problem is not nutrient deficiency, it’s nutrient excess.”

Some crop and horticultural land had bare land for much of the year and high nutrient levels well above any agronomic benefit, as well as loss of organic matter. There was localised concern on market gardens because of high nutrient levels.

The sites would continue to be monitored, identifying substandard land management practices and informing and engaging the farming industry to promote mitigation strategies and adopt sustainable practices, he said.
Cr Andra Neeley said the research showed the value of soil testing and nutrient management in reducing the costs to both farming and the environment.