Wednesday, July 6, 2022

Biologicals showing worth, trust member says

The Rotorua Lakes and Lands Trust, a joint venture between Te Arawa Federation of Maori Authorities and Pakeha farmers, has spent at least a decade studying nutrient management around the Central Plateau and is convinced that biological systems are a worthwhile tool against nutrient leaching.

Now all the trust wishes for is greater funding and sustained expertise to win more people over.

Farmers who have turned to biological systems are often anxious about the increased use of synthetic fertilisers that has caused economic and environmental concerns. Fertiliser costs and problems with water quality typically shape as the major problems.

In a presentation to a biological farming conference, Reporoa farmer and RLLT trustee Gifford McFadden said nutrient leaching had become a risk to the viability of many central North Island farming ventures, because farmers were compelled to reduce nutrient losses.

Gifford has more than a passing interest in the subject – he is the projects leader for the trust as it explores if biological farming systems can be used to achieve the same financial results as current farming practices while lowering nutrient leaching. The trust organised a national conference on biological farming systems and formed the NZ Biological Farming Systems Research Centre.

Gifford says farmers using biological farming systems have observed positive changes to soil and improvements in plant and animal health.

Based on this, he believes scientific investigation is warranted to establish the mechanisms and processes responsible and to ensure that potential benefits can be more widely adopted.

The trust has set up two experimental sites, one at Reporoa and one at Edgecumbe, with the trial product supplied by Eco-Logic Soil Improvement. 

At each site sets of 12 drainage flux-meters were installed on a biological and a neighbouring conventional dairy farm. The meters were used to measure amounts of drainage and nitrate concentrations in the soil water. In addition to nitrate, concentrations of ammonium, dissolved organic nitrogen and dissolved organic carbon were also measured in the soil water.

Preliminary leaching results from two experimental sites showed that, in general, the biological farms had significantly lower nitrate concentrations than the conventional farms. At the Edgecumbe site, which had biological farming for a longer period, the leaching of dissolved organic carbon was greater in the biological farm than in the conventional farm.

In 2008, the trust reviewed research areas for tools to lower nutrient leaching.  Interestingly, a recent document by Gifford has solutions graded according to what the trust regards as “political acceptability”.

Those areas are:

Farm systems: wintering pads, high sugar grasses etc.

Animal biology – reduction of N in urine, P movement over ground and in water

Stream attenuation – active management or riparian areas

Nutrient harvesting in lakes – algae and vegetation

Soil biology – can the soil biology be altered to capture N?

The Reporoa and Edgecumbe trials have been running just 14 months on threadbare resources but the comparative results so far are promising, Gifford says.

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