The poor quality of New Zealand pastures is one of the main reasons agricultural debt levels are so high, a leading soil scientist says.

Dairy cows are being presented too often with a nitrate-crude protein-rich pasture that does not provide them with enough energy, Graham Shepherd says.

It meant farmers brought in high levels of supplementary feed to give the rumen the energy required to process that type of pasture, he told farmers at a field day at Bryan and Jackie Clearwater's farm near Geraldine.

Cows should run on an 85 per cent pasture-15 per cent supplement diet, but this ratio was closer to 60:40 on many farms. This was a high cost and contributed to the high levels of debt in the dairy sector.

"A lot of our farms are farming for production, not for profit," he said.

This nitrate-crude protein-rich pasture could lead to animal health issues, Mr Shepherd said.

It also meant cows produced a large amount of nitrite in their faeces and suppressed some of the bacteria within the rumen used to digest herbage, resulting in poor feed efficiency.

This could be changed by improving the quality of the animal's nutrition by presenting it with good quality pasture, he said.

Being able to visually assess soil condition and pasture performance was in the best interests of the farmer. His visual soil analysis (VSA) system allowed farmers to do this, he said.

It allowed farmers to test the quality of their soils using several different parameters regardless of land use.

Knowing the limits for these indicators allowed farmers to know the condition of their soil.

The difference between good and poor soil was obvious to the trained eye when conducting a VSA, he said.

"The information your eyes are telling you provides a very, very powerful indication of the condition of the soil and its implications for farm management profitability and environmental outcomes.

"The trick is to train the untrained eye."

The system is based on a series of scorecards used by the farmer to rate soils and plants. The better the quality of the soil and plants, the higher the score.

Both cards have 10 visual indicators the farmers use to grade the quality of their soils and pasture performance.

The visual indicators for the soil include its structure, texture, colour, porosity, surface ponding and smell.

Soil smell, for example, was an indicator of the level of microbial fungi within the soil and a good earthy smelling soil was evidence of a high level of these microbes.

They were important because it provided a bridge that linked the soil to the plant.

They were evident in earthy smelling soil. A high colonisation of these microbial fungi provided good plant performance.

Getting these fungi into pastures provided a huge lift in performance, he said.

Pasture quality is the major indicator of pasture performance and include its level of quality measured on the percentage of green material and clover.

"What we want to do is present the cow or the stock with a salad. We have to get away from the monoculture of a ryegrass or a ryegrass clover."

It resulted in a more palatable feed for the stock.

Other pasture indicators were legume nodule health, weed levels and pasture root length and density.

Mr Shepherd then demonstrated the system out in the paddock on the Clearwater's farm, where it showed a lack of earthworms in the sample.

Mr Clearwater says the soil grading in the assessment added up higher than the pasture scores and believes low selenium levels were contributing to poor clover performance.

He says they will attempt to address this and other element deficiencies in a fertiliser mix being spread on last week.

The result was not surprising, Mr Clearwater says.

"We and the farm are not perfect. There are a number of areas within the soil management spectrum that need to be improved to enhance farm profitability and environmental services to the wider community."

Mr Clearwater said VSA led to better efficiency of nutrients that should be going into food and not lost into groundwater.

The assessments are fundamental to their farm business.

"Everything we do from the pasture we grow to the health of our cows to the food we produce to the wider environment.

"There are a lot of strands to the notion of organic farming."

VSA's were not restricted just for organic but to all types of farming, he says.

"It's part of where New Zealand needs to be and where we market ourselves."

- © Fairfax NZ News