Soil is key to Pingrup yields

24 Dec, 2001 10:00 PM
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IF YOU visit Pingrup farmer Gary Featherstone's farm chances are you will end up in front of a white board discussing soil tests, soil nutrients and soil structure.

Gary is one of a growing number of WA farmers who want to push beyond the boundaries of conventional wisdom when it comes to looking for answers to increasing crop and pasture yields.

Perhaps not surprisingly, strong clues to the answers are coming from the past in the form of practices espoused by a Missouri soil scientist called William Albrecht who was convinced that soils needed to be "balanced" for crops and pastures to grow better.

He developed what is now known as the Albrecht model based on the soil having at least 60pc calcium, 10pc magnesium, 3-5pc potassium, 0.5-3pc sodium, depending on soil type.

Calcium is the key for plants to be able to access and uptake nutrients while magnesium promotes nutrient and holding capacity of sandy and non-wetting soils.

Magnesium also has a role in transporting phosphorous and is important in seed formation and assisting in soil structure.

Potassium is a multiple role player in plant and seed development while sodium also has a role to play in plant growth.

According to Gary, the ideal calcium:magnesium ratio for his clay loamy soil is 68pc calcium and 12pc magnesium and around 60:20 for his more sandier soil which benefits structurally from a higher magnesium content.

Achieving the correct ratio also is beneficial in boosting the moisture holding capacity of non-wetting soils.

The starting point is a laboratory soil analysis of paddocks, which can deliver information on nutrient status in the soil and the desired levels to give an indication of the management of nutrient application.

This is where the "balancing" comes in because, for example, if your K (potassium) levels are too high it will suppress your Mg (Magnesium) levels while a high Mg reading will result in a high pH reading and will cause structural problems in clays and loams.

If your soil calcium ratio is below 60pc saturation, there's a strong likelihood you'll get a short term response to gypsum because sulphur will take out calcium. And with calcium above 60pc, sulphur will take out magnesium.

On soil pH, Gary says know what you're playing with.

"pH is a measurement of hydrogen so it's not a measure of soil fertility or nutrient status of the soil.

"You can have a perfect pH reading and nothing will grow.

"Ph is constructed from the different percentages of calcium, magnesium, potassium and sodium.

"You can construct magnesium and sodium, for example, to give a pH of 7.5 or a calcium and magnesium construct that reads 5.4.

"You can have a perfect pH and very low calcium so it's important to dissect the pH before you make any decisions."

"This is all old information but it has not been readily available to farmers in WA, because I think it was considered too complex a subject.

"And in the fifties we had soil that was half reasonable from clover ley farming."

With the advent of more emphasis on continuous cropping in the early seventies, Gary believes it saw the start of a general decline in soil fertility and soil structure throughout the wheatbelt.

"This has led to plants having difficulty accessing soil nutrients and we're only now starting to understand what might be the reasons," he said. "I certainly believe on evidence I've seen on my farm and other farms that have been using the Albrecht model, the importance of having a correct calcium/magnesium ratio in the soil."

Gary has been managing his soils using the Albrecht model for the past three years after chasing information for more than 15 years.

"We went into continuous cropping 25 years ago and we got good results for the first five to seven years," he said. "Then yield plateaued while costs continued to rise.

""We were putting on up to 140kg/ha of Agras with applications of copper and zinc and we weren't getting results.

"I got no answers to questions I asked on why we weren't achieving better yields.

"When I had the opportunity to study the Albrecht model when reading a book called Hands On Agronomy by Neil Kinsey, it turned on a light switch and I could understand why things weren't happening.

"Now we're applying dolomite, lime and gypsum to appropriate areas identified from soil testing.

"I don't expect to turn around overnight but I think we're on the pathway to growing better crops and pastures.

"When the soils get better I want to put more emphasis on growing pastures and looking at a more mixed farming enterprise with more focus on phased cropping."

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