RURAL

Gordon Gordon CREDIT: Media PA

If You Can't Test, Then You Can't Manage, Says Waikato Soil Scientist

Monday 9 May 2022, 10:26AM
By Media PA
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Slow-release products or “suspension fertiliser technology” is the future for pasture growth in New Zealand, according to soil scientist Dr Gordon Rajendram.

While fencing or planting trees along waterways to reduce phosphate loss is an expensive exercise, Dr Rajendram says more affordable methods exist.

“The cheapest way to reduce P [phosphate] is to change your product from a highly soluble one to a less soluble one,” he says in disclosing five factors that drive pasture growth.

Five years ago, at a soil seminar, Dr Rajendram says an elderly farmer had revealed to him the suspension method’s ability to apply 16 nutrients in one application. This technology ticks many boxes not only for pasture growth, but environmentally.

The Waikato-based independent fertiliser consultant outlines five factors that drive pasture growth:

1/. Soil temperature at 10cm is a good indicator. A drop down to 5 - 6 degrees C stunts growth.

2/. Falling below 25% of soil moisture content slows growth.

3/. The pH (acidity) level and 13 key elements are required for plant growth.

4/. Soil that isn’t porous robs roots and microbes of air.

5/. Soil biology

When testing the soil, he says it’s imperative to avoid dung and urine hotspot patches that can skew readings because of high nutrient levels. Animals excrete 66% of what they eat.

“If you can’t test, then you can’t manage.”

In a pasture of rye grass and clover, the former contributing to 19% of the protein in pasture and the latter 34%, as clover is a nitrogen fixer.

“So, that means the more clover you grow, the more [nitrogen] you’re fixing for free,” he explains.

Dr Rajendram says clover’s digestible quality yields more energy, compared with grasses. With clovers and most grasses ‘allergic’ to soil acidity, farmers need to monitor soil pH content to acquire 6.2- 6.5 soil pH levels.  These soil pH levels are based on many factors with Irish farmers also recommended these ideal pH levels.

Farmers must strike an “optimum” level to avoid low productivity but also not “overcook” to incur leaching costs.

“In Waikato, you become a bit of a slave to phosphate but, in Canterbury, you have more potential to lose it,” Dr Rajendram reveals. “It’s hard-earned money you don’t want to lose.”

April-to-October rain and drainage dictate the extent of leaching. Any nitrogen that plants fail to absorb drops incrementally by approximately a metre each year until it reaches aquifers and streams.

Anions (negative ions), such as nitrate and sulphate, attract and hold cations (positive ions), such as calcium and magnesium, in aiding leaching.

However, minute amounts of phosphate via runoff or leaching aren’t an economic issue, but an environmental one.

Contact Gordon:

Email: rajendram@xtra.co.nz

Phone: 021 466 077

Facebook: https://www.facebook.com/GordonRajendramSoilScientist

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