Robin Casey's claims of growing more with 90 per cent less nitrogen need to be tested

Whanganui fertiliser broker Robin Casey grows more for way less nitrogen than traditional recipies call for.

Independent Whanganui-based agricultural fertiliser broker Robin Casey is incredulous nobody is taking him seriously.

Casey has challenged long-held farming beliefs by claiming he can produce more dry matter using 90 per cent less nitrogen than traditional recipies call for.

Armed with data gathered over a six-year trial on a Whanganui farm, Casey has proof he can do what he claims, yet nobody appears interested in putting his claims to the test.

His findings say he can drastically reduce the amount of chemicals leaching into waterways.

In 2015 Casey completed the three-year trial using two adjacent paddocks on the same farm. On paddock 22, he used traditional solid fertiliser applications, while on paddock 21 he used his own liquid solution with Rapid N as the base product.

He has since repeated the same exercise over the past three years adding to his data gathered.

Concerns over chemicals in waterways centres mainly on nitrogen, which is well-known for its ability to substantially increase grass growth. However, Casey's trial revealed he could produce similar yields on paddock 21 over the three-year trial period with nowhere near the same quantities of nitrogen used on paddock 22.

"We averaged 16,414kg of dry matter (DM) over the trial period on paddock 21, compared to 16,700kg in paddock 22. Subsequent animal dietary analyses showed the quality was significantly better, too, in paddock 21," Casey said.

"The difference was that over the three year trial period the traditional applications included a total of 513kg tonnes of solid N, while in paddock 21 we used just 47kg of liquid - that's a huge drop and significantly important when it comes to cleaner waterways.

"Using Rapid N as the base, we could add various trace elements to act as grass-growth promotants and these are chemical-free. The trace elements used were dictated by traditional soil and herbage tests that revealed any deficiencies."

Reducing nitrogen is becoming mandatory and restrictions loom.

He said many doubted just as much quality grass could be grown using only a 10th the amount of N used by traditional methods.

"It really comes down to belief systems I guess. The generally held belief is more N equates to more grass, but my trial clearly illustrates we can produce just as much with a 10th the N traditionally applied," Casey said.

"I've been shouting this from the tree tops for the past few years, but nobody appears to want to listen. I would love someone to take me to task and put my claims to the sword - I know it works and have the proof."