Shortlands Station - Fertiliser Trials

June 2015

AgScience's Dr Peter Espie is running fertiliser trials on Shortlands Station

Peter Espie has carried out a large number of experiments testing the effectiveness of non-standard (alternative) fertilisers and comparing them with conventional recommended fertiliser applications. The experiments have shown that some alternative products give significant production advantages. Some large-scale tests have been done on Shortlands Station with very positive results. 

Any fertiliser company should be able to demonstrate to their clients or anyone else that their products perform as claimed and have the content that is claimed. This applies to “alternative” fertiliser producers just as much as any mainstream fertiliser company, according to Dr Peter Espie, a scientist specialising in soil/plant relationships who has carried out considerable research over many years in grassland ecology and fertiliser performance.

“My company runs many research trials in various locations for different fertiliser companies that require an independent assessment of their products,” says Peter.

“This is the third year of trials at Shortlands Station testing fertiliser products and we have shown that they work in a way that is statistically verifiable and meet the criteria of the science community, and the results generally support the use of those products.”

Major experiments have been carried out on the lower “flats” in two areas, each 1 ha in size. One area had never been fertilised in 150 years of pastoral farming; the second was on a site that had been developed into high fertility pastures. Experiments have been replicated on each area to highlight any differences between low and high fertility sites. Because of the drought the visual differences are subtle.

Trials have included:

  • Comparing guano with that of acidulated superphosphate as a source of P
  • The efficacy of foliar fertilisers
  • The effects of lime and dolomite
  • The interaction of foliar and solid fertilisers
  • The effects of adding humates 

The results are from scientific trials, not anecdotal, and potentially confounding factors have been excluded. They confirm that the results Shortlands Station has been getting from the application of biological fertilisers are genuine and not wishful thinking.

P supplied in guano has given higher yields to P supplied in superphosphate.

Adding humates to urea (essentially carbon coating of urea granules) has given increases of 50 – 80% in dry matter production over urea alone, and the more humates added, the greater the increase. This occurs on unfertilised sites as well as developed pasture, and shows that responses to biological fertilisers are not the result of “mining” of previous applications of P.

These results most likely reflect the stimulation of the action of soil microbes by humates plus a reduction in the volatilisation of urea. They are highly significant and go against conventional wisdom, but are consistent with results obtained in trials in two other parts of the country. They challenge some widely held views that humates are a “waste of time” and are likely to change the way soils are fertilised to increase pasture production.

The site for the Hieracium test is an intermediate terrace between the low and the high hills where Hieracium has invaded aggressively. Trials are examining the use of combinations of boron plus biological stimulants as a means of Hieracium control. Hieracium is more sensitive to boron than other typical pasture plants and so can be suppressed or killed without damaging pasture or adversely affecting its establishment.

“Soils on the hills soils are totally different in their chemistry and reactions, and we have major experiments looking at dolomite, lime, and guano and all combinations thereof,” says Peter. “We are also looking at the introduction of legumes and how that can affect the productivity up there. Because the hill site has never been fertilised, oversown or developed in any way, we planted a suite of reference legumes and one grass so that every plot has the same legumes and combinations. It means that we can use those as indicator plants and make valid comparisons.”

Results on the flats and hills have shown dramatic increases in dry matter production from biological fertilisers compared with recommended amounts of superphosphate on both unimproved and high fertility areas. One of the potential reasons for that is that the guano based phosphorus is supplying the nutrients in a form that assists the soil microbial populations to mineralise nutrients that make them plant available in a way that superphosphate does not appear to, and that’s the mechanism that we suspect may be operating. We have some evidence that that is the case but that evidence has not been released publicly yet.

“What we have found is that the guano based fertilisers are statistically no different in performance from superphosphate in terms of dry matter production.

“In one experiment we applied a guano based product and compared it with superphosphate applied at a rate recommended by a conventional fertiliser company. We then looked at the dry matter production per unit of phosphorus applied and found that the guano yielded 10 to 18 times the weight of dry matter production,” says Peter.

High free aluminium levels in South Island high country soils are toxic to pasture plants. This is exacerbated by applications of superphosphate and the growth of legumes is inhibited. Liming raises the pH and reduces free aluminium and use of guano supplies P without having an acidifying effect. The result has been that legumes have become well established. Peter points out that the beneficial effects of liming and applying P on these soils are well known, and these trials have established that the use of guano as a source of P is valid and may have an additional benefit of low acidity.

“The big story is that it opens up a huge range of the high country to the possibility of better production. The soils in the semi arid zones of the Maniototo have very low levels of organic matter and so they have very low buffering capabilities. If you apply an acid product like superphosphate it can have quite big effects on soil acidity because it is not mitigated by organic matter, which tends to slow the rate of change,” he says.

“This research is substantial and has the potential to change the way farmers manage high country soils. The traditional view of soil is that it is an inert barrel of marbles and we pour fertilisers into it which raises the fertility and then plants grow. The real soil system does not operate that way. Soil microbes can have an enormous effect on plant mineral nutrition and we need to think of the soil as a living system and we need to think about how the fertilisers that we are applying affect the biological systems.”

“We almost have a schizophrenic attitude in New Zealand agriculture where we are very happy using that approach without batting an eyelid when we talk about nitrogen fixation, which is a biological process supplying the key nutrient, but when it comes to the supply of phosphorus or sulphur we think that the only way to do that has been through applying it as the mineral nutrient.”

“Some of the results that we have been getting suggest that stimulation of the soil biological subsystem can increase the supply of sulphates and phosphorus to the plant and that’s why you get similar higher dry matter yields per unit of P applied. In my opinion these are useful leads for people to develop and think about.”

When farmers put on certain alternative forms of fertiliser, such as guano, the results are not just wishful thinking. According to Peter, there is a genuinely beneficial biological effect.   The underlying mechanisms involve improving the microbial systems that are the main drivers of improved soil structure, aeration, drainage and moisture supply. These factors can have major effects in terms of crop growth and they assist the supply of nutrients and water to plants, particularly in dry years.

“One thing we can be absolutely certain about is that people who have used alternative farming systems are not stupid or being taken in by smooth talking salesmen selling bogus products. The fact that they have been testing these products and the products have been performing well is something that will get a lot of farmers that thinking about how their soils are functioning, as opposed to simply treating them as inert objects that they put fertilisers on,” says Peter.

“What David has shown on a farm scale is that his approach has actually been yielding some very significant economic benefits as well as production benefits. It is a real story, it is not snake oil, it’s genuine, and the only caveat I put on it is that from a science perspective these results apply only to the products that we have tested, we can’t speculate beyond that.”

“So one of the key things is that if you are buying a product from any fertiliser company, be it a mainstream or alternative, then that company should be able to supply you with accurate lab information as to the quality and content of their product.”

“Field trials are very expensive and beyond the finances of many small companies, so while they are getting reports of very good responses from farmers these are anecdotal and so do not satisfy the scientific community.”