A curmudgeon takes on finangling
Alternative approaches to soil fertility have been challenged.
In August Dr Ants Roberts, the chief scientific officer for Ravensdown Fertiliser Co-operative, gave three lectures, the first at Massey University, the second at Ruakura Research Centre and the final one at Lincoln University, which is the custom for the recipient of the Ray Brougham Trophy. It’s awarded each year by the New Zealand Grasslands Trust to somebody who has made a significant contribution to pastoral agriculture in New Zealand.
Roberts talk was entitled Soil Fertility Finangling: A Curmudgeons View and he explained finangling as the use of trickery or craftiness to achieve ones aim, and curmudgeon as a crusty, illtempered,
He began with a quote from the Regeneration International website where proponents of ‘regenerative agriculture’ are critical of conventional agriculture claiming it to be degenerative agriculture. The quote stated, “The key to regenerative agriculture is that it not only ‘does no harm’ to the land but actually improves it, using technologies that regenerate and revitalise the soil and the environment. Regenerative agriculture leads to healthy soil, capable of producing high quality, nutrient dense food while simultaneously improving, rather than degrading land, and ultimately leading to productive farms and healthy communities and economies.’”
In the past couple of decades there have been a number of articles in the popular press and farming media on sustainable and regenerative agricultural practices by selfproclaimed experts who are critical of conventional fertiliser practices in relation to soil science which have worked well for many decades. In his talk Roberts discussed a number of these alternative approaches to soil fertility, yet which have failed to show merit when put through scientific rigour. His criticisms included Fine Particle Application (FPA) or liquification of mainstream fertilisers such as urea and DAP, Base Saturation Cation Ratio (BCSR) theory, sometimes referred to as Albrecht theory, the use of humates to build soil organic matter levels, and dicalcium phosphate compared with using superphosphate and lime.
With FPA or applying fertilisers in liquid form he referred to trial work which has shown that whether a product is sprayed on or applied in dry granular form, there’s no difference in overall production.It’s the quantity of nutrient applied which determines the response. Farmers and growers however who spray on soluble fertilisers and are also applying a plant growth hormone such as gibberellic acid may see extra production benefits, and obviously if one is including chemical sprays such as herbicides, pesticides or fungicides, so long as these are compatible with the fertiliser material, then there may be merit in fertilising and spraying these together in a single pass.
FPA has historically been promoted as needing less overall fertiliser material to achieve the same amount of production and Roberts’ talk showed this not to be the case.
The BCSR theory was first promoted by American soil scientists Drs Beare and Toth and later refined by Dr William Albrecht from Missouri State University in the 1940s and 1950s. The theory is that there is an ideal ratio of the positive elements (cations) calcium, magnesium, potassium and sodium which are attached to the negatively charged soil particles where calcium should make up 60-75 percent, magnesium 10-20 percent, potassium twoto five percent and sodium from 0.5 to five percent of the exchange sites of the soil’s Cation Exchange Capacity (CEC).
Later work by one of Albrecht’s own students, McLean, and others showed there is no ideal ratio, but that these elements should be applied to the soil based on whether they were deficient or not which is commonly referred to as the Sufficiency Level of Available Nutrients (SLAN) theory. We use this in New Zealand where it’s better known as MAF Units for calcium, magnesium, potassium and sodium. Their research showed that sufficiency levels are a better predictor of crop responses than using base saturation ratios.
After Roberts’ talk in Hamilton I mentioned to him some recent
research done by Dr Tim Reinbott of Missouri State University which he presented at the American Society of Agronomy and Soil Science Society of America annual conference last year. This research showed that using the Albrecht system gave improved yields in corn and soya bean crops and that there were some soil health improvements using the Albrecht approach compared with a conventional fertiliser input approach.
For me personally when advising farmers and growers I consider both base saturation ratios and sufficiency levels as I think there is some overlap in terms of production and quality and in the case of livestock, particularly dairy cows, that having correct calcium:potassium and magnesium:potassium ratios can improve animal health. For horticultural clients, having sufficient calcium and magnesium is vital in terms of shelf life and keeping quality in some fruit and vegetable crops.
When it came to the topic of humates which are products extracted from lignite and leonardite coal, Roberts showed that most of our soils already have large quantities of organic matter and soil carbon. Adding a small amount of humate products (humic acid, fulvic acid and humin) would make very little difference. He stressed the importance of trying to maintain good organic matter levels, and although this can be done with permanent pasture when it comes to continuous cropping, pulverising the soil to a pulp and thereby destroying soil structure and depleting the soil of valuable organic matter (carbon) lessens the soil quality and productive capacity.
Organic matter in the soil provides so many benefits including improved moisture and nutrient retention, reducing soil compaction and surface crusting, improving water infiltration, providing food and a valuable home for important soil micro-organisms and earthworms, preventing soil erosion and nutrient run-off and improving the macro and micro porosity of the soil.
As for reverted and dicalcium phosphate fertilisers which are blends of superphosphate and lime materials which are wetted and left to react and go hard, then crushed and re-screened, Roberts showed there was no greater value in using these compared with applying lime and superphosphate separately. Dicalcium phosphate products are less available to plants on application compared with monocalcium phosphate (superphosphate) fertilisers, and that the only exceptions where dicalcium phosphate products could be more beneficial than superphosphate are the pakihi sand soils of the West Coast and the podsol soils of Northland where the Anion Storage Capacity (ASC), sometimes referred to as phosphate retention percentage is very low. Consequently phosphorus is prone to leaching out, so having less soluble forms of phosphate might be advantageous.
Dr Ants Roberts’ talk can be viewed on-line at http://www.youtube.com/watch?v=4eCnFZ9Tros