New phosphorus products

PHOSPHORUS (P) BOOSTING PRODUCTS can benefit crop health and the environment, provided growers understand their soil fertility well and ensure they are incorporated in the right place at the right time.

“My playbook when you want to improve fertilizer response and economics are tight is to first have a soil test to know if you’re going to get a response, the second thing is to give organic amendments a credit if you’re applying them, and third, band the fertilizer if you’re not banding it today,” says Jonathan Zettler, an agronomist with Fieldwalker Agronomy Ltd.

Zettler was speaking as part of a panel at the Grey-Bruce Farmers Week Crops Day in January. Zettler and three fertilizer company representatives discussed the merits of different phosphorus improvement products. The panel was facilitated by Colin Elgie, soil fertility specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs.

THE PROBLEM

Phosphorus deficiency in crops shows up with purpling on the lower leaves of plants. The condition can lead to stunted root growth, plant development, and, ultimately, reduced yields. The target in most of Ontario for optimal P levels is 20 parts per million sodium bicarbonate in soil tests. This measure shows the amount of readily available phosphorus.

Factors that reduce phosphorus uptake in plants include its low mobility in the soil, the P binding with other minerals like aluminum in the soil, and cold temperatures (below 10 °C). Factors that improve phosphorus uptake include using banding or strip-till methods for more precise placement of the fertilizer near plant roots and the presence of other nutrients like nitrogen.

THE PRODUCTS

Top-Phos is a granular fertilizer additive offered by Timac Agro Canada that only activates when the plant needs it.

“If you put Top-Phos down in the fall, like in Chatham where they do strip-tilling, the phosphorus that’s banded in the fall will remain until there is a plant growing and taking it up,” says product manager Christopher Pertschy.

Among its benefits are that the mono- calcium phosphate is protected from fixing with other minerals, provides better root growth, is water soluble, and its gradual release to the plant means less phosphorus runoff and, therefore, a lower chance of polluting local waterways.

In trials comparing the product to single super phosphates (SSP), 87 per cent more of the Top-Phos was still available to plants 28 days after application. It works equally well in low pH (5.6) and high pH (8.5) soils. It is an additive compatible with any fertilizer blends that can go into starters and can be either banded or broadcast.

Crystal Green fertilizer is a magnesium ammonium phosphate (5-28-0 with 10 per cent magnesium) with minimal water solubility and is activated by organic acids naturally exuded by plant roots.

“You need to get it in the root zone so it can be applied with strip-till, banding, broadcast incorporated, or in the drill with the seed,” says Doug Sibbitt, regional sales manager with OSTARA. “It cuts the phosphorus load to the soil, and it can be applied in the spring or the fall.”

He cited research by North Dakota State University comparing mesh bags of Crystal Green, MAP (monoammonium phosphate) and DAP (diammonium phosphate) that were dug into the soil in the fall. It showed that Crystal Green remained available through freeze-up and spring thaw while more traditional MAP and DAP fertilizers had been significantly reduced through leaching.

Another advantage over more traditional fertilizers is that the product doesn’t disrupt the microbiome around the crop.

“Crystal Green is sparingly water soluble, so it’s not going to affect the fungi and bacteria in the soil,” he says.

He also added that Crystal Green is recognized by the 4R Nutrient Stewardship program and noted that if the product isn’t taken up by this year’s crop, it’s available for next year’s crop.

Synthos Nutrient Enhancer is a biological oil-based solution that is added to MAP or total NPK (nitrogen-phosphorus-potassium) blends or any other fertilizer to increase P uptake. It doesn’t need refrigeration, and its use rate is 2.8 litres per metric tonne. It lasts two years in the container, survives for 18 months in the soil and can be added to either organic or inorganic fertilizers.

“The best way to use Synthos is to get your retailer to apply it to the fertilizer when you’re picking it up,” says Bryce Geisel, senior agronomist, KOCH Agronomic Services. “It’s oil-based, so it helps reduce dust.”

A Canadian study using five trials conducted by the University of Alberta showed an increase in P uptake in MAP treated with Synthos versus untreated MAP. The researchers used plant tissue tests to determine P uptake.

CONSIDERATIONS

During the question-and-answer part of the panel presentation, a number of factors emerged that growers should recognize when deciding whether to use new P improvement products.

While most of the products presented were aimed at improving in-year crop performance, there could be a benefit of building P over time in the soil.

“Regardless of which product you may use, as you grow bigger crops and you’re returning crops to the field through residue, as long as you’re applying more than is taken out through crop removal, you’re probably building your soil test P whether it shows up through the material being applied or through residues breaking down,” says Zettler.

Determining the costs of using the products came down to understanding individual circumstances, including how the soil is managed, what kind of fertilizer is being used and the rate of application, among other factors.

The yield effects of the new products on the crop can be compromised by problems later in the year.

“Often people will avoid talking about yields with phosphorus because the benefits are seen in the early season, and there’s a lot that can happen through the rest of the year — disease, too much moisture, too little moisture, lodging issues and frost,” says Geisel.

He added there are still many advantages to using the products that improve phosphorous uptake.

“Have a conversation with your agronomist and your retailer, do the soil tests, look at new options and test them out where you think they’ll fit.” •