20 Agronomy New phosphorus products GREY-BRUCE FARMERS’ WEEK PANEL DISCUSS OPTIONS Lois Harris 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 monocalcium 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
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