Winter wheat needs phosphorus
By Jeanine Moyer
Since 1988, Peter Johnson has been has talking about the advantages of phosphorus (P) application in wheat. As the Ontario Ministry of Agriculture, Food and Rural Affairs’ cereal specialist, Johnson has studied the impact of P on wheat yields, crop uniformity and resiliency for almost 25 years and he is still astounded that approximately 10 percent of Ontario growers still don’t apply fertilizer to their wheat at all. Surprising as well, is the popularity of broadcasting starter fertilizer on wheat fields.
“At least one-third of Ontario growers are planting wheat without seed-placed fertilizer application with a drill,” says Johnson. Speed and convenience of seeding without a fertilizer box on drills has decreased the popularity of fertilizer boxes, but that doesn’t mean growers can’t find alternatives to applying seed-placed dry starter fertilizer, such as twin tank air carts, that allow in-furrow fertilizer application while seeding. Since most seed drills don’t have fertilizer boxes on them at all, it can be more difficult to apply starter fertilizer when seeding, but Johnson says growers still need to be conscious of their fertilizer application decisions and how they choose to apply the nutrients.
It is no secret that seed-placed dry starter fertilizer brings significant yield advantages – 7.5 bu/ac on average – and Johnson believes the majority of growers are aware of these benefits. Broadcast starter fertilizer is beneficial since the fields receive the valuable fertilizer, but Johnson says in-furrow application is still best. He says a standard MAP starter fertilizer (11-52-0) application rate of 100 lbs/ac is likely a grower’s most economical source of P that will deliver results.
Each year, Johnson plants side by side strips of winter wheat with and without seed-placed starter fertilizer. Strips without starter fertilizer sometimes have a 30 percent winter survival rate while those seeded with the valuable starter fertilizer have an 85 percent survival rate. Further supporting Johnson’s recommendation, he says similar results have been seen in corn planted with in-row starter fertilizer. Field trials of corn planted with in-row starter fertilizer have shown higher survival rates in circumstances where the seed has sat under water or has been exposed to excess moisture in the spring.
Studies have shown that, unlike corn, wheat doesn’t respond to potassium (K) in the same way. K is known to increase corn yields when applied in starter fertilizer, but, Johnson says, the same response is not seen in wheat. However, applying P in a seed-placed starter fertilizer on wheat, especially winter wheat, not only boosts yields, but also can establish stronger root systems, increase plant stress tolerance and create a better, more uniform stand overall.
Chad Anderson, Lambton county farmer and crop consultant, won’t grow winter wheat without seed-placed starter fertilizer, saying it can be the difference between a successful wheat crop and replanting that same land in soybeans the following spring due to winter kill. Anderson applies dry starter fertilizer with his seed drill and says it provides a better anchor and improves winter crop survival. Farming on heavy clay, Anderson says his wheat crops are prone to winter kill from late winter heaving and thawing of frost. “Wheat is an important part of our rotation and it takes starter fertilizer to ensure we have a crop to harvest,” says Anderson.
Recommending seed-placed dry starter fertilizer application in wheat isn’t just about boosting yields and creating stronger crop stands, says Johnson: growers need to be conscious of the economic and environmental implications of in-furrow and broadcast fertilizer application methods. While it is more convenient to apply liquid or broadcast starter fertilizer, Anderson points out that two to four times the volume of broadcast fertilizer would have to be applied to get the same yield responses and crop results from seed-placed dry starter fertilizer.
“Broadcast P left on the soil surface increases the risk of movement into watercourses,” says Johnson. “Not only can this be an environmental issue, but a rainfall can wash it away, causing growers to lose the money they invested in fertilizer.” Potassium is lost in two ways: particulate P, which is nutrient loss from surface runoff, often associated with soil erosion, and soluble P, which is nutrient loss from leaching.
Loss of P from leaching into waterways is less common in Ontario, but particulate P movement can be a real issue and the resulting transport of P in soil runoff contributes to freshwater eutrophication. By definition, eutrophication is the process by which excess nutrients, such as P, are dumped into bodies of fresh water and stimulate excessive plant growth. In Ontario, increased P levels cause algae blooms. When algae blooms die, either from nutrient shortage or from cold weather in the fall of the year, they remove oxygen from the water to decompose. This leads to reduced oxygen levels for the remaining plants and fish in our Great Lakes and associated waterways. These problems are often aggravated by the proximity of streams and lakes to agricultural land.
Because P is such an important nutrient to wheat production, reducing P loss should be an important factor in field management decisions. “In-field dry starter fertilizer application is a much more environmentally friendly and efficient way to handle phosphorus since there’s less chance of surface water runoff,” says Anderson.
Reducing dissolved P loss from leaching and runoff involves implementing practices that maximize crop P uptake, such as subsurface placement of fertilizer. “It’s simple: seed-placed fertilizer reduces the risk of particulate P loss since the fertilizer isn’t on the soil surface,” says Johnson. “And it doesn’t increase the risk of soluble P either.”
Tillage practices reduce nutrient loss
Conservation tillage practices are also known to reduce the movement of P into waterways. Johnson notes soil erosion in general and the associated particulate P loss was first identified in the 1980s as an environmental issue, which led to an increase in conservation tillage practices. “Conservation tillage has had a remarkable impact on reducing particulate matter in the Great Lakes,” says Johnson. To reduce the risk of soil erosion and runoff, conservation tillage requires 30 percent of residue be left on soil surfaces 100 percent of the time.
Particulate loss from erosion accounts for a significant percentage of overall P loss from cultivated land. And a recent shift away from conservation tillage practices is resulting in a return to more intensive tillage and increased soil erosion and nutrient losses into the Great Lakes. “Growers have access to the widest array of tillage tools ever seen to loosen soils and create ideal seedbeds,” says Johnson. “There’s no excuse to go back to mouldboard ploughing and intensive cultivation.” Overall, soil loss, particulate P and total P losses can be reduced using conservation tillage or no-till methods when compared to conventional tillage under Ontario conditions.
Seed-placed dry starter fertilizer could almost be a grower’s secret to success, especially if P application is emphasized. The economic benefits of increased yields, minimizing P loss and stronger crop stands are sound arguments for investing in the right fertilizer equipment for in-field application, says Johnson, not to mention the associated environmental benefits. Seed-placed dry starter fertilizer and the advantages of additional P nutrients on wheat shouldn’t be a surprise to wheat growers, but sometimes a reminder can help make good field management decisions even better.
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