Phosphorus and the No-Till Conundrum

by Patrick Kirchhofer, Peoria County Farm Bureau

You likely heard news reports of the large algae bloom in Lake Erie the first weekend in August. The affected site was Maumee Bay, which supplies water to the residents of Toledo, Ohio. Approximately 500,000 people were asked not to drink the municipal tap water due to this algae bloom.

Algae flourish in warm, shallow waters, and Lake Erie is the shallowest of the Great Lakes—one reason it’s more susceptible to algae blooms. From what I have read, this year's algae bloom wasn't necessarily larger than average, but a combination of northerly winds and currents helped trap the bloom near where the Maumee River brings the majority of nutrients into the lake… and right where Toledo's water intake happens to be.

Much of the ensuing discussion has focused on phosphorus runoff from farm fields as one of the contributing factors to the algae bloom. Algae thrive on phosphorus, and unfortunately, it’s likely true that phosphorus is a contributing factor. With high amounts of rainfall this spring, water runoff carried more phosphorus into Maumee Bay, where the current slows down, nutrients are deposited and algae blooms.

Along with potassium and nitrogen, phosphorus is one of the three primary nutrients needed by plants. In most applications, it’s applied to farm fields in the form of diammonium phosphate, commonly referred to as DAP. The formulation is 18-46-0, or 18 percent nitrogen, 46 percent phosphorus and zero percent potassium.

Phosphorus fertilizer is more than twice the price it was only a decade ago. The one thing farmers do not want is for expensive fertilizer—or expensive soil that’s rich in fertilizer—to leave their fields. Once it does, it's a significant financial loss they will never get back.

Ironically, farmers in Ohio have adopted conservation practices, such as no-till, more rapidly than most states. In fact, No-Till Farmer magazine indicates that Ohio farmers apply no-till conservation practices to nearly 40 percent of the state's farmland. At the National No-Tillage Conference I attended this past winter in Springfield, Illinois, many attendees and speakers were from Ohio and adamant about using conservation practices on their farms.

Farmers use no-till practices to prevent soil from eroding and leaving their farm fields. Healthy, rich topsoil is a farmer’s very livelihood and better, deeper topsoil generally leads to higher crop yields. No-till is an excellent conservation practice and like the name implies... no tillage is done on the soil, leaving residue on top and the soil protected from erosion.

Not wanting to disturb the soil in a true no-till program, farmers have the fertilizer, which can be a solid granular or liquid form, spread over the top of the field. The wishful thinking is that slow, gentle rains will fall, bringing the fertilizer into the soil profile and available to plants. Heavy rains after an application of fertilizer on the surface of the soil will carry some fertilizer with it.

The dilemma... Does a farmer use tillage, which mixes the fertilizer into the soil profile, but exposes it to runoff water erosion? Or adapt no-till and leave the soil surface undisturbed, but risk losing a higher percentage of fertilizer applied directly on the soil surface? If farmers knew what the weather was going to do—as well as the insect pressure, disease outbreaks, wind storms, temperatures, etc.—it would make the job much easier. The fact is, that's not the case, and it never will be.

Farmers are adapting precision fertilizer placement, seed placement, cover crops and the latest technological advancements available to them. It takes time to learn the processes.

One final note. This illustration is similar, in that the owner is trying to do the right thing, but nature didn't let it happen. Do you know anyone who had a fish kill this past winter in their pond? The freezing temperatures and high snowfall took a toll, as many farm ponds experienced a total loss of their fish populations. Ironically, the exact thing that makes for great fish habitat likely contributed to their demise. Decaying vegetation, such as cattails around a pond’s edge, takes up oxygen during the decomposition process. With a thick layer of ice and snow on a shallow pond surface, oxygen was not getting to the fish below. The decaying vegetation accelerated the oxygen used, hence suffocating the fish.

Even the best and most deliberate plans can veer off course. iBi

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