While producers are currently harvesting their 2021 crop, they also have a close eye on the rise in fertilizer prices. Due to increasing natural gas prices, nitrogen fertilizer prices are relatively high compared to recent years and are expected to remain high and possibly increase through next spring.
Dave Franzen, NDSU Extension soil science specialist says, “China has supplied about a third of the world’s phosphate, and it has essentially banned exports through 2022,” Franzen continues. “That puts the burden of supply on other countries, including the United States.”
According to Franzen, the U.S. is not in a great position for mine and production expansion due to serious environmental concerns. This means that phosphate prices, which are already high, will continue to increase at least through 2022.
Major crops that require higher rates of N fertilizer are corn, small grains, sunflower and canola. Most dry bean acres and flax require or receive N, but rates are modest compared to the four previously mentioned classes of crops.
To economically survive the higher N costs, Franzen recommends farmers consider implementing one or more of the following strategies:
- Soil sample by zone for two-foot depth residual soil nitrate. Soil nitrate N values are higher this year due to the drought and lower crop yields in 2021. Sampling in zone for accuracy allows farmers to take advantage of N already present in the soil and apply variable rate N if practical for the 2022 crop. This reduces rates without negative yield or profitability consequences.
- Use nitrogen calculators to determine N rates for corn, spring wheat/durum and sunflower. As N costs increase and grain prices stay level, profitable N rates decrease. The relationship between N rate and yield in crops is not a straight line. It is a curve with “shoulders” near the peak. NDSU offers several nitrogen calculator apps here.
- Fall N application is an option for most soils in North Dakota. Sandy soils and those with flooding potential near streams and rivers are not fall application soils. See the NDSU Crop and Pest Report article for details on fall application guidelines.
Major crops that require P are corn, sugarbeet, potato, small grains, canola, soybean, and dry bean. Sunflower and flax do not need supplemental P at any soil test value, no matter how low. Of P-requiring crops in a high phosphate price year, all of the P can be supplied by a seed-placed or near-seed-placed starter in sugarbeet, canola, small grains, and western North Dakota corn.
“Potato will always need high rates of phosphate,” says Franzen. “Corn always needs starter phosphate, but very low to low soil testing soils should receive supplemental broadcast, deep-banded or air-seeder-banded phosphate in addition. Soybean should not receive seed-placed phosphate due to yield reduction, and dry bean can receive small amounts of seed-placed phosphate or broadcast.”
Franzen recommends the following guidelines for reducing P costs and maximizing P use efficiency for the 2022 crop:
- Soil sample by zone and follow recommendations for each crop.
- NDSU spring wheat/durum research indicates that as P costs rise, the critical value of soil test P that results in profitable P application decreases. For soybean, NDSU Extension recommends a critical value of 6 ppm for a ‘normal’ P cost/soybean price relationship, but in today’s economic conditions, 5 ppm would be a more reasonable critical value.
- Despite many farmers remembering soil loss this past spring and either leaving volunteer cereals grow or planting a cover crop, or exploring strip-till/no-till, there are others who are leaving their soils black. These fields should not have any fall phosphate. If P is applied to these fields, even if worked into the soil an inch or two, the chances of it surviving into June at the rates applied are slim due to probable soil loss primarily from wind.
- Consider applying any broadcast rates of P for corn into soybean or wheat stubble with a drill or air-seeder. This will place that phosphate below a depth susceptible to water movement and wind movement during the fall, winter, and spring.
Potassium fertilizer prices are currently high and may move higher due to the pull from N and P.
“The most important strategy to use for potassium in North Dakota is to follow the NDSU recommendations for potassium for each crop, soil test by zone and use the North Dakota potassium calculator for corn to avoid any excessive and futile potassium application,” says Franzen.
Of course, see your local extension website for local recommendations.
For sandy soils with low real cation exchange capacity, it is unlikely these will ever test greater than 100 ppm no matter how much K is applied. For these soils in particular, it is important to use only what is required to grow the next crop knowing that the soil test will not “build” with additional K.