Fertilizer tends to be one of the highest costs for crop production. According to North Dakota Farm and Ranch Business Management’s “2022 State Averages”, the average producer spent $191,329 on fertilizer.
Economical fertilizer management starts with a soil test. That way you have a starting point and know the amount of nutrients in the soil. You should soil test every field every year. If you did not soil test last fall, you still have time this spring. Whole field soil testing is a good starting point, but zone sampling will most effectively manage fertilizer inputs. For soil tests, we are mainly concerned about the macro-nutrients nitrogen (nitrate), phosphorus, and potassium. Figure 1 has a cheat sheet on soil sampling depth, nutrients, and crops.
Nitrate nitrogen should be tested to a depth of 24 inches for all crops except for malting barley, sunflowers, and sugarbeets. Those three crops should have a nitrate soil test to a depth of 48 inches. If present, excess deeper nitrates can reduce barley malting quality and sugar content of sugarbeets. Sunflowers are deep rooted and efficient nutrient scavengers. A deeper soil nitrate test can reduce nitrogen fertilizer inputs.
Phosphorus, potassium, and other soil tests should be conducted at the 0-6 inch depth. The Olsen phosphorus test is recommended in North Dakota regardless of pH. The Olsen phosphorus test has been found to be very reliable across the pH spectrum of agricultural soils. Potassium recommendations were recently updated due to the clay minerology. Soils rich in the clay mineral smectite, where temporarily potassium tie-up can occur. As such, soils in the gray areas have higher potassium requirements.
Keep in mind, your fertility plan should focus on macro-nutrients. Most studies in North Dakota and adjacent states rarely observe a crop yield or quality improvement from the use of a micro-nutrients. The lack of response is likely due to our fertile prairie soils, relatively short growing season, and semi-arid to arid climate. However, depending on the crop some micro-nutrients should be considered.
Sulfate is a nutrient that canola can greatly benefit from. The problem is, the sulfate soil test is not a reliable test. For us south and west of the Missouri River, 20 pounds per (regardless of the soil test) is recommended. Sulfate fertilizers like ammonium sulfate and potassium thiosulfate tend to produce better yields than elemental sulfur. Small grains and corn are other crops that can benefit from 10 pounds of sulfate per acre.
Chloride is a nutrient to consider for small grains. Barley plumpness and wheat yield can improve from chloride. Chloride should be tested to a depth of 24 inches and 40 pounds per acre (fertilizer plus soil test chloride) is recommended. One other micronutrient to consider is zinc for flax, corn, and edible beans. The zinc recommendation is 10 pounds per acre and recommended if the zinc soil test is low or very low.
Agronomic fertilizer management is paramount to grow crops. Soil test every year and focus on macro-nutrients to most effectively manage fertilizer inputs. Don’t forget the 40 and 50 pounds per acre nitrogen credit from growing a legume and five or more years of no-till respectively.
For more information:
North Dakota Farm Business Management reports
Soil sampling as a basis of fertilizer application
