Holding the line on fertilizer costs
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
The expected increase in corn acreage has driven the price of nitrogen (N) fertilizers to all-time highs. The cost of nitrogen from urea and urea-ammonium nitrate (28 % N solution) is near 50 cents per pound of N (urea at $460/ton, and UAN at $280/ton). And the price is even higher for some of the other nitrogen materials, such as calcium nitrate. Hence, it is important to manage N inputs as effectively as possible to minimize loss and maximize plant uptake. During the first 4 to 5 weeks after seeding or transplanting, the requirement for N of vegetable crops is relatively low. Where possible, apply N, P and some K in a band near the transplant or seeded row. This will increase early utilization of these nutrients compared to broadcast incorporation. By banding fertilizer the early N rate may be reduced by 25 percent, e.g. 30 compared to 40 lbs N/acre. Then, make subsequent top or sidedress N applications as needed. Providing the N at the time when the crop has a greater requirement will increase plant uptake and minimize the potential for loss by leaching or denitrification if a heavy rainfall event should occur. A presidedress soil nitrogen test (PSNT) can be very helpful in applying the correct amount of N. The PSNT run on soil samples collected prior to sidedressing can indicate how much N is available in the soil, and the amount to apply can be adjusted accordingly. This can be especially important where cover crops, compost or animal manures have been incorporated.
Phosphate and potash prices are near record highs as well. Vegetable crops do require higher levels of available phosphorus than field crops, but the phosphorus level has been built up over time in many soils used for vegetable production. In mineral soils with a P soil test between 40 and 70 ppm, applying 30 to 40 lbs P2O5/ acre in a band is adequate and actually will equal crop removal for many vegetable crops.
The available potassium levels in the loam and sandy soils used for vegetable production tend to be less than adequate. Recommended amounts of K2O usually include an amount for building up the soil level plus an amount equal to removal in the harvested portion of the crop (maintenance amount). Where the budget for inputs is tight, applying only the maintenance amount of K2O will be adequate for production of top yields, unless the K soil test is less than 80 ppm in sandy soils or less than 100 ppm in loam soils. In muck soils, using only maintenance amounts is adequate as long as the soil test K value is above 220 ppm.
Soil testing is the primary key to long term cost effective nutrient management. In vegetable crop production it is important to soil test at least every two years, if not annually. It is very important to monitor the soil pH on a regular basis. Many times where crop growth problems occur, it is related to the soil being too acid. Fairly intense sampling can be beneficial in vegetable production. Collect soil samples according to variations in fields. This may mean delineating sampling zones that may only be 5 to 6 acres or less in size in some fields. During the growing season, observe the crop and note those areas where crop growth is not as good as the rest of the field. Soil sample these areas separate from the whole field. More information on the nutrient requirements of vegetable crops can be found in MSU Extension Bulletin E-2934, Nutrient recommendations for vegetable crops in Michigan.