Michigan State University Extension
Soils & Soil Management - Fertilizer - 06109713
07/10/97
Potato Fertilizer Recommendations Extension Bulletin E-2220, April 1990
Maurice L. Vitosh Extension Soil Specialist Department of Crop and Soil Sciences
Copper Recommendations
Copper (Cu) deficiency occurs in Michigan only on acid, peaty soils. A single application of 20 pounds of Cu per acre to these organic soils when they are brought into production will usually correct the problem. (See Table 7 for Cu recommendations to be used in starter fertilizers.) These recommendations are based on 1.0 N HCL extractable Cu levels and crop responsiveness to Cu fertilizer. Foliar applications of Cu have also been used successfully. In many instances, the Cu level in soil is Ample because of repeated applications of Cu fungicide dust or spray. ==================================================== Table 7. Copper fertilizer recommendations for potatoes grown on organic soils.
Soil test Copper recommendation -------------------------------- ppm lb cu/acre -------------------------------- 2 3 5 2 10 2 15 1 20 0 ==================================================== Copper Fertilizer Sources
Copper sulfate and copper oxide are the most commonly used Cu fertilizers. Foliar applications of Cu sulfate at 0.5 to 1 pound of Cu per acre in 30 gallons of water have been used successfully. Use the lower rate on small plants and the higher rate on larger plants. Soil Nitrate Testing
Nutrient Management to Protect Water Quality Extension Bulletin WQ-25, January 1996
Maurice L. Vitosh and Lee W. Jacobs Extension Soil Specialists Department of Crop and Soil Sciences Michigan State University
Nitrate is the form of nitrogen that is most available to plants and supplies to crops most of their N needs. Soil type, rainfall and temperature greatly affect the seasonal availability of N to plants. Under wet conditions, N losses can occur by leaching from the rooting zone and/or by denitrification from the soil. Denitrification is a microbial process that occurs rapidly when soils become water saturated and temperatures are warm (>50 degrees F). Nitrate leaching can occur at any soil temperature. Denitrification losses are greatest on fine-textured soils with poor internal drainage; leaching losses are greatest on coarse- textured sandy soils with good internal drainage. The seasonal availability of nitrate N should be assessed each year and matched to crop needs.
Soil nitrate testing is an excellent and inexpensive way of evaluating the available N status of your soil. Michigan State University research and demonstration studies have shown that many crop producers can reduce their N fertilizer application rate on corn without risk of reducing yields if they use the soil nitrate test. Nitrate testing can also help to prevent overuse of N fertilizers.
The soil nitrate test measures only nitrate N-it does not measure ammonium N or organic N. If samples are taken in June, much of the ammonium and some of the organic N will have been converted to nitrate and will show up in the test.
Although soil samples may be taken anytime for this test, the best time to take samples is in June after the soil has warmed up, when it usually contains the greatest amount of nitrate N. The June pre-sidedress nitrate test (PSNT) measures both residual nitrate N from the previous year and recently mineralized N from organic matter. Soil samples taken in early spring (April or May) will contain only residual nitrate. Although testing in early spring may still be helpful in assessing how much additional N is needed, samples taken just prior to sidedress time provide the greatest advantage in determining the appropriate rate of sidedress N.
Manured fields and legume fields will likely contain the most nitrate. Early sampling of these fields will not result in the maximum N credit because ammonium N and easily decomposed organic N will not yet have beer converted to nitrate and will not be measured by the test. Therefore, only the PANT is recommended for these fields.
Other fields that show high nitrate N levels are fields with medium- and fine-textured soils (loam, clay loam and clay) that have been heavily fertilized in previous years. Sandy soils, even though heavily fertilized the previous year, may not show much N carryover because nitrate N can be easily lost by leaching.
Soil sample boxes and information on taking soil samples for the PANT are available from your county Extension office or the MSU Soil and Plant Nutrient Laboratory, East Lansing, MI 48824-1325.