Michigan State University Extension
Soils & Soil Management - Fertilizer - 06109715
07/10/97
Potato Fertilizer Recommendations Extension Bulletin E-2220, April 1990
Maurice L. Vitosh Extension Soil Specialist Department of Crop and Soil Sciences
Iron
All Michigan soils contain adequate amounts of available iron (Fe) for potatoes. High Fe availability in organic soils usually creates problems of iron-induced Mn deficiency. Acid, sandy soils (pH) usually contain large amounts of both Fe and Mn and need to be limed to prevent toxicities from these elements. Timing of Nitrogen Fertilizer and Split Applications
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
Spring applications of N in the semi-humid regions of the United States, including Michigan, have clearly been shown to be superior to fall applications. Climatic conditions from fall to spring significantly affect the amount of N lost. Estimates of N losses from fall applications vary from 10 to 20 percent on fine- to medium-textured soils (clay, clay loams and loams) and from 30 to more than 50 percent on coarse-textured soils (sandy loams, loamy sands and sands). Though applying N in the fall on fine-textured soils may have certain economic benefits, the environmental risks of this practice generally outweigh the economic benefits. Fall applications of N are not warranted in Michigan and should be discontinued except for small applications on fall-seeded wheat.
Yield benefits of split or sidedress N applications for corn have frequently been observed on coarse-textured soils. Although the benefits of sidedress N on fine-textured soils are rarely seen, there is no question that sidedress N applications on fine-textured soils can improve N recovery. For these reasons, crop producers should seriously look at sidedress N applications on all soil types to improve N efficiency.
Waiting until the corn is well established before applying large amounts of N has two major advantages: nitrate N losses between preplan" and sidedress are eliminated, and yield potential can be more accurately determined at sidedress time. Poor stand, poor weed control and/or dry weather at sidedress time are good reasons for adjusting the yield goal downward and reducing the total amount of N to be applied. The risk of being unable to sidedress N because of wet weather can be greatly reduced if corn is sidedressed when it is 3 to 4 inches tall instead of 1 foot tall. The benefits of sidedressing N when the corn is 1 foot tall or higher, rather than 3 to 4 inches tall, are minimal.
Applying nitrogen fertilizer through an irrigation system, often referred to as nitrogation, offers several advantages for irrigators:
1. N can be applied when the crop's demand is greatest.
2. The technique requires little additional energy for application.
3. The practice is well suited to sandy soils where irrigation is needed and leaching is a problem.
Approximately two-thirds of the total N requirements of corn may be supplied by this method. For example, some irrigators choose to apply one-third of their N at planting, one-third at sidedress time and one-third through the irrigation system. Depending too much on the irrigation system to "spoon feed" a crop in Michigan can have its drawbacks, however. Rain during the early growing season may prevent crop producers from using their irrigation systems. If no previous N was applied, this could result in an N shortage early in the season. To eliminate this problem, some crop producers have modified their center pivot systems so they can apply only a very small amount of water in one application. This allows them to apply N through irrigation regardless of rainfall patterns. It is important not to over-irrigate during the early part of the growing period in June and July because nitrate concentrations, which are most subject to leaching loss, are highest during this time.