Development of guidelines for application of swine manure to optimize nitrogen management for corn

Results from on-farm trials were analyzed to develop guidelines that will help farmers evaluate and improve their manure-N management, including utilizing swine manure as a cost-effective substitute for commercial fertilizer. The experimental methods included use of the late-spring test for soil nitrate and the end-of-season test for cornstalk nitrate to measure N availability at each research site

How Much Nitrogen Do Soybeans Leave for Corn?

Many studies in Iowa have shown that the optimal rates of N fertilization for com following soybean tend to be less than the optimal rates for com following com. This conclusion is supported by data presented in Figure 1, which summarizes the results of 35 pairs of N-response trials having 10 rates of fertilizer N applied. Quadratic-plateau yield response curves were fit to the data from each site and analyzed to determine economic optimum rates of fertilization. The mean economic optimum rates of fertilization were 103lb N/acre for com following soybean and 163lb N/acre for com following com

Operating procedures for use of the late-spring soil test by fertilizer dealers and consultants in Iowa

The late-spring soil test for nitrate has been identified as a promising tool for improving nitrogen (N) management in Iowa. The test works by measuring the amount of nitrate iiv the top one-foot layer of soil when corn plants are 6 to 12 inches tall. Sampling is done as late as possible in the spring, but still early enough to allow sidedress applications of more fertilizer N if needed

Consider the Carbon in Animal Manure!

Animal manures contain substantial amounts of carbon (C) that is bound into organic compounds. This carbon influences the availability of nitrogen (N) in animal manures applied to soils, and these effects make the N in manures behave very differently than the N in commercial fertilizers. The basic effects of organic C on N transformations in soils have been known for decades, and they are discussed in most introductory textbooks relating to soil fertility

Losses of Fall-Applied Nitrogen

Applying N fertilizer to some fields in the fall instead of the spring offers several benefits to com producers and fertilizer suppliers. Benefits for producers often include paying less for fertilizer, reducing the amount of field work that must be accomplished in the spring, and avoiding soil compaction associated with application of fertilizer on wet soils in the spring. Benefits for suppliers include more time for movement of fertilizer materials from the manufacturers to the producers and more acres per year covered by each fertilizer applicator

Corn roots are just reaching anhydrous bands

Fall or early spring applications of anhydrous ammonia commonly are assumed to prevent deficiencies of nitrogen (N) in young corn plants. Corn plants in many fields this year indicate that this assumption should be questioned. Corn plants often show exactly when their roots first reach bands created by injection of anhydrous ammonia. This time is most detectable when the bands are not parallel to rows of plants. Plants directly over the bands benefit first. These plants become darker green and grow more rapidly than plants not directly over the bands. For a few days, streaks of green plants reveal the exact locations of the bands. These streaks tend to disappear as root systems develop enough that all plants reach the fertilizer

Sampling fields for nitrate in late spring

Recent research has provided new information that can be used to address spatial variability in soil nitrate concentrations in Iowa cornfields in late spring. Following is a summary of observations made and some tips for sampling fields this spring. The tips focus on efficient sampling techniques for farmers having several fields that are managed similarly and separated by only a few miles. The information given herein expands on guidelines given in Iowa State University Extension publication Pm 1714, Nitrogen Fertilizer Recommendations for Corn in Iowa

Nitrogen Management to Address Low Grain Prices

Nitrogen fertilizer is an essential but costly input into corn production. The recent decrease in corn grain prices has prompted questions about how N management practices can be adjusted to address this problem. This paper summarizes relevant information that has been learned during the past decade of intensive research in Iowa. The information is presented as a series of observations with a brief explanation of each