Michigan State University Extension
Soils & Soil Management - Fertilizer - 06039710
07/10/97
Tri-state Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa Extension Bulletin E-2567 (New), July 1995
M.L. Vitosh, Michigan State University; J.W. Johnson, The Ohio State University; D.B. Mengel, Purdue University; Co-editors
Tillage system and fertilizer source affect proper placement of fertilizer nitrogen. The most satisfactory way to apply anhydrous ammonia is by injection in a band. Knife spacing provides an application option for anhydrous ammonia. Injection into the soil by knives or spoke injector, spraying on the surface and surface banding are techniques used to apply fertilizer N solutions. Dry sources can be broadcast or placed in a band. The need to incorporate N sources placed on the surface depends on the tillage system and whether the N source contains urea.
The enzyme urease hydrolyzes urea to ammonia and carbon dioxide (NH2CONH2 + H2O - - - > 2NH3 + CO2). The ammonia vaporizes and is lost if this occurs at the soil surface. Urease is an enzyme common to soil organic matter and plant residue. Factors that enhance ammonia volatilization losses are: soil factors--high soil pH and low buffering capacity; environmental factors--warm temperature, moist soil surface that is drying and rapid air movement; management factors--surface application of high rates of urea-containing fertilizer, broadcast application, liquid fertilizer and crop residue on soil surface. Injecting or incorporating urea-containing fertilizer or receiving « inch or more of rainfall before hydrolysis occurs reduces or eliminates volatilization losses. Data shown in (Vis. 3, (Vis. 3, Vis. 4) illustrate the effect of application method in no-tillage for various N sources. Dribble or band application of urea-ammonium nitrate (WAN) solution concentrates the N solution, which reduces contact with urease enzyme. This application technique slows the conversion of urea to ammonia and carbon dioxide and lengthens the time N solutions can remain on the surface with minimum losses. Urease inhibitors show some promise in reducing volatilization losses. Though there is an advantage to soil incorporation on some soils, incorporating fertilizers containing urea conflicts with the objectives of maintaining crop residues on the surface and reducing tillage operations. The development of the spoke-wheel and high-pressure liquid applicators provides a method of injecting urea-ammonium nitrate solutions into the soil with minimum disturbance of crop residue and controlling the placement relative to the corn row.
Knife spacing is a consideration for sidedressing ammonia and in controlled traffic such as ridge-tillage systems. Data in (Vis. 5) show that an ammonia band between every other pair of rows is satisfactory compared to injecting in the middle of every inter-row. Ammonia applied preplant diagonally will result in corn roots reaching the N band at different times. This may result in a rolling appearance to the cornfield. The use of 20 to 40 pounds of N per acre applied as starter fertilizer with the planter or as a preplant broadcast application will minimize the rolling appearance of corn. This practice will also ensure adequate N nutrition early in the season before the corn roots reach the N in the ammonia band.
| Visual title - Visual size | Visual title - Visual size |
|---|---|
| The effect on grain yeld of no-till corn by N sources and methods - 14K | Corn grain yelds as affected by N management strategies, Ohio - 32K |
| Effect of knife spacing of ammonia applied at varying rates of N - 24K |
