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Fluid Journal : Fluid Journal 1993-1995
Dr. Donald J Eckert Nitrogen Management K Nitrogen Management K Nitrogen Management K Nitrogen Management K Nitrogen Management Key In ey In ey In ey In ey In Conser Conser Conser Conser Conservation Til liage Crop P vation Til liage Crop P vation Tilliage Crop P vation Tilliage Crop P vation Tilliage Crop Production roduction roduction roduction roduction Ohio studies show that method and timing of N placement have an effect on N-use efficiency. Winter 1995 Summary: Where growers practice conser- vation tillage, minimizing contact between urea-containing materials and urease-rich crop residues is critical in mitigating nitrogen losses and maintaining crop yields. Studies of different UAN placement and timing methods have shown that the least desirable method of placement for optimizing nitrogen-use efficiency is broadcasting. More desirable placement methods are injection, banding, and split applications. Some starter nitrogen is also recommended in any system where nitrogen is to be applied in a band away from the seedling. Generally, when proper nitrogen management practices are used, conserva- tion tillage and conventional tillage systems require about the same quantity of nitrogen to produce a crop. Efficient nitrogen (N) management in conservation tillage corn production (particularly no-till) has been of concern to producers since the early 1970s. It was then researchers first demonstrated that different N management programs could have more effect on crop yield in conservation tillage than in conventional tillage situations. While such research has identified several potential problems that should be addressed when managing N under conservation tillage conditions, it also has provided many solutions to these problems. Dealers, consultants, and producers have a number of options available to them for managing N efficiently when residue cover is present in fields. We'll review some of the problems and their solutions. Immobilization. Where there's a crop residue cover and N is placed on the soil surface, the N usually comes into much more intimate contact with the decomposing organic material than if both materials had been mixed into and diluted by the soil. More fertilizer-N may be consumed by microorganisms as they decompose residue under such conditions. This N immobiliza- tion may reduce the availability of N to the crop for some period of time, particularly early in the season. Delayed availability. Usually, immobi- lized N is released back into plant-available forms later in the season, but this delayed availability may reduce yields, particularly if the quantity of available N is already marginal. In fact, research often has shown that inadequate N rates have reduced corn yield more under no-till than conventional tillage conditions. Such yield depressions usually disappear when optimum rates are
Fluid Journal 1996-1998