Agronomy Library > Soil Conservation

Using Nitrogen Inhibitors & Coated N in Direct Seeding - Direct Seeding Advantage 2003
Author: Cynthia Grant, Agriculture & Agri-Food Canada
Date Created: November 18, 2003
Last Reviewed: November 18, 2003

Urea is the major granular fertilizer used on the Canadian prairies, because it has a high N analysis, is easy and safe to handle and store and is relatively low cost. Urea is readily soluble in water and can be used in the formulation of urea ammonium nitrate (UAN) and compound fertilizers. But, urea has two major drawbacks: 

1) It is subject to volatilization losses if surface applied;
2) It can produce severe seedling damage if seed-placed levels are too high. 

Banding or broadcast-incorporation application of urea will reduce seedling toxicity and volatilization loss, but this requires extra trips across the field, with extra costs and possible loss of moisture and seed-bed quality. With reduced tillage systems, the soil disturbance associated with incorporation or fertilizer banding may not be desirable, while in perennial forages or in forestry, these application methods may not be possible. Urease inhibitors may be an economical option to increase the efficiency of surface applications and reduce the toxicity of seed-placed urea. Controlled release coated N may also be effective in reducing seedling damage and improving N use efficiency under reduced tillage management. Agrotain is a commercially available urease inhibitor containing the active ingredient n-(n-butyl) thiophosphoric triamide (NBPT). A number of coated N products are available for high value crops, but are not yet economically viable for small grain or oilseed production. 

For any urease inhibitor or coated product to prove effective in a crop production system, several conditions must be met. Firstly, the urease inhibitor or coated product must work over a range of soil and environmental conditions. Secondly, potential seedling damage or volatile losses of urea-containing fertilizers must be sufficiently large to reduce crop yield or protein content. Thirdly, the product must not damage the crop, consumers of the crop or environmental health. Fourthly, the benefits must be enough to justify the cost of the product.

Open the PDF for the complete paper