Traditionally, producers on the Canadian prairies have tried to improve nutrient management by selecting fertilizer source, timing, placement to optimise nutrient use efficiency (Malhi et al. 2001; Grant et al. 2002). However, there are constraints to the adoption of the beneficial management practices available for nutrient management. Broadcast applications are still used in pastures, on winter wheat and for some no-till systems, even through they are relatively inefficient
(Malhi et al. 2001).
Although more than 75% of fertilizer applied in the prairies uses some form of in-soil banding to reduce the risk of nutrient loss or conversion to unavailable forms prior to crop uptake (http://www40.statcan.ca/l01/cst01/agrc25a.htm
), an extra banding operation separate from seeding requires increased time, labour, fuel and equipment and can result in soil moisture loss. Seed-placing fertilizer improves N use efficiency and eliminates the need for a separate banding operation, but the amount of N that can be safely placed with the seed without causing seeding damage is often lower than that required to optimise crop yield and quality
(Grant et al. 1999). Side-banding or mid-row banding separates the seed and fertilizer and reduces the risk of seedling damage in a one-pass operation, but increases equipment costs and draft requirements. Split application of N to synchronise N supply with crop uptake requires extra field operations and may be relatively inefficient if volatilization and immobilization losses are high, if moisture is not available to carry the fertilizer into the soil, or if the application is delayed due to adverse weather conditions. In spite of the beneficial nutrient management practices adopted by producers, N use efficiency is generally less than 50% in the year of application, with P use efficiency generally in the range of 30%.
Enhanced efficiency fertilizers use novel formulations to improve N use efficiency and/or the operational efficiency in crop production. Various additives or coatings are available that can improve nutrient use efficiency or increase the timing and placement options available to producers by controlling the speed of release or interfering with soil-fertilizer reactions. Products include nitrification inhibitors, urease inhibitors, and coated N fertilizers. There are also uncoated, slowly available compounds such as synthetic organic compounds like urea formaldehyde (UF) & methylene urea (MU), or isobutylidene diurea (IBDU), although these are used mostly in the turfgrass industry rather than in agriculture. A listing of these products can be found at: www.fertilizer.org/ifa/news/2005_17.asp. Under the right conditions, enhanced efficiency fertilizers can reduce fertilizer losses, slow the conversion to less available forms, or reduce the risk of seedling damage.
For any enhanced efficiency fertilizer to prove effective in a crop production system, several conditions must be met. Firstly, the product must work over a range of soil and environmental conditions. Secondly, losses must be sufficiently large to reduce crop yield or quality. 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.
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