1997 Trenkel IFA Controlled-Release and Stabilized Fertilizers in Agriculture
This publication presents agronomic reasons which have led to the development of controlled-release and stabilized fertilizers. The characteristics, the advantages and the possible disadvantages of controlled-release and nitrification/urease inhibitors are discussed.Particular attention is given to problems of legislation, registration, methodology and standardization. Leading manufacturers and their product ranges are listed.Universities and institutes engaged in research on controlled-release fertilizers and nitrification/urease inhibitors and the fields of their main research activities, are indicated. A comprehensive bibliography is added.As regards controlled-release fertilizers, the publication presents the reason why their production and their distribution costs are significantly higher than those of conventional fertilizers. The difference in cost is identified as the main reason restricting their use to high value crops, specific cultivation systems and non-agricultural sectors(professional horticulture, nurseries, greenhouses, golf courses, household consumers, turf, landscape gardeners and public parks).Only very limited quantities are used on agricultural crops such asfruit trees and high cash-value vegetables.The total amount of 562 000 t of synthetic controlled-release fertilizers which are applied represents only 0.15% of the world’s total mineral fertilizer consumption (approximately 380 mio t of fertilizer material).Even though in Japan 70% of polymer coated controlled-release fertilizers are used on rice, it is doubtful whether this innovative cultivation system can be transferred to other rice growing countries and to other agricultural crops. Unless the cost of controlled-release fertilizers can be significantly lowered, it is unlikely that these speciality fertilizers will gain widespread use on low value agricultural crops.With no technical breakthrough in sight, it seems that controlled-release fertilizers will have no impact on world food production in the foreseeable future.In contrast to controlled-release fertilizers, nitrification and urease inhibitors are used almost exclusively on agricultural crops. By improving the efficiency of nitrogen use, their application results either in higher and more consistent yields of agricultural crops, or in unchanged yields with reduced nitrogen application rates. The amount of nitrogen applied can be reduced by 15 to 20 % without reducing the yield level. However, even though the economics of their use are much more favourable to farmers compared to controlled-release fertilizers, to date their application has been restricted to very few agricultural crops(mainly corn and root crops), and special climatic conditions.Apart from the agronomic aspects of controlled-release and nitrification/urease inhibitors, the environmental aspects of their use deserve close attention. Controlled-release fertilizers and nitrificationand urease inhibitors, can contribute significantly to environmental protection either by reducing the leaching of nitrate or by reducing the emissions of nitrous oxide and the volatilization losses of ammonia.Hence, in future the impact of controlled-release fertilizers and nitrification/urease inhibitors may become increasingly important because of the environmental aspects. If environmental legislation should place restrictions on the application of nitrogen on farmland where there is a possibility of polluting groundwater, streams and lakes, farmers may be forced to give preference to these types of nitrogen fertilizers and products.As regards the volatilization losses of ammonia from amide-N containing fertilizers which are surface applied or applied under flooded conditions, the introduction onto the United States agricultural market in 1996 of the first urease inhibitor, will be observed with great interest.