Efficient utilization of native nutrient sources
2015
Yli-Halla, M., University of Helsinki (Finland). Dept. of Food and Environmental Sciences
Agriculture around the Baltic Sea is not the most intensive user of plant nutrients in Europe but our Sea is highly vulnerable to eutrophication. In spite of still deficient wastewater treatment in a few major cities, agricultural land is recognized as a major source of N and P transported to the Baltic Sea. Our agriculture should focus on more efficient use of domestic nutrient sources. Moreover, for certain time period, there are obvious possibilities to take the advantage of P stocks accumulated into the soil in past fertilizations with manure or mineral P; starting from medium P status, only minor or non-existent responses have been obtained with new P additions. Soil testing should be used for monitoring how long this nutrient mining is sustainable in a field concerned. These observations have been made on the western coast of Finland on acid sulfate soil where unfertilized potato yielded 41 t haE-1 with a highly negative N balance and only a 2 - t haE-1 yield increase upon N application. Potassium (K) used to be the least expensive of the three major nutrients but its price has drastically increased since 2008. Fine and medium textured soils commonly have abundant K reserves. If these soils have a coarse or organic plough layer and only the topsoil is analyzed, these reserves go unnoticed and more than adequate amounts of K may be applied. This presentation calls upon more efficient utilization of native N, P and K resources from different substance flows or those present in soil. More work is required to guarantee the fertilizer effect of these sources, and to safeguard that soil quality is not compromised by the use of waste materials. Soil testing is needed to monitor how long nutrient mining can be pursued in a sustainable manner and to recognize areas and soil types with abundant N, P and K reserves.
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