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Determination of nitrogen release by organic fertilizers as influenced by fertilizer type and soil characteristics

Paul Kinoti Ng’ang’a, Karoline Maria Jezik, Bernhard Freyer

University of Natural Resources and Life Sciences, Vienna Gregor Mendel Strasse 33, A-1180 Wien, Austria

Key words: Oat, grain legumes, nitrogen, soil.


Milky-Oat-seed1Incubation and pot experiments were carried out at the University of Natural Resources and Life Sciences, Vienna, Austria during the months of July to October 2011 to investigate suitability of grain legume seeds (pea, yellow lupin and faba bean) and organic fertilizers of industry-processed plant and microbial residues (Maltaflor®-spezial, Phytoperls®, Agrobiosol® and Rizi-Korn) as possible substitute for animal based organic fertilizers. Incubation experiment investigated fertilizer net N mineralization using one soil type, while pot experiment determined apparent N utilization using four soil types and oat as a test plant. In both experiments, treatments were laid down in a Complete Randomized Design and replicated four times. The objective of this study was to determine fertilizer and soil characteristics that influence N release of the tested fertilizers. Results showed that, seventy percent of total net mineralization occurred within the first two weeks of incubation. Total net N mineralization was influenced by fertilizer type and ranged between 42 – 61 % and was closely related to N content (r2 = 0.97***) than C/N ratio (r2 = 0.79***). Similar results but with weaker relationship (r2 = 0.60***) was obtained from pot experiment which also showed that, apparent N utilization of oat was influenced by both soil texture and organic matter when the N content was low. These results suggest that, N content of the tested fertilizers is a good indicator for the N release although soil can modify this process.

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