Controlled experiment to determine nitrogen availability for seven organic fertilisers in three contrasting soils

ABSTRACT Organic production systems have generated new technology and management tools, including the use of different nutrient sources. To support to the selection of appropriate organic N fertilisers, based on their N availability over time, a controlled experiment was carried out in three soils with contrasting physical-chemical properties. Seven organic fertilisers, a control without fertiliser and a reference with a conventional fertiliser were used, all providing a total N dose of 100 mg kg−1 soil. Soils were incubated under aerobic conditions for 7, 14, 28, 56 and 112 days, to determine the availability of ammonium, nitrate, and available N. This enabled classification of the fertilisers, according to N availability rates for the total incubation period, as fertilisers with low (compost), medium (Fertil, lupin meal and blood meal), or high (sodium nitrate, Purely Grow and Purely Lysine) N availability rates. According to the speed of N delivery, fertilisers were classified as having a rapid (Purely Grow and sodium nitrate), intermediate (Purely Lysine, blood meal and Fertil), or slow (lupin meal and compost) N delivery speed. The results can be used to support decision making in organic production by enabling the selection of N fertilisers according to their N availability rate and to adjust fertiliser applications to the requirements of the crop.