agronomic evaluation of a fertilizer with d-coder ‎technology: a new mechanism for the slow ‎ release of nutrients

d-coder is a fertilizer with a new slow-release mechanism consisting of an organo-mineral matrix that releases the nutrients only in the presence of growing plants. pot and field experiments were carried out to study the release pattern of n from d-coder. the experiments included grown and bare soil plots. the fertilizer treatments were d-coder, ammonium nitrate (anpreplant), and the control. a fourth treatment was added to the cultivated plots, consisting of splitting the ammonium nitrate application of 25% at preplant and 75% as top-dressing (ansplit). in the bare soil pots, 35 days after the fertilizer application (dafa), no3-n concentrations in the extracts of anion exchange membranes incubated in the soil for anpreplant, d-coder, and the control treatments were 118.5, 82.5 and 34.5 mg l-1, respectively, suggesting that part of n from d-coder had not yet been released. in the pots cultivated with ryegrass, 209 dafa, n recoveries for d-coder, anpreplant, and control treatments were 0.94, 0.86 and 0.20 g pot-1, respectively, suggesting that in the presence of the growing plants the release of n from d-coder had not been restricted. furthermore, soil no3-n levels in the bare soil plots of the field experiment were significantly higher in d-coder (38.1 and 6.8 mg kg-1 on november and march) in comparison to anpreplant (26.3 and 5.1 mg kg-1 on nov. and march) treatments, suggesting that n from d-coder was better protected from leaching. in the absence of growing plants, d-coder provided some protection of n at least until 65 dafa. in cultivated soils, it seemed less effective, particularly if the risk of nitrate leaching persisted for a long period of time. in these situations, a split application of n was a better strategy.