D-CODER is a fertilizer with a new slow-release mechanism consisting of an organomineral
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 DCODER,
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 DCODER
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
