
TY  - JOUR
A1  - Mundy, GN 
A1  - Mason, WK 
T1  - The effect of flood irrigation and nitrogen source on the fate of nitrogen fertilizer applied to pasture
JF  - Australian Journal of Agricultural Research
JO  - Aust. J.  Agric. Res.
Y1  - 1989
VL  - 40
IS  - 1
SP  - 107
EP  - 116
KW  - 
UR  - https://doi.org/10.1071/AR9890107 
N2  - The effects of flood irrigation on soil inorganic nitrogen (N) and on the recovery of 15N from 15N-labelled fertilizers were studied in two pasture experiments. In the first, changes in soil inorganic N were measured during a flood irrigation cycle after fertilization with 0 or 100 kg N ha-1 as ammonium nitrate (NH4NO3). In the second experiment, the recovery of 15N from 15N -labelled fertilizers (50 kg N ha-1 as NH4NO3, urea or urea plus nitrapyrin) was determined in field microplots under three irrigation regimes (0, 6 and 24 h ponding).Soil inorganic N in the unfertilized pasture remained relatively low (< 12 kg N ha-') during the irrigation cycle with ammonium (NH4+) the dominant form of inorganic N. In pasture fertilized with NH4N03 there was a rapid decline in both NH4+ and nitrate (NO3-) in the soil during the 48 h period after the first irrigation. The decline in NH4+ was less rapid than that of NO3-. Presumably immobilization, nitrification and pasture uptake contributed to the disappearance of NH4+ from the soil.In the second experiment total recovery of applied 15N ranged from 65 to 91%, with about half recovered from the pasture and half from the soil plus roots. The lowest recoveries of applied N occurred with NH4NO3with 24 h ponding.Recovery of the urea nitrogen was unaffected by ponding time, making it a more efficient form of N to apply to irrigated pastures. 
ER  -

