Loading...
Monitoring of Potential N Losses from Dairy and Organic Farming Systems
Ryan, Michael Fanning, A. Noonan, D.
Ryan, Michael
Fanning, A.
Noonan, D.
Citations
Altmetric:
Keywords
Date
2001-03-01
Collections
Files
Loading...
eopr-4482.pdf
Adobe PDF, 1.4 MB
Research Projects
Organizational Units
Journal Issue
Citation
Ryan, M., Fanning, A., Noonan, D., Monitoring of Potential N Losses from Dairy and Organic Farming Systems, End of Project Reports, Teagasc, 2001.
Abstract
The project was carried out at Johnstown Castle and was concerned with
monitoring potential nitrogen (N) leaching losses from organic and dairy
farming systems. Some plots were cut for silage in year one; only grazed
plots were used in year two. There were low input manure N plots in the
organic system with low and high input fertiliser N plots in the dairy
system.
Soil samples, in 15 cm intervals from the surface to 90cm deep, were
taken in triplicate from one plot of each treatment on three successive
days per month from October to March in year 1 and from September to
March in year 2. Extraction of nitrate-N (NO3-N) and ammonium-N (NH4-
N) was carried out on un-bulked soil cores by taking a 20 g sub-sample
and using 100 ml 2 molar KCl. A 20 g sub-sample of each day`s bulked
replicates was dried at 105 degrees C overnight for moisture
determination. The concentrations of NO3-N and NH4-N in the extracts
were determined on an automatic analyser and the results were
converted to kg per ha using the following bulk densities for the soil
layers: 0-15, 15-30, 30-60, 60-90, 1.3, 1.4, 1.6, 1.75 g per cm3,
respectively. In year 1 the results showed no significant difference
between treatments in the level of NO3-N, NH4-N and total mineral N in
the soil layers and total amounts to 90 cm. On four of the six dates,
November, December, January, early-March, the level of total mineral N
was lowest in the low N treatment. Among treatments, NH4-N was lowest
in the low N treatment on four dates, November, December, January,
early-March while NO3-N was also lowest on four dates, November,
December, early-March and late-March. At the November, December,
January and early-March sampling, the organic farm NH4-N data to 90
cm was highest which was reflected in the total mineral N results to 90
cm for November, December and early-March. In year 2 the results
showed no significant difference between treatments in the level of NO3-
N, NH4-N and total mineral N in the soil layers and total amounts to 90
cm. In September, October, November, December and February, total
mineral N to 90 cm was highest in the high N treatment. This was a
reflection of high NO3-N levels in that treatment for those sampling dates.
Among treatments, total mineral N to 90 cm was lowest in the organic
farm samples in September, October, November, December and
February. This result reflected, among treatments, lowest NH4-N levels
in September, October, November, December, February and lowest NO3-
N levels in November and December.
Estimates of the amounts of applied N leached, averaged over the two
years of the experiment, were 22% for the Low N treatment and 12% for
the High N treatment. An equation, developed from studies carried out in County Cork
(Richards, 1999), gave predictions of N available for leaching in
November from the N treatments in year 2 which were in very good
agreement at low N and within 23% of those actually recorded at high N.
Assessment of available N leaching models led to the conclusion that the
relatively simple UK `N Cycle` model was most adaptable to Irish
conditions since other European and US models require input
parameters not readily available including those for soil texture, soil
hydrology and soil organic matter.