The objective of this work is to collect a robust dataset of nitrogen and phosphorus losses from drainage water in New Zealand cropping rotations. An important part of the project is to examine the environmental risks indicated by the data and to identify on-farm management practices that could reduce losses.
In 2014, passive wick drainage fluxmeters were installed at sites on twelve New Zealand cropping farms with mixed arable and vegetable rotations. The installation depth is 1.2m, below the active rootzone for many crops. Since then, drainage water has been collected and measured and the concentration of nitrogen and phosphorus in the drainage sample has been analysed. After 4 ½ years of data collection we are able to see where and when the risks for nitrogen and phosphorus losses occur.
Annual Cumulative Nitrogen Losses in the last three years
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Annual Nitrogen losses in Kg/ha for 2016-2017 and 2017-2018 and the spring and summer drainage volume for 2018-2019 in mm. *estimated from water balance model because of flooding in the fluxmeter units. N/A because units have been re installed at a new site. |
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Site # |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
9 |
10 |
11 |
12 |
|
Sep 16-Aug 17 |
182 |
48 |
61 |
201 |
143 |
31 |
52 |
35 |
171 |
192 |
92 |
|
Sep 17-Aug 18 |
21 |
23 |
161 |
328 |
123 |
14 |
26 |
60 |
31 |
218 |
125 |
|
Sep 18-Feb 19 |
13 |
1 |
3 |
178 |
11 |
<1 |
N/A |
9 |
28 |
37 |
15 |
The data set has revealed the size and dynamic nature of N losses from mixed cropping systems. The challenge is tease out farm management effects from the biophysical characteristics of the farm which influence nutrient losses and to develop farm management strategies to mitigate these losses.