title: Nitrogen leaching from effluent irrigated pasture

authors: Treweek, Glen

subjects: sewage

abstract: The surface waters of the Taupo region are of high quality and are sensitive to inputs of nitrogen. To reduce the amount of nitrogen discharged to surface water, the Taupo District Council (TDC) has employed a land treatment scheme (LTS), where treated municipal wastewater is irrigated onto ryegrass pasture. To limit the possibility of nitrogen pollution, regulations govern the amount of effluent that TDC may irrigate. This study reports the results from the first year of a five year trial where nitrogen leaching from the Taupo LTS was measured.
To measure nitrogen leaching from the Taupo LTS, 48 intact monolith lysimeters were installed beneath effluent irrigation from two centre pivot irrigators. Four treatments based on nitrogen loading rates were trialled, nominally no-N (0 kg N ha-¹yr-¹), low-N (350 kg N ha-¹yr-¹ or less), mid-N (between 350 and 450 kg N ha-¹yr-¹), and high-N (greater than 450 kg N ha-¹yr-¹). Leachate was collected at least monthly and analysed for total nitrogen (TN), nitrate/nitrite nitrogen (NO₃-N), ammoniacal nitrogen (NH₄-N), dissolved organic nitrogen (DON), and total Kjeldahl nitrogen (TKN). The pasture was removed from the lysimeters to determine dry-matter production and pasture nitrogen concentration to calculate nitrogen uptake.
Effluent irrigation significantly increased pasture growth and nitrogen leaching compared to the un-irrigated treatments (P<0.001). The mean rate of pasture growth from the irrigated treatments was 15,800 ± 1,700 kg DM ha-¹yr-¹, but there were no significant difference between the rate of pasture growth between the irrigated treatments. The pasture of the high-N treatments had a significantly higher nitrogen concentration than the low-N treatments (P<0.001), consequently the high-N treatment removed 390 kg N ha-¹, compared to 310 kg N ha-¹ removed from the mid-N and low-N treatments. On average, the pasture removed 84 % of the nitrogen that was irrigated.
After 12 months, the no-N treatments leached 5 ± 3 kg TN ha-¹, the low-N treatment leached 15 ± 1 kg TN ha-¹, the mid-N treatment leached 17 ± 8 kg TN ha-¹, and the high-N treatment leached 26 ± 4 kg TN ha-¹. The high-N treatments leached significantly more TN than the low-N (P<0.005), but there was no significant difference in TN leached between the high-N and mid-N, or the mid-N and low-N treatments. The TN leached was poorly correlated with the rate of effluent irrigation. TN leached was positively correlated with the volume of water that drained through the soil (R2=0.7). The nitrogen in the leachate of the irrigated treatments comprised on average, 53 % NO₃-N, and 45 % DON, while the leachate of the un-irrigated treatments comprised, on average, 26 % NO₃-N and 72 % DON. NH₄-N accounted for approximately 2% of all nitrogen leached. Most of the NO₃-N leached throughout the year was leached after rain during summer and autumn. The mean concentration of NO₃-N leached from the irrigated treatments was 1.3 g N m-³. The concentration of NO₃-N in the leachate never exceeded Ministry of Health guidelines (11.3 g N m-³). The mean concentration of DON leached from the irrigated treatments was 1.2 g N m-³.
Removing nitrogen in the pasture is the solution to avoid excess nitrogen leaching from the Taupo LTS. There is potential to recover more nitrogen in the pasture by improving the pasture cover and frequency of harvest.

text: Nitrogen leaching from effluent irrigated pasture The surface waters of the Taupo region are of high quality and are sensitive to inputs of nitrogen. To reduce the amount of nitrogen discharged to surface water, the Taupo District Council (TDC) has employed a land treatment scheme (LTS), where treated municipal wastewater is irrigated onto ryegrass pasture. To limit the possibility of nitrogen pollution, regulations govern the amount of effluent that TDC may irrigate. This study reports the results from the first year of a five year trial where nitrogen leaching from the Taupo LTS was measured.
To measure nitrogen leaching from the Taupo LTS, 48 intact monolith lysimeters were installed beneath effluent irrigation from two centre pivot irrigators. Four treatments based on nitrogen loading rates were trialled, nominally no-N (0 kg N ha-¹yr-¹), low-N (350 kg N ha-¹yr-¹ or less), mid-N (between 350 and 450 kg N ha-¹yr-¹), and high-N (greater than 450 kg N ha-¹yr-¹). Leachate was collected at least monthly and analysed for total nitrogen (TN), nitrate/nitrite nitrogen (NO₃-N), ammoniacal nitrogen (NH₄-N), dissolved organic nitrogen (DON), and total Kjeldahl nitrogen (TKN). The pasture was removed from the lysimeters to determine dry-matter production and pasture nitrogen concentration to calculate nitrogen uptake.
Effluent irrigation significantly increased pasture growth and nitrogen leaching compared to the un-irrigated treatments (P<0.001). The mean rate of pasture growth from the irrigated treatments was 15,800 ± 1,700 kg DM ha-¹yr-¹, but there were no significant difference between the rate of pasture growth between the irrigated treatments. The pasture of the high-N treatments had a significantly higher nitrogen concentration than the low-N treatments (P<0.001), consequently the high-N treatment removed 390 kg N ha-¹, compared to 310 kg N ha-¹ removed from the mid-N and low-N treatments. On average, the pasture removed 84 % of the nitrogen that was irrigated.
After 12 months, the no-N treatments leached 5 ± 3 kg TN ha-¹, the low-N treatment leached 15 ± 1 kg TN ha-¹, the mid-N treatment leached 17 ± 8 kg TN ha-¹, and the high-N treatment leached 26 ± 4 kg TN ha-¹. The high-N treatments leached significantly more TN than the low-N (P<0.005), but there was no significant difference in TN leached between the high-N and mid-N, or the mid-N and low-N treatments. The TN leached was poorly correlated with the rate of effluent irrigation. TN leached was positively correlated with the volume of water that drained through the soil (R2=0.7). The nitrogen in the leachate of the irrigated treatments comprised on average, 53 % NO₃-N, and 45 % DON, while the leachate of the un-irrigated treatments comprised, on average, 26 % NO₃-N and 72 % DON. NH₄-N accounted for approximately 2% of all nitrogen leached. Most of the NO₃-N leached throughout the year was leached after rain during summer and autumn. The mean concentration of NO₃-N leached from the irrigated treatments was 1.3 g N m-³. The concentration of NO₃-N in the leachate never exceeded Ministry of Health guidelines (11.3 g N m-³). The mean concentration of DON leached from the irrigated treatments was 1.2 g N m-³.
Removing nitrogen in the pasture is the solution to avoid excess nitrogen leaching from the Taupo LTS. There is potential to recover more nitrogen in the pasture by improving the pasture cover and frequency of harvest.

year: 2011

title: A projection-based solution to the SP(2N) state labeling problem

authors: Gould, M.D.

subjects: Mathematics

abstract: A projection-based solution to the symplectic group state labeling problem is presented. The approach yields a nonorthogonal Gel'fand–Tsetlin basis for the irreducible representations of Sp(2n). A method for evaluating the corresponding overlap coefficients is discussed. The action of the Sp(2n) generators, in the basis obtained, is determined and some matrix element formulas are derived. The results obtained are comparable to the matrix element formulas for O(n) and U(n).

text: A projection-based solution to the SP(2N) state labeling problem A projection-based solution to the symplectic group state labeling problem is presented. The approach yields a nonorthogonal Gel'fand–Tsetlin basis for the irreducible representations of Sp(2n). A method for evaluating the corresponding overlap coefficients is discussed. The action of the Sp(2n) generators, in the basis obtained, is determined and some matrix element formulas are derived. The results obtained are comparable to the matrix element formulas for O(n) and U(n).

year: 1985-07

title: Moving away from home: Some social consequences for Tūhoe migrating to the Waikato

authors: Nikora, Linda Waimarie

subjects: psychology

abstract: To better understand the social consequences of migration away from traditional iwi regions, Tūhoe researchers intensively interviewed 40 Tūhoe people who had moved to the Waikato. It was found that most missed whanau and the community and made regular visits back home. Participants reported utilizing extensive whanau links to set themselves up in the Waikato, and many joined the Tūhoe associations in the Waikato. Others who did not join reported liking the idea that Tūhoe were there if needed. Some participants felt stronger in their Tūhoe identity since moving, and most reported noticing changes occurring in themselves or those back home over this period (they felt more worldly but saw those back home as more insular). While they did not interact much with tangata whenua, or participate in tangata whenua events, many said that they had a better appreciation of the local Tainui and the Kīngitanga groups since migrating. Finally, most would like to return to their iwi region for employment if it were available but saw little chance of this happening, and most reported wanting to retire there. The policy implications of both these points are explored.

text: Moving away from home: Some social consequences for Tūhoe migrating to the Waikato To better understand the social consequences of migration away from traditional iwi regions, Tūhoe researchers intensively interviewed 40 Tūhoe people who had moved to the Waikato. It was found that most missed whanau and the community and made regular visits back home. Participants reported utilizing extensive whanau links to set themselves up in the Waikato, and many joined the Tūhoe associations in the Waikato. Others who did not join reported liking the idea that Tūhoe were there if needed. Some participants felt stronger in their Tūhoe identity since moving, and most reported noticing changes occurring in themselves or those back home over this period (they felt more worldly but saw those back home as more insular). While they did not interact much with tangata whenua, or participate in tangata whenua events, many said that they had a better appreciation of the local Tainui and the Kīngitanga groups since migrating. Finally, most would like to return to their iwi region for employment if it were available but saw little chance of this happening, and most reported wanting to retire there. The policy implications of both these points are explored.

year: 2004