title: The effects of irrigation on soil carbon and nitrogen stocks of pumice soils

authors: Millar, Jamie Alexandra

subjects: Carbon

abstract: The use of irrigation has become important for sustaining the production of food, fibre and biofuel. In New Zealand (NZ), irrigation of pastures is increasing in areas with seasonal water deficits, such as the Central North Island. Nationally, there was an estimated 794,443 ha of land under irrigation in 2017. A synthesis of the literature showed that soil C and N stocks response to irrigation was dependent on the initial soil organic matter content and climatic zone. However, most of the literature focused on arid/semiarid climate regimes where cereals and other crops were grown, with few studies conducted on pastoral land in temperate climates. However Mudge et al. (2017), measured a decrease in soil carbon (C) (6.99 t C ha⁻¹) and nitrogen (N) (0.58 t N ha⁻¹) to 0.3 m depth in irrigated grazed pastures relative to adjacent non-irrigated grazed pastures. Of their 34 paired sites across NZ, only seven were sampled from the Pumice Soil order, which was insufficient to determine whether this soil order was vulnerable to soil C and N loss.
The main objective of this thesis was to compare the total soil C and N stocks of irrigated and non-irrigated Pumice Soils. A second objective was to determine where there were any trends in changes in soil C and N in relation to irrigation duration.
Fourteen paired irrigated and adjacent non-irrigated sites were sampled in the Reporoa Basin, north of Taupo and soil C and N stocks were measured accounting for differences in soil bulk density. Most sites where sampled to 0.6 m depth, however, due to high water tables and buried soils, some sites were only sampled to 0.4 m or 0.5 m depth. One site was omitted from statistical analysis due to high residuals (F11-35) and was considered an outlier that potentially represented a poorly matched pair of sites. On average, for the remaining 13 paired sites, irrigated soils had significantly (P < 0.05) lower soil C stocks (5.93 t C ha⁻¹) to 0.2 m depth and lower N stocks (0.24 t N ha⁻¹) to 0.1 m depth in comparison to adjacent non-irrigated soils. When considering the full depth of the sampled soils (0-0.6 m), there were no significant changes in soil C and N stocks (P > 0.05). Using this coring method, I was able to detect a change of about 6.9 % in soil C stocks and a 4.8 % in soil N stocks. This study also found no evidence of a relationship between soil response to irrigation and duration of irrigation.
With the loss of soil C and N under irrigation comes potential release of CO₂ to the atmosphere and N leaching into surrounding water bodies. Based on the findings in this thesis, there is a need for further investigation on the effects of irrigation for different Soil Orders. This research will aid farmers in understanding their land management on-farm and inform them of their potential effects on greenhouse gas emissions on a national scale.

text: The effects of irrigation on soil carbon and nitrogen stocks of pumice soils The use of irrigation has become important for sustaining the production of food, fibre and biofuel. In New Zealand (NZ), irrigation of pastures is increasing in areas with seasonal water deficits, such as the Central North Island. Nationally, there was an estimated 794,443 ha of land under irrigation in 2017. A synthesis of the literature showed that soil C and N stocks response to irrigation was dependent on the initial soil organic matter content and climatic zone. However, most of the literature focused on arid/semiarid climate regimes where cereals and other crops were grown, with few studies conducted on pastoral land in temperate climates. However Mudge et al. (2017), measured a decrease in soil carbon (C) (6.99 t C ha⁻¹) and nitrogen (N) (0.58 t N ha⁻¹) to 0.3 m depth in irrigated grazed pastures relative to adjacent non-irrigated grazed pastures. Of their 34 paired sites across NZ, only seven were sampled from the Pumice Soil order, which was insufficient to determine whether this soil order was vulnerable to soil C and N loss.
The main objective of this thesis was to compare the total soil C and N stocks of irrigated and non-irrigated Pumice Soils. A second objective was to determine where there were any trends in changes in soil C and N in relation to irrigation duration.
Fourteen paired irrigated and adjacent non-irrigated sites were sampled in the Reporoa Basin, north of Taupo and soil C and N stocks were measured accounting for differences in soil bulk density. Most sites where sampled to 0.6 m depth, however, due to high water tables and buried soils, some sites were only sampled to 0.4 m or 0.5 m depth. One site was omitted from statistical analysis due to high residuals (F11-35) and was considered an outlier that potentially represented a poorly matched pair of sites. On average, for the remaining 13 paired sites, irrigated soils had significantly (P < 0.05) lower soil C stocks (5.93 t C ha⁻¹) to 0.2 m depth and lower N stocks (0.24 t N ha⁻¹) to 0.1 m depth in comparison to adjacent non-irrigated soils. When considering the full depth of the sampled soils (0-0.6 m), there were no significant changes in soil C and N stocks (P > 0.05). Using this coring method, I was able to detect a change of about 6.9 % in soil C stocks and a 4.8 % in soil N stocks. This study also found no evidence of a relationship between soil response to irrigation and duration of irrigation.
With the loss of soil C and N under irrigation comes potential release of CO₂ to the atmosphere and N leaching into surrounding water bodies. Based on the findings in this thesis, there is a need for further investigation on the effects of irrigation for different Soil Orders. This research will aid farmers in understanding their land management on-farm and inform them of their potential effects on greenhouse gas emissions on a national scale.

year: 2018

title: A Meta-Analysis of interventions to reduce disruptive behaviour in classroom settings

authors: Frame, Belinda

subjects: classroom management

abstract: I conducted a meta-analysis of 48 single-case and small-group experimental design studies from 1997 to 2024 that investigated interventions to reduce disruptive behaviour in classroom settings. I extracted data from graphs displaying behavioural data resulting from interventions to reduce disruptive behaviour and then I calculated Tau-U effect sizes. A total of 180 effect sizes from the 48 studies produced a total mean effect size of -0.82 indicating that 82% of students experienced a reduction in their disruptive behaviour. Interventions designed for individual students produced a very large mean effect size (ES = -0.85, SD = 0.31) compared to class-wide strategies (ES = -0.76, SD = 0.30). The most prevalent intervention was group contingencies included in 13 studies. The most utilised intervention within this group was the Good Behaviour Game. All interventions provided in the studies included in this meta-analysis resulted in a reduction in disruptive behaviour, however not all interventions had a strong representation across the studies and therefore have limitations. A small number of experiments trialling an intervention may produce a large effect size, however, due to the need for replication to evoke confidence in the efficacy of an intervention, these results are tentative at best. There is also a strong theme for more training for teachers in classroom management skills as many teachers are reporting that they are not equipped for managing disruptive behaviour in the classroom.

text: A Meta-Analysis of interventions to reduce disruptive behaviour in classroom settings I conducted a meta-analysis of 48 single-case and small-group experimental design studies from 1997 to 2024 that investigated interventions to reduce disruptive behaviour in classroom settings. I extracted data from graphs displaying behavioural data resulting from interventions to reduce disruptive behaviour and then I calculated Tau-U effect sizes. A total of 180 effect sizes from the 48 studies produced a total mean effect size of -0.82 indicating that 82% of students experienced a reduction in their disruptive behaviour. Interventions designed for individual students produced a very large mean effect size (ES = -0.85, SD = 0.31) compared to class-wide strategies (ES = -0.76, SD = 0.30). The most prevalent intervention was group contingencies included in 13 studies. The most utilised intervention within this group was the Good Behaviour Game. All interventions provided in the studies included in this meta-analysis resulted in a reduction in disruptive behaviour, however not all interventions had a strong representation across the studies and therefore have limitations. A small number of experiments trialling an intervention may produce a large effect size, however, due to the need for replication to evoke confidence in the efficacy of an intervention, these results are tentative at best. There is also a strong theme for more training for teachers in classroom management skills as many teachers are reporting that they are not equipped for managing disruptive behaviour in the classroom.

year: 2025

title: Investigating the Social Supports of Successful Māori Undergraduate Appellants at the University of Waikato

authors: Diamond, Danielle Jade

subjects: Social Supports

abstract: Educational disparities between Māori and non-Māori tertiary students are evident in regards to participation, retention, and completion rates at secondary and tertiary levels. Instead of focusing on negative statistics, it was of interest to investigate Māori students who had failed sufficient papers to initially be denied re-entry to university study, yet continued to attain their degrees, as a result of a successful appeal. Māori undergraduate students, who had successfully appealed from 2003-2012, were recruited for my research. The availability and utilisation of social supports were investigated, along with the decision to make an appeal, the role of cultural expectations, and barriers experienced by participants. A mixed method approach was utilised in this research through use of an adapted overarching Kaupapa Māori framework, statistical analysis, and 13 interviews. My research found that social supports were beneficial for participants throughout their appeal, as they provided: emotional, instrumental, appraisal, and informational support. Although the social supports utilised by participants were satisfactory, barriers to accessing formal supports were also found, which included: perceived stigma having failed their papers, pride, as well as being whakamā. The appeal process was a beneficial intervention from the University of Waikato, which provided participants another opportunity to overcome the factors that contributed to their initial failure. Post appeal, participants implemented strategies to address and reduce their factors in order to become academically engaged. Participants were deemed to be resilient from their continued pursuit of degree attainment, implementation of their strategies, and their use of perceived social supports.

text: Investigating the Social Supports of Successful Māori Undergraduate Appellants at the University of Waikato Educational disparities between Māori and non-Māori tertiary students are evident in regards to participation, retention, and completion rates at secondary and tertiary levels. Instead of focusing on negative statistics, it was of interest to investigate Māori students who had failed sufficient papers to initially be denied re-entry to university study, yet continued to attain their degrees, as a result of a successful appeal. Māori undergraduate students, who had successfully appealed from 2003-2012, were recruited for my research. The availability and utilisation of social supports were investigated, along with the decision to make an appeal, the role of cultural expectations, and barriers experienced by participants. A mixed method approach was utilised in this research through use of an adapted overarching Kaupapa Māori framework, statistical analysis, and 13 interviews. My research found that social supports were beneficial for participants throughout their appeal, as they provided: emotional, instrumental, appraisal, and informational support. Although the social supports utilised by participants were satisfactory, barriers to accessing formal supports were also found, which included: perceived stigma having failed their papers, pride, as well as being whakamā. The appeal process was a beneficial intervention from the University of Waikato, which provided participants another opportunity to overcome the factors that contributed to their initial failure. Post appeal, participants implemented strategies to address and reduce their factors in order to become academically engaged. Participants were deemed to be resilient from their continued pursuit of degree attainment, implementation of their strategies, and their use of perceived social supports.

year: 2013