title: Development of a Rhizosheath Selection Tool for screening perennial ryegrass (Lolium perenne L.) for reduced root competition against white clover (Trifolium repens L.) for soil phosphorus

authors: Yeates, Rebecca Maree

subjects: Agriculture

abstract: Perennial ryegrass (Lolium perenne L.) outcompetes white clover (Trifolium repens L.) for soil phosphorus [P], resulting in higher P fertiliser rates to overcome the competition. Perennial ryegrass has long, dense root hairs compared to white clover, which increase the root contact with soil (soil exploration) and root surface area for P uptake. This study was conducted to test whether the selection of perennial ryegrass with reduced root hair length and density would reduce root competition for P with no detrimental effect on the perennial ryegrass growth. 
A Rhizosheath Selection Tool [RST] was developed to select ryegrass populations with contrasting root hair length and density. The RST protocol used rhizosheath traits (the width and coverage of soil adhered to the extracted root system) along with the total seedling weight to select two distinct ryegrass populations. The low rhizosheath population had shorter, sparser root hairs on seminal roots and sparser root hairs on adventitious roots than the high rhizosheath population.
The two populations were then grown at five soil P levels in a glasshouse experiment and demonstrated that the rhizosheath trait selection had no detrimental effect on growth. There were no significant differences between the two population’s dry weight (g) and P concentration (mg P g-1 dry weight). However there was evidence to indicate that the high rhizosheath population was sometimes more efficient at P uptake with a larger total P content (mg P). 
The two perennial ryegrass populations were then grown with companion white clover in Olsen P 12 and 19 mg L⁻¹ soil with partitions separating the shoot systems to avoid shoot competition for light. The low rhizosheath population had reduced root competition with the companion white clover. In Olsen P 12 mg L⁻¹ soil, more P was partitioned to the white clover than the ryegrass, measured by total P content (mg P), and achieved a greater dry weight (g) than when grown with the HRS ryegrass. In Olsen P 19 mg L⁻¹ soil there was no rhizosheath selection effect on white clover growth, possibly because of the reduced need for soil exploration by roots under the higher soil P availability. 
The findings from this study confirmed that the RST for the selection of a perennial ryegrass population with a reduced capacity for root competition against white clover for soil P is effective. Furthermore, the RST selection had no detrimental effect to the ryegrass growth. This research highlights the importance of root traits in forage plant breeding, and the potential environmental and economic benefits a low rhizosheath perennial ryegrass could have in New Zealand’s pastoral farming system.

text: Development of a Rhizosheath Selection Tool for screening perennial ryegrass (Lolium perenne L.) for reduced root competition against white clover (Trifolium repens L.) for soil phosphorus Perennial ryegrass (Lolium perenne L.) outcompetes white clover (Trifolium repens L.) for soil phosphorus [P], resulting in higher P fertiliser rates to overcome the competition. Perennial ryegrass has long, dense root hairs compared to white clover, which increase the root contact with soil (soil exploration) and root surface area for P uptake. This study was conducted to test whether the selection of perennial ryegrass with reduced root hair length and density would reduce root competition for P with no detrimental effect on the perennial ryegrass growth. 
A Rhizosheath Selection Tool [RST] was developed to select ryegrass populations with contrasting root hair length and density. The RST protocol used rhizosheath traits (the width and coverage of soil adhered to the extracted root system) along with the total seedling weight to select two distinct ryegrass populations. The low rhizosheath population had shorter, sparser root hairs on seminal roots and sparser root hairs on adventitious roots than the high rhizosheath population.
The two populations were then grown at five soil P levels in a glasshouse experiment and demonstrated that the rhizosheath trait selection had no detrimental effect on growth. There were no significant differences between the two population’s dry weight (g) and P concentration (mg P g-1 dry weight). However there was evidence to indicate that the high rhizosheath population was sometimes more efficient at P uptake with a larger total P content (mg P). 
The two perennial ryegrass populations were then grown with companion white clover in Olsen P 12 and 19 mg L⁻¹ soil with partitions separating the shoot systems to avoid shoot competition for light. The low rhizosheath population had reduced root competition with the companion white clover. In Olsen P 12 mg L⁻¹ soil, more P was partitioned to the white clover than the ryegrass, measured by total P content (mg P), and achieved a greater dry weight (g) than when grown with the HRS ryegrass. In Olsen P 19 mg L⁻¹ soil there was no rhizosheath selection effect on white clover growth, possibly because of the reduced need for soil exploration by roots under the higher soil P availability. 
The findings from this study confirmed that the RST for the selection of a perennial ryegrass population with a reduced capacity for root competition against white clover for soil P is effective. Furthermore, the RST selection had no detrimental effect to the ryegrass growth. This research highlights the importance of root traits in forage plant breeding, and the potential environmental and economic benefits a low rhizosheath perennial ryegrass could have in New Zealand’s pastoral farming system.

year: 2018

title: Unsteady free surface flow induced by a line sink in a fluid of finite depth

authors: Stokes, Tim E.

abstract: The unsteady withdrawal of fluid from a reservoir of finite depth with a free surface through a line sink is considered. A numerical method is used to investigate the evolution of a free surface in several different geometric and initial configurations, and it is shown that there are some critical flow parameters at which the flow changes its nature. The existence of steady states is also considered. Results both with and without surface tension are included and placed in context with previous work. Inclusion of surface tension reveals that solutions either evolve to a steady state or drawdown. As the sink is moved off the base, the behaviour becomes consistent with flows in a fluid of infinite depth, and consequently flows can be classified as either “shallow” or “deep” depending on their drawdown behaviour.

text: Unsteady free surface flow induced by a line sink in a fluid of finite depth The unsteady withdrawal of fluid from a reservoir of finite depth with a free surface through a line sink is considered. A numerical method is used to investigate the evolution of a free surface in several different geometric and initial configurations, and it is shown that there are some critical flow parameters at which the flow changes its nature. The existence of steady states is also considered. Results both with and without surface tension are included and placed in context with previous work. Inclusion of surface tension reveals that solutions either evolve to a steady state or drawdown. As the sink is moved off the base, the behaviour becomes consistent with flows in a fluid of infinite depth, and consequently flows can be classified as either “shallow” or “deep” depending on their drawdown behaviour.

year: 2008

title: Racial inequalities in engineering employment in Aotearoa New Zealand

authors: Roy, Rituparna

abstract: This report presents findings from research on racism and inequality in engineering employment in New Zealand. Conducted as part of the Working to End Racial Oppression (WERO) research programme (see: https://wero.ac.nz/), this study examines how racial discrimination operates in recruitment and career progression within the engineering sector. The research was carried out with the support of Engineering New Zealand | Te Ao Rangahau and the Association of Consulting and Engineering New Zealand. 

This research involves two phases of in-depth interviews. The first phase entails interviews with industry key informants such as human resources staff, managers, or people from diversity and culture teams for different engineering firms that ranged from very small to large in size. In the second phase, currently employed engineers from different ethnic groups were undertaken, including Māori, Pacific, Pākehā, Asian and Middle Eastern, Latin American and African (MELAA). The findings from these two sets of interviews are presented respectively in Section 3 and 4. 

The research also included an analysis of the workforce composition and wage gaps in Engineering based on analysis of Census and New Zealand Income Survey data. This analysis, which is presented in Section 1, revealed the disproportionately low number of female engineers, and of Māori and Pacific people employed as engineers. Analysis of average median hourly wages revealed notable differences, with Māori and Pacific engineers having median wages that are around 80% of the overall median. 

There has been a significant emphasis on Diversity, Equity and Inclusion (DEI) in recruitment and human resource management in Engineering in recent years. This emphasis reflects industry efforts to address known ethnic and gender imbalances in the workforce. Industry informants, however, highlighted several challenges, tensions, and contradictions they faced in integrating and practicing DEI in recruitment. Employers often struggle to balance competing frameworks such as equity, meritocracy, and people-focused approaches, making recruitment decisions complex. Despite initiatives like blind CV screening, targeted graduate programmes and preferential shortlisting of Māori and Pacific applicants, the industry remains heavily merit-driven. Additionally, DEI efforts are largely gender-focused, lacking an intersectional approach that considers overlapping social inequities. 

The interviews with engineers revealed that individuals from different ethnic groups face distinct barriers and challenges in securing employment and advancing their careers. For Māori and Pacific engineers, the pathway into engineering is severely limited, with only a small number entering the profession each year. Those currently employed often experience what has been described V as a ‘cultural tax’—being expected to take on cultural responsibilities in addition to their technical roles, without monetary compensation or clear career advancement opportunities. Racialised immigrant engineers, on the contrary, reported devaluation and deskilling of their qualifications and experience based on their ethnic and national origins. Despite extensive work experience in their home countries, they were often required to restart their careers in graduate or entry-level positions. Several participants shared experiences of unfair promotions, where White, European, and Anglophone employees were favoured for leadership roles. When discussing their own career trajectories, most non-Pākehā and nonEuropean participants expressed scepticism about ever being promoted to senior positions with decision-making authority. 

The accounts of discriminations and racial inequalities shared by engineers have profound implications for their employment, career progression, well-being, and society at large. Navigating a predominantly monocultural work environment—marked by challenges like cultural taxation, glass ceilings, and the ‘white boys’ club’—places additional burdens on racialised groups. The pressure to constantly prove their worth further exacerbates these issues, leading to serious retention problems. If not addressed, the sector risks losing engineers from diverse ethnic backgrounds, exacerbating gender and ethnic pay gaps, worsening representation and diversity issues, and reinforcing systemic racial inequities. 

Addressing monoculturalism and the ‘white boys’ club’ culture and fostering a genuinely inclusive profession will require systemic changes within engineering firms and in accepted norms in the profession and industry. Without a shift in workplace culture, efforts to recruit more engineers from underrepresented backgrounds will remain ineffective, as many will continue to leave due to unwelcoming environments. To create lasting change, DEI initiatives must go beyond recruitment and actively reshape the structures, policies, and day-today practices that define the industry. This requires the mindful integration of diverse cultural values and practices into every layer of organisational functions, including recruitment, career advancement frameworks, and job descriptions.

text: Racial inequalities in engineering employment in Aotearoa New Zealand This report presents findings from research on racism and inequality in engineering employment in New Zealand. Conducted as part of the Working to End Racial Oppression (WERO) research programme (see: https://wero.ac.nz/), this study examines how racial discrimination operates in recruitment and career progression within the engineering sector. The research was carried out with the support of Engineering New Zealand | Te Ao Rangahau and the Association of Consulting and Engineering New Zealand. 

This research involves two phases of in-depth interviews. The first phase entails interviews with industry key informants such as human resources staff, managers, or people from diversity and culture teams for different engineering firms that ranged from very small to large in size. In the second phase, currently employed engineers from different ethnic groups were undertaken, including Māori, Pacific, Pākehā, Asian and Middle Eastern, Latin American and African (MELAA). The findings from these two sets of interviews are presented respectively in Section 3 and 4. 

The research also included an analysis of the workforce composition and wage gaps in Engineering based on analysis of Census and New Zealand Income Survey data. This analysis, which is presented in Section 1, revealed the disproportionately low number of female engineers, and of Māori and Pacific people employed as engineers. Analysis of average median hourly wages revealed notable differences, with Māori and Pacific engineers having median wages that are around 80% of the overall median. 

There has been a significant emphasis on Diversity, Equity and Inclusion (DEI) in recruitment and human resource management in Engineering in recent years. This emphasis reflects industry efforts to address known ethnic and gender imbalances in the workforce. Industry informants, however, highlighted several challenges, tensions, and contradictions they faced in integrating and practicing DEI in recruitment. Employers often struggle to balance competing frameworks such as equity, meritocracy, and people-focused approaches, making recruitment decisions complex. Despite initiatives like blind CV screening, targeted graduate programmes and preferential shortlisting of Māori and Pacific applicants, the industry remains heavily merit-driven. Additionally, DEI efforts are largely gender-focused, lacking an intersectional approach that considers overlapping social inequities. 

The interviews with engineers revealed that individuals from different ethnic groups face distinct barriers and challenges in securing employment and advancing their careers. For Māori and Pacific engineers, the pathway into engineering is severely limited, with only a small number entering the profession each year. Those currently employed often experience what has been described V as a ‘cultural tax’—being expected to take on cultural responsibilities in addition to their technical roles, without monetary compensation or clear career advancement opportunities. Racialised immigrant engineers, on the contrary, reported devaluation and deskilling of their qualifications and experience based on their ethnic and national origins. Despite extensive work experience in their home countries, they were often required to restart their careers in graduate or entry-level positions. Several participants shared experiences of unfair promotions, where White, European, and Anglophone employees were favoured for leadership roles. When discussing their own career trajectories, most non-Pākehā and nonEuropean participants expressed scepticism about ever being promoted to senior positions with decision-making authority. 

The accounts of discriminations and racial inequalities shared by engineers have profound implications for their employment, career progression, well-being, and society at large. Navigating a predominantly monocultural work environment—marked by challenges like cultural taxation, glass ceilings, and the ‘white boys’ club’—places additional burdens on racialised groups. The pressure to constantly prove their worth further exacerbates these issues, leading to serious retention problems. If not addressed, the sector risks losing engineers from diverse ethnic backgrounds, exacerbating gender and ethnic pay gaps, worsening representation and diversity issues, and reinforcing systemic racial inequities. 

Addressing monoculturalism and the ‘white boys’ club’ culture and fostering a genuinely inclusive profession will require systemic changes within engineering firms and in accepted norms in the profession and industry. Without a shift in workplace culture, efforts to recruit more engineers from underrepresented backgrounds will remain ineffective, as many will continue to leave due to unwelcoming environments. To create lasting change, DEI initiatives must go beyond recruitment and actively reshape the structures, policies, and day-today practices that define the industry. This requires the mindful integration of diverse cultural values and practices into every layer of organisational functions, including recruitment, career advancement frameworks, and job descriptions.

year: 2025