title: The effects of intensive grazing on nitrogen fixation by white clover

authors: Menneer, John Christopher

abstract: The effects of the grazing animal (treading, defoliation, and excreta) on N2 fixation were investigated in an intensively managed legume-based dairy pasture in the Waikato region, North Island, New Zealand. Two major 12-month field experiments were conducted in a long-term (>30 years) permanent mixed pasture of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) to determine the full effect of grazing animals on legume growth and N2 fixation. Each study was commenced in spring ( 1998 and 1999), when pasture was taken out of grazing and the relevant treatments applied in a randomised block design. Subsequently, pasture was defoliated by mowing at regular intervals and the herbage dry matter yield and pasture species composition determined. N2 fixation was estimated using the 15N isotope dilution technique to give an integrated estimate of the proportion of clover N derived from atmospheric N2 (%Ndfa) at each harvest. 
The first experiment (initiated in October 1998) investigated the effects of urine additions on N2 fixation in pasture managed with light and moderately severe cutting treatments. Urine application (equivalent to 746 kg N ha-1) increased average annual production by 85%, but did not significantly impact on clover production, except in the light cutting treatment at days 50-100. Urine application reduced %Ndfa to 25% of the control (as measured by 15N methods), with recovery taking almost a year, thus reducing total fixed N in clover herbage from 232 to 145 kg N ha-1 yr-1. Four methods of estimating %Ndfa from 15N data were used in the urine treated plots. The use of 15N-labelled urine gave estimates of  %Ndfa that were 20-30% below values calculated using conventional 15N-labelling during the first 161 days. These differences were probably due to differences in the rooting depth between ryegrass and white clover in conjunction with treatment differences in 15N distribution with depth. The 15N natural abundance technique gave highly variable estimates of %Ndfa (-56 to 24%) during the first 23 days after urine application, but thereafter estimates of %Ndfa were similar to those using 15N-labelling methods. Defoliation severity had no immediate effect on N2 fixation, but during summer and autumn %Ndfa inmoderately-severe plots was consistently higher than under light defoliation. The greater abundance and productivity of vigorous growing weed and summer-grass species recorded in moderately-severe plots during summer and autumn indicate that these species were probably regulating N2 fixation by changing soil N availability. Overall, total N fixed increased by 36% under moderately-severe defoliation compared to light defoliation. Defoliation severity had no significant effect on clover production. 
The second major experiment (initiated in September 1999), examined the effects of pugging intensity on pasture growth and N2 fixation. A single pugging event at stocking rates of 4.5 cows 100 m-2 for 1.5 or 2.5 hours on a wet silt loam soil initiated the experiment, and was equivalent to a moderate or severe pugging event in spring. Fixed N in clover herbage decreased significantly from 76 kg N ha-1 yr-1 in the non-pugged control, to 66 kg N ha-1 yr-1 and 36 kg N ha-1 yr-1 under moderate and severe pugging, respectively. The decrease in fixed N was mainly due to treading damage to clover plants and an associated reduction in clover production which persisted for up to 259 days under severe pugging. Detailed clover morphology measurements revealed an increase in stolon fragmentation and a decrease in plant density, which heightened the vulnerability of plants to dry soil conditions following pugging. A medium-term reduction in grass growth under pugging probably led to increased soil inorganic N and would account for an observed decline in %Ndfa that occurred during the first 3-months of the study .Although pugging caused a major disturbance and rearrangement of the soil surface layers this only had a marginal short-term effect on soil physical properties. Soil aeration was reduced for approximately 21 days and did not measurably affect N2 fixation. However, an increase in denitrification during the first 21 days after pugging suggested biological process were affected by the reduction in soil aeration. 
A conceptual model is proposed to describe the principal processes that affect N2 fixation by grazing animals in intensively managed clover-grass pastures. The use of a whole farm dairying model of N cycling to further investigate animal impacts in legume-based pastures highlighted the need to consider pasture management strategies and interactions between treading, defoliation and excreta. In the future, more complex models specifically dealing with legume-based pasture ecosystems will be needed to integrate detailed animal-plant-soil components and thus assist in identifying how N2 fixing efficiency can be improved.

text: The effects of intensive grazing on nitrogen fixation by white clover The effects of the grazing animal (treading, defoliation, and excreta) on N2 fixation were investigated in an intensively managed legume-based dairy pasture in the Waikato region, North Island, New Zealand. Two major 12-month field experiments were conducted in a long-term (>30 years) permanent mixed pasture of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) to determine the full effect of grazing animals on legume growth and N2 fixation. Each study was commenced in spring ( 1998 and 1999), when pasture was taken out of grazing and the relevant treatments applied in a randomised block design. Subsequently, pasture was defoliated by mowing at regular intervals and the herbage dry matter yield and pasture species composition determined. N2 fixation was estimated using the 15N isotope dilution technique to give an integrated estimate of the proportion of clover N derived from atmospheric N2 (%Ndfa) at each harvest. 
The first experiment (initiated in October 1998) investigated the effects of urine additions on N2 fixation in pasture managed with light and moderately severe cutting treatments. Urine application (equivalent to 746 kg N ha-1) increased average annual production by 85%, but did not significantly impact on clover production, except in the light cutting treatment at days 50-100. Urine application reduced %Ndfa to 25% of the control (as measured by 15N methods), with recovery taking almost a year, thus reducing total fixed N in clover herbage from 232 to 145 kg N ha-1 yr-1. Four methods of estimating %Ndfa from 15N data were used in the urine treated plots. The use of 15N-labelled urine gave estimates of  %Ndfa that were 20-30% below values calculated using conventional 15N-labelling during the first 161 days. These differences were probably due to differences in the rooting depth between ryegrass and white clover in conjunction with treatment differences in 15N distribution with depth. The 15N natural abundance technique gave highly variable estimates of %Ndfa (-56 to 24%) during the first 23 days after urine application, but thereafter estimates of %Ndfa were similar to those using 15N-labelling methods. Defoliation severity had no immediate effect on N2 fixation, but during summer and autumn %Ndfa inmoderately-severe plots was consistently higher than under light defoliation. The greater abundance and productivity of vigorous growing weed and summer-grass species recorded in moderately-severe plots during summer and autumn indicate that these species were probably regulating N2 fixation by changing soil N availability. Overall, total N fixed increased by 36% under moderately-severe defoliation compared to light defoliation. Defoliation severity had no significant effect on clover production. 
The second major experiment (initiated in September 1999), examined the effects of pugging intensity on pasture growth and N2 fixation. A single pugging event at stocking rates of 4.5 cows 100 m-2 for 1.5 or 2.5 hours on a wet silt loam soil initiated the experiment, and was equivalent to a moderate or severe pugging event in spring. Fixed N in clover herbage decreased significantly from 76 kg N ha-1 yr-1 in the non-pugged control, to 66 kg N ha-1 yr-1 and 36 kg N ha-1 yr-1 under moderate and severe pugging, respectively. The decrease in fixed N was mainly due to treading damage to clover plants and an associated reduction in clover production which persisted for up to 259 days under severe pugging. Detailed clover morphology measurements revealed an increase in stolon fragmentation and a decrease in plant density, which heightened the vulnerability of plants to dry soil conditions following pugging. A medium-term reduction in grass growth under pugging probably led to increased soil inorganic N and would account for an observed decline in %Ndfa that occurred during the first 3-months of the study .Although pugging caused a major disturbance and rearrangement of the soil surface layers this only had a marginal short-term effect on soil physical properties. Soil aeration was reduced for approximately 21 days and did not measurably affect N2 fixation. However, an increase in denitrification during the first 21 days after pugging suggested biological process were affected by the reduction in soil aeration. 
A conceptual model is proposed to describe the principal processes that affect N2 fixation by grazing animals in intensively managed clover-grass pastures. The use of a whole farm dairying model of N cycling to further investigate animal impacts in legume-based pastures highlighted the need to consider pasture management strategies and interactions between treading, defoliation and excreta. In the future, more complex models specifically dealing with legume-based pasture ecosystems will be needed to integrate detailed animal-plant-soil components and thus assist in identifying how N2 fixing efficiency can be improved.

year: 2003

title: Methods for linear radial motion estimation in time-of-flight range imaging

authors: Streeter, Lee

abstract: Motion artefacts in time-of-flight range imaging are treated as a feature to measure. Methods for measuring linear radial velocity from range imaging cameras are developed and tested. With the measurement of velocity, the range to the position of the target object at the start of the data acquisition period is computed, effectively correcting the motion error. A new phase based pseudo-quadrature method designed for low speed measurement measures radial velocity up to ±1.8 m/s with RMSE 0.045 m/s and standard deviation of 0.09-0.33 m/s, and new high-speed Doppler extraction method measures radial velocity up to ±40 m/s with standard deviation better than 1 m/s and RMSE of 3.5 m/s.

text: Methods for linear radial motion estimation in time-of-flight range imaging Motion artefacts in time-of-flight range imaging are treated as a feature to measure. Methods for measuring linear radial velocity from range imaging cameras are developed and tested. With the measurement of velocity, the range to the position of the target object at the start of the data acquisition period is computed, effectively correcting the motion error. A new phase based pseudo-quadrature method designed for low speed measurement measures radial velocity up to ±1.8 m/s with RMSE 0.045 m/s and standard deviation of 0.09-0.33 m/s, and new high-speed Doppler extraction method measures radial velocity up to ±40 m/s with standard deviation better than 1 m/s and RMSE of 3.5 m/s.

year: 2017

title: Cultural diversity and identity discourses in the design and implementation of the New Zealand curriculum key competencies: a Bernsteinian analysis

authors: Glogowski, Sonia Theresa

subjects: Culture

abstract: The key competencies as a curriculum construct have appeared in several national curricula from the early 2000s. Many have their origins in the Definition and Selection of Key Competencies Project (DeSeCo), commissioned by the supra-national Organisation for Economic Co-operation and Development (OECD). A number of international critiques have highlighted tensions between neoliberal ideologies that underpin the key competencies, and broader socio-cultural and social justice issues within their respective countries (e.g., Crick, 2008; Sjøberg, 2016; Takayama, 2013).
This research investigated who and what influenced the design and implementation of the key competencies in the 2007 New Zealand Curriculum, and how students’ cultural diversity and identities were considered as part of this. Data for this case study were collected from three sources: interviews with key policy officials and academic consultants six years after the launch of the official curriculum; analysis of policy documents and discussion papers from government archives, and focus group interviews with teachers from two schools seven years into implementation. Bernstein’s (2000) theory of the pedagogical device, was used to focus analysis on the agents, influences, debates and events that impacted on the design and implementation of the curriculum. Fraser’s (1989) needs’ discourse theory was used to examine interpretations of cultural diversity and identity, and the implications of implicit valued attitudes and behaviours of the key competencies.
Findings indicated that in the New Zealand educational policy context, the roles and interactions between agents and processes in the fields of production and reproduction were more ‘fluid’ and consultative than Bernstein’s (2000) structuralist model would suggest. This may be reflective of New Zealand’s small population and more informal collaboration between agents in different fields. The development of this curriculum prioritised the ‘process’ of understanding curriculum through consultation and feedback, compared to previous curricula which were more focussed on curriculum as a ‘product’.
New Zealand’s socio-political climate, and its bicultural Treaty of Waitangi, appeared to impact on how the key competencies were conceived, and how student diversity and identity were interpreted at different points in the curriculum design and implementation process. Interviews with key policy officials and academic consultants revealed that cultural diversity was largely associated with ethnicity, and in particular, differences between indigenous Māori and Pākehā (New Zealand European). Less attention was given to the concept of multiple identities and intersections between ethnicity, socio economic class, gender and so on, and how these might influence interpretations of the key competencies. This was despite evidence of early discussion papers highlighting these complexities.
At the curriculum implementation level, Bernstein (2000) argues that schools and teachers can often ‘reproduce’ middle class values and expected behaviours through ‘invisible’ pedagogical practices, with little awareness of potential disjuncts for disadvantaged groups. Yet he also states that this is not necessarily deterministic, and the finding for the two school focus groups demonstrated this. Despite no evidence that student diversity was a specific aspect of their professional development on key competencies, the teachers discussed some complexities of student diversity in their schools and how the key competencies might be interpreted in different ways. However, given the case study schools were considered to be particularly ‘diverse’, this type of discussion and consideration may not be typical of other New Zealand schools.
The findings support the notion that the New Zealand curriculum key competencies were ‘weakly classified’ and ‘strongly framed’ (Bernstein, 2000). This means a high level of interpretation was located with school leaders and teachers, within the context of a permissive curriculum and thus presents both opportunities and risks.
This case study highlights the importance of agents in every field understanding the complexities and implications of diversity in education. In addition, if the key competencies genuinely seek to enhance both vocational and social justice outcomes for a more cohesive and equitable society, then education for diversity would seem to be important.
This research contributes new knowledge in relation to the process of curriculum design, highlighting the impact of a unique socio-political context on the interpretation of a curriculum construct, and the implications of ‘valued’ attitudes and behaviours of the key competencies on diverse students. It provides an example of how Bernstein’s (2000) theory of the pedagogical device can be used to identify important influences and processes that impact on the different stages of a curriculum design and implementation process. It also illustrates how the device can be usefully complemented by another theory, in this case Fraser’s (1989) needs discourse theory, to examine more closely the discourse that relates to a particular lens of the research.

text: Cultural diversity and identity discourses in the design and implementation of the New Zealand curriculum key competencies: a Bernsteinian analysis The key competencies as a curriculum construct have appeared in several national curricula from the early 2000s. Many have their origins in the Definition and Selection of Key Competencies Project (DeSeCo), commissioned by the supra-national Organisation for Economic Co-operation and Development (OECD). A number of international critiques have highlighted tensions between neoliberal ideologies that underpin the key competencies, and broader socio-cultural and social justice issues within their respective countries (e.g., Crick, 2008; Sjøberg, 2016; Takayama, 2013).
This research investigated who and what influenced the design and implementation of the key competencies in the 2007 New Zealand Curriculum, and how students’ cultural diversity and identities were considered as part of this. Data for this case study were collected from three sources: interviews with key policy officials and academic consultants six years after the launch of the official curriculum; analysis of policy documents and discussion papers from government archives, and focus group interviews with teachers from two schools seven years into implementation. Bernstein’s (2000) theory of the pedagogical device, was used to focus analysis on the agents, influences, debates and events that impacted on the design and implementation of the curriculum. Fraser’s (1989) needs’ discourse theory was used to examine interpretations of cultural diversity and identity, and the implications of implicit valued attitudes and behaviours of the key competencies.
Findings indicated that in the New Zealand educational policy context, the roles and interactions between agents and processes in the fields of production and reproduction were more ‘fluid’ and consultative than Bernstein’s (2000) structuralist model would suggest. This may be reflective of New Zealand’s small population and more informal collaboration between agents in different fields. The development of this curriculum prioritised the ‘process’ of understanding curriculum through consultation and feedback, compared to previous curricula which were more focussed on curriculum as a ‘product’.
New Zealand’s socio-political climate, and its bicultural Treaty of Waitangi, appeared to impact on how the key competencies were conceived, and how student diversity and identity were interpreted at different points in the curriculum design and implementation process. Interviews with key policy officials and academic consultants revealed that cultural diversity was largely associated with ethnicity, and in particular, differences between indigenous Māori and Pākehā (New Zealand European). Less attention was given to the concept of multiple identities and intersections between ethnicity, socio economic class, gender and so on, and how these might influence interpretations of the key competencies. This was despite evidence of early discussion papers highlighting these complexities.
At the curriculum implementation level, Bernstein (2000) argues that schools and teachers can often ‘reproduce’ middle class values and expected behaviours through ‘invisible’ pedagogical practices, with little awareness of potential disjuncts for disadvantaged groups. Yet he also states that this is not necessarily deterministic, and the finding for the two school focus groups demonstrated this. Despite no evidence that student diversity was a specific aspect of their professional development on key competencies, the teachers discussed some complexities of student diversity in their schools and how the key competencies might be interpreted in different ways. However, given the case study schools were considered to be particularly ‘diverse’, this type of discussion and consideration may not be typical of other New Zealand schools.
The findings support the notion that the New Zealand curriculum key competencies were ‘weakly classified’ and ‘strongly framed’ (Bernstein, 2000). This means a high level of interpretation was located with school leaders and teachers, within the context of a permissive curriculum and thus presents both opportunities and risks.
This case study highlights the importance of agents in every field understanding the complexities and implications of diversity in education. In addition, if the key competencies genuinely seek to enhance both vocational and social justice outcomes for a more cohesive and equitable society, then education for diversity would seem to be important.
This research contributes new knowledge in relation to the process of curriculum design, highlighting the impact of a unique socio-political context on the interpretation of a curriculum construct, and the implications of ‘valued’ attitudes and behaviours of the key competencies on diverse students. It provides an example of how Bernstein’s (2000) theory of the pedagogical device can be used to identify important influences and processes that impact on the different stages of a curriculum design and implementation process. It also illustrates how the device can be usefully complemented by another theory, in this case Fraser’s (1989) needs discourse theory, to examine more closely the discourse that relates to a particular lens of the research.

year: 2020