title: Effect of winter cover crops on nutrition and weeds of maize

authors: Sakala, Aaron

subjects: cover crops

abstract: Cover crops are being used in New Zealand to manage soil nutrients and weeds and can have positive or negative effects on the growth of the following main crop. 
This study investigated the causes of lower yield of maize following a ryegrass cover crop compared to fallow or other cover crops at the Foundation for Arable Research Northern Crop Research site. Cover crops were sown in mixtures faba (Vicia faba L.), gland clover (Trifolium glanduliferum Boiss.) and rye (Lolium perenne L.) with fallow as a control and followed by maize. The effects on soil carbon to nitrogen ratios, and maize growth, yield and nutrition were monitored. Additional experiments in the laboratory and glasshouse investigated the effect of cover crops on weed seed germination. 
Winter cover crops affected nutrient dynamics during growth of the maize crop. The total soil carbon to nitrogen (CN) ratio decreased as the proportion of clover in the cover crop mix increased. In the fallow and clover treatments nutrients were available earlier for maize to grow rapidly, resulting in higher yields compared to the rye and rye faba treatments. In the rye treatment, the CN ratio had fallen and nutrients had become available to the crop by harvest time, resulting in lower maize tissue CN ratios and higher tissue nutrient contents. Rye had a clear effect on the CN ratio in the cover crop mix whether sown at full rate or half rate. Rye also appeared to suppress clover and faba in the mixed treatments, possibly reducing the potential for supplementation of nutrients through the nitrogen fixation process. A clover-based cover crop was better than a rye-based cover crop, probably because it resulted in a lower soil CN ratio and higher extractable soil nitrogen at the time of establishment of the main crop, and may therefore release nutrients faster for the benefit of the main crop. 
A laboratory experiment tested the inhibition effect of cover crop extracts on the germination of weed and crop species. Five gram aliquots of cover crop powder were soaked for 24 hours in 100 ml of water and the filtered extracts diluted before application to seeds of a range of test species. Cover crop extracts almost always inhibited seed germination, by up to approximately 40%, but the inhibitory effects on seed germination varied with the species of cover crop and the test species. Serial dilution of extracts indicated that there was a dose response effect in the level of germination suppression by the cover crop species. Clover had the largest potential for reducing the weed and crop species germination and therefore was the most promising cover crop for exhibiting a true allelopathic effect on weed seed germination.
To further test the inhibition effect of clover and rye cover crops on germination of weed and crop species in the soil, root and shoot residues were tested on seeds of weed and crop species planted in pots. Root residues inhibited germination of volunteer and planted test species more than shoot residues, possibly because of a higher availability of inhibitory compounds, or because of differences in the time of setting up the root and shoot pots. The inhibitory effect on germination exerted by cover crop varied with the test species. This was shown by inhibition affecting one species but not others, which might suggest that some species were more sensitive to a particular cover crop treatment. Cover crop roots were more likely to affect germination, but cover crop shoots were more likely to reduce the growth of planted test species. The lack of a root effect on growth might be explained by loss or dilution of any allelopathic compounds that affected germination, or because their mode of action was specific to germination.
Overall, clover root and shoot treatments have the potential to inhibit germination and growth of weed and crop species. The results support the hypothesis that clover either as a crop residue or as an extract has a higher potential to suppress germination of other species compared to rye and is the most promising cover crop for exhibiting a true allelopathic effect on germination of weed seeds. It was also shown that a clover-based winter cover crop might be better than a rye-based cover crop in terms of its effects on nutrient availability to the main crop. The results have implications for the decision to keep crop residues in the field to reduce the germination and growth of weeds. There may be an economic benefit from using cover crop shoots for other activities (e.g. silage or cut-and-carry forage) while still benefiting from the weed controlling effects of roots residues that are left in the field. Further experiments on the effects of winter cover crops for maize production in New Zealand are recommended.

text: Effect of winter cover crops on nutrition and weeds of maize Cover crops are being used in New Zealand to manage soil nutrients and weeds and can have positive or negative effects on the growth of the following main crop. 
This study investigated the causes of lower yield of maize following a ryegrass cover crop compared to fallow or other cover crops at the Foundation for Arable Research Northern Crop Research site. Cover crops were sown in mixtures faba (Vicia faba L.), gland clover (Trifolium glanduliferum Boiss.) and rye (Lolium perenne L.) with fallow as a control and followed by maize. The effects on soil carbon to nitrogen ratios, and maize growth, yield and nutrition were monitored. Additional experiments in the laboratory and glasshouse investigated the effect of cover crops on weed seed germination. 
Winter cover crops affected nutrient dynamics during growth of the maize crop. The total soil carbon to nitrogen (CN) ratio decreased as the proportion of clover in the cover crop mix increased. In the fallow and clover treatments nutrients were available earlier for maize to grow rapidly, resulting in higher yields compared to the rye and rye faba treatments. In the rye treatment, the CN ratio had fallen and nutrients had become available to the crop by harvest time, resulting in lower maize tissue CN ratios and higher tissue nutrient contents. Rye had a clear effect on the CN ratio in the cover crop mix whether sown at full rate or half rate. Rye also appeared to suppress clover and faba in the mixed treatments, possibly reducing the potential for supplementation of nutrients through the nitrogen fixation process. A clover-based cover crop was better than a rye-based cover crop, probably because it resulted in a lower soil CN ratio and higher extractable soil nitrogen at the time of establishment of the main crop, and may therefore release nutrients faster for the benefit of the main crop. 
A laboratory experiment tested the inhibition effect of cover crop extracts on the germination of weed and crop species. Five gram aliquots of cover crop powder were soaked for 24 hours in 100 ml of water and the filtered extracts diluted before application to seeds of a range of test species. Cover crop extracts almost always inhibited seed germination, by up to approximately 40%, but the inhibitory effects on seed germination varied with the species of cover crop and the test species. Serial dilution of extracts indicated that there was a dose response effect in the level of germination suppression by the cover crop species. Clover had the largest potential for reducing the weed and crop species germination and therefore was the most promising cover crop for exhibiting a true allelopathic effect on weed seed germination.
To further test the inhibition effect of clover and rye cover crops on germination of weed and crop species in the soil, root and shoot residues were tested on seeds of weed and crop species planted in pots. Root residues inhibited germination of volunteer and planted test species more than shoot residues, possibly because of a higher availability of inhibitory compounds, or because of differences in the time of setting up the root and shoot pots. The inhibitory effect on germination exerted by cover crop varied with the test species. This was shown by inhibition affecting one species but not others, which might suggest that some species were more sensitive to a particular cover crop treatment. Cover crop roots were more likely to affect germination, but cover crop shoots were more likely to reduce the growth of planted test species. The lack of a root effect on growth might be explained by loss or dilution of any allelopathic compounds that affected germination, or because their mode of action was specific to germination.
Overall, clover root and shoot treatments have the potential to inhibit germination and growth of weed and crop species. The results support the hypothesis that clover either as a crop residue or as an extract has a higher potential to suppress germination of other species compared to rye and is the most promising cover crop for exhibiting a true allelopathic effect on germination of weed seeds. It was also shown that a clover-based winter cover crop might be better than a rye-based cover crop in terms of its effects on nutrient availability to the main crop. The results have implications for the decision to keep crop residues in the field to reduce the germination and growth of weeds. There may be an economic benefit from using cover crop shoots for other activities (e.g. silage or cut-and-carry forage) while still benefiting from the weed controlling effects of roots residues that are left in the field. Further experiments on the effects of winter cover crops for maize production in New Zealand are recommended.

year: 2019

title: Chinese postgraduates' explanation of the sources of sentence initial bundles in their thesis writing

authors: Li, Liang

subjects: computer science

abstract: Lexical bundles, recurrent multiword combinations in a register, are extremely common and important discourse building blocks in academic writing. An increasing number of studies have investigated lexical bundles in academic writing in recent years, but few studies have explored L2 learners’ interpretations of their own bundle production, particularly sentence initial bundle production. Investigating the sources that have appeared to influence learners’ choices and knowledge of bundles is important as it complements what we know about the structural and functional features of lexical bundles and provides useful first-hand information for second language writing pedagogy. The present study interviewed five Chinese postgraduate students to probe possible reasons for their use of the typical sentence initial bundles identified in the self-built Chinese Masters and PhD thesis corpora. The interviews revealed diverse explanations including interlingual transfer, classroom learning, noticing in reading, a lack of rhetorical confidence, and misunderstanding of rhetorical conventions. The results suggest the need for raising students’ awareness of the common sentence starters in postgraduate academic writing, increasing their confidence as student writers, familiarizing them with rhetorical conventions, and incorporating effective corpus-based tools into pedagogical practices.

text: Chinese postgraduates' explanation of the sources of sentence initial bundles in their thesis writing Lexical bundles, recurrent multiword combinations in a register, are extremely common and important discourse building blocks in academic writing. An increasing number of studies have investigated lexical bundles in academic writing in recent years, but few studies have explored L2 learners’ interpretations of their own bundle production, particularly sentence initial bundle production. Investigating the sources that have appeared to influence learners’ choices and knowledge of bundles is important as it complements what we know about the structural and functional features of lexical bundles and provides useful first-hand information for second language writing pedagogy. The present study interviewed five Chinese postgraduate students to probe possible reasons for their use of the typical sentence initial bundles identified in the self-built Chinese Masters and PhD thesis corpora. The interviews revealed diverse explanations including interlingual transfer, classroom learning, noticing in reading, a lack of rhetorical confidence, and misunderstanding of rhetorical conventions. The results suggest the need for raising students’ awareness of the common sentence starters in postgraduate academic writing, increasing their confidence as student writers, familiarizing them with rhetorical conventions, and incorporating effective corpus-based tools into pedagogical practices.

year: 2018

title: Taonga tuku iho: Intergenerational transfer of raranga and whatu

authors: Te Kanawa, Kahutoi Mere

subjects: Intergenerational Knowledge Transfer through Raranga and Whatu

abstract: The intergenerational transfer of Māori weaving knowledge is based on the succession and continuum of raranga and whatu skills. This study will show how the genesis of inherent know-ledge and skills imbues the nature and continuity of our own cultural practice, especially specific to raranga, whatu and wider areas such as tukutuku. Kaupapa Māori research methodology u-sing the framework of Te Aho tapu provides the methodological approach for this research.  In particular I draw upon the experiences of our whānau and the pedagogical processes used by five generations to define the fundamental underpinnings of a Kaupapa Māori approach to knowledge transfer within, and between, generations of whānau and hapū. Another important driving force behind this work is a need to express the actual practice of intergenerational trans-mission as evidence of the centrality of ako or Māori pedagogy in terms of raranga.
The research questions I pose, are based around the difference between, mōhiotanga, mātauranga, māramatanga and mahi within in a raranga and whatu context.
What is the importance of indigenous intergenerational knowledge transmission through raranga/whatu?
Is it possible to understand the skills and intricacies of an artefact that gives us knew, yet old knowledge from the expertise left by our kairaranga?
The creative component of this research includes as a feature the reproduction of a kete pūkoro, also known as a pututu, especially in the northern tribal dialects (Williams, 2005). The pūkoro is held in the the Otago Museum and the kairaranga has not been identified. The Ngai Tahu dialect emphasise this kete is a pūkoro (Dr J.Williams, personal communication, 2015) which is the term I utilise throughout this research as an acknowledgement to the kairaranga from the southern region of Otakau. A kete pūkoro is a finely woven kete which was used to squeeze the juice from the tutu berries (Beever, 1991). The pūkoro is the only known such taonga that exists and is so fragile that it‘s no longer exhibited. The fragility of the piece is prone to damage through touch, movement and light exposure, so is kept in a temperature controlled draw in the Otago Museum, Dunedin. The uniqueness of this piece of work is the construction, form and the function. The pūkoro sits at the centre of the practice for this research as an example of intergenerational knowledge transfer of the taonga. The raranga technique will be analyzed and the function and form will be replicated to understand more about the kairaranga through the making of the pūkoro. The artefact will be researched and analyzed considering every detail possible, documenting, and reflecting on the processes. Whilst the pūkoro is the centre piece that shows the refinement of knowledge of the kairaranga, it demonstrated the skills and ability to produce a taonga that could be used as a practical kete for sieving out the poisonous kernels of the tutu, only allowing the juice to be strained through it.
Why the pūkoro?
When I first came upon the pūkoro, it was only by osmosis. The pūkoro was stored away in a dark area, and I was attracted to the space where it was stored while viewing kete whakairo that were put out for display for me. I was the kaiako at Otago University for the Toi Onamata classes within Te Tumu, the Māori and Pacific studies Faculty. I arranged with the museum curator to view the kete whakairo in their collection.
I felt drawn to that part of the museum after feeling a strong sense of needing to see what was kept in the dark. I had a strong feeling and attraction to viewing what was kept in the dark, so I asked the curator if I could see what was kept in that space. I was told it was a very fragile kete made of harakeke which they considered was an un-usual shape and it was noted that it was a very old piece. and that the shape of it was unusual, and it was a very old. This made me more curious, as there was something particularly that I was alluring about me to this taonga.
When closely analysing the piece, I realised I could not see the commencement or completion. With closer inspection of the construction, it became more obvious to me, as a kairaranga that the skills and technical detail of horizontal and vertical twills of overlaying patterns used, were woven that way for a purpose.
From that first viewing, I was able to tell the curator, exactly what this artefact was used for, what material it was made out of and that the technical construction of the kete pūkoro was different from others I had viewed before.
It was this moment in time, that I had an epiphany, that this piece of work could tell a story of the unknown kairaranga. I decided right from that point, that I would try my best to bring to light the technical ability of the raranga weave and why it was constructed in such a way.
Like anything, further research needed to be done on the pūkoro, to understand the purpose of this fine piece of work. This was the impetus of my study. The questions I asked myself were:
Why was I attracted to this dark space? For me it was my wairuatanga, alluring me to a space with a deep sense that there was a reason I needed to be there at that time. It was that strong spiritual belief that enabled me to listen to that and to go into the space the pūkoro was being held.
How did I know and understand the construction of the kete pūkoro?. This was about my Mōhiotanga, using my own tacit knowledge, years of observation and passion to engage with a taonga left from a kairaranga of the past century.
What was the purpose of reconstructing this taonga? – This is about the mātauranga imbued in the construction of the Kete Pūkoro. It was to engage in further research to find out more detail beyond what I already knew.
How can I best share this knowledge and practice? – This is about Māramatanga, as I have been always taught, there is no point knowing a skill, and information if it is not shared.

text: Taonga tuku iho: Intergenerational transfer of raranga and whatu The intergenerational transfer of Māori weaving knowledge is based on the succession and continuum of raranga and whatu skills. This study will show how the genesis of inherent know-ledge and skills imbues the nature and continuity of our own cultural practice, especially specific to raranga, whatu and wider areas such as tukutuku. Kaupapa Māori research methodology u-sing the framework of Te Aho tapu provides the methodological approach for this research.  In particular I draw upon the experiences of our whānau and the pedagogical processes used by five generations to define the fundamental underpinnings of a Kaupapa Māori approach to knowledge transfer within, and between, generations of whānau and hapū. Another important driving force behind this work is a need to express the actual practice of intergenerational trans-mission as evidence of the centrality of ako or Māori pedagogy in terms of raranga.
The research questions I pose, are based around the difference between, mōhiotanga, mātauranga, māramatanga and mahi within in a raranga and whatu context.
What is the importance of indigenous intergenerational knowledge transmission through raranga/whatu?
Is it possible to understand the skills and intricacies of an artefact that gives us knew, yet old knowledge from the expertise left by our kairaranga?
The creative component of this research includes as a feature the reproduction of a kete pūkoro, also known as a pututu, especially in the northern tribal dialects (Williams, 2005). The pūkoro is held in the the Otago Museum and the kairaranga has not been identified. The Ngai Tahu dialect emphasise this kete is a pūkoro (Dr J.Williams, personal communication, 2015) which is the term I utilise throughout this research as an acknowledgement to the kairaranga from the southern region of Otakau. A kete pūkoro is a finely woven kete which was used to squeeze the juice from the tutu berries (Beever, 1991). The pūkoro is the only known such taonga that exists and is so fragile that it‘s no longer exhibited. The fragility of the piece is prone to damage through touch, movement and light exposure, so is kept in a temperature controlled draw in the Otago Museum, Dunedin. The uniqueness of this piece of work is the construction, form and the function. The pūkoro sits at the centre of the practice for this research as an example of intergenerational knowledge transfer of the taonga. The raranga technique will be analyzed and the function and form will be replicated to understand more about the kairaranga through the making of the pūkoro. The artefact will be researched and analyzed considering every detail possible, documenting, and reflecting on the processes. Whilst the pūkoro is the centre piece that shows the refinement of knowledge of the kairaranga, it demonstrated the skills and ability to produce a taonga that could be used as a practical kete for sieving out the poisonous kernels of the tutu, only allowing the juice to be strained through it.
Why the pūkoro?
When I first came upon the pūkoro, it was only by osmosis. The pūkoro was stored away in a dark area, and I was attracted to the space where it was stored while viewing kete whakairo that were put out for display for me. I was the kaiako at Otago University for the Toi Onamata classes within Te Tumu, the Māori and Pacific studies Faculty. I arranged with the museum curator to view the kete whakairo in their collection.
I felt drawn to that part of the museum after feeling a strong sense of needing to see what was kept in the dark. I had a strong feeling and attraction to viewing what was kept in the dark, so I asked the curator if I could see what was kept in that space. I was told it was a very fragile kete made of harakeke which they considered was an un-usual shape and it was noted that it was a very old piece. and that the shape of it was unusual, and it was a very old. This made me more curious, as there was something particularly that I was alluring about me to this taonga.
When closely analysing the piece, I realised I could not see the commencement or completion. With closer inspection of the construction, it became more obvious to me, as a kairaranga that the skills and technical detail of horizontal and vertical twills of overlaying patterns used, were woven that way for a purpose.
From that first viewing, I was able to tell the curator, exactly what this artefact was used for, what material it was made out of and that the technical construction of the kete pūkoro was different from others I had viewed before.
It was this moment in time, that I had an epiphany, that this piece of work could tell a story of the unknown kairaranga. I decided right from that point, that I would try my best to bring to light the technical ability of the raranga weave and why it was constructed in such a way.
Like anything, further research needed to be done on the pūkoro, to understand the purpose of this fine piece of work. This was the impetus of my study. The questions I asked myself were:
Why was I attracted to this dark space? For me it was my wairuatanga, alluring me to a space with a deep sense that there was a reason I needed to be there at that time. It was that strong spiritual belief that enabled me to listen to that and to go into the space the pūkoro was being held.
How did I know and understand the construction of the kete pūkoro?. This was about my Mōhiotanga, using my own tacit knowledge, years of observation and passion to engage with a taonga left from a kairaranga of the past century.
What was the purpose of reconstructing this taonga? – This is about the mātauranga imbued in the construction of the Kete Pūkoro. It was to engage in further research to find out more detail beyond what I already knew.
How can I best share this knowledge and practice? – This is about Māramatanga, as I have been always taught, there is no point knowing a skill, and information if it is not shared.

year: 2022