INTRODUCTION It is common in agronomic experiments to have data on a range of plant traits across treatments comprising levels of one factor,combinations of two or more factors,and/or repeat measures across time or so...INTRODUCTION It is common in agronomic experiments to have data on a range of plant traits across treatments comprising levels of one factor,combinations of two or more factors,and/or repeat measures across time or some other entity such as soil depth.In this case,traditional univariate ANOVA,which examines the measured traits one by one and is amenable to the development of complex statistical models,risks missing overarching patterns that might emerge if the data were analyzed as an interacting set where multivariate trait associations can be elucidated.Multivariate analyses,on the other hand,do consider multiple traits simultaneously but often struggle to accommodate complex treatment combinations.For more complex agronomic data sets,the writer has often used principal component analysis(PCA)as a data exploration and pattern detection tool,to identify the salient features of a data set from a multivariate perspective.This editorial aims to introduce PCA to readers unfamiliar with it,illustrate by example how PCA works,and to demonstrate the versatility of PCA by outlining some applications of PCA that the writer has developed for particular data sets during a 40‐year research career.It is not possible in a brief editorial to provide a textbook‐level and statistically robust coverage of the topic of PCA;detailed expositions of PCA have been produced by Joliffe(1986,2002)and many others.A motivation to write has been that I often see PCA results published in ways that reflect incomplete understanding of its mathematical properties and behavior.However,these notes are not intended as a substitute for consultation with a professional statistician.展开更多
In this editorial,I will attempt to capture some thoughts for reflection and discussion on the science publication process,as it currently presents to researchers.Publication-communication of findings-is both a natura...In this editorial,I will attempt to capture some thoughts for reflection and discussion on the science publication process,as it currently presents to researchers.Publication-communication of findings-is both a natural sequel to and an integral part of research,and critical to researchers'career development.Unfortunately,while there are many positives,there are also some significant emerging issues needing to be resolved in today's science publication sector.展开更多
This editorial sets out my personal professional journey with metabolic energy budgeting(MEB)and concludes that the methodology deserves to be more widely used.I compiled my first metabolic energy budget for calculati...This editorial sets out my personal professional journey with metabolic energy budgeting(MEB)and concludes that the methodology deserves to be more widely used.I compiled my first metabolic energy budget for calculation of feed requirements of ruminants grazing pasture around 30 years ago when a colleague left our Department at Massey University,New Zealand,and I took over his teaching.The student assignment for my colleague's section of the course presented details of cow numbers on a dairy farm in each month of the year,their body weights and milk production on the one hand and the pasture growth and available supplementary feed sources and quantities on the other hand.Class members were required to compile,in a Microsoft Excel spreadsheet,a feed budget for the farm showing the animal feed requirements calculated using metabolic energy equations and the combinations of different feeds used to meet those requirements in different months of the year,all in common units of kg DMha^(-1) day^(-1).To decide if I would adopt my colleague's assignment in my own teaching of his course,or develop an alternative of my own,I set aside an evening after dinner and completed the assignment myself.展开更多
This editorial revisits the topic of plant allometry.This topic is the subject of a large volume of literature,so coverage here is necessarily selective,focusing on points of interest for grassland research.In my fina...This editorial revisits the topic of plant allometry.This topic is the subject of a large volume of literature,so coverage here is necessarily selective,focusing on points of interest for grassland research.In my final year of undergraduate study(1983),three different courses I took included a module based on Yoda's 1963 study,“Self-thinning in overcrowded pure stands”(Yoda et al.,1963).Principles elucidated in that paper were seen as fundamental to the theoretical understanding of crop-specific husbandry recommendations for yield optimization.展开更多
Background:Oil palm is a tropical crop with worldwide plantings approaching 20 million ha and large areas in Indonesia,Malaysia and Thailand.The plantations are readily managed as silvopastoral systems incorporating c...Background:Oil palm is a tropical crop with worldwide plantings approaching 20 million ha and large areas in Indonesia,Malaysia and Thailand.The plantations are readily managed as silvopastoral systems incorporating cattle grazing(Oil Palm Silvopastoral System for Cattle,OPSC)but there is a need for analytical tools and data to understand system herbage supply and feed conversion efficiency(FCE).Methods:Metabolic energy budgeting was used to estimate herbage harvested by cattle in three OPSC subsystems,9 and 12 years after oil palm establishment,and FCE of the subsystems was determined.Understorey herbage was also analysed for nutritive value,botanical composition and herbage accumulation within one grazing‐regrowth cycle.Results:The herbage‐harvested estimate was 2.0−2.4 t dry matter(DM)ha^(-1) year^(-1) for 9 year old subsystems and 1.4-1.7 tDMha^(-1) year^(-1) for a 12 year old subsystem.Herbage metabolisable energy(ME)was 8.3−8.5 MJ kg^(-1) DM and crude protein(CP)was 15%-16%DM.FCE values for subsystems ranged from 32 to 94 kg DM kg^(-1) liveweight‐gain.Conclusions:Herbage DM yield is declining,while herbage ME is marginal but CP is adequate.FCE is suboptimal but can be optimised by defining the trajectory of declining herbage production with canopy closure as plantations age and matching stocking rate to herbage supply using a comparativestocking‐rate‐type statistic.展开更多
New Zealand is well known for export of meat and dairy products from low cost pastoral systems. These farm systems are continually evolving for increased efficiency, in part through the use of metabolic energy modelin...New Zealand is well known for export of meat and dairy products from low cost pastoral systems. These farm systems are continually evolving for increased efficiency, in part through the use of metabolic energy modeling tools by farmers and farm consultants to explore alternative farm system configurations and identify new efficiencies. One recent innovation is the introduction of a herb pasture area, such as plantain. We used metabolic energy modeling to quantify seasonal feed flows in two successive years in a New Zealand hill country farm system, and to analyze the impact of the introduction of an area of plantain. Models employed were a self-built Microsoft Excel spreadsheet and a commercial New Zealand farm systems modeling package, FARMAX.Herbage production, animal performance and financial results for a base farm scenario created from the average of survey data for hill farms in the southern North Island, and the same farm with 10% and 20% of the area in plantain for the years 2010–2011 and 2011–2012 were modeled. The self-built model performed similarly to the commercial model. The system configuration of the base farm stockpiles surplus autumn feed for release to animals in winter and also incorporates flexibility that confers resilience to interannual weather variation through varying dates animals are purchased or sold. The introduction of an area of plantain was predicted to increase herbage production, animal performance and financial returns.The predicted benefit was higher for the year 2010–2011 where a drought occurred in summer than for the following year with higher summer rainfall. This demonstrates the profitability of introducing a plantain area to New Zealand hill farm systems, and suggests plantain will assist to mitigate adverse effects of warmer and drier summer conditions associated with current climate change trends.展开更多
Background:This study investigated the effects of daughter tiller removal on parent tiller development in Lolium perenne.Methods:Plants of L.perenne were grown hydroponically to allow separation of roots by phytomer p...Background:This study investigated the effects of daughter tiller removal on parent tiller development in Lolium perenne.Methods:Plants of L.perenne were grown hydroponically to allow separation of roots by phytomer position on the tiller axis and allowed to form two daughter tillers.In Experiment 1,adult daughter tillers were excised and effects on subsequent main tiller growth were observed for 16 days,on average.In Experiment 2,the growth of main tillers with or without daughter tillers was compared over 90–100 days.Two cultivars,‘Alto’bred from New Zealand germplasm and‘Aberdart’bred from United Kingdom germplasm were tested.Results:Excision of adult daughter tillers reduced the dry weight of older roots at the base of parent tiller axes and accelerated new phytomer appearance.Preventing tillers from forming daughter tillers by new tiller excision resulted in increased individual leaf and root dry weight in tillers without daughter tillers.Conclusions:The data indicated that daughter tillers contributed substrate for root development of their parent tillers.The presence of daughter tillers reduced the size of their main tiller but greatly enhanced whole plant yield.展开更多
When I was born in 1951,earth's atmospheric CO_(2)concentration was around 310 mg kg^(-1)(i.e.,parts per million),with an annual rate of increase averaging some 0.8 mg kg^(-1)per year(NOAA,2024).When I commenced m...When I was born in 1951,earth's atmospheric CO_(2)concentration was around 310 mg kg^(-1)(i.e.,parts per million),with an annual rate of increase averaging some 0.8 mg kg^(-1)per year(NOAA,2024).When I commenced my research career in 1984,atmospheric CO_(2)concentration was 340 mg kg^(-1),with a decadal average increase for the 1980s of 1.6 mg kg^(-1)per year.In August 2024,atmospheric CO_(2)concentration was reported as 423 mg kg^(-1),with the decadal mean annual increase for the 2010s nearing 2.5 mg kg^(-1)per year(NOAA,2024).In the same period,Earth's human population has increased from 2.5 to 8.0 billion.Science says the increase in atmospheric CO_(2),together with other trace gases,notably methane and nitrous oxide,will decrease the proportion of insolation received by earth that is reflected back into space,and so warm the planet.The expectation of global temperature increase is the climate change story;it has been told repeatedly in many forums such as the IPCC documents and debated at great length by“believers”and“deniers.”I will not dwell on it here.展开更多
It has been an observation of mine over the last few years that in articles dealing with animal allocation to pasture or rangeland in various countries,there are differences between authors in the units used for some ...It has been an observation of mine over the last few years that in articles dealing with animal allocation to pasture or rangeland in various countries,there are differences between authors in the units used for some common terms such as stocking rate,stocking density or grazing intensity when reporting experiment treat-ments and data.Some authors are using units incorrectly,in my opinion.Hence,I thought that it would be useful to write an editorial for Grassland Research,setting out a logical framework and units for authors'consideration when preparing manuscripts on this topic.This is neither an in-depth review nor an attempt to redefine terms and concepts,but simply a call for authors to use units correctly within the currently accepted framework and definitions.展开更多
文摘INTRODUCTION It is common in agronomic experiments to have data on a range of plant traits across treatments comprising levels of one factor,combinations of two or more factors,and/or repeat measures across time or some other entity such as soil depth.In this case,traditional univariate ANOVA,which examines the measured traits one by one and is amenable to the development of complex statistical models,risks missing overarching patterns that might emerge if the data were analyzed as an interacting set where multivariate trait associations can be elucidated.Multivariate analyses,on the other hand,do consider multiple traits simultaneously but often struggle to accommodate complex treatment combinations.For more complex agronomic data sets,the writer has often used principal component analysis(PCA)as a data exploration and pattern detection tool,to identify the salient features of a data set from a multivariate perspective.This editorial aims to introduce PCA to readers unfamiliar with it,illustrate by example how PCA works,and to demonstrate the versatility of PCA by outlining some applications of PCA that the writer has developed for particular data sets during a 40‐year research career.It is not possible in a brief editorial to provide a textbook‐level and statistically robust coverage of the topic of PCA;detailed expositions of PCA have been produced by Joliffe(1986,2002)and many others.A motivation to write has been that I often see PCA results published in ways that reflect incomplete understanding of its mathematical properties and behavior.However,these notes are not intended as a substitute for consultation with a professional statistician.
文摘In this editorial,I will attempt to capture some thoughts for reflection and discussion on the science publication process,as it currently presents to researchers.Publication-communication of findings-is both a natural sequel to and an integral part of research,and critical to researchers'career development.Unfortunately,while there are many positives,there are also some significant emerging issues needing to be resolved in today's science publication sector.
文摘This editorial sets out my personal professional journey with metabolic energy budgeting(MEB)and concludes that the methodology deserves to be more widely used.I compiled my first metabolic energy budget for calculation of feed requirements of ruminants grazing pasture around 30 years ago when a colleague left our Department at Massey University,New Zealand,and I took over his teaching.The student assignment for my colleague's section of the course presented details of cow numbers on a dairy farm in each month of the year,their body weights and milk production on the one hand and the pasture growth and available supplementary feed sources and quantities on the other hand.Class members were required to compile,in a Microsoft Excel spreadsheet,a feed budget for the farm showing the animal feed requirements calculated using metabolic energy equations and the combinations of different feeds used to meet those requirements in different months of the year,all in common units of kg DMha^(-1) day^(-1).To decide if I would adopt my colleague's assignment in my own teaching of his course,or develop an alternative of my own,I set aside an evening after dinner and completed the assignment myself.
文摘This editorial revisits the topic of plant allometry.This topic is the subject of a large volume of literature,so coverage here is necessarily selective,focusing on points of interest for grassland research.In my final year of undergraduate study(1983),three different courses I took included a module based on Yoda's 1963 study,“Self-thinning in overcrowded pure stands”(Yoda et al.,1963).Principles elucidated in that paper were seen as fundamental to the theoretical understanding of crop-specific husbandry recommendations for yield optimization.
基金The Government of Malaysia through Universiti Malaysia Sabah and the Ministry of Higher Education of Malaysia,Grant/Award Numbers:GKP0019‐STWN‐2016,SDK0010‐2017。
文摘Background:Oil palm is a tropical crop with worldwide plantings approaching 20 million ha and large areas in Indonesia,Malaysia and Thailand.The plantations are readily managed as silvopastoral systems incorporating cattle grazing(Oil Palm Silvopastoral System for Cattle,OPSC)but there is a need for analytical tools and data to understand system herbage supply and feed conversion efficiency(FCE).Methods:Metabolic energy budgeting was used to estimate herbage harvested by cattle in three OPSC subsystems,9 and 12 years after oil palm establishment,and FCE of the subsystems was determined.Understorey herbage was also analysed for nutritive value,botanical composition and herbage accumulation within one grazing‐regrowth cycle.Results:The herbage‐harvested estimate was 2.0−2.4 t dry matter(DM)ha^(-1) year^(-1) for 9 year old subsystems and 1.4-1.7 tDMha^(-1) year^(-1) for a 12 year old subsystem.Herbage metabolisable energy(ME)was 8.3−8.5 MJ kg^(-1) DM and crude protein(CP)was 15%-16%DM.FCE values for subsystems ranged from 32 to 94 kg DM kg^(-1) liveweight‐gain.Conclusions:Herbage DM yield is declining,while herbage ME is marginal but CP is adequate.FCE is suboptimal but can be optimised by defining the trajectory of declining herbage production with canopy closure as plantations age and matching stocking rate to herbage supply using a comparativestocking‐rate‐type statistic.
文摘New Zealand is well known for export of meat and dairy products from low cost pastoral systems. These farm systems are continually evolving for increased efficiency, in part through the use of metabolic energy modeling tools by farmers and farm consultants to explore alternative farm system configurations and identify new efficiencies. One recent innovation is the introduction of a herb pasture area, such as plantain. We used metabolic energy modeling to quantify seasonal feed flows in two successive years in a New Zealand hill country farm system, and to analyze the impact of the introduction of an area of plantain. Models employed were a self-built Microsoft Excel spreadsheet and a commercial New Zealand farm systems modeling package, FARMAX.Herbage production, animal performance and financial results for a base farm scenario created from the average of survey data for hill farms in the southern North Island, and the same farm with 10% and 20% of the area in plantain for the years 2010–2011 and 2011–2012 were modeled. The self-built model performed similarly to the commercial model. The system configuration of the base farm stockpiles surplus autumn feed for release to animals in winter and also incorporates flexibility that confers resilience to interannual weather variation through varying dates animals are purchased or sold. The introduction of an area of plantain was predicted to increase herbage production, animal performance and financial returns.The predicted benefit was higher for the year 2010–2011 where a drought occurred in summer than for the following year with higher summer rainfall. This demonstrates the profitability of introducing a plantain area to New Zealand hill farm systems, and suggests plantain will assist to mitigate adverse effects of warmer and drier summer conditions associated with current climate change trends.
基金supported by a‘Massey University Vice‐Chancellor's Doctoral Scholarship’and study leave from Bangladesh Agricultural University.
文摘Background:This study investigated the effects of daughter tiller removal on parent tiller development in Lolium perenne.Methods:Plants of L.perenne were grown hydroponically to allow separation of roots by phytomer position on the tiller axis and allowed to form two daughter tillers.In Experiment 1,adult daughter tillers were excised and effects on subsequent main tiller growth were observed for 16 days,on average.In Experiment 2,the growth of main tillers with or without daughter tillers was compared over 90–100 days.Two cultivars,‘Alto’bred from New Zealand germplasm and‘Aberdart’bred from United Kingdom germplasm were tested.Results:Excision of adult daughter tillers reduced the dry weight of older roots at the base of parent tiller axes and accelerated new phytomer appearance.Preventing tillers from forming daughter tillers by new tiller excision resulted in increased individual leaf and root dry weight in tillers without daughter tillers.Conclusions:The data indicated that daughter tillers contributed substrate for root development of their parent tillers.The presence of daughter tillers reduced the size of their main tiller but greatly enhanced whole plant yield.
文摘When I was born in 1951,earth's atmospheric CO_(2)concentration was around 310 mg kg^(-1)(i.e.,parts per million),with an annual rate of increase averaging some 0.8 mg kg^(-1)per year(NOAA,2024).When I commenced my research career in 1984,atmospheric CO_(2)concentration was 340 mg kg^(-1),with a decadal average increase for the 1980s of 1.6 mg kg^(-1)per year.In August 2024,atmospheric CO_(2)concentration was reported as 423 mg kg^(-1),with the decadal mean annual increase for the 2010s nearing 2.5 mg kg^(-1)per year(NOAA,2024).In the same period,Earth's human population has increased from 2.5 to 8.0 billion.Science says the increase in atmospheric CO_(2),together with other trace gases,notably methane and nitrous oxide,will decrease the proportion of insolation received by earth that is reflected back into space,and so warm the planet.The expectation of global temperature increase is the climate change story;it has been told repeatedly in many forums such as the IPCC documents and debated at great length by“believers”and“deniers.”I will not dwell on it here.
文摘It has been an observation of mine over the last few years that in articles dealing with animal allocation to pasture or rangeland in various countries,there are differences between authors in the units used for some common terms such as stocking rate,stocking density or grazing intensity when reporting experiment treat-ments and data.Some authors are using units incorrectly,in my opinion.Hence,I thought that it would be useful to write an editorial for Grassland Research,setting out a logical framework and units for authors'consideration when preparing manuscripts on this topic.This is neither an in-depth review nor an attempt to redefine terms and concepts,but simply a call for authors to use units correctly within the currently accepted framework and definitions.
