Identification of yield deficits early in the growing season for cereal crops (e.g., Triticum aes... more Identification of yield deficits early in the growing season for cereal crops (e.g., Triticum aestivum) could help to identify more precise agronomic strategies for intervention to manage production. We investigated how effective crop canopy properties, including leaf area index (LAI), leaf chlorophyll content, and canopy height, are as predictors of winter wheat yield over various lead times. Models were calibrated and validated on fertiliser trials over two years in fields in the UK. Correlations of LAI and plant height with yield were stronger than for yield and chlorophyll content. Yield prediction models calibrated in one year and tested on another suggested that LAI and height provided the most robust outcomes. Linear models had equal or smaller validation errors than machine learning. The information content of data for yield prediction degraded strongly with time before harvest, and in application to years not included in the calibration. Thus, impact of soil and weather var...
Leaf area index (LAI) estimates can inform decision-making in crop management. The European Space... more Leaf area index (LAI) estimates can inform decision-making in crop management. The European Space Agency’s Sentinel-2 satellite, with observations in the red-edge spectral region, can monitor crops globally at sub-field spatial resolutions (10–20 m). However, satellite LAI estimates require calibration with ground measurements. Calibration is challenged by spatial heterogeneity and scale mismatches between field and satellite measurements. Unmanned Aerial Vehicles (UAVs), generating high-resolution (cm-scale) LAI estimates, provide intermediary observations that we use here to characterise uncertainty and reduce spatial scaling discrepancies between Sentinel-2 observations and field surveys. We use a novel UAV multispectral sensor that matches Sentinel-2 spectral bands, flown in conjunction with LAI ground measurements. UAV and field surveys were conducted on multiple dates—coinciding with different wheat growth stages—that corresponded to Sentinel-2 overpasses. We compared chloroph...
Climate, nitrogen (N) and leaf area index (LAI) are key determinants of crop yield. N additions c... more Climate, nitrogen (N) and leaf area index (LAI) are key determinants of crop yield. N additions can enhance yield but must be managed efficiently to reduce pollution. Complex process models estimate N status by simulating soil-crop N interactions, but such models require extensive inputs that are seldom available. Through model-data fusion (MDF), we combine climate and LAI time-series with an intermediate-complexity model to infer leaf N and yield. The DALEC-Crop model was calibrated for wheat leaf N and yields across field experiments covering N applications ranging from 0 to 200 kg N ha−1 in Scotland, UK. Requiring daily meteorological inputs, this model simulates crop C cycle responses to LAI, N and climate. The model, which includes a leaf N-dilution function, was calibrated across N treatments based on LAI observations, and tested at validation plots. We showed that a single parameterization varying only in leaf N could simulate LAI development and yield across all treatments—t...
An improved method for measuring soil N2O fluxes using a quantum cascade laser with a dynamic cha... more An improved method for measuring soil N2O fluxes using a quantum cascade laser with a dynamic chamber.
Atmospheric Chemistry and Physics Discussions, 2015
The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly ... more The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (N r) from human activities, estimated to be 193 Tg N yr −1 in 2010 which is approximately equal to the sum of biological N fixation in terrestrial and marine ecosystems. According to current trajectories, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 Tg N yr −1 by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion related emissions implemented. Some N cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of N r is the emission to the atmosphere of NH 3 , which is estimated to increase from 65 Tg N yr −1 in 2008 to 93 Tg N yr −1 in 2100 assuming a change in surface temperature of 5 • C even in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH 3 emissions to 132 Tg N yr −1. Another major change is the effect of changes in aerosol composition combined with changes in temperature. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH 4) 2 SO 4 in the 1970s to 1980s, and large reductions in emissions of SO 2 have removed most of the SO
chapter headings rather than an in-depth analysis. The book is, however, up-to-date in terms of t... more chapter headings rather than an in-depth analysis. The book is, however, up-to-date in terms of topic information and example data sets. However, most of these refer to IPM as practiced in the USA. This is a pity, because IPM is widely practiced globally, albeit on smaller scales than in the USA, for example, in many developing countries where pesticides and advanced technologies are often too expensive for farmers. Regarding specific chapters, I was particularly impressed with coverage of the use of biocontrol agents, breeding for pest or disease resistance, and the use of pheromones and plant derived semiochemicals. Chapters covering IPM case studies for cotton and field vegetables were also well presented and informative. In summary, the book is a good introduction to the many facets of IPM for university graduates but is perhaps less useful to researchers and crop protection advisors, who would probably want more in-depth information on specific topics.
A novel approach to the problem of improving nitrogen supply in organic farming is to use intercr... more A novel approach to the problem of improving nitrogen supply in organic farming is to use intercropping of cereals with a legume to provide nitrogen transfer within a season and/or to following crops. The affects of intercropping were studied in a column experiment using mixtures of winter wheat (Triticum aestivum cv. Claire), with white clover (w.c.) (Trifolium repens cv. Barblanca) and with red clover (r.c.) (Trifolium pratense cv. Britta). The effects of cutting and removal above ground clover material with and without additional soil disturbance were compared to leaving clover plants in situ and intercropped with wheat in a split root design. Wheat and clover plants, as monocultures, were used for the controls. 15 N ammonium nitrate solution was applied. The wheat seeds were sown into the column without nitrogen. We found that the cutting treatment produced the highest yield of wheat. Available ammonium-N in the soil was greatest in the clover control treatment for the column with only red clover roots and in the cutting+soil disturbance treatment for the column with only white clover roots. Available nitrate-N was greatest in the soil disturbance treatment in the column with clover and wheat roots for both red and white clover. The cutting treatment produced the highest yield of wheat.
Quantifying the carbon footprint of crop production can help identify key options to mitigate gre... more Quantifying the carbon footprint of crop production can help identify key options to mitigate greenhouse gas emissions from agriculture. Using farm survey data from eastern China, the carbon footprints of three major grain crops (rice, wheat and maize) were assessed by quantifying the greenhouse gas emissions from individual inputs and farming operations with a full life cycle assessment methodology. The farm carbon footprint in terms of farm area was estimated to be 6.0 ± 0.1, 3.0 ± 0.2, and 2.3 ± 0.1 t CO 2-eq ha À1 , and the product carbon footprint in terms of grain produced was 0.80 ± 0.02, 0.66 ± 0.03, and 0.33 ± 0.02 t CO 2-eq t À1 grain for rice, wheat and maize, respectively. Use of synthetic nitrogen fertilizers contributed 44e79% and mechanical operations 8e15%, of the total carbon footprints. Irrigation and direct methane emission made a significant contribution by 19% and by 25%, on average respectively for rice production. However, irrigation was only responsible for 2e3% of the total carbon footprints in wheat and maize. The carbon footprints of wheat and maize production varied among climate regions, and this was explained largely by the differences in inputs of nitrogen fertilizers and mechanical operations to support crop management. Moreover, a significant decrease (22e28%) in the product carbon footprint both of wheat and maize was found in large sized farms, compared to smaller ones. This study demonstrated that carbon footprint of crop production could be affected by farm size and climate condition as well as crop management practices. Improving crop management practices by reducing nitrogen fertilizer use and developing large scaled farms with intensive farming could be strategic options to mitigate climate change in Chinese agriculture.
1 Scotland’s Rural College (SRUC), West Mains Road, Edinburgh EH93JG, UK 2 Rothamsted Research, N... more 1 Scotland’s Rural College (SRUC), West Mains Road, Edinburgh EH93JG, UK 2 Rothamsted Research, North Wyke, Devon, EX20 2SB, UK 3 ADAS Group Ltd, Pendeford House, Pendeford Business Park, Wolverhampton WV9 5AP, UK 4 Institute of Biological, Environmental and Rural Sciences, Gogerddan, Aberystwyth SY23 3EE, UK. 5 School of Environment, Natural Resources and Geography, Bangor University, Bangor LL57 2UW, UK Email: Bob.Rees@sruc.ac.uk
The IPCC assume a linear relationship between nitrogen (N) application rate and nitrous oxide (N ... more The IPCC assume a linear relationship between nitrogen (N) application rate and nitrous oxide (N 2 O) emissions in inventory reporting, however, a growing number of studies show a nonlinear relationship under specific soil-climatic conditions. In the North China plain, a global hotspot of N 2 O emissions, covering a land as large as Germany, the correlation between N rate and N 2 O emissions remains unclear. We have therefore specifically investigated the N 2 O response to N applications by conducting field experiments with five N rates, and high-frequency measurements of N 2 O emissions across contrasting climatic years. Our results showed that cumulative and yieldscaled N 2 O emissions both increased exponentially as N applications were raised above the optimum rate in maize (Zea mays L.). In wheat (Triticum aestivum L.) there was a corresponding quadratic increase in N 2 O emissions with the magnitude of the response in 2012-13 distinctly larger than that in 2013-14 owing to the effects of extreme snowfall. Existing empirical models (including the IPCC approach) of the N 2 O response to N rate have overestimated N 2 O emissions in the North China plain, even at high N rates. Our study therefore provides a new and robust analysis of the effects of fertilizer rate and climatic conditions on N 2 O emissions.
Soil carbon sequestration is being considered as a potential pathway to mitigate climate change. ... more Soil carbon sequestration is being considered as a potential pathway to mitigate climate change. Cropland soils could provide a sink for carbon that can be modified by farming practices, however, they can also act as a source of greenhouse gases (GHG), including not only nitrous oxide (N O) and methane (CH ), but also the upstream carbon dioxide (CO ) emissions associated with agronomic management. These latter emissions are also sometimes termed "hidden" or "embedded" CO . In this paper, we estimated the net GHG balance for Chinese cropping systems by considering the balance of soil carbon sequestration, N O and CH emissions, and the upstream CO emissions of agronomic management from a life cycle perspective during 2000-2017. Results showed that although soil organic carbon (SOC) increased by 23.2±8.6 Tg C yr , the soil N O and CH emissions plus upstream CO emissions arising from agronomic management added 269.5±21.1 Tg C-eq yr to the atmosphere. These findings ...
The potential of biological nitrogen fixation (BNF) to provide sufficient N for production has en... more The potential of biological nitrogen fixation (BNF) to provide sufficient N for production has encouraged re-appraisal of cropping systems that deploy legumes. It has been argued that legume-derived N can maintain productivity as an alternative to the application of mineral fertilizer, although few studies have systematically evaluated the effect of optimizing the balance between legumes and non N-fixing crops to optimize production. In addition, the shortage, or even absence in some regions, of measurements of BNF in crops and forages severely limits the ability to design and evaluate new legume-based agroecosystems. To provide an indication of the magnitude of BNF in European agriculture, a soil-surface N-balance approach was applied to historical data from 8 experimental cropping systems that compared legume and non-legume crop types (e.g., grains, forages and intercrops) across pedoclimatic regions of Europe. Mean BNF for different legume types ranged from 32 to 115 kg ha(-1) an...
Intercropping systems with legumes as a component can simultaneously provide symbiotically fixed ... more Intercropping systems with legumes as a component can simultaneously provide symbiotically fixed nitrogen (N) and increase yield through improved resource use efficiency. Key objectives investigated in this project were: a) to determine if there are yield or environmental benefits from the intercropping phase in a rotation compared to the associated monocrops and b) to determine if there are cumulative benefits of the cereal-legume intercrop over more than one growing season. Experiments were established at two sites in 2006 in Scotland, UK. Treatments include spring barley (Hordeum vulgare cv. Westminster), oat (Avena sativa cv. Firth) and pea (Pisum sativum cv. Zero 4 or cv. Nitouche) monocultures and intercrops of the cereals with white clover (Trifolium repens cv. Alice) or peas with all treatments followed by an oat crop in spring 2007. No fertilisers, herbicides or pesticides were used. This paper presents grain yield data, land equivalent ratio (LER) estimates as well as esti...
Intercropping systems that include legumes can provide symbiotically fixed nitrogen (N) and poten... more Intercropping systems that include legumes can provide symbiotically fixed nitrogen (N) and potentially increase yield through improved resource use efficiency. The aims of the present study were: a) to evaluate the effects of different legumes (species and varieties) and barley on grain yield, dry matter production and N uptake of the intercrop treatments compared with the associated cereal sole crop; b) to assess the effects on the yields of the next grain crop and c) to determine the accumulation of N in shoots of the crops in a low input rotation. An experiment was established near Edinburgh, UK, consisting of 12 hydrologically isolated plots. Treatments were a spring barley (Hordeum vulgare cvar Westminster) sole crop and intercrops of barley/white clover (Trifolium repens cvar Alice) and barley/pea (Pisum sativum cvar Zero4 or cvar Nitouche) in 2006. All the plots were sown with spring oats (Avena sativa cvar Firth) in 2007 and perennial ryegrass in 2008. No fertilizers, herbi...
The Science of the total environment, Jan 27, 2015
Nitrous oxide emitted to the atmosphere via the soil processes of nitrification and denitrificati... more Nitrous oxide emitted to the atmosphere via the soil processes of nitrification and denitrification plays an important role in the greenhouse gas balance of the atmosphere and is involved in the destruction of stratospheric ozone. These processes are controlled by biological, physical and chemical factors such as growth and activity of microbes, nitrogen availability, soil temperature and water availability. A comprehensive understanding of these processes embodied in an appropriate model can help develop agricultural mitigation strategies to reduce greenhouse gas emissions, and help with estimating emissions at landscape and regional scales. A detailed module to describe the denitrification and nitrification processes and nitrogenous gas emissions was incorporated into the SPACSYS model to replace an earlier module that used a simplified first-order equation to estimate denitrification and was unable to distinguish the emissions of individual nitrogenous gases. A dataset derived fr...
... The direct application of phosphate rock is generally successfully used where (i) local sourc... more ... The direct application of phosphate rock is generally successfully used where (i) local sources represent an economically viable option, a situation often found in developing countries (Nishanth and Biswas 2008), (ii) properties of soil-cropping systems offer conditions favorable ...
This is the final report of a project lasting for 12 months which started in April 2007. The work... more This is the final report of a project lasting for 12 months which started in April 2007. The work was funded by a contract of £62,349 from HGCA (Project No. 3287). The Home-Grown Cereals Authority (HGCA) has provided funding for this project but has not conducted the research or written this report. While the authors have worked on the best information available to them, neither HGCA nor the authors shall in any event be liable for any loss, damage or injury howsoever suffered directly or indirectly in relation to the report or the research on which it is based. Reference herein to trade names and proprietary products without stating that they are protected does not imply that they may be regarded as unprotected and thus free for general use. No endorsement of named products is intended nor is it any criticism implied of other alternative, but unnamed, products.
Identification of yield deficits early in the growing season for cereal crops (e.g., Triticum aes... more Identification of yield deficits early in the growing season for cereal crops (e.g., Triticum aestivum) could help to identify more precise agronomic strategies for intervention to manage production. We investigated how effective crop canopy properties, including leaf area index (LAI), leaf chlorophyll content, and canopy height, are as predictors of winter wheat yield over various lead times. Models were calibrated and validated on fertiliser trials over two years in fields in the UK. Correlations of LAI and plant height with yield were stronger than for yield and chlorophyll content. Yield prediction models calibrated in one year and tested on another suggested that LAI and height provided the most robust outcomes. Linear models had equal or smaller validation errors than machine learning. The information content of data for yield prediction degraded strongly with time before harvest, and in application to years not included in the calibration. Thus, impact of soil and weather var...
Leaf area index (LAI) estimates can inform decision-making in crop management. The European Space... more Leaf area index (LAI) estimates can inform decision-making in crop management. The European Space Agency’s Sentinel-2 satellite, with observations in the red-edge spectral region, can monitor crops globally at sub-field spatial resolutions (10–20 m). However, satellite LAI estimates require calibration with ground measurements. Calibration is challenged by spatial heterogeneity and scale mismatches between field and satellite measurements. Unmanned Aerial Vehicles (UAVs), generating high-resolution (cm-scale) LAI estimates, provide intermediary observations that we use here to characterise uncertainty and reduce spatial scaling discrepancies between Sentinel-2 observations and field surveys. We use a novel UAV multispectral sensor that matches Sentinel-2 spectral bands, flown in conjunction with LAI ground measurements. UAV and field surveys were conducted on multiple dates—coinciding with different wheat growth stages—that corresponded to Sentinel-2 overpasses. We compared chloroph...
Climate, nitrogen (N) and leaf area index (LAI) are key determinants of crop yield. N additions c... more Climate, nitrogen (N) and leaf area index (LAI) are key determinants of crop yield. N additions can enhance yield but must be managed efficiently to reduce pollution. Complex process models estimate N status by simulating soil-crop N interactions, but such models require extensive inputs that are seldom available. Through model-data fusion (MDF), we combine climate and LAI time-series with an intermediate-complexity model to infer leaf N and yield. The DALEC-Crop model was calibrated for wheat leaf N and yields across field experiments covering N applications ranging from 0 to 200 kg N ha−1 in Scotland, UK. Requiring daily meteorological inputs, this model simulates crop C cycle responses to LAI, N and climate. The model, which includes a leaf N-dilution function, was calibrated across N treatments based on LAI observations, and tested at validation plots. We showed that a single parameterization varying only in leaf N could simulate LAI development and yield across all treatments—t...
An improved method for measuring soil N2O fluxes using a quantum cascade laser with a dynamic cha... more An improved method for measuring soil N2O fluxes using a quantum cascade laser with a dynamic chamber.
Atmospheric Chemistry and Physics Discussions, 2015
The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly ... more The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (N r) from human activities, estimated to be 193 Tg N yr −1 in 2010 which is approximately equal to the sum of biological N fixation in terrestrial and marine ecosystems. According to current trajectories, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 Tg N yr −1 by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion related emissions implemented. Some N cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of N r is the emission to the atmosphere of NH 3 , which is estimated to increase from 65 Tg N yr −1 in 2008 to 93 Tg N yr −1 in 2100 assuming a change in surface temperature of 5 • C even in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH 3 emissions to 132 Tg N yr −1. Another major change is the effect of changes in aerosol composition combined with changes in temperature. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH 4) 2 SO 4 in the 1970s to 1980s, and large reductions in emissions of SO 2 have removed most of the SO
chapter headings rather than an in-depth analysis. The book is, however, up-to-date in terms of t... more chapter headings rather than an in-depth analysis. The book is, however, up-to-date in terms of topic information and example data sets. However, most of these refer to IPM as practiced in the USA. This is a pity, because IPM is widely practiced globally, albeit on smaller scales than in the USA, for example, in many developing countries where pesticides and advanced technologies are often too expensive for farmers. Regarding specific chapters, I was particularly impressed with coverage of the use of biocontrol agents, breeding for pest or disease resistance, and the use of pheromones and plant derived semiochemicals. Chapters covering IPM case studies for cotton and field vegetables were also well presented and informative. In summary, the book is a good introduction to the many facets of IPM for university graduates but is perhaps less useful to researchers and crop protection advisors, who would probably want more in-depth information on specific topics.
A novel approach to the problem of improving nitrogen supply in organic farming is to use intercr... more A novel approach to the problem of improving nitrogen supply in organic farming is to use intercropping of cereals with a legume to provide nitrogen transfer within a season and/or to following crops. The affects of intercropping were studied in a column experiment using mixtures of winter wheat (Triticum aestivum cv. Claire), with white clover (w.c.) (Trifolium repens cv. Barblanca) and with red clover (r.c.) (Trifolium pratense cv. Britta). The effects of cutting and removal above ground clover material with and without additional soil disturbance were compared to leaving clover plants in situ and intercropped with wheat in a split root design. Wheat and clover plants, as monocultures, were used for the controls. 15 N ammonium nitrate solution was applied. The wheat seeds were sown into the column without nitrogen. We found that the cutting treatment produced the highest yield of wheat. Available ammonium-N in the soil was greatest in the clover control treatment for the column with only red clover roots and in the cutting+soil disturbance treatment for the column with only white clover roots. Available nitrate-N was greatest in the soil disturbance treatment in the column with clover and wheat roots for both red and white clover. The cutting treatment produced the highest yield of wheat.
Quantifying the carbon footprint of crop production can help identify key options to mitigate gre... more Quantifying the carbon footprint of crop production can help identify key options to mitigate greenhouse gas emissions from agriculture. Using farm survey data from eastern China, the carbon footprints of three major grain crops (rice, wheat and maize) were assessed by quantifying the greenhouse gas emissions from individual inputs and farming operations with a full life cycle assessment methodology. The farm carbon footprint in terms of farm area was estimated to be 6.0 ± 0.1, 3.0 ± 0.2, and 2.3 ± 0.1 t CO 2-eq ha À1 , and the product carbon footprint in terms of grain produced was 0.80 ± 0.02, 0.66 ± 0.03, and 0.33 ± 0.02 t CO 2-eq t À1 grain for rice, wheat and maize, respectively. Use of synthetic nitrogen fertilizers contributed 44e79% and mechanical operations 8e15%, of the total carbon footprints. Irrigation and direct methane emission made a significant contribution by 19% and by 25%, on average respectively for rice production. However, irrigation was only responsible for 2e3% of the total carbon footprints in wheat and maize. The carbon footprints of wheat and maize production varied among climate regions, and this was explained largely by the differences in inputs of nitrogen fertilizers and mechanical operations to support crop management. Moreover, a significant decrease (22e28%) in the product carbon footprint both of wheat and maize was found in large sized farms, compared to smaller ones. This study demonstrated that carbon footprint of crop production could be affected by farm size and climate condition as well as crop management practices. Improving crop management practices by reducing nitrogen fertilizer use and developing large scaled farms with intensive farming could be strategic options to mitigate climate change in Chinese agriculture.
1 Scotland’s Rural College (SRUC), West Mains Road, Edinburgh EH93JG, UK 2 Rothamsted Research, N... more 1 Scotland’s Rural College (SRUC), West Mains Road, Edinburgh EH93JG, UK 2 Rothamsted Research, North Wyke, Devon, EX20 2SB, UK 3 ADAS Group Ltd, Pendeford House, Pendeford Business Park, Wolverhampton WV9 5AP, UK 4 Institute of Biological, Environmental and Rural Sciences, Gogerddan, Aberystwyth SY23 3EE, UK. 5 School of Environment, Natural Resources and Geography, Bangor University, Bangor LL57 2UW, UK Email: Bob.Rees@sruc.ac.uk
The IPCC assume a linear relationship between nitrogen (N) application rate and nitrous oxide (N ... more The IPCC assume a linear relationship between nitrogen (N) application rate and nitrous oxide (N 2 O) emissions in inventory reporting, however, a growing number of studies show a nonlinear relationship under specific soil-climatic conditions. In the North China plain, a global hotspot of N 2 O emissions, covering a land as large as Germany, the correlation between N rate and N 2 O emissions remains unclear. We have therefore specifically investigated the N 2 O response to N applications by conducting field experiments with five N rates, and high-frequency measurements of N 2 O emissions across contrasting climatic years. Our results showed that cumulative and yieldscaled N 2 O emissions both increased exponentially as N applications were raised above the optimum rate in maize (Zea mays L.). In wheat (Triticum aestivum L.) there was a corresponding quadratic increase in N 2 O emissions with the magnitude of the response in 2012-13 distinctly larger than that in 2013-14 owing to the effects of extreme snowfall. Existing empirical models (including the IPCC approach) of the N 2 O response to N rate have overestimated N 2 O emissions in the North China plain, even at high N rates. Our study therefore provides a new and robust analysis of the effects of fertilizer rate and climatic conditions on N 2 O emissions.
Soil carbon sequestration is being considered as a potential pathway to mitigate climate change. ... more Soil carbon sequestration is being considered as a potential pathway to mitigate climate change. Cropland soils could provide a sink for carbon that can be modified by farming practices, however, they can also act as a source of greenhouse gases (GHG), including not only nitrous oxide (N O) and methane (CH ), but also the upstream carbon dioxide (CO ) emissions associated with agronomic management. These latter emissions are also sometimes termed "hidden" or "embedded" CO . In this paper, we estimated the net GHG balance for Chinese cropping systems by considering the balance of soil carbon sequestration, N O and CH emissions, and the upstream CO emissions of agronomic management from a life cycle perspective during 2000-2017. Results showed that although soil organic carbon (SOC) increased by 23.2±8.6 Tg C yr , the soil N O and CH emissions plus upstream CO emissions arising from agronomic management added 269.5±21.1 Tg C-eq yr to the atmosphere. These findings ...
The potential of biological nitrogen fixation (BNF) to provide sufficient N for production has en... more The potential of biological nitrogen fixation (BNF) to provide sufficient N for production has encouraged re-appraisal of cropping systems that deploy legumes. It has been argued that legume-derived N can maintain productivity as an alternative to the application of mineral fertilizer, although few studies have systematically evaluated the effect of optimizing the balance between legumes and non N-fixing crops to optimize production. In addition, the shortage, or even absence in some regions, of measurements of BNF in crops and forages severely limits the ability to design and evaluate new legume-based agroecosystems. To provide an indication of the magnitude of BNF in European agriculture, a soil-surface N-balance approach was applied to historical data from 8 experimental cropping systems that compared legume and non-legume crop types (e.g., grains, forages and intercrops) across pedoclimatic regions of Europe. Mean BNF for different legume types ranged from 32 to 115 kg ha(-1) an...
Intercropping systems with legumes as a component can simultaneously provide symbiotically fixed ... more Intercropping systems with legumes as a component can simultaneously provide symbiotically fixed nitrogen (N) and increase yield through improved resource use efficiency. Key objectives investigated in this project were: a) to determine if there are yield or environmental benefits from the intercropping phase in a rotation compared to the associated monocrops and b) to determine if there are cumulative benefits of the cereal-legume intercrop over more than one growing season. Experiments were established at two sites in 2006 in Scotland, UK. Treatments include spring barley (Hordeum vulgare cv. Westminster), oat (Avena sativa cv. Firth) and pea (Pisum sativum cv. Zero 4 or cv. Nitouche) monocultures and intercrops of the cereals with white clover (Trifolium repens cv. Alice) or peas with all treatments followed by an oat crop in spring 2007. No fertilisers, herbicides or pesticides were used. This paper presents grain yield data, land equivalent ratio (LER) estimates as well as esti...
Intercropping systems that include legumes can provide symbiotically fixed nitrogen (N) and poten... more Intercropping systems that include legumes can provide symbiotically fixed nitrogen (N) and potentially increase yield through improved resource use efficiency. The aims of the present study were: a) to evaluate the effects of different legumes (species and varieties) and barley on grain yield, dry matter production and N uptake of the intercrop treatments compared with the associated cereal sole crop; b) to assess the effects on the yields of the next grain crop and c) to determine the accumulation of N in shoots of the crops in a low input rotation. An experiment was established near Edinburgh, UK, consisting of 12 hydrologically isolated plots. Treatments were a spring barley (Hordeum vulgare cvar Westminster) sole crop and intercrops of barley/white clover (Trifolium repens cvar Alice) and barley/pea (Pisum sativum cvar Zero4 or cvar Nitouche) in 2006. All the plots were sown with spring oats (Avena sativa cvar Firth) in 2007 and perennial ryegrass in 2008. No fertilizers, herbi...
The Science of the total environment, Jan 27, 2015
Nitrous oxide emitted to the atmosphere via the soil processes of nitrification and denitrificati... more Nitrous oxide emitted to the atmosphere via the soil processes of nitrification and denitrification plays an important role in the greenhouse gas balance of the atmosphere and is involved in the destruction of stratospheric ozone. These processes are controlled by biological, physical and chemical factors such as growth and activity of microbes, nitrogen availability, soil temperature and water availability. A comprehensive understanding of these processes embodied in an appropriate model can help develop agricultural mitigation strategies to reduce greenhouse gas emissions, and help with estimating emissions at landscape and regional scales. A detailed module to describe the denitrification and nitrification processes and nitrogenous gas emissions was incorporated into the SPACSYS model to replace an earlier module that used a simplified first-order equation to estimate denitrification and was unable to distinguish the emissions of individual nitrogenous gases. A dataset derived fr...
... The direct application of phosphate rock is generally successfully used where (i) local sourc... more ... The direct application of phosphate rock is generally successfully used where (i) local sources represent an economically viable option, a situation often found in developing countries (Nishanth and Biswas 2008), (ii) properties of soil-cropping systems offer conditions favorable ...
This is the final report of a project lasting for 12 months which started in April 2007. The work... more This is the final report of a project lasting for 12 months which started in April 2007. The work was funded by a contract of £62,349 from HGCA (Project No. 3287). The Home-Grown Cereals Authority (HGCA) has provided funding for this project but has not conducted the research or written this report. While the authors have worked on the best information available to them, neither HGCA nor the authors shall in any event be liable for any loss, damage or injury howsoever suffered directly or indirectly in relation to the report or the research on which it is based. Reference herein to trade names and proprietary products without stating that they are protected does not imply that they may be regarded as unprotected and thus free for general use. No endorsement of named products is intended nor is it any criticism implied of other alternative, but unnamed, products.
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Papers by Robert M Rees