title: Carbon inputs to soil from roots of two contrasting pasture swards

authors: McNally, Samuel Rae

subjects: Soil Carbon

abstract: The soil carbon (C) pool is one of the largest pools of C in the terrestrial environment. Soil management strategies to increase soil C are of interest globally to reduce atmospheric CO₂ concentrations which are contributing to climate change. Changes in land use and land management can result in gains, or losses of soil C, and consequently change in atmospheric CO₂ concentrations. Increasing the C inputs to soil by either increasing plant root mass has been suggested as one method to increase soil C. 
In New Zealand, pastoral agriculture is dominated by the use of perennial ryegrass and white clover pastures which are typically shallow rooting species. The use of more diverse pastures including additional species such as lucerne, chicory and plantain, may increase root mass or rooting depth. However, there is limited data on root mass and C inputs from roots to soil under ryegrass-clover pasture systems and no data on more diverse pasture swards in New Zealand pasture systems. The objective of this research was to investigate whether more diverse pasture swards had greater root mass and C inputs to soil compared to ryegrassclover and whether diverse pastures offered scope to increase soil C. 
Root mass was measured under a moderately diverse and a ryegrass-clover pasture in an existing plant diversity trial at a research dairy farm (Scott Farm, DairyNZ) containing 6 replicate paddocks of each pasture type. Soil cores were collected seasonally over one year to 300 mm depth and divided into three 100 mm depth sections (0 – 100, 100 – 200, 200 – 300 mm) and root mass measured after soil was washed off. There was greater root mass (0 – 300 mm) under the moderately diverse pasture (5320-9350 kg ha⁻¹ ) compared to the ryegrass-clover pasture (3810-5700 kg ha⁻¹) for all seasons. Additionally, there was greater root mass lower in the soil profile (100 – 200, 200 – 300 mm) in the moderately diverse pasture. The increased root mass in the moderately diverse pasture resulted in an estimated additional C input to soil of about 1203 kg C ha⁻¹ y⁻¹ (0 – 300 mm) but this estimate did not include contributions from root exudates. Root trait measurements of individual plant species also demonstrated a greater diversity of root traits (specific root length, surface area, and diameter) in the moderately diverse pasture, which may be important for the C input and C stabilisation processes in soil. 
Root turnover and C input to soil was measured on three replicate paddocks each of moderately diverse and ryegrass-clover pastures, also at Scott Farm. An isotope (¹³CO₂) pulse labelling method was used whereby clear chambers (1 m² ) were placed over pasture and ¹³CO₂ taken up following photosynthesis. Labelling was carried out once weekly for a period of five weeks, giving a total of 5 labelling events. Soil cores were collected at regular intervals following isotope labelling for up to 138 days and δ13C measured in the roots (0 – 100, 100 – 200 mm depth) and soil (0 – 100 mm depth) to calculate root turnover and C input. 
There was no difference in root turnover rates between the moderately diverse (298 days) and ryegrass-clover (260 days) pastures, with a combined root turnover rate of 276 days for both pastures. However, large variability in data meant that the ability to detect differences between pasture swards was low. The average C input to soil for both pastures was 58 kg C ha⁻¹ d⁻¹ over an 88 day period which was greater than other reported studies in New Zealand. A likely cause of this high C input from roots to soil was the severe drought conditions during the study that may have increased root death and C inputs from roots to soil.
While previous work determined similar root turnover and C inputs under both conventional and moderately diverse pastures, a final experiment focussed on whether pasture renewal of a ryegrass-clover pasture could result in increased root turnover, and therefore, greater C input to soil. Root turnover and C input to soil under ryegrass-clover pasture with and without pasture renewal was measured using an isotope pulse labelling method. Pastures (paired plots in 3 replicate paddocks) were labelled with ¹³CO₂ daily for five days within clear chambers (1 m² ) before one replicate in each pair was sprayed with herbicide and seed direct drilled. Soil cores were collected (0 – 100, 100 – 200 mm depths) at regular intervals over a 89 day period following isotope labelling and root turnover and C input measured by following the decline in ¹³C in extracted roots. 
Following herbicide application, there was an initial rapid increase in root turnover (17 days) followed by a more similar turnover (524 days) compared to the unsprayed treatment (585 days). The increased root turnover following the use of herbicide resulted in increased C input to the soil in the sprayed treatment (3238 kg C ha⁻¹ ) compared to the unsprayed ryegrass-clover treatment (1726 kg C ha⁻¹ ). This suggested that during pasture renewal there is a large input of C. However, the proportion of this C that is stabilised in soil requires further investigation. 
This research demonstrated there is potential to increase soil C by using more diverse pastures through increased root mass and rooting depth. This work also provided the first measurements of root mass and C input to soil under moderately diverse pastures in New Zealand and adds to the limited information on the root mass, root turnover and C input under ryegrass-clover pasture systems. Furthermore, this work provided the first measurements of root turnover and C input to soil during a pasture renewal event involving herbicide. The data from this research will contribute better information for use in modelling and increase the knowledge and understanding of soil C under grazed pasture systems in New Zealand. 
Further research on investigating the root dynamics under more diverse pastures with respect to root traits such as diameter, surface area and specific root length within these pastures and how these traits influence the root turnover and C input to soil would be beneficial. Improving the understanding on the quantity of C that is stabilised and the C stabilisation processes in these pasture systems is also important in order to achieve meaningful reductions in atmospheric CO₂ concentrations.

text: Carbon inputs to soil from roots of two contrasting pasture swards The soil carbon (C) pool is one of the largest pools of C in the terrestrial environment. Soil management strategies to increase soil C are of interest globally to reduce atmospheric CO₂ concentrations which are contributing to climate change. Changes in land use and land management can result in gains, or losses of soil C, and consequently change in atmospheric CO₂ concentrations. Increasing the C inputs to soil by either increasing plant root mass has been suggested as one method to increase soil C. 
In New Zealand, pastoral agriculture is dominated by the use of perennial ryegrass and white clover pastures which are typically shallow rooting species. The use of more diverse pastures including additional species such as lucerne, chicory and plantain, may increase root mass or rooting depth. However, there is limited data on root mass and C inputs from roots to soil under ryegrass-clover pasture systems and no data on more diverse pasture swards in New Zealand pasture systems. The objective of this research was to investigate whether more diverse pasture swards had greater root mass and C inputs to soil compared to ryegrassclover and whether diverse pastures offered scope to increase soil C. 
Root mass was measured under a moderately diverse and a ryegrass-clover pasture in an existing plant diversity trial at a research dairy farm (Scott Farm, DairyNZ) containing 6 replicate paddocks of each pasture type. Soil cores were collected seasonally over one year to 300 mm depth and divided into three 100 mm depth sections (0 – 100, 100 – 200, 200 – 300 mm) and root mass measured after soil was washed off. There was greater root mass (0 – 300 mm) under the moderately diverse pasture (5320-9350 kg ha⁻¹ ) compared to the ryegrass-clover pasture (3810-5700 kg ha⁻¹) for all seasons. Additionally, there was greater root mass lower in the soil profile (100 – 200, 200 – 300 mm) in the moderately diverse pasture. The increased root mass in the moderately diverse pasture resulted in an estimated additional C input to soil of about 1203 kg C ha⁻¹ y⁻¹ (0 – 300 mm) but this estimate did not include contributions from root exudates. Root trait measurements of individual plant species also demonstrated a greater diversity of root traits (specific root length, surface area, and diameter) in the moderately diverse pasture, which may be important for the C input and C stabilisation processes in soil. 
Root turnover and C input to soil was measured on three replicate paddocks each of moderately diverse and ryegrass-clover pastures, also at Scott Farm. An isotope (¹³CO₂) pulse labelling method was used whereby clear chambers (1 m² ) were placed over pasture and ¹³CO₂ taken up following photosynthesis. Labelling was carried out once weekly for a period of five weeks, giving a total of 5 labelling events. Soil cores were collected at regular intervals following isotope labelling for up to 138 days and δ13C measured in the roots (0 – 100, 100 – 200 mm depth) and soil (0 – 100 mm depth) to calculate root turnover and C input. 
There was no difference in root turnover rates between the moderately diverse (298 days) and ryegrass-clover (260 days) pastures, with a combined root turnover rate of 276 days for both pastures. However, large variability in data meant that the ability to detect differences between pasture swards was low. The average C input to soil for both pastures was 58 kg C ha⁻¹ d⁻¹ over an 88 day period which was greater than other reported studies in New Zealand. A likely cause of this high C input from roots to soil was the severe drought conditions during the study that may have increased root death and C inputs from roots to soil.
While previous work determined similar root turnover and C inputs under both conventional and moderately diverse pastures, a final experiment focussed on whether pasture renewal of a ryegrass-clover pasture could result in increased root turnover, and therefore, greater C input to soil. Root turnover and C input to soil under ryegrass-clover pasture with and without pasture renewal was measured using an isotope pulse labelling method. Pastures (paired plots in 3 replicate paddocks) were labelled with ¹³CO₂ daily for five days within clear chambers (1 m² ) before one replicate in each pair was sprayed with herbicide and seed direct drilled. Soil cores were collected (0 – 100, 100 – 200 mm depths) at regular intervals over a 89 day period following isotope labelling and root turnover and C input measured by following the decline in ¹³C in extracted roots. 
Following herbicide application, there was an initial rapid increase in root turnover (17 days) followed by a more similar turnover (524 days) compared to the unsprayed treatment (585 days). The increased root turnover following the use of herbicide resulted in increased C input to the soil in the sprayed treatment (3238 kg C ha⁻¹ ) compared to the unsprayed ryegrass-clover treatment (1726 kg C ha⁻¹ ). This suggested that during pasture renewal there is a large input of C. However, the proportion of this C that is stabilised in soil requires further investigation. 
This research demonstrated there is potential to increase soil C by using more diverse pastures through increased root mass and rooting depth. This work also provided the first measurements of root mass and C input to soil under moderately diverse pastures in New Zealand and adds to the limited information on the root mass, root turnover and C input under ryegrass-clover pasture systems. Furthermore, this work provided the first measurements of root turnover and C input to soil during a pasture renewal event involving herbicide. The data from this research will contribute better information for use in modelling and increase the knowledge and understanding of soil C under grazed pasture systems in New Zealand. 
Further research on investigating the root dynamics under more diverse pastures with respect to root traits such as diameter, surface area and specific root length within these pastures and how these traits influence the root turnover and C input to soil would be beneficial. Improving the understanding on the quantity of C that is stabilised and the C stabilisation processes in these pasture systems is also important in order to achieve meaningful reductions in atmospheric CO₂ concentrations.

year: 2016

title: Developments in non-mandatory disclosures in annual reports of companies: A case study

authors: Sharma, Umesh Prasad

subjects: non-mandatory disclosure

abstract: The paper investigates the extent of non-mandatory disclosure of information (NMD) in the annual reports of the 17 companies listed on the South Pacific Stock Exchange (SPSE) in Fiji, a developing country, and whether NMD by these companies has changed over time providing additional and useful information to stakeholders.  The empirical data was gathered from the years 2008 to 2010 to provide a clear picture of the change in the level and extent of NMD, and its influences over the periods 2008 to 2010. It can be seen from the Fiji perspective that the mandatory requirements tend to have a financial focus. However, it would be expected that the level of company disclosures would have changed over time, with not only global market forces but through differing societal values which have increased the frequency and demand of non-mandatory reporting by companies.  All companies showed some degree of NMD, and on average this demonstrates an increasing trend. The stakeholders are receiving more information about a company’s activities. The companies were analysed in light of recent developments in corporate governance by the Capital Markets Development Authority (CMDA) implementing their 10 corporate governance principles. This became a major driver of the increase in NMD levels of the disclosures in the annual reports of the listed companies. However, a large variation still exists between the level and extent of the NMD and the different listed companies. The minimum disclosure level found over the three years was 9.09 percent, which has increased to a minimum of 13.66 percent in 2010, and the maximum disclosure level over the three years was 81.82 percent. The findings for the extent of NMD was also similar where the minimum words used in NMDs was 114, increasing to 854 in 2010, and the maximum disclosure extent over the three years was 21,414 words. However, it was found that the measurement of counting words tended to fluctuate over different periods where significant events took place that affected the company. Therefore, it was established that disclosure is impacted by what happens in the reporting period, and can explain why one period may have greater disclosure than another. The paper aims to extend earlier work of Sharma & Davey (2013) on the extent of NMD in Fijian context.  While Sharma & Davey (2013) considered voluntary disclosure from 1999-2005, our study reviews NMD over 2008-2010.  The study has shown that corporate governance code issued in 2009 by Capital Market Development Authority has influenced the level of NMD.

text: Developments in non-mandatory disclosures in annual reports of companies: A case study The paper investigates the extent of non-mandatory disclosure of information (NMD) in the annual reports of the 17 companies listed on the South Pacific Stock Exchange (SPSE) in Fiji, a developing country, and whether NMD by these companies has changed over time providing additional and useful information to stakeholders.  The empirical data was gathered from the years 2008 to 2010 to provide a clear picture of the change in the level and extent of NMD, and its influences over the periods 2008 to 2010. It can be seen from the Fiji perspective that the mandatory requirements tend to have a financial focus. However, it would be expected that the level of company disclosures would have changed over time, with not only global market forces but through differing societal values which have increased the frequency and demand of non-mandatory reporting by companies.  All companies showed some degree of NMD, and on average this demonstrates an increasing trend. The stakeholders are receiving more information about a company’s activities. The companies were analysed in light of recent developments in corporate governance by the Capital Markets Development Authority (CMDA) implementing their 10 corporate governance principles. This became a major driver of the increase in NMD levels of the disclosures in the annual reports of the listed companies. However, a large variation still exists between the level and extent of the NMD and the different listed companies. The minimum disclosure level found over the three years was 9.09 percent, which has increased to a minimum of 13.66 percent in 2010, and the maximum disclosure level over the three years was 81.82 percent. The findings for the extent of NMD was also similar where the minimum words used in NMDs was 114, increasing to 854 in 2010, and the maximum disclosure extent over the three years was 21,414 words. However, it was found that the measurement of counting words tended to fluctuate over different periods where significant events took place that affected the company. Therefore, it was established that disclosure is impacted by what happens in the reporting period, and can explain why one period may have greater disclosure than another. The paper aims to extend earlier work of Sharma & Davey (2013) on the extent of NMD in Fijian context.  While Sharma & Davey (2013) considered voluntary disclosure from 1999-2005, our study reviews NMD over 2008-2010.  The study has shown that corporate governance code issued in 2009 by Capital Market Development Authority has influenced the level of NMD.

year: 2013

title: Māori, census 2018 and data sovereignty

authors: Kukutai, Tahu

abstract: This webinar explores the issues with the 2018 Census data collection and examines what the implications could be for communities and funding.  See below to read some relevant articles prior to the webinar.

Our presenters also discuss iwi data sovereignty and data bias and the reasons why we should all pay more attention to the quality of the data we provide, use and collect.

text: Māori, census 2018 and data sovereignty This webinar explores the issues with the 2018 Census data collection and examines what the implications could be for communities and funding.  See below to read some relevant articles prior to the webinar.

Our presenters also discuss iwi data sovereignty and data bias and the reasons why we should all pay more attention to the quality of the data we provide, use and collect.

year: 2019