Root carbon inputs under moderately diverse sward and conventional ryegrass-clover pasture: implications for soil carbon sequestration
- 920 Downloads
Background and aims
A strategy to increase soil C under pasture-based systems is to increase the root mass inputs or increase rooting depth of plants. Our objective in this study was to measure the seasonal dynamics of root mass and C inputs under two different pasture types (ryegrass-clover vs moderately diverse) that differ in plant diversity and which are commonly used in New Zealand agriculture.
This study was carried out on an existing plant diversity field trial containing six replicate paddocks of both moderately-diverse and ryegrass-clover pastures. Soil cores (0-100-200-300 mm sections) were collected seasonally across 1 year and individual root traits assessed from all species.
The moderately diverse pasture had greater root mass (5320–9350 kg ha−1) than the ryegrass-clover pasture (3810–5700 kg ha−1) for all seasons and had greater root mass lower in the soil profile. A secondary objective demostrated no significant difference in root mass between high and low sugar ryegrass cultivar. Increased root mass results in an estimated increase of C input to the soil of about 1203 kg C ha−1 (0–300 mm depth) under the moderately diverse pasture, excluding root exudates. Root trait measurements demonstrated a greater diversity of root traits in the moderately diverse sward compared to the ryegrass-clover pasture.
Moderately diverse pasture systems offer scope to increase soil C under grazed pastures through increased root mass inputs and rooting depth.
KeywordsGrazed pastures Root mass Soil C Moderately diverse pasture Ryegrass-clover
We would like to acknowledge funding received from the New Zealand Agricultural Greenhouse Gas Research Centre, DairyNZ, and the University of Waikato Doctoral Scholarship. We would also like to acknowledge the various people who have helped with this study through field and laboratory work and to DairyNZ and Scott Farm for being helpful and accommodating throughout this work.
- Chapman DF, Rawnsley RP, Cullen BR, Clark DA (2013) Inter-annual variability in pasture herbage accumulation in temperate dairy regions: causes, consequences, and management tools. Proceedings of the 22nd International Grassland Congress: revitalising grasslands to sustain our communitiesGoogle Scholar
- Cosgrove GP, Burke JL, Death AF, Hickey MJ, Pacheco D, Lane GA (2007) Ryegrasses with increased water soluble carbohydrate: evaluating the potential for grazing dairy cows in New Zealand. Proc N Z Grassl Assoc 69:179–185Google Scholar
- Cosgrove GP, Koolaard J, Luo D, Burke JL, Pacheco D (2009) The composition of high sugar ryegrasses. Proc N Z Grassl Assoc 71:187–193Google Scholar
- Crush JR, Nichols SN (2010) Progress towards forage plant root systems for sustainable dairying. pp. 50–52. Proceedings of the 4th Australasian Dairy Science SymposiumGoogle Scholar
- Dodd MB, Crush JR, Mackay AD, Barker DJ (2011) The “root” to more soil carbon under pastures. Proc N Z Grassl Assoc 73:43–50Google Scholar
- Edwards GR, Parsons AJ, Rasmussen S, Bryant RH (2007) High sugar ryegrasses for livestock systems in New Zealand. Proc N Z Grassl Assoc 69:161–171Google Scholar
- Gerrish J (2001) Species stability in diverse pasture mixtures. Forage Systems Update. University of Missouri. 10:No. 2Google Scholar
- Hewitt AE (1993) New Zealand soil classification. Manaaki Whenua Press, LincolnGoogle Scholar
- Johnen BG, Sauerbeck DR (1977) A tracer technique for measuring growth, mass and microbial breakdown of plant roots during vegetation. Ecol Bull 366–373Google Scholar
- Matthew C (1996) Seasonal patterns of root, tiller and leaf production in a Grasslands Ruanui ryegrass sward. N Z Grassl Assoc 58:73–76Google Scholar
- McKenzie BA, Gyamtsho P, Lucas RJ (1990) Productivity and water use of lucerne and two lucerne-grass mixtures in Canterbury. Proc N Z Grassl Assoc 52:35–39Google Scholar
- NIWA (2015) Cliflo National Climate Database. National Institute of Water and Atmospheric Research (2015). Retrieved 20 March 2015 from: http://www.cliflo.niwa.co.nz
- Pacaldo RS, Volk TA, Briggs RD (2014) Carbon Sequestration in Fine Roots and Foliage Biomass Offsets Soil CO2 Effluxes along a 19-year Chronosequence of Shrub Willow (Salix x dasyclados) biomass crops. BioEnergy Res 1–8Google Scholar
- MPI (2013) The 2012–13 drought: an assessment and historical perspective. Ministry for Primary Industries Technical Paper No. 2012/18, ISBN No. 978-0-478-41494-3, http://www.mpi.govt.nz/news-resources/publications.aspx
- Saggar S, Mackay AD, Hedley CB (1999) Hill slope effects on the vertical fluxes of photosynthetically fixed 14C in a grazed pasture. Soil Res 37:655–666Google Scholar
- Woodward SL, Waugh CD, Roach CG, Fynn D, Phillips J (2013) Are diverse species mixtures better pastures for dairy farming. Proc N Z Grassl Assoc 75:79–84Google Scholar