Management PracHce Overview from Reef Plan ScienHfic Consensus Statement: Sediments, Nutrients and PesHcides

Transcription

1 Management PracHce Overview from Reef Plan ScienHfic Consensus Statement: Sediments, Nutrients and PesHcides Peter Thorburn 1, Sco0 Wilkinson 2 and Mark Silburn 3 1 CSIRO Ecosystem Sciences 2 CSIRO Land and Water 3 Qld Dept Natural Resources and Mines

2 Structure 1. Sources of pollutants Sediments Pollutant in its own right Vector for nutrients and pes9cides Nutrients Nitrogen par9culate and dissolved Phosphorus mainly par9culate Pes9cides Sorbed to sediments and dissolved 2. Management of pollutants Sediments Nutrients Pes9cides 3. Can improved prac9ces meet WQ targets? 4. Knowledge gaps 5. Conclusions

3 Pollutant sources by locahon Total suspended solids Erosion of grazing lands supplies 74% of fine sediments Sub- surface erosion supplies >70% of TSS in Burdekin and Fitzroy Scalds, gullies, riparian frontages Kroon et al (2013) SCSU Chap 4

4 Pollutant sources by locahon Nutrients Par9culates comprise the largest propor9on of TN and TP (grazing) DIN is supplied predominantly from cropping: sugarcane biggest source Kroon et al (2013) SCSU Chap 4

5 Pollutant sources by locahon PSII herbicides Sugarcane the dominant source Cropping and grazing small contributors Risk and sources of other pes9cides need to be examined Kroon et al (2013) SCSU Chap 4

6 Management of sediments 1. General principle: Loads are reduced by Maintaining ground cover and enhancing infiltra9on Redistribu9ng the pressure of agricultural ac9vi9es away from areas vulnerable to erosion 2. In grazing lands Sustainable forage u9lisa9on is 10 30% of standing biomass More profitable in med- long term >50% of grazing land has exceeded that in past droughts Excluding stock from and revegeta9ng riparian frontages, rills, scalds and gullied areas Ground cover at different forage utilisation rates (Whish, Silburn et al.) Cover (%) Very low productivity LT - Springvale 0 Av = 60% 10 Av = 50% 15 Av = 31% 20 Av = 23% Av = 12% Series7

7 Management of sediments 2. Grazing cont. Reversing degrada9on takes from years to decades Affected by star9ng condi9on Physical remedia9on works may be useful in highly- eroding areas 3. In cropped lands Reduce or eliminate 9llage Maximise soil cover (via crop residue reten9on) Controlled traffic, opportunity cropping, contour embank, etc 4. Targe9ng areas of high erosion can increase effec9veness For example, the Burdekin Fall Dam traps >60% of fine sediment from upstream Recovery of native perennials Bartley et al (2010)

8 Nutrients - causes 1. N losses driven by fer9liser, esp. surplus Expect the same principle to apply to P 2. N surpluses kg/ha/yr in intensively managed crops P surpluses < 70 kg/ha/yr Field scale Webster et al. (2012) Basin scale Thorburn et al (2013) N surplus and N rate Thorburn & Wilkinson (2013)

9 Nutrients - management 1. Managing crops for poten9al yields causes nutrient surpluses What is the minimum surplus needed? How do we manage for nutrients from organic sources? 2. At low surpluses, tac9cs to increase efficiency should help Splihng applica9ons, slow release N fer9liser, etc. 3. Improving irriga9on efficiency should help reduce losses Sugar industry BMP Target yield for fertiliser applic n to sugarcane Schroeder et al. (2010)

10 Management of peshcides 1. Reduce vectors of movement Runoff Sediment movement Herbicides losses by tillage and spraying (Masters et al. 2013) Broadcast Banded Tilled No till Timing of application w.r.t. wet season run off (Armour et al.) 2. Manage pes9cide input and 9ming Reduce amount applied, e.g. banded spraying Increase 9me between applica9on and runoff Close to wet season Before wet season

11 Management of peshcides 1. Apply products with rapid degrada9on rates, e.g. knockdown herbicides 2. Pes9cide management should be undertaken within the context of integrated pest or weed management, managing resistance and considering ecotoxicology 3. Pes9cides can be dilutes aier they leave fields Target management ac9on to fields close to receiving creek systems Managing pes9cide in irriga9on areas Pesticide conc and creek flow (Davis et al. 2013)

12 Can improved agricultural management meet water quality targets? Study / prachce Pollutant Fine sediments Total P Total N Dissolved inorganic N PSII herbicides Target: # 50 Thorburn and Wilkinson (2013) empirical modelling All BMP 15 nd nd All Agri Env Prac9ce 19 nd nd Waters et al. (2013) catchment modelling All B- Class All A- Class Pollutant sources and management prac9ce effec9veness Peter Thorburn

13 Knowledge gaps - Sediments Forage budge9ng procedures for graziers Time- scales of land condi9on recovery from reduced forage u9lisa9on Cost- effec9veness and op9mum design of gully/d- condi9on remedia9on and riparian fencing Soil sodicity & nutrient content, gully density, stream power Mapping the spa9al panerns in cost- effec9veness of each prac9ce change A spa9ally- explicit Property calculator Property cover shows the potential for targeting (Wilkinson et al., RRRD)

14 Knowledge gaps - Nutrients Re- framing nutrient management: Apply nutrients for the crops actually grown in each field (as opposed to wide scale poten9als) What is the minimum N Surplus needed to maintain crop yields? 50 kg N ha - 1? How is this affected by soils types and tac9cs like splihng, slow release fer9lisers, precision ag, etc? Relate management to risk of yield loss / probability of yield gain Organic nutrient sources are these a local or regional problem? Validate ideas on P Sugarcane N response exp, Bundaberg (Thorburn et al. 2003, 2013)

15 Knowledge gaps - PesHcides Breakdown in tropical condi9ons; in soils, on crop residues, in streams Emerging products

16 Conclusions 1. Principles behind pollutant genera9on generally well known Over grazing a reduced ground cover a higher erosion Nitrogen fer9liser applica9ons a nitrogen losses Pes9cide applica9ons a pes9cide losses 2. Substan9al increase in knowledge about pollutant management in last five years 3. Number of proven ac9ons to improve water quality 4. Bener knowledge of where to focus efforts 5. There are s9ll knowledge gaps...

17 InformaHon 1. Thorburn et al. (2013). Sources of sediment, nutrients, pes9cides and other pollutants in the Great Barrier Reef catchment ( hnp:// consensus- statement/sources- of- pollutants.aspx) 2. Thorburn et al. (2013). Water quality in agricultural lands draining to the Great Barrier Reef: Review of causes, management and priori9es. Agriculture Ecosystems and Environment, in press 3. Thorburn and Wilkinson (2013). Conceptual frameworks for es9ma9ng the water quality benefits of improved agricultural management prac9ces in large catchments. Agriculture Ecosystems and Environment, in press

18 Presenta9on 9tle Presenter name Page 18

19 Management of sediments 1. General principle: Loads are reduced by Maintaining ground cover and enhancing infiltra9on Redistribu9ng the pressure of agricultural ac9vi9es away from areas vulnerable to erosion 2. In grazing lands Sustainable forage u9lisa9on is 10 30% of standing biomass More profitable in med- long term >50% of grazing land has exceeded that in past droughts Excluding stock from and revegeta9ng riparian frontages, rills, scalds and gullied areas $ Moderate Variable Heavy 1400 Profitability at different forage utilisation rates (O Reagain et al., 2011) $ ) a$ h 0$ /1 $9 000 ($ M $6 000 G A $ ) m l (m fa in a R $ 0 0 Year