RURAL Farming Challenges and Opportunities Managing water and nutrient at the farm and paddock scale Roger MacGibbon National Technical Director Opus Rural November 2016
Opus Rural Our Rural team comprises farm systems advisors, rural finance experts, engineers, scientists, planners and project managers and we provide an independent, technically-focussed service in the following areas: Land and water management: Farm Environment Plans, soil testing, riparian and wetland design and installation Farm infrastructure and engineering: culverts, bridges, feedlots, underpasses, effluent systems, farm conversions Rural planning: resource consents and planning advice Irrigation system design On-farm technical risk assessments and management plans: effluent, water and nutrient management; property purchase due diligence We provide an objective, impartial technical service We are rurally based with 16 local offices with rural staff throughout NZ
RURAL Managing Phosphorus, Sediment and Faecal Pathogens on New Zealand Farms
Principles of nutrient, sediment and faecal pathogen movement on farms RURAL Understanding water movement on your farm is most critical because water is the transport mechanism for most nutrients, sediment and faecal pathogens across the farm and into waterways. Nutrient loss is greatest where and when the volume and speed of water flow is greatest. Two routes for water flow: 1. Across the surface = surface runoff. This is the principal transport mechanism for phosphorus, sediment and pathogens 2. Down through the soil = leaching. This is the principal transport mechanism for nitrogen.
Principles of nutrient, sediment and faecal pathogen movement on farms RURAL Once nitrate descends below the root zone there are very few additional opportunities to intercept and extract it. Phosphorus, sediment and faecal bacteria can be intercepted and extracted anywhere where runoff can be trapped and stored for a period. There are two situations where leached nitrate can be intercepted for a second hit: - Springs and seeps - Sub-surface drainage
Phosphorus sources (how does P get on to the farm?) RURAL P fertiliser Livestock manure Attached to sediment from upstream/upcatchment Transported by water
What are the causes of P loss? RURAL High P source potential + High P transport potential = CRITICAL SOURCE AREA (CSA) Typically, 80% of the P losses come from 20% of the farm area Concentrating P management effort on Critical Source Areas is likely to be the most cost-effective strategy
What are the causes of P loss? RURAL P loss is greatest when: soil P levels are high surface water runoff is most likely soils are saturated soil/ sediment is exposed Where there is sediment erosion there will be P loss Sediment and faecal pathogen loss is also greatest under the same conditions.
Livestock management Exclude cattle from all permanent waterways. Cattle in streams are a major cause of P and faecal contamination RURAL
Livestock management RURAL Exclude cattle from all permanent waterways. Cattle in streams are a major cause of P and faecal contamination 15th of March, 2016 Site name Dissolved Reactive Phosphorus (mg/l) E-Coli (cfu/100ml) Nitrite/Nitrate Nitrogen (mg/l) Ammoniacal Nitrogen (mg/l) Schedule 15 limit at flows less than median 0.100 0.026 260 0.444 Nth Branch at SH90 0.026 0.028 2500 0.420 Sth Branch Black Gully Rd East (2) 0.016 0.049 470 0.260 Nth Branch at Fleming Rd (1) 0.025 0.03 3100 0.660 Nth Branch at Fleming Rd (2) 0.066 0.2 8000 0.530 Sth Branch Black Gully Rd East (1) 0.012 0.032 6900 0.230 Nth Branch at Cabbage Tree Rd West (1) 0.067 0.17 6000 1.400 Nth Branch at Cabbage Tree Rd West (2) 0.074 0.21 8800 2.400 Nth Branch at Black Gully Rd West (1) 0.015 0.14 4700 1.600 Nth Branch at Black Gully Rd West (2) 0.310 0.49 33000 7.300 Sth Branch at Mill Rd 0.012 0.038 970 0.820 Nth Branch at Walker Rd West 0.016 0.16 5700 1.300 Sth Branch at Walker Rd East 0.010 0.039 3200 0.092 Gibson Rd 0.014 0.067 5100 0.460 Wooded Hill Rd 0.011 0.046 950 0.440 Red Cells indicate levels are above the limit Median Flow at reference site (m3/s or cumecs) 15.48 Flow on day of sampling (m3/s or cumecs) 5.6 Below median
Livestock management Fence cattle out of areas that are wet for all or most of the year eg. seeps, drainage gullies, to avoid pugging and compaction
Livestock management Put a hotwire around seasonally wet seeps
Livestock management Hold stock in feedlots or standoff areas to avoid damage to pasture BUT the drainage water must be contained and managed/treated (eg. sediment retention devices, retention bunds)
RURAL Feed / pasture management
Drainage RURAL Farm tracks and races
Drainage RURAL Manage runoff from tracks so that it does not run directly to waterways. Use cut-outs to draw water off track and swales or sediment detention ponds to intercept and settle out dung and sediment
Drainage managing water movement RURAL
Drainage RURAL Sediment retention traps
Drainage RURAL Sediment retention traps
Sub-surface drainage Install subsurface drainage to reduce period of soil saturation BUT the drained water must be captured and treated (sediment retention pond for P and sediment; wetland for N and faecal)
Sub-surface drainage Release subsurface drainage into wetlands not directly into streams
Waterways RURAL Fence all cattle from waterways
Riparian buffers / filters what do they do? Riparian filter strips and planted margins do very little for N management Riparian planting can reduce P and sediment loss but only at points where runoff enters streams Trees and shrubs are not good filters of surface runoff
Waterways Establish riparian filter/buffer strips in areas where water converges (this may not be along the margins of a stream) Source: R McDowell AgResearch
Management of faecal pathogen contamination of water ways RURAL Faecal bacteria and viruses are killed by UV light. The longer the exposure to sunlight the higher the mortality. 90% + mortality of faecal pathogens can be achieved by passing drainage water through a shallow wetland.
Constructed wetlands Can extract up to 60-70% of nitrate and total nitrogen if the wetland size is between 2 and 3% of the catchment size and water residence time is at least one day. Phosphorus and sediment removal is usually less than nitrogen but can be enhanced with construction of retention ponds upstream of the wetland.
Surface flow restored and constructed wetlands
Surface flow wetlands
Surface flow wetlands
Surface flow wetlands Owl Farm Cambridge Once fully functional this 0.4 ha wetland could reduce the overall farm leaching rate from the current level of 34 kg N/ha/yr to 28 kg N/ha/yr
Surface flow wetlands Owl Farm Cambridge Once fully functional this 0.4 ha wetland could reduce the overall farm leaching rate from the current level of 44 kg N/ha/yr to 38 kg N/ha/yr
Seepage wetlands
Interpreting water quality data RURAL What do these figures mean? 1st of March, 2016 Dissolved Reactive Phosphorus (mg/l) E-Coli (cfu/100ml) Nitrite/Nitrate Nitrogen (mg/l) Site name Ammoniacal Nitrogen (mg/l) Schedule 15 limit at flows less than median 0.100 0.026 260 0.444 Nth Branch at SH90 0.025 0.013 370 0.460 Sth Branch Black Gully Rd East (2) 0.010 0.035 450 0.220 Nth Branch at Fleming Rd (1) 0.009 0.017 930 0.790 Nth Branch at Fleming Rd (2) 0.033 0.083 210 0.430 Sth Branch Black Gully Rd East (1) 0.029 0.021 560 0.500 Nth Branch at Cabbage Tree Rd West (1) 0.017 0.023 240 1.300 Nth Branch at Cabbage Tree Rd West (2) 0.031 0.11 590 0.630 Nth Branch at Black Gully Rd West (1) 0.010 0.039 410 1.000 Nth Branch at Black Gully Rd West (2) 0.050 0.11 250 0.520 Sth Branch at Mill Rd 0.024 0.018 300 0.190 Nth Branch at Walker Rd West 0.013 0.036 460 0.770 Sth Branch at Walker Rd East 0.005 0.026 18 0.180 Gibson Rd 0.013 0.041 850 0.450 Wooded Hill Rd 0.009 0.038 330 0.660 Red Cells indicate levels are above the limit Median Flow at reference site (m3/s or cumecs) 15.48 Flow on day of sampling (m3/s or cumecs) 7.45 Below median
Interpreting water quality data RURAL Understanding the baseline
Interpreting water quality data RURAL Understanding the baseline South Branch Black Gully Road East (2) - average readings 29 Oct 2015-30 May 2016 Ammoniacal Nitrogen (mg/l) Dissolved Reactive Phosphorus (mg/l) E-Coli (cfu/100ml) Nitrite/Nitrate Nitrogen (mg/l) Site name Schedule 15 limit at flows less than median 0.100 0.026 260 0.444 Average (over 16 samples periods) 0.015 0.040 287 0.391 High reading 0.120 0.130 2500 4.800 Low reading 0.005 0.020 3 0.055 Red Cells indicate levels are above the limit
Interpreting water quality data RURAL Suggested improvements in water quality data collection and use Establish a real baseline sample location that is outside the influence of farming Measure Total Phosphorus as a measure of P and sediment loss via runoff Set up one or more weather stations to help interpret the data Take measurements from drains and tributaries on farm to better understand problem areas and sources If a stream flows through your farm, measure water quality where it enters the property and where it leaves the property to better understand the effect of your faming practices.
Nutrient, sediment and faecal pathogen movement on farms RURAL Some take home messages: There are many actions on most farms that can significantly reduce nutrient losses at little or no net cost. The best recipe to reduce nutrient loss will be different for each farm. Soils and hydrology: Farmers who develop an understanding of how (and when) water and nutrients move across the farm surface and through the soil profile will be in the best position to make the best and most cost-effective decisions about the actions to take to reduce nutrient loss. Don t commit to expensive nutrient management practices until you fully understand the sources, causes and transport modes of nutrients on your farm.
Nutrient, sediment and faecal pathogen movement on farms RURAL Some take home messages: There are no magic solutions or generic cure-alls that will manage all nutrient, bacterial and sediment problems. Eg. standard riparian margin planting may do nothing to reduce nitrate loss Determine the priority problems that need management and then select the practices that will best mitigate the type, nature and source of the problems on your farm. Apply the 80:20 rule. Don t waste money on practices that can t address the priority problems on your farm. The requirements to become compliant with the rules may be different to those necessary to reduce the environmental footprint of your farm.
RURAL Thank you Contact details: Roger MacGibbon National Technical Director Opus Rural Mobile: 027 496 1365 Email: roger.macgibbon@opus.co.nz