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Mackay Whitsunday Paddock to Reef Regional Paddock Trials Summary Report 2011

Mackay Whitsunday Paddock to Reef Regional Paddock Trials Summary Report 2009-2010

Adam Folkers, Reef Catchments

The Methods and Results presented in this report have been summarised from K. Rohde and A. Bush (2011) Paddock to Sub-catchment Scale Water Quality Monitoring of Sugarcane Management Practices – Interim Report 2009/2010 wet season. Department of Environment and Resource Management, Mackay, Queensland. For further information please refer to this report. 1) Executive Summary

To understand the water quality impacts of improved sugarcane management practices, detailed water quality monitoring of seven treatments was undertaken at two sites in the Sandy Creek catchment, located near Mackay. Site 1 (Victoria Plains soil) Controlled traffic (1.8 m row spacing) compared to conventional traffic (1.5 m row spacing) reduced runoff by 18% (665 mm and 810 mm, respectively from 1636 mm rainfall). Controlled traffic also resulted in lower concentrations of sediment (TSS) (1.8 m row spacing; 631 mg/L 1.5 m row spacing; 826 mg/L) and delayed runoff by ~6 minutes. Herbicide residues of Diuron and Hexazinone were elevated in the first two runoff events (within 14 days of application) from Treatment 1 (Velpar K4 applied). These two runoff events represented 64% and 91% of the season’s Diuron and Hexazinone losses, respectively (but only 11% of the runoff). Atrazine residues were detected in both treatments, despite not being applied during the study. Site 2 (Marian soil) NOx concentrations were similar between the five treatments, and show exhaustion and degradation over the wet season. Initial runoff concentrations were 400-600 µg N/L, 10-fold less than at Site 1 with surface soil NOx concentrations also being 3-fold less than those at Site 1, both contributing to lower concentrations in runoff. Initial herbicide concentrations were much lower than those detected at Site 1, but still declined through the wet season. Herbicides were applied 88 days prior to the first runoff event, compared to 8 days at Site 1, highlighting the effect of timing on management practices in relation to rainfall.

2) Introduction The Paddock to Reef program was implemented in the Mackay Whitsunday region to quantify water quality in runoff and drainage from differing levels of sugarcane management practices (A, B and C classes). Information on nutrient, sediment and chemical loads moving off farm has been collected through detailed water quality monitoring sites. This information will be used to provide feedback on the effectiveness of management practices regionally as well as populate models to calculate catchment load reductions. Several water quality studies have shown sugar cane to export high concentrations of dissolved inorganic nitrogen (compared to “natural” sites) (Bainbridge et al. 2009; Bramley and Roth 2002; Hunter and Walton 2008; Rohde et al. 2008). Sugar cane has also been identified as the major contributor of residual herbicides ametryn, atrazine, diuron and hexazinone found in surface waters in the GBR region (Bainbridge et al. 2009; Faithful et al. 2006; Lewis et al. 2009; Rohde et al. 2008). To improve the water quality of the GBR lagoon, Reef Rescue funding is increasing the adoption of land management practices that reduce the runoff of nutrients, pesticides and sediment from agricultural land. To understand the relative effectiveness from the adoption of improved sugar cane management practices implemented through Reef Rescue, detailed monitoring sites have been established in the Sandy Creek Catchment. The sites utilise differing levels of soil management, nitrogen and herbicide applications to determine how management practices (A, B and C classes) affect water quality. Rainfall, flow and water quality data measured over the 2009/2010 wet season is presented.


3) Methods The Mackay Whitsunday Paddock to Reef trials are located in the Sandy catchment, south-west of Mackay. The trials consist of seven paddock scale monitoring treatments located over 2 monitoring sites (Figure 1). Site 1 is located near Mt. Vince west of Mackay and consists of 2 treatments on a Victoria Plains soil type with a slope of 1.1%, in a plant cane crop after a soybean fallow. Victoria Plains soil is a uniform clay derived from quaternary alluvium. The soil across the site can be generally described as a deep (>1.6 m) black to dark grey self-mulching medium clay. Site 2 is located near North Eton south west of Mackay and includes 5 treatments located on a Marian soil with a slope of 0.4%, in a plant cane crop after a plough out and replant fallow. The soil is a duplex derived from quaternary alluvium. The soil across the monitoring site can be generally described as a 0.3 m deep, very dark brown (sometimes greyish) to black sandy or silty clay loam. Runoff from both a multi-block (catchment area of 53.5 ha) and multi-farm (catchment area approximately 2965 ha) scale were also collected and analysed for water quality from sugarcane management practices at larger scales, but are not presented within this report.

Figure 1. Location of monitoring sites in the Sandy Creek catchment - Mackay Whitsunday

Region. A description of management practices and A, B, C classification undertaken at a paddock scale over the 2009/2010 wet season are described in Table 1.


Table1. Soil, Nutrient and Herbicide management practices ABCD

Classification Soil Management

Nutrient Management

Herbicide Management 1

Site 1. Victoria Plains soil. Treatment 1 CCC 1.5 m current

practice Generalised recommendation (133 kg N/ha) 6

Residual 7

Treatment 2 BAA 1.8 m controlled traffic

N replacement (38 kg N/ha)

Knockdown 8

Site 2. Marian soil. Treatment 1 CCC 1.5 m current

practice Generalised recommendation (191 kg N/ha)

Residual 2

Treatment 2 BCC 1.8 m controlled traffic

Generalised recommendation (191 kg N/ha)

Residual 2

Treatment 3 BBB 1.8 m controlled traffic

Six easy steps (172 kg N/ha)

Knockdown/Residual 3

Treatment 4 BAA 1.8 m controlled traffic

N replacement (97 kg N/ha)

Knockdown 4

Treatment 5 ABB 1.8 m controlled traffic, skip row

Six easy steps (164 kg N/ha)

Knockdown/Residual 5

Notes: referring to soil, nutrient and herbicide management classes, respectively. 1 – All treatments had Amicide at 1L/ha (2,4- amicide at 625 g/ha) knockdown herbicide applied for broadleaf weed and

vine control and Hero (ethoxysulfuron 150 g/ha) for nutgrass control. 2 – Atradex 900 and Diurex 900 residual herbicides at 2.2 kg/ha each (Atrazine 1980 g/ha and Diuron 1980 g/ha) 3 – Combination of low or banded rate of residual and knockdown herbicides Dual Gold 1.2 kg/ha (s-metolachlor 1152

g/ha). 4 – Application of knockdown herbicides MCPA 625 (MCPA 625 g/ha) at 1 L/ha and Starane 400 (fluroxypyr 120g/ha) at 0.3

L/ha. 5 – Combination of low or banded rate of residual herbicides on cane rows; MCPA 625 (MCPA 625 g/ha) at 1 L/ha and

Starane 400 (fluroxypyr 120g/ha) at 0.3 L/ha. 6 – Nitrogen rate applied does not take into account the contribution from the soybean crop 7 – Velpar K4 at 4kg/ha (Diuron at 1872 g/ha and Hexazinone at 528 g/ha), Gramoxone 250 (paraquat 250g/ha) at 1 L/ha,

Baton (2, 4-d amine 560 g/ha) at 0.7 kg/ha, MCPA (MCPA 938 g/ha) at 1.5 L/ ha and Starane 400 (fluroxypyr 200 g/ha) at 0.5 L/ha.

8 – Gramoxone 250 (paraquat 250g/ha) at 1 L/ha, Baton (2, 4-d amine 560 g/ha) at 0.7 kg/ha, MCPA (MCPA 938 g/ha) at 1.5 L/ha and Starane 400 (fluroxypyr 200 g/ha) at 0.5 L/ha.

Sampling description

Each treatment monitoring site is controlled using a Campbell Scientific CR800 data logger. When runoff water begins to flow through the San Dimas flumes (see following), the station will begin the pre-programmed sampling routine. Rainfall is measured at each site using a Hydrological Services TB4 tipping bucket rain gauge and recorded by the data logger allowing for measurements of rainfall volume and intensity San Dimas flumes (300 mm; Figure 2) are used to measure the discharge from each treatment. Rubber belting is used as bunding to collect runoff from inter-rows and direct the runoff water into the flume for discharge measurement and sample collection. Water depth is measured using a Campbell Scientific CS450 stainless steel SDI-12 pressure transducer installed in a stilling well at the side of the San Dimas flume Water samples are collected using an Isco Avalanche refrigerated auto-sampler. The logger is programmed to take a sub-sample (~160 mL) for every 3 mm of runoff, filling each bottle consecutively. The bulked samples were sub-sampled and analysed for total suspended solids (TSS), nutrients (total and filtered), and herbicides where possible (depending on volume collected). Two soil water solution samplers were installed in each treatment (in close proximity to the subsurface EnviroSCAN’s,) at a depth of 0.9 m to collect drainage water quality below the rooting depth.


Figure 2. A 300 mm San Dimas flume (left) and critical design dimensions (right) Events, such as farm operations (including tillage, nutrient and pesticide applications), action that change ground cover and growth stages of the crop (including date of emergence, canopy closure, crop destruction) were recorded in a comprehensive field diary. 4) Results Fifteen rainfall events causing runoff occurred over the 2009/10 wet season at Site 1 and thirteen runoff events at Site 2. Persistent flooding at Site 2 created challenges in collecting accurate water quality samples at the lower end of the site (primarily treatments 1 and 4). To maintain scientific integrity automatic samplers were switched off during site flooding and samples that were collected while the flumes were inundated were discarded. Due to the uncertainty in flow rates through the flumes nutrient, sediment and herbicide loads were not calculated for this site.

Site 1. (Victoria Plains Soil) Runoff events from Treatment 2 (1.8 m row spacing) averaged 18% less than Treatment 1 (1.5 m row spacing) (665 mm and 810 mm, respectively) (Figure 3). Runoff from Treatment 1 was delayed by ~6 minutes compared with Treatment 2, and the peak runoff rate was ~2% lower, all contributing to reduced runoff.


Total Event Rainfall and Runoff Victoria Plains Treatments

0

50

100

150

200

250

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Rainfall Event

Tota

l (m

m)

Rainfall

Runoff T1

Runoff T2

Figure 3. Rainfall and runoff for Site 1 treatments in the 2009/10 wet season TSS concentrations ranged from 97 to 3000 mg/L in Treatment 1 with an average of 826 mg/L. TSS in Treatment 2 ranged from 35 to 1200 mg/L with an average TSS concentration of 631 mg/L (see Figure 4). Turbidity detected in runoff showed no obvious patterns between treatments and throughout the wet season.

Total Suspended Solids

0

500

1,000

1,500

2,000

2,500

3,000

3,500

23/12/2009 2/01/2010 12/01/2010 22/01/2010 1/02/2010 11/02/2010 21/02/2010 3/03/2010

Date

Con

cent

ratio

n (m

g/L)

Victoria Plains T1Victoria Plains T2

Figure 4. Event mean TSS concentrations measured in paddock runoff from Site 1. Nitrogen oxide concentrations from Treatment 1 (high N) ranged from 13,626 µg N/L in the first runoff event to 58 µg N/L in the final event (Figure 5). The average and median NOx concentrations recorded were 905 µg N/L and 204 µg N/L respectively. Treatment 2 (low N) concentrations ranged between 4604 µg N/L in the first runoff event and 191 µg N/L in latter events, with a mean of 1087 µg N/L and a median of 473 µg N/L.


NOx

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

23/12/2009 2/01/2010 12/01/2010 22/01/2010 1/02/2010 11/02/2010 21/02/2010 3/03/2010

Date

Con

cent

ratio

n (u

g N

/L)

Victoria Plains T1Victoria Plains T2

Figure 5. Event mean NOx concentrations in runoff from Site 1 treatments In Treatment 1, Diuron and Hexazinone were detected in all samples. Concentrations decreased exponentially with time over the two month sampling period (R2 values of 0.776 and 0.866 respectively) (Figure 6 and Figure 7).

Diuron

y = 10.475e-0.0526x

R2 = 0.776

y = 0.4208e-0.0395x

R2 = 0.85440

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60

Days after first runoff

Diu

ron

(ug/

L)

T1T2Expon. (T1)Expon. (T2)

Figure 6 Regression analysis of event mean Diuron concentrations in runoff from Site 1 In Treatment 2, trace levels of Atrazine (and its breakdown products), Diuron and Hexazinone were detected in all runoff samples at concentrations of 1 µg/L or lower (Figure 6, Figure 7, and Figure 8). These levels, found for both treatments, are thought to be residual concentrations from previous applications.


Hexazinone

y = 31.376e-0.1492x

R2 = 0.8661

y = 0.3571e-0.0611x

R2 = 0.75830

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60


Hex

azin

one

(ug/

L)


Figure 7 Regression analysis of event mean Hexazinone concentrations in runoff from Site 1

Atrazine

y = 0.7076e-0.0253x

R2 = 0.4965

y = 0.6456e-0.0356x

R2 = 0.6292

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50 60


Atr

azin

e (u

g/L)


Figure 8 Regression analysis of event mean Atrazine concentrations in runoff from the Site

1 treatments Soil water solution samples were collected twice (at a depth of 0.9m) from each treatment in the wet season, in late January and mid February. Both sites recorded residual Atrazine and its breakdown products in low concentrations with concentrations never exceeding 0.1 µg/L in Treatment 1.

Site 2 (Marian soil) A total of 1782.6 mm of rainfall was recorded at Site 2 between December 1st 2009 and March 31st 2010 resulting in thirteen runoff events occurring. Event rainfall and runoff at Site 2 are shown in Figure 9.


Total Event Rainfall and Runoff Marian Sites

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12 13

Rainfall Event

Tota

l (m

m)

RainfallRunoff T1Runoff T2Runoff T3Runoff T4Runoff T5

Figure 9 Rainfall and runoff for Site 2 treatments in the 2009/10 wet season Total Suspended Solids (TSS) concentrations varied from 36-330 mg/L, with 78% of samples having TSS concentrations less than 200 mg/L. The Turbidity ranged from 64-490 NTU, with the average similar between treatments (206-230 NTU). No immediate treatment effects are evident for either TSS or Turbidity. The Relationship between Total Suspended Solids and Turbidity can be seen in Figure 10.

Total Suspended Solids and Turbidity

y = 1.1308x + 70.431R2 = 0.7451

0

100

200

300

400

500

600

0 50 100 150 200 250 300 350

Total Suspended Solids (mg/L)

Turb

idity

(NTU

)

Figure 10 Relationship between event mean Total Suspended Solids concentration and

Turbidity at Site 2 Despite Treatment 1 and Treatment 2 having the highest applications of nitrogen fertilisers (190 kg N/ha), Treatment 3 (172 kg N/ha) produced the greatest concentration of NOx runoff (523 µg N/L) in the first runoff event which was more than 100 µg N/L greater than Treatment 2 and more than 250 µg N/L greater than Treatment 1 (Figure 11). Treatments with larger data sets appear to show an exponential decline in NOx concentrations throughout the wet season.


NOx

0

100

200

300

400

500

600

23/12/2009 2/01/2010 12/01/2010 22/01/2010 1/02/2010 11/02/2010 21/02/2010 3/03/2010

Date

Con

cent

ratio

n (u

g N

/L)

Marian T1Marian T2Marian T3Marian T4Marian T5

Figure 11 NOx event mean concentrations in runoff from Site 2 Two soil water solution samples were collected from each treatment. Higher NOx concentrations were recorded in each treatment in the first sampling. Treatment 2 (High N treatment) recorded concentrations that were more than 15 times greater than any other treatment (8,029 and 3,584 µg N/L) including Treatment 1 (111 and 23 µg N/L), the other High N treatment. Despite only being applied to Treatments 1 and 2, Atrazine and it breakdown products (Desethyl Atrazine and Desisopropyl Atrazine) were found in all treatments and in the majority of analysed water samples (Figure 12). Further investigations of block history will be undertaken to try and explain the source of Atrazine in those treatment where it was not applied. The highest recorded concentrations of Diuron (0.12 and 0.04 µg/L) were found in runoff from T1 on two occasions, late in January and late in February. All other sites recorded concentrations of 0.02 µg/L or less. The first runoff event at Site 2 occurred 88 days after residual herbicide applications and runoff concentrations were lower accordingly, for instance, compared to those measured at Site 1 where the first runoff event occurred 8 days after herbicide applications.


Atrazine

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

23/12/2009 2/01/2010 12/01/2010 22/01/2010 1/02/2010 11/02/2010 21/02/2010 3/03/2010

Date

Con

cent

ratio

n (u

g/L)

Marian T1Marian T2Marian T3Marian T4Marian T5

Figure 12. Atrazine event mean concentrations in runoff water from Site 2 5) Discussion

The 2009 – 2010 wet season was in the top 20% of the wettest years since 1989. The particularly wet year has seen high runoff volumes from the seven treatments that potentially caused higher losses of pollutants than would occur in drier and nearer to average years. The wet year may also have led to less response to soil management practices, as the soil remained wet for much of the year.

Runoff from 1.8 m controlled traffic system reduced the volume of runoff water by 18% compared to a conventional 1.5 m system. The 1.8 m system also reduced sediment loss by ~ 23%. These reductions are potentially due to matched wheel traffic, reducing the compaction of cane row beds and improving infiltration. Reducing nitrogen rates to as precise as possible (to meet crop requirements) may result in nitrogen concentrations in runoff that were 3-fold lower compared to conventional nitrogen rates. Banding residual herbicides on top of the bed (using knockdown in the interspaces) and using weather forecasting to avoid heavy rainfall within 7 days of application may greatly reduce herbicide losses in runoff water. 6) References Bainbridge, Z.T., Brodie, J.E., Faithful, J.W., Sydes, D.A. and Lewis, S.E. (2009). Identifying the

land-based sources of suspended sediments, nutrients and pesticides discharged to the Great Barrier Reef from the Tully - Murray Basin, Queensland, Australia. Marine and Freshwater Research 60, 1081-1090.

Bramley, R.G.V. and Roth, C.H. (2002). Land-use effects on water quality in an intensively managed catchment in the Australian humid tropics. Marine and Freshwater Research 53, 931-940.

Hunter, H.M. and Walton, R.S. (2008). Land-use effects on fluxes of suspended sediment, nitrogen and phosphorus from a river catchment of the Great Barrier Reef, Australia. Journal of Hydrology 356, 131-146.

Rohde, K., Masters, B., Fries, N., Noble, R. and Carroll, C. (2008). Fresh and Marine Water Quality in the Mackay Whitsunday Region 2004/05 to 2006/07. Queensland Department of Natural Resources and Water for the Mackay Whitsunday Natural Resource Management Group, Australia.


Rohde, K and Bush, A (2011) Plot to Catchment Scale Water Quality Monitoring – Interim Report 2009/2010 wet season. Department of Environment and Resource Management, Mackay, Queensland

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