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TECHNICAL REPORTS

Waste Management

Tile Water Quality following Liquid Swine Manure Application into Standing Corn

^a Agriculture & Agri-Food Canada, Southern Crop Protection & Food Research Centre, 1391 Sandford Street, London, ON, Canada N5V 4T3
^b Agriculture & Agri-Food Canada, Southern Crop Protection & Food Research Centre, Delhi, ON, Canada, N4B 2W9
^c Agriculture & Agri-Food Canada, Eastern Cereal Oilseed Research Centre, 960 Carling Ave., Ottawa, ON K1A 0C6

^* Corresponding author (ballb{at}agr.gc.ca)

Received for publication August 3, 2006.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
The quality of water draining fields fertilized with liquid swine (Sus scrofa) manure (LSM) sidedressed into standing corn (Zea mays L.) at rates ranging from 0 to 94 m³ ha^–1, either topdressed (TD) onto the surface, or injected (INJ) into the soil once annually for each of three consecutive years was evaluated. Liquid swine manure application rate was a critical driver of preferential flow of LSM to tile as detected by turbidity, concentrations of NH₄⁺–N, dissolved reactive phosphorus (DRP), and the presence of enteric bacteria (Escherichia coli). Contaminant movement to drains occurred immediately after 75 and 94 m³ LSM ha^–1 were injected (e.g., 2.5 mg DRP L^–1, 3-yr average). With injection of 56 m³ ha^–1 or less, drainage water was not turbid and concentrations of NH₄⁺–N, DRP, and enteric bacteria were dramatically lower than with the higher rates, even when tiles flowed freely during manure application. Application method also affected tile water quality. With TD applications (37 and 56 m³ ha^–1), nutrients and bacteria did not move to tiles at the time of application, but with rains that fell within 3 d after application, concentrations increased (e.g., 0.1 mg DRP L^–1), although less than with INJ. Overall, sidedress injection rates that supplied adequate crop nutrients did not compromise drainage water quality.

Abbreviations: DRP, dissolved reactive phosphorus • INJ, inject • LSM, liquid swine manure • TD, topdress

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
THE fertilizer value of manure can be optimized by carefully matching application rates and timing with crop nutrient needs. Improving nutrient use efficiency will also reduce the availability of nitrogen and phosphorus that can be transported to adjacent water, or be converted to radiative trace gases, an important environmental benefit. Many confined livestock production systems store their manure as a slurry. In Canada for example, about 85% of swine and 43% of dairy cattle are produced on farms that use liquid manure storage systems (Statistics Canada, 2002). The uniformity in the chemical and physical composition of liquid swine manure (LSM) make it amenable to precise application into standing crops. Sidedressing provides an opportunity to synchronize LSM application with periods of high evapotranspiration and nutrient absorption by crops. On tile drained land, scheduling manure applications when soil and plant conditions are most amenable for absorbing liquid materials, may be beneficial for reducing the potential for contaminant movement to surface waters as well as minimizing soil compaction resulting from additional field trafficking (Geohring et al., 2001; Hodgkinson et al., 2002). Another advantage of sidedress application is the availability of tools to determine optimal rates more precisely such as the pre-sidedress nitrate test. If the slurry is subsurface-applied through injection, nutrients are placed directly into the root zone, N is immediately available to the crop, and runoff potential, N loss through ammonia volatilization, and offensive odors are minimized. In the case of topdressing, bacteria may be inactivated more quickly than when material is incorporated (Hutchison et al., 2004), but the risk of contaminant movement to surface waters by runoff is increased and N loss reduces yield (Ball Coelho et al., 2005). Some disadvantages of sidedressing manure include matching row lengths to tank volumes to minimize traffic and labor requirements and risk of not completing the application due to adverse weather conditions.

We have determined LSM sidedress rates that are agronomically optimal for grain corn produced under commercial conditions in southern Ontario, Canada (Ball Coelho et al., 2005, 2006). As with all forms of manure or biosolids application to fields, there are variable risks associated with contaminating adjacent water through surface runoff or leaching to tile drains (Dean and Foran, 1992; Shipitalo and Gibbs, 2000). In southwestern Ontario, about 80% of cropped land is artificially drained (Spaling and Smit, 1995). The transport of LSM constituents to tile drainage water, in particular by preferential flow at the time of application or shortly thereafter must be managed to avoid contaminating adjacent water (e.g., Akhand et al., 2006). Although sidedressing has been shown to be agronomically beneficial, the impact of sidedressing on environmental quality, specifically tile drain contamination potential, has not been adequately elucidated (Ball Coelho et al., 2005). Thus, the purpose of the research undertaken here was to characterize the movement of nutrients and enteric bacteria from tiles draining fields receiving LSM via sidedressing. Our specific objectives were to: evaluate the impact of sidedress LSM application rates and delivery methods (surface banding vs. subsurface injection) on tile water quality over three production seasons.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Cultural Practices and Site Characterization
Eight sidedress manure treatments were arranged in a randomized strip plot design with two replicates as illustrated in Ball Coelho et al. (2006), on a Typic Hapludalf, Huron silt loam series on a commercial farm in southwestern Ontario (43°44' N, 81°01' W). The site had been cropped with wheat before the experiment, had no known history of manure application, and continued to be managed under conventional till (fall plow followed by spring secondary tillage) for the duration of the experiment. Each 12-row plot (9.1 m wide by 206 m long) was centered over a different drainage tile line (installed 20 yr previously). Corn (hybrid NK3030 in 2000 and DKC4222 in 2001 and 2002) was planted in late April or early May each year in 75-cm rows, with 47 L ha^–1 6-26-6 in-furrow. Final population was 73000 plants ha^–1 in 2000 and 75000 plants ha^–1 in 2001, but less in 2002 (47000 plants ha^–1), mainly due to poor emergence during several weeks of cold weather after planting followed by soil crusting.

Sidedressing was completed within 24 h each year in mid- to late June (30 June–1 July 2000, 19 June 2001, and 19 June 2002). Injected (INJ) application rates were 0, 37.4, 56.1, 74.8, and 93.5 m³ LSM ha^–1 in 2000; 0, 18.7, 37.4, 56.1, and 74.8 m³ LSM ha^–1 in 2001; and 0, 28.1, 37.4, 56.1, and 74.8 m³ LSM ha^–1 in 2002. Surface-applied (topdress, TD) rates were 0, 37.4, and 56.1 m³ LSM ha^–1 each year. Liquid swine manure from a finishing hog barn with wet/dry feeders was agitated in the lagoon during loading, in the nurse tanks (used in 2001 and 2002 to minimize treatment application time), and in the applicator tank to ensure that uniform material was applied to all treatments each year (Table 1). Manure was applied using a 15 m³ row-crop applicator with in-tank mixing (Nuhn Industries, Sebringville, ON) and an electronic flow control system (Green Lea Ag Centre, Mount Elgin, ON). The six-row tool bar was equipped with Vibro Shank (Kongskilde Ltd., Strathroy, ON) injectors (15-cm share) on 75-cm centers with one coulter mounted in front of each injector. In 2001 and 2002 disk hillers were mounted behind each injector, which provided better coverage of the manure with soil given the shallow placement. Injectors were set at a depth of 10 to 15 cm for the INJ treatments, and raised 15 to 25 cm above the soil surface for the TD treatments. Physical effects due to compaction or entrainment of the injectors through the soil were normalized in unmanured control plots as follows. The tractor and loaded manure tanker were driven over these plots, with the injectors either above the soil surface (LSM₀ TD) or in the soil (LSM₀ INJ), but no manure was applied. Further details regarding application equipment, cultural practices, and corn grain yields are reported in Ball Coelho et al. (2005).

Two tipping bucket rain gauges (TE525, Campbell Scientific Inc., Edmonton, AB) and two (2000) to four (2001 and 2002) automated reflectometers (CS-615, Campbell Scientific Inc., Edmonton, AB) to monitor soil water content were located at the site from 1 June to 13 Nov. 2000, 10 May to 29 Oct. 2001, and 11 May to 3 Nov. 2002. Reflectometers were placed in the top 15 cm of soil (45° angle) and were calibrated using soil from the experimental area as described in Ball Coelho et al. (2003).

Tile Water Sampling and Analyses
Access holes to collect tile water were excavated at the downstream ends of the plots (i.e., one per plot) and stabilized using plastic barrels (Ball Coelho et al., 2006). Initially (June 2000) holes were excavated in only the LSM₀, LSM_56.1, and LSM_93.5 INJ, and LSM_56.1 TD treatment plots, then access to all treatment plots was completed in October 2000. Depth to tile at the access points ranged from 55 to 79 cm. Grab samples were taken in 2000 and 2001 until approximately fall freeze-up (November or December). In 2002, automated water samplers (Isco Inc., Lincoln, NE) were used to collect water from all but four tile outlets (both replicates of LSM₀ TD and LSM_28.1 INJ), where samples were collected manually. Automated (float-triggered) sump pumps placed in the access barrels removed any standing water and prevented back-flow up the tile. Liquid level actuators (Isco Inc., Lincoln, NE) were used to trigger the samplers whenever flow occurred. When flow was continuous, samplers were programmed for collection every 15 min for the first few hours after application (to capture preferential flow), and for every hour thereafter. Samples were collected in triplicate one after the other (i.e., within 1 min or as soon as the next 500 mL accumulated). In 2002, a Com100 Motorola cellular transceiver and Com200 modem were used to call the data logger remotely to determine the occurrence of rainfall events. Tile flow rate was estimated using either the time required to collect a given volume of sample (manually collected samples) or recorded trigger times (automated sampling). Occasionally (on 10 July and 2 Aug. 2000) tiles could not be sampled due to flooding, i.e., tile flow rate exceeded pumping capacity of the access area or the stream level was above the header outlet and flow reversed.

Total coliforms and Escherichia coli (E. coli) in selected water samples were measured by membrane filtration. In 2000, bacteria were measured at a commercial laboratory (A & L Laboratories, London, Canada) within 24 h of collection. Subsequently, total coliforms (2001) and E. coli (2001, 2002) in water were enumerated at Agriculture and Agri-Food Canada using Standard Methods 9222B and 9222D modified by the use of BCIG in the mFC medium (Cieben et al., 1995; APHA, 1998). Water was filtered through sterile 0.45 µm pore size, 47 mm cellulose acetate filters (Pall Gelman GN-6, VWR Int., Mississauga, ON). Filters were aseptically transferred to mEndo agar for enumeration of total coliforms, or mFC-BCIG agar (Difco, Fisher Sci., Mississauga, ON) for enumeration of E. coli.

Water from all sampling occasions was filtered (0.45 µm) and frozen before determination of NH₄⁺–N (Liao, 1999) and molybdate-reactive phosphorus (Diamond, 2000) concentrations by flow injection (Lachat Instruments, Milwaukee, WI) colorimetry. Amounts of NH₄⁺–N and dissolved reactive phosphorus (DRP) transferred to tiles the week following application were estimated from flow and concentration (plot basis) and converted to an area basis using the 9.1 m systematic tile spacing.

Statistical Analyses
Treatment effects on NH₄⁺–N and DRP concentrations in drainage water were immediate (within 1 h) but short-lived. To facilitate comparisons, data collected within approximately the week of application when treatment effects were highly evident each year, were analyzed separately from data collected throughout the remainder of the season and into the following spring. The Mixed procedure for repeated measures (SAS Institute, 1999) was used, with sampling event within a year specified as the repeated effect (replicate pooled across method x rate as the subject). Replicate was specified random and the Akaike Information Criterion for goodness of fit (Littell et al., 1998) was used to determine the appropriate structure of the covariance matrix. All tile water NH₄⁺–N concentration datasets and DRP concentrations near the time of application were transformed logarithmically (base 10) to achieve or improve normality. When treatment effects were significant, means were compared using the protected LSD at a 0.05 probability level. Correlations (r) between injection rate and E. coli, total coliforms, and DRP and NH₄⁺–N concentrations in tile water near the time of application each year (except bacteria in 2001 when fewer samples were enumerated) were obtained using PROC CORR (SAS Institute, 1999).

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Soil Background
Soil organic matter, texture, and bulk density to below tile depth are given in Table 2. Soil pH in the top 20 cm was 7.1. Initially, sodium bicarbonate-extractable P in topsoil averaged 30 mg kg^–1. After the 3 yr of study, bicarbonate-extractable P increased to 40 mg kg^–1 where the application rate was 74.8 m³ ha^–1. At the surface, K_fs and _ae averaged less where LSM was topdressed than where injected (Table 2). Below the tillage layer (at 20 cm deep), K_fs and _ae did not vary with treatment. Thus there was potentially some unknown influence of treatment on these hydraulic properties. When sidedressing occurred each year, topsoil water content ranged from 0.40 to 0.42 m³ water m^–3 soil, near to saturation (0.44 m³ m^–3), but suitable with respect to trafficability.

View larger version (66K): [in this window] [in a new window]   Fig. 1. Daily rainfall and flow, and logarithm of number of Escherichia coli and total coliforms and of NH4+–N and dissolved reactive phosphorus (DRP) concentrations in tile drainage water near the time of inject (INJ) or topdress (TD) application of different rates of sidedressed liquid swine manure (LSM) in (A) 2000, (B) 2001, and (C) 2002 (all but total coliforms). LSM subscript indicates rate in m3 ha–1. Time scales are logarithmic and labeled so that 0 = time of LSM application for each plot (negative values on the time scale thus refer to sampling events before application). Breaks in the x axis separate sections of data with different time scales or indicate instances when no samples were collected.

Correlations (r) between NH₄⁺–N concentrations in tile water near the time of application and injection rate were 0.34 (P < 0.02) in 2000, 0.39 (P < 0.005) in 2001, and 0.36 (P < 0.0001) in 2002. Tile water DRP concentrations were similarly correlated with injection rate in 2000 (r = 0.33, P < 0.03), 2001 (r = 0.39, P < 0.0004), and 2002 (r = 0.54, P < 0.0001). Escherichia coli numbers were correlated with injection rate (r = 0.42, P < 0.01 in 2000; r = 0.39, P < 0.0001 in 2002) whereas total coliforms numbers were not (r = 0.24, P < 0.16 in 2000). The significant correlations indicate that contamination increased with injection rate. The relation was not likely linear, as indicated by treatment comparisons and quantification of nutrient loads (Table 4)—above a threshold around 56 m³ ha^–1 there was a dramatic increase with rate.

Liquid Swine Manure Sidedress Method and Rate Effects on Quantity of Ammonium Nitrogen and Dissolved Reactive Phosphorus Moving to Surface Water
The amounts of NH₄⁺–N and DRP (on a hectare basis) transported to tiles within the week following application were more sensitive to the LSM application rate than the application method. In 2000, NH₄⁺–N and DRP transport was greater from LSM_93.5 than LSM_56.1 (INJ), though quantities were small relative to other years (Table 4), probably due to less flow that year (Fig. 1). All accessible tiles were flowing on 30 June 2000 (date of application for LSM_56.1 INJ and LSM_56.1 TD). The following day (1 July 2000) flow had stopped, but was initiated by injection of 93.5 m³ ha^–1. Flow continued for approximately 3 h and ceased in the evening of 1 July. In both 2001 and 2002, tiles were flowing at the time of application (Fig. 1). Transport generally increased with application rate in 2001. Increased NH₄⁺–N and DRP transport to tile with rate was most clearly demonstrated in 2002, when sampling intensity was greatest, with the largest increases occurring between LSM_56.1 and _74.8 INJ (Table 4).

Amounts of NH₄⁺–N and DRP transported through tiles to surface water during the week following application were sometimes affected by method of application. In 2000 and 2002, transport of NH₄⁺–N and DRP was greater with INJ than TD (Table 4). Method effects were relatively minor, likely because the comparisons were being made across rates that were lower than those causing significant preferential flow. Considering only small improvement in tile water quality with TD, injection application is a better practice than TD if similar (to our study) volumes and equipment (aggressive subsurface tillage action) are used, because of important advantages such as N conservation in the soil–plant system and reduction of odors (Ball Coelho et al., 2006). While decline of some bacteria species can be more rapid when wastes are left on the surface rather than incorporated, risk of their movement by other pathways such as insects, wildlife (Hutchison et al., 2004), and runoff directly into surface waters, is greatly increased.

Fortunately, injection at rates below that resulting in preferential flow supplied adequate nutrients for crop production. Provided that LSM contains at least 4 g N kg^–1, sidedress injection rates in excess of 46 m³ ha^–1 will not promote greater corn grain yields (Ball Coelho et al., 2005). Given this, LSM sidedress rates can be adjusted to achieve maximum economic yield benefit while maintaining a minimal risk of tile drainage water contamination. Achieving the maximum yield benefit with LSM that has a lower N content will necessitate the application of higher volumes, an environmentally unwelcome practice as shown by our results. Therefore, maintaining the N content at or above 4 g N kg^–1, most easily achieved by minimizing the amount of water that dilutes the slurry and managing dilution of the stored LSM by precipitation, should be considered a key component of LSM sidedress better management practices. While results presented here are site-specific, particularly with respect to soil structure, risk of movement under different conditions can be dealt with using a modeling approach (Akhand et al., 2006).

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Generally concentrations of NH₄⁺–N and DRP in tile water were low to undetectable before application (background), increased with manure application rates, and returned to pre-application values within 1 wk each of the 3 yr of the sidedress experiment. Application method, INJ (75-cm spacing) or TD compared at 56 m³ ha^–1, had only a minor impact on contaminant movement to tiles. Concentrations of NH₄⁺–N, DRP, and E. coli increased immediately following injection, whereas increases were usually not observed until several days after topdressing, and were related to rain events. The rate of application had a consistently significant impact on LSM movement to tile each year. With high (74.8 or 93.5 m³ ha^–1) sidedress rates (INJ only), NH₄⁺–N, DRP, and E. coli concentrations increased, particularly in the 24 h immediately following application. At lower application rates, which encompassed volumes sufficient to supply crop nutrient requirements, concentrations were dramatically reduced. A rate cap of 56 m³ ha^–1 with 75-cm injector spacing or 112 m³ ha^–1 with 38-cm spacing would be a reasonable restriction for minimizing preferential movement of slurry to tiles. Sidedressing is agronomically important (Ball Coelho et al., 2005) and this study has shown that highest tile drain contamination results from preferential flow of LSM to tile during and immediately following sidedress application; a process that can occur during non-sidedress application practices (Dean and Foran, 1992). Such preferential flow contamination risk is apparently manageable in terms of rate and application practice. Therefore sidedressing (in form discussed here) would appear to be no more of an environmental liability than similar forms of application pre-plant or post-harvest, since for sidedressing at least, there is uptake of nutrients by the standing crop that might otherwise be available for subsequent transport to tile drain systems. Overall, this work has shown that injection of LSM into a standing corn crop, using adapted equipment and judicious application rates and timing, can achieve optimal crop yield without significant transport of manure constituents to drainage tiles.

	ACKNOWLEDGMENTS

 
This work was funded by Ontario Pork and Agriculture and Agri-Food Canada's Matching Investment Initiative. We thank Nuhn Industries, Green Lea Ag Centre, A and L Laboratories, Great Lakes New Holland, Dekalb, Ontario Ministry of Agriculture and Food, T. Groenestegue, V. Hulsof, A. Bruin, A. More, K. Henning, A. Scott, M. Edwards, and AAFC-farm operations for their contributions to this study.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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