Slurry-application implement tine modification of soil hydraulic properties under different soil water content conditions for silt–clay loam soils

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Abstract

Tillage action associated with liquid slurry application systems/management practices can modify soil infiltration properties. The degree or nature of such modification will depend largely on the type of tillage implement used, and the soil conditions at time of tillage activity. The specific objective of this study is to evaluate differences in soil infiltration properties, as measured using pressure infiltrometers and Guelph permeameters, resulting from the immediate tine action of two commonly used slurry application tillage implements (Kongskilde Vibro-Flex (S-tine) and the AerWay SSD (rolling aerator-type tine)) over a variety of silt–clay loam soil water content conditions. The results indicated that there were consistent negative correlations between field saturated hydraulic conductivity and soil water content for all tine-disturbed and undisturbed soil treatments. For Kongskilde, field-saturated hydraulic conductivity was, on average, lower in tine-influenced furrow bottoms, relative to those measured in undisturbed conditions at similar depths for most water content conditions. Generally, the Kongskilde tine-action reduced macropore-based infiltration in the bottom of the furrow for most soil conditions, albeit, this effect was most pronounced at the higher soil water contents. For AerWay, the tine-disturbed soils had generally higher field saturated hydraulic conductivities than undisturbed soil treatments over the observed water content range. This effect was manifested to a greater degree at higher, relative to lower observed water contents.

Introduction

Odour following land application of liquid manures and biosolids can be greatly reduced by soil injection, relative to surface broadcasting (Hanna et al., 2000, Smith et al., 2000). Some other advantages of injection include reduced potential for surface runoff (Van Vliet and Kenney, 2000, Daverede et al., 2004) and increased uniformity or precision in application patterns (Bittman et al., 2002, Ball Coelho et al., 2005). Nevertheless, slurry injection approaches can be associated with higher leaching of nutrients/chemicals (Fleming and Bradshaw, 1992, Smith and Chambers, 1997, Ball Coelho et al., 2007). Fleming and Bradshaw (1992) found that the cumulative loading of N-NH4 to the tile drains was greatest in a manure injected treatment followed by manure broadcast, manure broadcast on previously chiselled ground, and no manure (control) treatments. Ball Coelho et al. (2007) found that the higher the liquid swine manure application rate the greater the tile contamination (dissolved reactive P), and that injection was more problematic for tile drain contamination resulting from macropore flow than surface topdressing.

Macropores are large pores that can transmit fluids and entrained contaminants rapidly via gravity flow processes to groundwater and tile drainage systems effectively bypassing rooting zones where nutrients are needed for crop production (Azooz and Arshad, 1996, Bandaranayake et al., 1998). Finer textured soils that retain macropore memory and functional structure more efficiently than more friable soils (e.g., sands), may be especially prone to these types of macropore-based problems (Flury et al., 1994).

Tillage activities can alter soil structural elements and consequently, can modify soil infiltrability and macropore flow potential (Shipitalo et al., 2000, Wahl et al., 2004). Although there have been many studies that have evaluated tillage effects on soil physical properties, there are fewer studies that examine immediate modification of liquid transmission properties of the soil resulting from tine–soil interaction, under different antecedent soil conditions (Harrigan et al., 2004). Such research is required to define the ability of various kinds of tillage implements to modify macroporosity (infiltrability) in the slurry application zone under a variety of soil conditions that might be experienced during a farming season. The research reported in this paper is a study of infiltration modification under different soil conditions in a clay–loam soil by two tillage implements, the Kongskilde Vibro-Flex and the AerWay SSD.

The Kongskilde Vibro-Flex is a popular tillage implement used with slurry injection systems (e.g., Ball Coelho et al., 2007, McLaughlin et al., 2006). Slurry drop tubes attached to the back of the tines inject slurry onto the bottoms of the newly formed furrows. The tines are designed to augment liquid sorptivity, but can potentially seal off large macropores in the furrow via soil smearing. The AerWay SSD (sub surface deposition) slurry application system uses an aerator-type rolling tine approach in order to enhance sorptivity and lateral infiltration. Moreover, the AerWay system produces, via a tine-twisting action, discrete “soil pockets” that can act as “dead-end” slurry reservoirs. Slurry drop tubes (with openings close to the ground) located behind each tine at the back of the SSD system, immediately bands the slurry over the tine disturbed soils (e.g., Bittman et al., 2002, Bittman et al., 2005). We anticipate that the degree to which said tillage implements will modify soil macroporosity/infiltrability, and subsequently modify potential for tile and groundwater contamination, will depend partially on soil physical conditions (e.g., soil plasticity, soil strength, water content, cracking, etc.) at time of tillage activities.

The global purpose of this research is to elucidate the impact of slurry-application implement tine modification of soil infiltrability in order to help inform slurry application management practice water quality risk assessment efforts (e.g., Akhand et al., 2006). The specific objective of this study is to quantify and evaluate differences in soil infiltrability (via macropore modification) resulting from the tillage action of two contrasting shallow-tillage approaches (Kongskilde Vibro-Flex and the AerWay SSD), over a variety of silt–clay loam soil water content conditions.

Section snippets

Field site

The study site is located on a tile-drained field located near Winchester, Ontario, Canada (lat. 45°03′N, long. 75°21′W) (Fig. 1). The soil is classified as a North Gower clay loam (Orthic Humic Gleysol). The field had been under timothy and brome grass for 9 years prior to 1996 and was never tilled while under hay production. In 1996, the field was subdivided into crop plots, 300 m long and 13 m wide. From 1996 to 2002, the field was under livestock (corn–corn–alfalfa–alfalfa) and cash

Results

Overall, the variability in bulk densities for Kongskilde and AerWay measured over the field were not considered extreme (Fig. 5). Moreover, there were no distinctive measurable and systematic differences between UK and DK bulk density values. The average upper plastic limit determined from 48 samples over the field was 47% (standard error mean (S.E.M.) = 0.47) and the average lower plastic limit was 30% (S.E.M. = 0.31). All soil observations were below the upper plastic limit, and run 11 in

Kongskilde discussion

The data suggest that the Kongskilde tines modestly reduced Kfs along the bottom of the furrow; perhaps the most important tillage zone with respect to vertical liquid transport potential. Hence, infiltration measurements focussed on furrow bottoms in this study. For approximately 80% of the runs, the run average Kfs for the tine disturbed soils were lower than those for the undisturbed soils. Flow limitations induced by smearing and truncation of soil macropores by the tine were visually

Conclusions

The study provided some field-based quantification of AerWay aerator-type tine and Kongskilde vibro-shank tine effects on soil infiltrability under different silt–clay loam initial soil water content conditions: general findings are as follows:

  • (i)

    Infiltrability parameters for Kongskilde (furrow bottom) and AerWay (soil pockets) treatments (and respective undisturbed measures) were measured using pressure infiltrometers and well-based Guelph permeameters, respectively. For both tillage treatments,

Acknowledgements

We wish to acknowledge inputs by Dr. W.D. Reynolds (Agriculture and Agri-Food Canada, Harrow, Ontario), David Irving (University of Guelph-Kemptville), Allen Smith (University of Guelph-Kemptville), Steve Burtt (Agriculture and Agri-Food Canada, Ottawa, Ontario), and Scott Patterson (Agriculture and Agri-Food Canada, Ottawa, Ontario). Funding for this study was provided via the Agriculture and Agri-Food Canada Matching Investment Initiative in cooperation with Ontario Federation of Agriculture,

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