title: Effects of severe cattle treading on soil physical properties and pasture productivity

authors: Zegwaard, Karsten E.

abstract: Severe cattle treading can result in compaction and pugging, of which the latter was the focus of this thesis. Pugging is one of the severest forms of treading damage to soil, and occurs when soil is grazed while near saturation, resulting in plastic and liquid soil deformation. The research objectives were to quantify effects from one-off treading events, at different severities, on soil physical properties and sward characteristics, to monitor recovery from the one-off treading event, and to develop methods of estimating potential effects of treading on pasture productivity. 
Three field experiments were carried out on a Te Kowhai silt loam soil (NZ soil classification, Typic Orthic Gley; USDA soil taxonomic classification, Typic Endoaqualj) supporting a mixed sward of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). A oneoff treading event of either O ( control), 3, 9, or 24 hours was carried out using lactating Holstein-Friesian cattle (300 cows ha- 1) at three soil moisture contents (65%, 71 %, and 81 % gravimetric soil moisture content). Soil physical properties, soil surface features, and sward characteristics were monitored for up to 34 weeks after the treading event. 
Longer treading durations at wetter soil conditions had increasingly detrimental effects on soil macroporosity, saturated hydraulic conductivity (Ksai), unsaturated hydraulic conductivity (K_40), surface roughness, depths of pug prints, bare ground area, ryegrass tiller density, and herbage accumulation. Soil dry bulk density and total porosity did not change, even under the severest of treading damage, because decreases in macroporosity were offset by increases in microporosity (r2 = 0.63; P <0.001). 
The area of bare ground increased to up to 87% of the soil surface and correlated with decreased in herbage accumulation (r2 = 0.73; P <0.001). Sward botanical composition did not change after treading damage, except when large patches of bare ground persisted into spring, resulting in the establishment of broad-leaved plantain (Plantago major L.). 
Soil and sward recovered (i.e. no significant difference compared to simultaneous controls) following treading damage and when the pasture continued to be rotationally grazed. The recovery of macroporosity, Ksat, and K_40 indicated that the soil had an increased susceptibility to further treading damage for up to 13 weeks after the initial treading event. However, soil susceptibility to direct hoof damage after a one-off severe treading damage event may persist for up to 25 weeks, as sward recovery (decreases in area of bare ground) took longer than the recovery of soil physical properties. 
When the gravimetric soil moisture content was >71 %, a three hour grazing caused a total decline of 1,100 kg OM ha- 1 in pasture productivity, however, at lower soil moisture contents grazing of ::,;3 hours was unlikely to cause significant pasture productivity decline. 
When ~50% of soil penetrations using the AgResearch Penetrometer are ~2 cm, a three hour grazing with 300 cows ha -I is likely to result in pasture productivity decline. Statistical models (multivariate regression models) were used to describe the relationship of soil physical and sward properties with pasture productivity after treading. Assuming that during the grazing rotation no further severe treading damage takes place before recovery is complete, the models can be used to estimate potential pasture productivity decline from a one-off severe treading event on a pugging susceptible Te Kowhai soil using variables measured immediately before or after cattle treading. The models with the best potential for practical applications were: 

DPP*= -1770.98 + l 96.35HR - 4.47HR2 + 32.1 lAP 	                r2 = 0.72, P <0.001
DPP = -1057.55 + 43.17BG 				                                r2 = 0.61, P <0.001
DPP = -863.78 + 179.lOSR					                        r2 = 0.78, P <0.001
DPP = -701.16- 155.89HR + 5.49HR2 + 26.61PD + 122.68SR 	r2 = 0.84, P <0.001
RT* = -6.94 + l .35HR - 0.032HR2 + 0.16AP 		                        r2 = 0.78, P <0.001
RT  = -6.10 + 0.36HR + 0.1 OAP+ 0.58SR 			                r2 = 0.80, P <0.001

Where:
DPP= total decline in pasture productivity (kg OM ha- 1) 
RT= time (weeks) required until no significant difference in herbage accumulation compared to controls 
HR = proposed or actual hours of treading 
AP = AgResearch Penetrometer results (% of readings penetrating soil by ~2 cm) immediately before treading 
BG= proportion of bare ground ('Yc,) after treading 
SR= soil surface roughness index(%) after treading 
PD= mean depth of pug prints (mm) after treading 
* = models using only pre-treading variables 

The declines in spring pasture productivity correlated with declines in macroporosity (r2 = 0.70, P <0.001) and Ksat (r2 = 0.61, P <O.OI ), complementing findings from similar treading studies carried out on soils with compaction rather than pugging damage. A Treading Field Guide was constructed, using bare ground, soil surface roughness, depth of pugging, and photography, which indicated the likely pasture productivity decline. The likely pasture productivity declines were also combined with the potential benefits of using stand-off pads to derive a cost-benefit model.

text: Effects of severe cattle treading on soil physical properties and pasture productivity Severe cattle treading can result in compaction and pugging, of which the latter was the focus of this thesis. Pugging is one of the severest forms of treading damage to soil, and occurs when soil is grazed while near saturation, resulting in plastic and liquid soil deformation. The research objectives were to quantify effects from one-off treading events, at different severities, on soil physical properties and sward characteristics, to monitor recovery from the one-off treading event, and to develop methods of estimating potential effects of treading on pasture productivity. 
Three field experiments were carried out on a Te Kowhai silt loam soil (NZ soil classification, Typic Orthic Gley; USDA soil taxonomic classification, Typic Endoaqualj) supporting a mixed sward of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). A oneoff treading event of either O ( control), 3, 9, or 24 hours was carried out using lactating Holstein-Friesian cattle (300 cows ha- 1) at three soil moisture contents (65%, 71 %, and 81 % gravimetric soil moisture content). Soil physical properties, soil surface features, and sward characteristics were monitored for up to 34 weeks after the treading event. 
Longer treading durations at wetter soil conditions had increasingly detrimental effects on soil macroporosity, saturated hydraulic conductivity (Ksai), unsaturated hydraulic conductivity (K_40), surface roughness, depths of pug prints, bare ground area, ryegrass tiller density, and herbage accumulation. Soil dry bulk density and total porosity did not change, even under the severest of treading damage, because decreases in macroporosity were offset by increases in microporosity (r2 = 0.63; P <0.001). 
The area of bare ground increased to up to 87% of the soil surface and correlated with decreased in herbage accumulation (r2 = 0.73; P <0.001). Sward botanical composition did not change after treading damage, except when large patches of bare ground persisted into spring, resulting in the establishment of broad-leaved plantain (Plantago major L.). 
Soil and sward recovered (i.e. no significant difference compared to simultaneous controls) following treading damage and when the pasture continued to be rotationally grazed. The recovery of macroporosity, Ksat, and K_40 indicated that the soil had an increased susceptibility to further treading damage for up to 13 weeks after the initial treading event. However, soil susceptibility to direct hoof damage after a one-off severe treading damage event may persist for up to 25 weeks, as sward recovery (decreases in area of bare ground) took longer than the recovery of soil physical properties. 
When the gravimetric soil moisture content was >71 %, a three hour grazing caused a total decline of 1,100 kg OM ha- 1 in pasture productivity, however, at lower soil moisture contents grazing of ::,;3 hours was unlikely to cause significant pasture productivity decline. 
When ~50% of soil penetrations using the AgResearch Penetrometer are ~2 cm, a three hour grazing with 300 cows ha -I is likely to result in pasture productivity decline. Statistical models (multivariate regression models) were used to describe the relationship of soil physical and sward properties with pasture productivity after treading. Assuming that during the grazing rotation no further severe treading damage takes place before recovery is complete, the models can be used to estimate potential pasture productivity decline from a one-off severe treading event on a pugging susceptible Te Kowhai soil using variables measured immediately before or after cattle treading. The models with the best potential for practical applications were: 

DPP*= -1770.98 + l 96.35HR - 4.47HR2 + 32.1 lAP 	                r2 = 0.72, P <0.001
DPP = -1057.55 + 43.17BG 				                                r2 = 0.61, P <0.001
DPP = -863.78 + 179.lOSR					                        r2 = 0.78, P <0.001
DPP = -701.16- 155.89HR + 5.49HR2 + 26.61PD + 122.68SR 	r2 = 0.84, P <0.001
RT* = -6.94 + l .35HR - 0.032HR2 + 0.16AP 		                        r2 = 0.78, P <0.001
RT  = -6.10 + 0.36HR + 0.1 OAP+ 0.58SR 			                r2 = 0.80, P <0.001

Where:
DPP= total decline in pasture productivity (kg OM ha- 1) 
RT= time (weeks) required until no significant difference in herbage accumulation compared to controls 
HR = proposed or actual hours of treading 
AP = AgResearch Penetrometer results (% of readings penetrating soil by ~2 cm) immediately before treading 
BG= proportion of bare ground ('Yc,) after treading 
SR= soil surface roughness index(%) after treading 
PD= mean depth of pug prints (mm) after treading 
* = models using only pre-treading variables 

The declines in spring pasture productivity correlated with declines in macroporosity (r2 = 0.70, P <0.001) and Ksat (r2 = 0.61, P <O.OI ), complementing findings from similar treading studies carried out on soils with compaction rather than pugging damage. A Treading Field Guide was constructed, using bare ground, soil surface roughness, depth of pugging, and photography, which indicated the likely pasture productivity decline. The likely pasture productivity declines were also combined with the potential benefits of using stand-off pads to derive a cost-benefit model.

year: 2006

title: A probabilistic dynamic programming model of rape seed harvesting

authors: Foulds, James Richard

subjects: crop harvesting

abstract: We discuss a practical scenario from an operations scheduling viewpoint involving commercial contracting enterprises that visit farms in order to harvest rape seed crops. We report on a probabilistic dynamic programming formulation that was designed specifically for scenarios of the type described. The paper is an extension of previous work from the deterministic one-farm case to allow for: the specific considerations necessary to harvest a particular crop, namely rape seed, harvesting at multiple farms, machine failure, and the fact that activity duration times are uncertain. The computational times experienced in solving practical instances of the formulation are encouraging.

text: A probabilistic dynamic programming model of rape seed harvesting We discuss a practical scenario from an operations scheduling viewpoint involving commercial contracting enterprises that visit farms in order to harvest rape seed crops. We report on a probabilistic dynamic programming formulation that was designed specifically for scenarios of the type described. The paper is an extension of previous work from the deterministic one-farm case to allow for: the specific considerations necessary to harvest a particular crop, namely rape seed, harvesting at multiple farms, machine failure, and the fact that activity duration times are uncertain. The computational times experienced in solving practical instances of the formulation are encouraging.

year: 2006

title: Indigenous bodies: Ordinary lives

authors: Hokowhitu, Brendan

abstract: Ambivalence is the overwhelming feeling that haunts my relationship with physicality. Not only my body, but the bodies of an imagined multitude of Indigenous peoples dissected and made whole again via the violent synthesis of the colonial project. Like my own ambivalence (and by “ambivalence” I refer to simultaneous abhorrence and desire), the relationship between Indigenous peoples and physicality faces the anxiety of representation felt within Indigenous studies in general.

text: Indigenous bodies: Ordinary lives Ambivalence is the overwhelming feeling that haunts my relationship with physicality. Not only my body, but the bodies of an imagined multitude of Indigenous peoples dissected and made whole again via the violent synthesis of the colonial project. Like my own ambivalence (and by “ambivalence” I refer to simultaneous abhorrence and desire), the relationship between Indigenous peoples and physicality faces the anxiety of representation felt within Indigenous studies in general.

year: 2016