APBI402-6

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Table 1

Size distribution of water-stable aggregates and mean weight diameter (MWD) at 0-7.5 cm depth under 3 grazing systems and 2 stocking rates. [G=grazing system, SR=stocking rate, G ´ SR=grazing by stocking rate interaction]

Parameter Grazing System
Fall FS Spring Source of variation (P Template:Efn )
0 AUM 0.6 AUM 0 AUM 0.6 AUM 0 AUM 0.6 AUM G SR G x SR
kg kg-1 soil
2-6 mm 0.55 0.50 0.55 0.44 0.53 0.50 0.915 0.001 0.019
kg kg-1 soil
1-2 mm 0.09 0.09 0.09 0.09 0.10 0.10 0.666 0.319 0.223
kg kg-1 soil
0.25-1 mm 0.06 0.07 0.06 0.07 0.06 0.07 0.938 0.159 0.903
kg kg-1 soil
<0.25 mm 0.30 0.34 0.31 0.40 0.31 0.34 0.746 0.009 0.105
mm
MWD 2.4 2.2 2.4 2.0 2.3 2.2 0.896 0.003 0.036

Mean weight diameter (MWD) represents the sum of the mean diameter of each size fraction (Di) and the proportion of the sample weight occurring in the corresponding size fraction (Wi) (Nimmo and Perkins, 2002). The summation is carried out over all four size fractions, including the one that passed the 0.25-mm sieve (). Corrections were made for the sand fraction retained on each sieve to avoid biased interpretations of water stable aggregates.

Reference:

Nimmo, J.R. and K.S. Perkins. 2002. Aggregate stability and size distribution. In: A. J.H. Dane and G.C. Topp (Ed.) Methods of soil analysis: Physical methods. Part 4. Number 5 in the Soil Science Society of America Book Series. Madison, WI. pp. 317-328.

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Table 2

Soil bulk density under 3 grazing systems and 2 stocking rates. [G=grazing system, SR=stocking rate, G ´ SR=grazing by stocking rate interaction]

Table 3

Soil water content under 3 grazing systems and 2 stocking rates. [G=grazing system, SR=stocking rate, G ´ SR=grazing by stocking rate interaction]

Table 4

Soil chemical properties under 3 grazing systems and 2 stocking rates. [G=grazing system, SR=stocking rate, G ´ SR=grazing by stocking rate interaction]

Figure 1

Soil penetration resistance under three grazing systems. Error bars represent standard error of the mean (n=24, i.e. two pastures, four sampling units, and three soil profiles per sampling unit) and they are shown only on means that are significantly different (P < 0.05).

Figure 2

Soil penetration resistance under two stocking rates. Error bars represent standard error of the mean (n=24, i.e. two pastures, four sampling units, and three soil profiles) and they are shown only on means that are significantly different (P < 0.05).