A-horizon


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Related to A-horizon: soil profile
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Synonyms for A-horizon

the top layer of a soil profile

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In the study area, the geometric mean concentration of SOC in A-horizon soils was 1.18%, ranging from 0.04% to 5.03%.
The archaeological features and sediments of M24/11 are largely found within or derive from a shallow (30-50 cm) black sand topsoil (A-Horizon) that has developed on a natural shelly sand substrate.
However, a stepwise regression with more variables (such as slope, A-horizon clay content, or bulk density) also indicated cover as the only significant predictor.
Overall, however, the loss of A-horizon thickness is greatest from 1934 to 1968, averaging close to 10 in (25 cm) during that time period.
In the topsoil moder changes into raw humus (Orm) and in the sour A-horizon As eluviation begins by podzolization: AsEp (not so clearly visible in the photo).
The plant humus of both ground litter and of the recently formed A-horizon are similar.
The average thickness of the A-horizon was equal to 17.7 cm.
Physical and chemical properties of bulk samples of the A-horizon sand and the B-horizon clay-rich subsoil from Coonalpyn and Bordertown, South Australia Values in parentheses represent standard deviation Soil horizon Dry bulk density % Clay % Sand (kg [m.sup.-3]) (<2 [micro]m) (20-2000 [micro]m) Coonalpyn, South Australia A-horizon sand 1551 (13) 1 97 B-horizon 1723 (21) 28 71 Bordertown, South Australia A-horizon sand 1499 (11) 2 92 B-horizon 1806 (19) 47 61 Soil horizon PH EC (dS [m.sup.-1]) (1:5 soil : water) (1:5 soil : water) Coonalpyn, South Australia A-horizon sand 6.2 0.02 B-horizon 7.1 0.04 Bordertown, South Australia A-horizon sand 6.5 0.02 B-horizon 8.4 0.18 Table 2.
The stratigraphy in these 10 non-garden test pits consisted of an intact non-culturally modified A-horizon, with either an underlying B-horizon or weathering bedrock.
After recalculations of the depths of sand for the A- and Bw-horizons (4.63 and 1.55 cm, respectively), the solum proved accumulative at the expense of silt in the A-horizon and silt and clay in the Bw-horizon altogether by 14% of initial sandstone (Table 5).
Nutrient availability Geologic Mississippi source River, Loess, Blackland (8) Past use and Undisturbed; present cover near-virgin forest cover, cultivated [less than] 5 yr (5) Organic matter [greater than] 2% (A-horizon) (4) Depth of topsoil [greater than] 6" or no profile (A-horizon) development (3) Soil age Young, no profile development (Entisols) (3) pH (in rooting 5,5 - 7.5 zone) (3) Factor 4.
The traditional approach describes variation of soil morphological features in soil horizons, such as A-horizon thickness and depth to mottles in B-horizons.
As mentioned in 1980, in the second of the series of what are now the ISCO Conferences, improving conditions for organic activity in soils is likely to have benefits in terms of accelerated formation of the A-horizon, better crop growth and less runoff and erosion, with increased likelihood of soils' productivity being sustainable well into the future.
Trend tables were developed for 0-7.5 cm %C, pH([H.sub.2]O), and P retention, and A-horizon total C, total N, exchangeable Ca, and A-horizon thickness.