We have quantified the effect of land use change by measuring soil physiochemical changes in sandy soils under intensive agriculture, grasslands, and pine forest in the central sands plain of Wisconsin, USA. The soils under agriculture (corn, potato, soybeans, and peas) are irrigated (280 mm yr–1), limed, fertilized, and leveled. Soil observations were made in 82 pedons, and soil horizons, texture, and pH were measured. The soils are all very sandy and somewhat excessively drained. In all pedons, sand percent increases with depth from 88 to 98%; silt content is around 8% until the C horizons where the silt content decreases to 2% on average. Coarse fragments increase at 60 to 100 cm and decrease below 140 cm. Topsoil thickness under agriculture ranged from 20 to 42 cm (mean 28 cm), topsoils under forest ranged from 3 to 27 cm, and topsoils under grassland ranged from 14 to 26 cm. It was found that the soils under agriculture are less acidic, have thicker topsoil horizons, and have slightly more clay, possibly as a result of enhanced mineral weathering. These sandy soils have changed in three decades from Udipsamments and Hapludalfs into Argiudolls and Hapludolls, while some soils have changed from Hapludalfs into Udipsamments. Topsoil depth changes in the Wisconsin Central Sand Plain are the result of intensive agriculture.
Proximal sensing, such as electromagnetic induction, has been used to map the spatial distribution of soil properties; however, the response of these instruments to short-interval variability associated with Vertisols has not been studied. Meter-scale circular landscape features called gilgai, which are associated with surface and subsurface variability, make sampling these soils difficult, especially if the surface has been plowed. The EM38 is an electromagnetic induction tool with a relatively small spatial footprint (1 m 2), which may be fine enough to identify subsoil variability associated with gilgai. In 2011, an EM38 survey was conducted for a 40 by 50 m field with intact circular gilgai in the Texas Blackland Prairies. Soil properties including gravimetric water content, bulk density, inorganic C content, and electrical conductivity of the soil solution were measured. In 2012, half of the field was plowed, and another EM38 survey was conducted. The EM38 was able to locate subsurface variability in soil properties between mirohighs and microlows under both intact and plowed conditions. Semivariance of soil properties increased with increasing distance and reached maximum variance at 3 meters, corresponding to the average diameter of gilgai features. The overall variability across the study site decreased after plowing. Water content and inorganic C content were the primary soil properties that forced the response of the EM38 in these landscapes, and the partial correlation coefficient suggests the effects of water content and inorganic C content on EM38 response are independent. In calcareous Vertisols, the EM38 can be used to identify subsurface variability and may be useful in developing sampling schemes for Vertisol classification, soil sampling, and fine-scale digital soil mapping.
Soil Survey Horizons was first published in 1960, and the 50th volume was published in 2009. Here we analyze what has been published in those 50 volumes (5575 pages). We classified 1080 contributions as to their focus (e.g., mapping, soil genesis), geographic origin, and what U.S. Soil Taxonomy order was described or studied. Almost 40% of all contributions focused on soil mapping. The number of soil mapping contributions had its peak in the mid‐1980s and then gradually dropped but has been on the increase since 2005. Soil genesis, soil classification, and soil morphology were the focus of more than 150 contributions each. Soil Survey Horizons always has had a steady number of contributions, which we classified as “reflections on the discipline,” and has published a number of ideas that were ahead of their time. Most of the contributions have come from the Central and Midwest part of the United States, and a considerable number of those have focused on Mollisols. Less than 10% of the contributions have been from outside the United States. In the past 50 years, Soil Survey Horizons has developed from a U.S. Midwest pedology and soil survey newsletter into a broader publication with research articles and reports.
Stands, root lengths, root weights, and root−top ratios of birdsfoot trefoil, and botanical composition of orchardgrass−birdsfoot trefoil swards were not significantly influenced by 28 kg/ha (25 lb/A) of nitrogen starter fertilizer. In general, there was no significant influence of method of planting on “established” stands of birdsfoot trefoil. Seeding trefoil alone resulted in larger individual plants than when seeded with a grass.
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