Lucian W. Zelazny

Soil solution Al as a measure of al toxicity to alfalfa in acid soils

Abstract The root system of alfalfa (Medicago sativa L.), known for extreme sensitivity to Al toxicity, has been observed to penetrate acid subsoil horizons high in exchangeable Al. In our previous studies we noted that root penetration into acid subsurface horizons occurred where lime had been surface applied under both no‐till and conventional tillage management systems. In order to more fully understand this seeming contradiction, the present study was undertaken. It was hypothesized that exchangeable Al may not be an adequate indicator of the activity of Al in solution and consequently the potential toxicity to the plant may be over estimated. To test this hypothesis, concentrations and activities of Al, Ca, and other major macro and micro elements and pH were determined in an Ernest silt loam (fine‐loamy, mixed, mesic Aquic Fragiudult) soil solution and compared with soil exchangeable levels. Soil samples were taken from the surface (0–5 cm) and 1 m depth in soils that had received 13 Mg/ha surface d...

Bioavailability of Heavy Metals in Biosolids‐Amended Soil

Abstract A single biosolids application was made to 1.5×2.3 m confined plots of a Davidson clay loam (Rhodic Kandiudult) in 1984 at 0, 42, 84, 126, 168, and 210 Mg ha−1. The highest biosolids application supplied 750 and 600 kg ha−1 of Cu and Zn, respectively. Corn (Zea mays L.), from 1984 to 2000, and radish (Raphanus sativus L.) and romaine lettuce (Lactuca sativa var. longifolia), from 2001 to 2004, were grown at the site to assess heavy‐metal bioavailability. Extractable (0.005 diethylenetriamine (DTPA) and Mehlich 1) Cu and Zn were determined on 0 to 15‐cm depth samples from each plot. Corn yield increased with biosolids rate each year until 1993 to 1997, when yield decreased with biosolids rate because of phytotoxicity induced by low (<5.0) soil pH. The corn yield reduction was reversed between 1998 and 2000 upon raising the soil pH to approximately 6.0 by limestone addition following the 1997 season. Between 2001 and 2004, radish and lettuce yields were either not affected or slightly increased with biosolids rate, even as soil pH declined to below 5.5. Plant‐tissue metal concentrations increased with biosolids rate and as pH declined but were always within the normal range of these crops. Mehlich 1 and DTPA extractable metals increased linearly with biosolids rate. Extractability of Cu and Zn decreased approximately 50% over the past 20 years despite a decrease in soil organic matter concentration and greater than 95% conservation of the metals.

Pre-Wisconsinan glacial stratigraphy, chronology, and paleomagnetics of west-central Wisconsin

Detailed evaluation of pedogenic, geologic, and paleomagnetic properties has enabled the identification of several pre-Wisconsinan stratigraphic units in west-central Wisconsin. The older unit is the Pierce Formation, consisting of the Hersey Member, which contains gray, calcareous, loam-textured till, and the Kinnickinnic Member, which contains rhythmically bedded lacustrine sediments deposited in a complex network of proglacial lakes. Paleomagnetic and pedogenic data from the Pierce Formation suggest that the Hersey Member was deposited during either the Emperor reversed event or the Matuyama reversed polarity epoch and that deposition of the Kinnickinnic Member spanned either the Emperor-Brunhes or the Matuyama-Brunhes boundary ∼460,000 or 730,000 B.P., during Pre-Illinoian time. The younger, pre-Wisconsinan unit is the River Falls Formation, which contains a reddish-brown, sandy-clay-loam-textured till and associated sand and gravel. Soil-profile development and regional correlation indicate that this unit is Illinoian in age. These results contradict previously published studies which suggested that tills of the Hersey Member and the River Falls Formation were deposited by the same Wisconsinan ice advance and that no pre-Wisconsinan sediment is present in western Wisconsin.

KINETICS OF ALUMINUM AND SULFATE RELEASE FROM FOREST SOIL BY MONO- AND DIPROTIC ALIPHATIC ACIDS

A batch equilibration study evaluated the influence of naturally occurring low-molecular-weight mono- and diprotic aliphatic acids on the rate of Al and SO42− release in a Cecil soil (Typic Hapludult). We adjusted the pH of the organic acids (OAs) and of the soil suspension (3.8% w/w) to pH 4.0 and allowed them to equilibrate thermally before the experiment. After rapid addition of OAs to the soil suspension, we took solution samples at various time intervals and analyzed for Al, SO42−, and OA concentration. The initial concentration of OA in suspension was 1 × 10−5 mol liter−1. Both Al and SO42− release followed pseudo-first-order kinetics, whereas OA adsorption obeyed simple first-order kinetics. The rate of Al release (k1) was more rapid for the diprotic OA treatment (20.4 × 10−8 mol s−1), as was SO42− release (1.63 × 10−8 mol s−1), compared to the monoprotic OA treatment. The rate of Al release varied inversely with OA chain length and the distance between - COOH functional groups. The addition of substituent - OH groups between the - COOH groups further reduced k1. A similar trend was observed for the rate of SO42− release (k1) into solution. Monoprotic OAs were more rapidly adsorbed to the particle surfaces than were diprotic OAs. We postulate that removal of Al and SO42− from solution occurs via selective mineral precipitation.