Impact of long-term cultivation on the status of organic matter and cadmium in soil

Abstract

Research has suggested a link between the bioavailability of soil Cd and total soil organic matter. However, some research suggested a negative relationship between total soil organic matter and bioavailable soil Cd while other research suggested a positive relationship. This study investigated the relationship between soil Cd and both the quantity and quality of soil organic matter as influenced by long-term cultivation. Two Orthic Chernozemic surface soil samples, one from a virgin prairie and the other from an adjacent cultivated prairie, were collected from each of 12 different sites throughout southern Saskatchewan, Canada. The samples were analyzed for total organic C, total Cd, Cd availability index (CAI), and pH. The nature of the soil organic matter was investigated with 13C Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy (13C CPMAS NMR). The total soil Cd, CAI, and total soil organic C of the cultivated soils were significantly lower than those of the virgin soils whereas the opposite trend was observed for the soil pH and the aromaticity of the organic C. The reduced CAI in the cultivated soils was related to the increase in both the soil pH and the aromaticity of the organic C. No relationship was found between the CAI and the soil organic C content, but a significant positive correlation was found between total organic C and total Cd in both the virgin and the cultivated soils. As well, a significant positive correlation was found between the fraction of total Cd removed from the soil after long-term cultivation and the corresponding fraction of organic C removed. Key words: Long-term cultivation, soil organic matter, 13C CPMAS NMR, cadmium

Long-term cultivation effects on the quantity and quality of organic matter in selected Canadian prairie soils

“…The significant increase in aromaticity of the organic matter as a result of long-term cultivation appears to be the result of the cultivation enhanced degradation of aliphatic relative to aromatic C. Charcoal formed by crop residue burning may also contribute to the increased aromaticity; charcoal produces a large peak in the aromatic regions of 13 C NMR spectra (Golchin et al, 1997a,b;Schmidt et al, 1999;Skjemstad et al, 1996Skjemstad et al, , 1999aPonomarenko and Anderson, 2001). Increasing aromaticity of soil organic matter with prolonged cultivation was also reported by Schulten et al (1995), Lessa et al (1996), Kiem et al (2000), and McArthur et al (2001). …”

“…It has been found that long-term cultivation results in a statistically significant decrease in the total amount of SOM (soil organic matter) (Blank and Fosberg, 1989;Schulten et al, 1995;Kiem et al, 2000;McArthur et al, 2001). As well, it has been shown that the aromaticity of the SOM increases as a result of long-term cultivation Lessa et al, 1996;Kiem et al, 2000;McArthur et al, 2001).…”

“…Long-term cultivation subjects formerly uncultivated soil to conditions that significantly change the physical and chemical properties of the soil (McArthur et al, 2001). It has been found that long-term cultivation results in a statistically significant decrease in the total amount of SOM (soil organic matter) (Blank and Fosberg, 1989;Schulten et al, 1995;Kiem et al, 2000;McArthur et al, 2001).…”

Tillage impacts on the fractions and compositions of soil organic carbon

“…Tillage mainly changed the environment for micro-organisms and distribution of SOC to affect SOC concentration, thus long-term tillage resulted in a significant loss of total soil organic matter (McArthur et al, 2001). However, some reports agreed with the inverse result, that is, an increase of SOC concentration was observed in PT vs. NT systems (e.g.…”

Cadmium accumulation in potato tubers produced in Quebec

“…Soil organic matter, clay content, Fe, Al, and Mn oxides may increase the adsorption of Cd by soils and thus decrease soil Cd plant availability (McLaughlin et al 1996;McArthur et al 2001). Soil P, K, and S may increase Cd availability through different mechanisms McLaughlin et al 1996;Grant et al 1998).…”