Soil solution chemistry and alfalfa response to CaCO3 and MgCO3 on an acidic Gleysol

Soil acidity is a limiting factor for forage production. Liming is a common agricultural practice for acid soils, yet there is limited information on the effects of soil solution chemistry in response to liming. Soil from the Ap horizon of an Orthic Humic Gleysol was amended with 0, 2.5 or 5.0 g CaCO3 kg−1 and 2.1 or 4.2 g MgCO3 kg−1 to determine the changes due to liming in soil solution composition before planting and after three cuts of alfalfa (Medicago sativa L.). The soil solution samples were extracted by immiscible displacement with C2Cl4. The low equivalent rate of CaCO3 and MgCO3 decreased the concentrations of Fe from 889 to less than 22 μM, Mn from 286 to less than 6 μM, Al from 45 μM to undetectable level before plant growth. Soil pH, dissolved organic carbon (DOC), Cu and NH4-N concentrations in the soil solutions extracted after the third cut of alfalfa were increased compared with those measured before planting. Concentrations of Ca, Mg, K, Na, Mn, Zn, Fe, Al, NO3-N, SO4 and Si were all decreased after the third cut compared with those measured before planting. Step-wise multiple regression analysis indicated that the dry matter (DM) yield of the first cut was positively correlated to NO3-N and negatively correlated to Mn concentration in the soil solutions (R2 = 0.65**); whereas the DM yield of the second and third cuts and of the roots were negatively correlated with Mn concentrations (R2 = 0.75**, 0.63**, and 0.60**, respectively). The regression analysis supported visual Mn toxicity, suggesting that Mn toxicity, not Al concentration, was the main limitation to alfalfa growth in unlimed soil. Key words: Alfalfa, liming, soil solution chemistry, immiscible displacement, plant nutrition

Download Full-text

Soil and soil solution chemistry of a New Zealand pasture soil amended with heavy metal-containing sewage sludge

Soil Research ◽

10.1071/sr01061 ◽

2003 ◽

Vol 41 (1) ◽

pp. 1 ◽

Cited By ~ 18

Author(s):

H. J. Percival

Keyword(s):

Heavy Metals ◽

New Zealand ◽

Sewage Sludge ◽

Soil Solution ◽

Metal Ion ◽

Solution Chemistry ◽

Soil Solution Chemistry ◽

Soil Solutions ◽

Free Metal ◽

Soil Metal

The disposal of wastewater treatment sewage sludge onto agricultural land in New Zealand has led to the development of guidelines for the upper limit concentrations for total heavy metals in the underlying soil. However, those soil biological and biochemical processes now known to be most sensitive to environmental change are being used internationally to set new soil limits. The soil solution chemistry of a pasture soil amended with heavy metals has been used to assess the bioavailability of several important heavy metals. Field trial plots were treated with both spiked (Cu, Ni, or Zn) and unspiked sewage sludge to raise total soil metal concentrations, both above and below the current New Zealand guideline values. Soils were sampled pre-amendment in 1997 and post-amendment in 1998, 1999, and 2000. Soil solutions were extracted by centrifugation and analysed for pH, for concentrations of heavy metals, major cations and anions, and dissolved organic carbon. Heavy metal speciation was calculated with the GEOCHEM-PC model.Soil solution concentrations of Cu, Ni, and Zn increased with increasing levels of metal in the spiked sludge, reflecting increases in total soil metal concentrations. Cu concentrations changed little with time, but those of Ni and Zn tended to decrease. Cu was much more adsorbed by the soil than was Ni or Zn. The free metal ions, Cu2+, Ni2+, and Zn2+ (representing the most 'bioavailable' fraction), were the dominant metal species in the soil solutions. Variations in free metal ion percentages with metal-spiking level depended on the balance between organic and sulfate complexation for Cu, but on sulfate complexation alone for Ni and Zn. Cu and Ni free metal-ion activities in soil solution were relatively low even at the highest metal loadings in the soil, but may be high enough to cause toxicity problems. Zn activities were very much higher, and at the regulatory limit for zinc likely to affect sensitive biological and biochemical properties of the soil.

Download Full-text

Soil solution chemistry of contrasting soils amended with heavy metals

Soil Research ◽

10.1071/sr98055 ◽

1999 ◽

Vol 37 (5) ◽

pp. 993 ◽

Cited By ~ 20

Author(s):

H. J. Percival ◽

T. W. Speir ◽

A. Parshotam

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Metal Ions ◽

Cation Exchange ◽

Soil Solution ◽

Solution Chemistry ◽

Percentage Increase ◽

Soil Solution Chemistry ◽

Soil Solutions ◽

Wide Range

The soil solution chemistry of heavy metal amended soils is of great importance in assessing the bioavailability of heavy metals and their toxicity to the soil biota. Three contrasting soils were amended with Cd(II), Cu(II), Ni(II), Pb(II), Zn(II), and Cr(III) nitrate salts at rates of 10–100 mmol/kg. This concentration range was chosen to encompass a wide range of effects on sensitive soil biochemical properties as part of a larger project. Soil solutions were extracted and analysed for pH, and for concentrations of heavy metals, and major cations and anions. Heavy metal speciation was calculated with the GEOCHEM-PC model. Heavy metal concentrations in the soil solutions increased both in absolute terms and as a percentage of added heavy metal as amendment rates increased. This observation is due to decreasing specific adsorption (caused by decreasing pH induced by the amendments), and to increasing saturation of cation exchange sites. For all 3 soils, the percentage increase commonly follows the order Cr(III) < Pb < Cu < Ni < Cd < Zn. The percentage of each metal held in the soil solution increased from soil to soil as cation exchange capacity, and therefore sorptivity, decreased. Both the concentration and activity of free heavy metal ions were substantially lower than the corresponding total metal concentration. This was ascribed to ion-pairing of metal ions with anions, particularly nitrate introduced in the amending solutions, as well as to increases in ionic strength as a result of amendment. Metal-anion species were mainly inorganic but where Cu and Pb were relatively low in concentration because of strong adsorption by the soils, organic complexation was likely to be significant. Speciation trends were similar for the 3 soils but different in magnitude.

Download Full-text