Site-specific evaluation of Cu, Zn, Fe and Mn availability in arable soils

Abstract

Investigations were undertaken on an agricultural farm (52 ha) located at the Wielkopolska region, Western Poland. Soil samples (294) were collected at 0-30 cm depth from 6 fields after harvesting of winter triticale, winter wheat, winter barley, grass mixtures, winter oilseed rape and sugar beet. The following properties were determined: silt and clay, organic carbon (C org ), pH (in 0.01 moles CaCl 2 dm -3 ), cation exchange capacity (CEC). Copper (Cu), zinc (Zn), iron (Fe) and manganese (Mn) were extracted by aqua regia test (total content) and 0.005 moles diethylene triamine pentaacetic acid (DTPA), pH 7.3 (active and potentially available forms). Potential availability and soil physical as well as chemical changes of these micronutrients were evaluated by using availability factors and thermodynamic parameters (Gibbs free energy change, ∆G°). Data show that 83% of all tested soil samples were characterised by C org < 25 g kg -1. Moreover, the variability in pH was very high (4.7 < pH CaCl2 > 7.8), ca 1/6 of investigated soils (16%) were acid, but on the other hand, 82% exhibited pH > 5.5. The mean CEC value amounted to 12.0 cmol (+) kg -1 , with 71% of soils representing CEC < 12.0 cmol (+) kg -1. In fact, the range 12.0 ≤ CEC ≥ 25.0 cmol (+) kg -1 , designating moderate buffering properties, shared ca 55%. The DTPA-based availability factor (AF) followed the order Zn > Cu > Fe > Mn, with respective indices 22.9 > 19.8 > 5.5 > 0.42. Next, linear relationships established for the pairs C org vs DTPA Cu,Zn,Fe,Mn resulted in the following correlation coefficients (r): C org vs DTPA Cu , r = 0.67**; C org vs DTPA Zn , r = 0.60**; C org vs DTPA Fe , r = 0.56*; C org vs DTPA Mn , r = 0.50*. It appeared that in the case of increasing or decreasing pH, the reactions of Cu, Mn and Fe in the soil solution should be similar, i.e. progressive unavailability or progressive availability, respectively. Thermodynamic changes (ΔG° values) calculated for Zn, Cu, Fe and Mn were the basis for establishing the following operational ranges: −5.0 ≤ ∆G°, readily available (for Zn); −5.0 ≥ ∆G° ≥ −10.0, moderately available (for Cu); −10.0 ≥ ∆G° ≥ −15.0, slightly available (for Fe); ∆G° ≤ −15.0, hardly available (for Mn). The ∆G°-based values showed that micronutrient availability criteria should not be restricted to quantitative evaluation only.

Effect of forest fire on changes in the content of total and available forms of selected heavy metals and catalase activity in soil

“…An unfavourable behaviour of the metals analysed is related to soil reaction and the content of organic carbon. Those two parameters are essential for the control of the availability of microelements, directly affecting their solubility (Obrador et al 2007, Diatta et al 2014.…”

Assessment of Soil Fertility and Crop Nutrient Status in Agricultural Soils Near a Brick Kiln Cluster

“…Soil pH showed a significant negative correlation (p < 0.001) with Cd and Pb, which may suggest that pH influenced the distributions of these metals in soils. Soil pH is one of the major factors in controlling the available content of heavy metals in solution as it affects directly their solubility along within the soil environment (Diatta, Grzebisz, Frackowiak-Pawlak, Andrzejewska, & Brzykcy, 2014;Sikder et al, 2015). Heavy metal cations are most mobile in acid soils.…”

Assessment of the Status of Microelements in the Selected ERPP Irrigation Schemes in Unguja and Pemba Islands, Zanzibar

“…. The high levels of Fe in all the surveyed mapping units in Machigini irrigation scheme could be attributed to the low pH and nature of the parent material from which the soil were formed [57] which may contain minerals like feldspar, magnetite, hematite and limonite [58]. These results suggest that DTPA -extractable Fe status in Machigini Irrigation scheme is not a threat to crop production.…”