Patricia Almendros

The influence of moisture on the residual effects of natural zinc chelates applied to two different soils

The aim of this study was to compare the behavior of residual Zn from three natural chelates (Zn-aminolignosulfonate (Zn-AML),Zn-polyhydroxyphenylcarboxylate (Zn-PHP) and Zn-ethylenediamine disuccinate (Zn-EDDS)) applied at different rates (0, 5 and 10 mg Zn/kg soil) to a flax crop grown during the previous year. This incubation experiment was carried out over 75 days under two different moisture conditions (60% field capacity and waterlogged) in two different soils (acidic (Soil acid )and calcareous (Soil calc )). The potential available Zn concentration and short- term available Zn were estimated under both moisture conditions using the diethylenetriaminepentaacetic acid - triethanolamine (DTPA-TEA) and low-molecular-weight organic acids (LMWOAs) methods, respectively. Water- soluble Zn was estimated in both soils under 60% field capacity conditions. Immediately available Zn (the Zn concentration in the soil solution) was estimated under waterlogged conditions. The pH and Eh were also determined in both soils. Incubation of both soils under both moisture conditions led to decreases in the potential available Zn and short-term available Zn concentrations. Water-soluble Zn concentrations in soils under 60% field conditions, immediately available Zn in soils and the Eh parameter under waterlogged conditions also decreased with time. The residual effect of Zn-AML applied at a rate of 10 mg Zn/kg in Soil acid produced the highest available and short-term Zn concentrations, and the residual effect of Zn-EDDS produced the highest short-term Zn concentration in Soil calc .

Mobility in soil and availability to triticale plants of copper fertilisers

The mobility and availability to plants of copper (Cu) applied through inorganic and organic fertilisers can be important for crop production and also in terms of its environmental impact. Column and greenhouse experiments were conducted on a Typic Xerorthent soil (pH 7.09, sandy clay loam texture with moderate permeability) to study the relative migration and extractability of Cu sources in a reconstructed soil profile and the response of a triticale crop (X Triticosecale Wittmack) to the Cu supplied. The soil Cu status and quantity of Cu in the leachates were established in the soil columns according to layer depth and experimental time. Most of the Cu applied though natural (Cu-lignosulfonate, Cu-gluconate, Cu-galacturonatemonogluconate, Cu-bis(ethoxydihydroxydiethylamino)sulfate) and inorganic (Cu-oxychloride) fertilisers remained in the top soil and Cu-HEDTA migrated to a soil depth of 20 cm. Only when Cu was applied as Cu-EDTA and Cu-DTPA-HEDTA-EDTA did a large percentage of Cu remain in the top soil, initially in the water soluble fraction. The Cu associated with this fraction migrated and became distributed throughout the soil column, producing significant Cu losses due to leaching. For a 2.120 pore volume of collected leachate and an experimental time of 200 days, the leaching rates were respectively 23% and 51% of the total amount of Cu applied. The high potential availability of Cu to plants from these two sources, and to a lesser extent for Cu-lignosulfonate (applied at 2 and 3 mg Cu kg–1 rate), were correlated with the higher concentrations and uptakes of Cu by triticale grain. The advantage of this last source is that it does not produce losses due to leaching.

Influence of Moisture Conditions on Residual Zn Concentrations Applied as Synthetic Chelates

The aim of this study was to compare the behavior of residual zinc (Zn) from different synthetic chelates containing the chelating agents EDTA (ethylenediaminetetraacetate acid), HEDTA (hydroxyethyl-ethylenediaminetriacetate acid), and DTPA (diethylenetriaminepentaacetate acid) applied at different rates. This incubation experiment was carried out under two different moisture conditions (60 percent field capacity and waterlogged) and in two different soils from the central region of Spain (Soilacid, Typic Haploxeralf, and Soilcalc, Typic Calcixerept). The potentially available Zn concentration and short-term available Zn were estimated using the DTPA-TEA (diethylenetriaminepentaacetic acid–triethanolamine) and LMWOAs (low-molecular-weight organic acids) methods. In both soils, the amount of water-soluble Zn was estimated under 60 percent field-capacity conditions. Immediately available Zn was estimated under waterlogged conditions. The Zn concentrations depended on the soil type, the experimental time, and the Zn chelate used. Under both moisture conditions, the soil characteristics caused the residual effects of Zn-EDTA in Soilacid and Zn-DTPA-HEDTA-EDTA applied to Soilcalc, to produce the greatest Zn concentrations.