Distribution and forms of iron in the vertisols of Serbia

Soil of arable land and meadows from the Ap horizon, taken from ten different localities, were investigated for different forms of Fe, including total (HF), pseudo-total (HNO3), 0.1 M HCl extractable and DTPA (diethylenetriaminepentaacetic acid)-extractable. A sequential fractional procedure was employed to separate the Fe into fractions: water soluble and exchangeable Fe (I), Fe specifically adsorbed with carbonates (II), reducibly releasable Fe in oxides (III), Fe bonded with organic matter (IV) and Fe structurally bonded in silicates (residual fraction) (V). The soil pH, cation exchange capacity, and size fractions (clay and silt) had a strongest influence on the distribution of the different forms of Fe. The different extraction methods showed similar patterns of the Fe content in arable and meadow soils. However, the DTPA iron did not correspond with the total iron, which confirms the widespread incidence of iron-deficiency in vertisols is independent of the total iron in soils. The amount of exchangeable (fraction I) and specifically adsorbed (II) iron showed no dependence on its content in the other fractions, indicating low mobility of iron in vertisols. The strong positive correlation (r = 0.812 and 0.956) between the content of iron in HNO3 and HF and its contents in the primary and secondary minerals (fraction – V) indicate a low content of plant accessible iron in the vertisol. The sequential fractional procedure was confirmed as suitable for accessing the content and availability of iron in the vertisols of Serbia

Changes in soil carbon stock under the wheat-based cropping systems at Vojvodina province of Serbia

The aim of this study was to assess the changes in soil organic carbon (SOC) stock in relation to the carbon (C) input from nine wheat-based cropping systems and untilled grass. The SOC pool ranged from 32.1 to 49.4 Mg ha(-1) at 0-20 cm and from 94 to 171 Mg ha(-1) at 0-100 cm for the arable soil, while in untilled grassland, it was higher (54 and 185 Mg C ha(-1), respectively). SOC stock was observed to be lower at the unfertilized 2-year rotation and higher at the 4-year rotation with manure and mineral fertilization. The study showed a winter wheat yield decrease of 176.8 kg ha(-1) for a 1- Mg ha(-1) SOC stock change in the 0-20-cm soil depth. The estimated C input for SOC stock maintenance was from 266 to 340 g C m(-2) year(-1) for winter wheat and rotations, respectively. Additional C input did not increase the SOC pool, suggesting that arable plots had a limited ability to increase SOC. These results provide guidance for the selection of management practices to improve C sequestration