ABSTRACT
The increased magnesium (Mg) concentration in vegetables may be reduced due to inter-ionic inhibition caused by the concentration of other water-soluble cations that are mainly associated to low molecular weight organic anions. However, it is not known whether the levels of these compounds in crop residues are modified by increasing the Mg soil application. This study aimed to assess the effects of the Mg application on the contents of water soluble cations [potassium (K+), calcium (Ca2+), magnesium (Mg2+), cooper (Cu2+), iron (Fe2+), manganese (Mn2+), and zinc (Zn2+)] on common bean plant residues. The experiment was conducted under greenhouse conditions with Ustoxix Quatzipsamment in completely randomized design in 4×5 factorial scheme, with three replicates. The treatments consisted of four rates of Mg [0, 50, 100 and 200 mg kg−1, source magnesium chloride (MgCl2)] and five varieties of common bean of the carioca group [BRS Estilo, BRS Ametista, IPR Campos Gerais (CG), IPR Tangará and IAPAR 81]. The Mg rates affected the contents of water soluble Ca2+, Mg2+, Cu2+, Fe2+ and Mn2+ in the extracts of bean residue. The soluble Mg2+ showed a significant correlation with foliar Mg content, indicating the need for further research on the method used to assess nutrient availability in vegetables. The bean varieties showed different responses regarding balance of ions in cation exchange capacity (CEC) and in the Ca/Mg, Ca/K and Mg/K ratios in the soil.
Acknowledgments
Our thanks go to CAPES, for the Masters scholarship, to Londrina State University (UEL), for the opportunity offered, and to Embrapa Soybean (CNPSO), for the logistical support to carry out the experiments and laboratory analyzes.