Application of paper recycling residues in acid soil: II – Maize and soybean yield and heavy metal levels in grains

Soil acidity is a limiting factor to maize and soybean yield. In general, lime is used to increase the soil pH. However, some industrial residues can be used to reduce soil acidity such as paper recycling residues. On the other hand, due to heavy metals presence in this residue, whose high concentration in food is dangerous to health, it is necessary to evaluate the heavy metal levels in the grains. Thus, the objective of this study was to evaluate the effects of paper recycling residue application in an acid soil on maize and soybean yield and on nutrients and heavy metal levels in the grains. A trial was carried out in Papanduva, SC, Brazil, in a complete blocks randomized design, with three replications. The evaluations were carried out in doses of paper recycling residues of 64, 127, 191, 254, 382 and 509t/ha in wet mass – 65% of water. In addition, treatments with lime and without residues or lime were evaluated. The residues and lime were incorporated to the soil up to 20cm deep through a plowing and two harrowings in June, 2004. Maize was cultivated in the 2004/05 and 2006/07 crop seasons, and soybean in the 2005/06 crop
season in the experimental site. The applied residue increased the maize and soybean grain yields. The P and Cu levels in the maize and soybean grains were changed by the paper residue application in acid soil. However, Hg, Pb, Ni, Cd, Cr and Zn levels were not affected by the residue application, even in high doses.