Resumo A influência de resíduos farmacêuticos e metais pesados em organismos vivos tem recebido atenção global. O presente estudo avaliou o efeito de resíduos de antibióticos e metais pesados no solo, como alimentos contaminados com cádmio (Cd) e oxitetraciclina (OTC), sobre o isópode Porcellio laevis, o qual foi alimentado com folhas frescas de plantas contaminadas com diferentes concentrações de cádmio, Cd + OTC1000 ppm, Cd + OTC2000 ppm e Cd + OTC3000 ppm, por quatro semanas. As mudanças nos padrões de alimentação, proteína, peroxidação lipídica (LPO), atividade da catalase (CAT) e aminoácidos livres totais (TFAA) foram registradas. Houve diferenças significativas nos resultados obtidos, em que o Cd reduziu a taxa de excreção (ER), no entanto o OTC aumentou essa proporção. A análise bioquímica mostrou que a combinação entre OTC e Cd inibe os efeitos tóxicos do Cd em baixa concentração (1.000 ppm), enquanto, em alta concentração (3.000 ppm), aumenta a toxicidade. Estudos detalhados são necessários para uma maior compreensão da interação entre OTC e metais pesados, e seu impacto sobre os animais do solo, bem como para melhorar a avaliação de risco do solo.

Abstract The influence of pharmaceutical residues and heavy metals on living organisms has received global attention. The present study assessed the interactive effect of antibiotic residues and heavy metals in soil, as contaminated food with cadmium (Cd) and oxytetracycline (OTC) on the isopod Porcellio leavis. It was fed on fresh plant leaves contaminated with different concentrations of cadmium, Cd+OTC1000 ppm, Cd+OTC2000 ppm and Cd+OTC3000 ppm for 4 weeks. The changes in the feeding patterns, protein, lipid peroxidation (LPO), catalase activity (CAT), and total free amino acids (TFAA) were recorded. There were significant differences in the obtained results where Cd reduced the egestion ratio (ER) however, OTC enhanced this ratio. Biochemical analysis illustrated that combination between OTC and Cd inhibits the toxic effects of Cd at low concentration (1000 ppm), while at high concentration (3000 ppm) raise the toxicity. Detailed studies are required for further understanding of the interaction between OTC and heavy metals, and also its impact on soil animals and for improving soil risk evaluation.

Crop productivity, soil organic carbon (SOC), fertilizer nitrogen and water use efficiency (WUE) in rainfed dry area is influenced by tillage, rotation and crop residues management. Field experiments were conducted during 2004-09 to study the effect of tillage, rotation and crop residues on wheat yield, nitrogen fertilizer and water use efficiency and SOC under semi-arid condition in north-west Pakistan. The treatments consisted of three rotations: i) Wheat-fallow-wheat (farmers' practice) ii) Wheat- summer legume-wheat and iii) Wheat-summer cereal-wheat with two tillage and crop residues management treatments: i) Tillage (crop residues removed) and Tillage (crop residues retained) and ii) No-tillage (crop residues removed) and No-tillage (crop residues retained). Basal doses of N60: P60 (kg ha-1) to wheat, N90: P60 and N20: P60 (kg ha-1) to summer cereals and legumes rotation crops were applied respectively. Labeled urea having 1% 15N atom excess at 60 kg N ha-1 was applied to wheat as an aqueous solution in micro plot within each treatment plot. Changes in soil water storage were monitored with neutron moisture probe for calculation of WUE. The results revealed that the wheat grain and straw yield was not increased by the tillage treatment. Crop residues retention significantly enhanced the wheat grain and straw yield. Crop residues with no-tillage resulted in 520 kg ha-1 greater wheat grain yield than residues removed treatment. Similarly WUE, N yield and fertilizer N utilization by wheat was increased significantly by crop residues under no-tillage compared to the tillage treatment. Maximum N fertilizer utilization 24.1 %, 62.7 % and 38.0 % in wheat were obtained under no-tillage + residues treatment during 2006, 2007 and 2008 respectively. The SOC in surface soil (0-15 cm) was higher in wheat-fallow-wheat and wheat-legume-wheat rotation under no-tillage + residues treatment. The results showed that no-tillage + crop residues and legume based rotation treatment were beneficial under the rainfed (dry) conditions.