Evaluation of nitrogen management in maize cultivation grows on soil amended with sewage sludge and urea

This paper analyses the data of a 3 years’ research on the agronomical use of sewage sludge, from a urban waste water plan, to grow maize (Zea mays L.). The experiment was conducted in order to test possible combinations of sewage sludge and urea as source of nitrogen for maize. The experiment comprised a randomized block design composed of a control and 8 treatments with four replicates. Three urea rates (0; 100 kg N ha−1 and 200 kg N ha−1) were assigned combined with three sewage sludge rates (0; 5 t ha−1 and 10 t ha−1), exceeding the limits permitted by the law, and the unfertilized control. Maize was sown and harvested for 2 years (April–September 2006 and 2007) and wheat (Triticum vulgare L.) was sown in October 2007 and harvested in May 2008 without adding any fertilizer or sewage sludge, in order to evaluate the residual effects of the organic fertilizer.The batch that gave the highest grain production was the one that received 10 t ha−1 DM of sewage sludge and 100 kg N ha−1 from urea, reaching values of 16.17 ± 0.97 t ha−1 DM in the first year and 17.52 ± 0.68 t ha−1 DM in the second one, while the effect of the organic fertilization was still available where wheat was grown. ANR values showed a significant increase between the first and the second year: the average value for the treatment 3 (exclusive use of sludge in maximum dose) has shown an increase from 24.3% in 2006 to 63.4% in 2007, highlighting the effect of the sewage sludge. Yields and nitrogen uptake during and after the experiment and the nitrate losses by leachates have been evaluated: linear correlations were statistically significant, with an improvement in the second year of the trial, between yields and the nitrogen applied (R2 = 0.757) and yields and the nitrogen removal rate (R2 = 0.843).

► We tested combinations of sewage sludge and urea as source of nitrogen for maize.
► We evaluate the effects of sewage sludge on yields, nitrogen plant uptake, soil carbon and soil nitrogen contents and on nitrogen losses.
► We evaluated the residual effects of sewage sludge on wheat, sown after maize, in terms of yields and nitrogen uptake.
► The sewage sludge application had determine a significantly increase of grain yields, minimized the nitrogen losses.
► The effect of the organic fertilizer was evident in the second rotation crop (wheat), which gave higher yields where the sewage sludge was applied the prior years.