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Carbon and nitrogen cycling in a tropical Brazilian soil cropped with sugarcane and irrigated with wastewater |
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| Authors: | Rafael Marques Pereira Leal Lilian Pittol Firme Adriel Ferreira da Fonseca Carlos Tadeu dos Santos Dias |
| Institution: | a Laboratório de Ecotoxicologia, Centro de Energia Nuclear na Agricultura - CENA/USP, P.O. Box 96, 13400-970, Piracicaba (SP), Brazil b Núcleo de Pesquisa em Geoquímica e Geofísica da Litosfera (NUPEGEL), Universidade de São Paulo (USP), P.O. Box 09, 13418-900, Piracicaba (SP), Brazil c Departamento de Ciência do Solo e Engenharia Agrícola (DESOLO), Universidade Estadual de Ponta Grossa (UEPG), 84030-900, Ponta Grossa (PR), Brazil d Laboratório de Análise Ambiental e Geoprocessamento, Centro de Energia Nuclear na Agricultura (CENA), USP, 13400-970, Piracicaba (SP), Brazil e Departamento de Ciências Exatas, Escola Superior de Agricultura Luiz de Queiroz (ESALQ), USP, 13418-900, Piracicaba (SP), Brazil f Departamento de Ciência do Solo, Escola Superior de Agricultura Luiz de Queiroz (ESALQ), USP, 13418-900, Piracicaba (SP), Brazil |
| Abstract: | Carbon (C) and nitrogen (N) dynamics in agro-systems can be altered as a consequence of treated sewage effluent (TSE) irrigation. The present study evaluated the effects of TSE irrigation over 16 months on N concentrations in sugarcane (leaves, stalks and juice), total soil carbon (TC), total soil nitrogen (TN), NO3−-N in soil and nitrate (NO3−) and dissolved organic carbon (DOC) in soil solution. The soil was classified as an Oxisol and samplings were carried out during the first productive crop cycle, from February 2005 (before planting) to September 2006 (after sugarcane harvest and 16 months of TSE irrigation). The experiment was arranged in a complete block design with five treatments and four replicates. Irrigated plots received 50% of the recommended mineral N fertilization and 100% (T100), 125% (T125), 150% (T150) and 200% (T200) of crop water demand. No mineral N and irrigation were applied to the control plots. TSE irrigation enhanced sugarcane yield but resulted in total-N inputs (804-1622 kg N ha−1) greater than exported N (463-597 kg N ha−1). Hence, throughout the irrigation period, high NO3− concentrations (up to 388 mg L−1 at T200) and DOC (up to 142 mg L−1 at T100) were measured in soil solution below the root zone, indicating the potential of groundwater contamination. TSE irrigation did not change soil TC and TN. |
| Keywords: | Wastewater irrigation Water reuse Saccharum spp Nitrate Dissolved organic carbon Tropical soil |
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