Controle das perdas de nutrientes, solo e água pela cobertura morta de bagaço de cana e sua eficiência no aumento do nível da matéria orgânica e da produtividade do solo.

• Ano de defesa: 1996
• Autor(a) principal: Cavalcante, José Ramos Lopes
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Agronomia
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/44998

A concomitant study, developed with this research, on a Podzolic of Fortaleza (CE), demonstrated the benefits of triturated sugarcane bagasse mulch in decreasing erosion rates, in improving soil physical properties and in increasing cassava/cowpea intercrop yields. However, which were the effects of this technique on nutrient, soil and water losses control, particularly associated to the most erosive rainfalls of the year, and how it would contribute to the improvement of soil chemical properties, and productivity remained unknown. The need to answer these questions, leaded to this study which was developed on four erosion plots connected to sediments and runoff collecting tanks where the effects of two mulch treatments with or without suplementar N were compared to two other where the soil remained deprived of this protection. Nutrients contents of the sediments and runoff collected in the tanks and determined in soil and water laboratory analysis showed the effects of the treatments which were tested for erosion losses control against the five most erosive rainfalls of the humid season of 1994. A control plot of the intercrop, deprived of any conservationist practice was used as a reference for comparison of cassava and cowpea yields. Determination of the erosivity revealed that from 57 precipitations of the period totaling 1,812.9 mm only five selected rainfalls amounting to 675,6 mm were responsible for 44,8% (3,328.5 MJ.mm/ha.h) of 7,407,1 MJ.mm/ha.h of the period. Effectiveness of the sugarcane bagasse mulch was clearly demonstated through reduction of an average of 85.1 % of erosion on protected plots (2.6 t/ha) against 17.4 t/ha caused by the tive selected rainfalls and detected on plots where there was no mulch protection. Water losses followed a similar trend and a reduction of 52,4% favouring mulched plots (129 mm) against unprotected plots (270.9 mm). Nutrient status was also enhanced on mulched treatments since while their average losses of N, P, K, Ca and Mg were only 5.7, 0.03, 2.8, 8.4, and 4.4 kg/ha, respectively, those of the uncovered treatments increased, in this same order, by 65%, 200%, 107%, 211% and 211%, therefore remarking the damages to productivity on unprotected soils as well as the effectiveness of the conservationist practice under analysis. Considering the organic matter content of the mulched plots before the experiment (0.7%), the sugarcane bagasse mulch promoted the highest increase (43%) of this soil component since after the crops harvest it amounted to 1.0% as compared to the increase of the uncovered plots (29%) which showed 0.7% and 0.9% before and after the experiment, respectively. Adding to the improvement of physical conditions the decreases in soil and nutrient losses provided by the sugarcane bagasse mulch contributed to average increases of 4.9 t/ha for cassava (18.3 t/ha) as compared to uncovered plots (13.4 t/ha) and of 0.5 t/ha for cowpea on protected plots (1.3 t/ha) with relation to those deprived of the mulch protection (0.8 t/ha). Improvement of the soil organic matter and N status and associated microbiological conditions, nutrients retention and recycling, and reduction of losses of P, K, Ca and Mg were chemical attributes responsible for the excellence of this erosion control practice on the improvement and conservation of the Podzolic productivity.