Nutrition of Tithonia diversifolia and attributes of the soil fertilized with biofertilizer in irrigated system/ Nutricao de Tithonia diversifolia e atributos do solo adubado com biofertilizante em sistema irrigado

The fertilization with biofertilizer associated with the use of irrigation favors nutrient uptake by plants and soil chemical properties; however, these effects are little studied in Tithonia diversifolia in semiarid regions. This study evaluated the effect of doses of bovine biofertilizer and irrigation on accumulation of nutrients in the leaves of Tithonia diversifolia plants and on soil chemical attributes. The study was carried out from December 3, 2014 to November 28, 2015, and arranged in a 2 x 5 factorial scheme, consisting of five doses of bovine biofertilizer (0, 40, 80, 120 and 160 [m.sup.3] [ha.sup.-1]), combined with and without irrigation. The experiment was set in a randomized block design, using three replicates. Irrigation promoted increased accumulation of N, P, K, Ca, Mg, S, Zn, Fe, Mn, Cu and B in leaves of Tithonia diversifolia in the first cutting. However, the high bicarbonate concentration in the irrigation water and the occurrence of rainfall during the second crop increased the accumulation of Cu in the leaves of Tithonia diversifolia under rainfed condition, compared with irrigated plants. The increase in biofertilizer doses contributed to the increment of base saturation and the contents of organic matter, P and K in soil. Key words: organic fertilizer Tithonia nutrient content rainfed crop forage Associada ao uso de irrigacao, a adubacao com biofertilizante favorece a absorcao de nutrientes pelas plantas e as propriedades quimicas dos solos, porem tais efeitos sao pouco estudados no cultivo de Tithonia diversifolia em regioes semiaridas. Avaliaram-se os efeitos de doses de biofertilizante bovino e da irrigacao no acumulo foliar de nutrientes em plantas de Tithonia diversifolia e nos atributos quimicos do solo. O estudo foi conduzido entre 3 de dezembro de 2014 e 28 de novembro de 2015 e distribuido em esquema fatorial 5 x 2, consistindo de cinco doses de biofertilizante bovino (0, 40, 80, 120 e 160 [m.sup.3] [ha.sup.-1]), combinado com e sem irrigacao. O delineamento estatistico do experimento foi em blocos casualizados com tres repeticoes. A irrigacao promoveu aumento no acumulo de N, P, K, Ca, Mg, S, Zn, Fe, Mn, Cu e B em folhas de Tithonia diversifolia no primeiro corte; entretanto, a alta concentracao de bicarbonato na agua de irrigacao e a presenca de chuvas durante o segundo cultivo aumentaram o acumulo de Cu nas folhas de Tithonia diversifolia em sequeiro quando comparado as plantas irrigadas. O aumento das doses de biofe