Nitrogen fertilizer effect in production, nutrient accumulation and nitrogen efficiency use of second ratoon sugarcane harvested without straw burning

Sugarcane harvest after straw burning implies rapid mineralization of biomass and greenhouse gas emissions. In this context, maintenance of sugarcane straw on the soil is as a new strategy to circumvent the harmful environmental effects, but imposes a new dynamic regarding nitrogen in the soil-plant system. This study sought to evaluate the effect of nitrogen fertilization on biomass production and nutrient accumulation in leaf (senescent and young) and stalks of sugarcane plant from the second sugarcane ratoon, variety SP 83-2847, harvested mechanically in 2007 after six years without straw burning for six years. This study adopted a randomized block design with five nitrogen doses application (0, 60, 120, 180 and 240 kg ha-1) in the form of ammonium nitrate and four replications. Nitrogen fertilization promoted an increase in leaf (senescent and young) and stalk production of the sugarcane plants. However, excess nitrogen decreased accumulation of macro and micronutrients and nitrogen use efficiency by sugarcane due to dilution effect. Although straw deposition on the soil surface of the sugarcane field had occurred for six years, but mineralization of organic matter from the straw did not provide sufficient nitrogen for the growth of sugarcane plants in control treatments, requiring nitrogen application via fertilization. There is a need to adopt new nitrogen fertilization strategies in order to increase nitrogen use efficiency for greater production of sugarcane.