Agronomic efficiency of nitrogen fertilizers in sugarcane harvested without burning

Abstract

The sugarcane-cropped area is expanding in Brazil. The appropriate fertilization is essential for obtaining higher yields, especially regarding nitrogen addition. The increase in area harvested without burning the residues left on the soil surface cause a problem for the incorporation of fertilizer. Accordingly, sources with more stable forms of N represent an agronomic and economic advantage compared to urea because this form's more stable could be applied directly over the straw. The objective of this study is to evaluate alternative sources of N for fertilization of ratoon sugarcane harvested without burning. Two experiments will be set up under field conditions in Novo Horizonte, Sao Paulo. The experimental design will be in the randomized complete block, with four replications and nine treatments: control (without N), Yarabela Nitromag (50, 100, 150 and 200 kg N ha-1), Urea (100 kg N ha-1), Ammonium Nitrate (100 kg N ha-1), Ajifer (100 kg N ha-1) and organic co-product (100 kg N ha-1). The experiments will be installed in September of 2012 and the harvest will be carried out in August of 2013. Soil sampling will be performed before installation and after harvesting the fields at depths of 0 to 20 and 20 to 40 cm, aiming to assess the effects of treatments on soil chemical properties. Measurements of stalk yield and technological attributes of sugarcane will be performed in order to assess the effect of treatments on yield and sucrose accumulation in the sugarcane. Short-term laboratory incubation will be performed, using the same soil from the fields and measuring the inorganic N production (NH4+-N and NO3--N) and soil pH changes after fertilizer application, over the incubation period.(AU)