Sources and doses of nitrogen in plant cane production and residual effect on the first ratoon of sugarcane in a savannah Red Oxisol

The expansion of sugarcane cultivation, especially in areas with low natural soil fertility, such as savannah regions, requires greater efficiency in the application of nutrients, mainly nitrogen (N). The objectives of this study were to evaluate the effects of the application of different sources and doses of nitrogen on the dry matter yield and productivity of sugarcane in the plant cane cycle and the residual effect of such application on the first ratoon cycle of sugarcane (var. SP80-1816) cultivated in a dystrophic Red Oxisol. The experimental design was a randomized complete block design analyzed in a factorial scheme of 2 × 4 with three replications. The evaluated factors consisted of two sources of N (ammonium nitrate (AN) and urea (U)) and four doses of N (0, 60, 120 and 180 kg ha-1). Samples of the aerial part of the sugarcane were collected. The structural components of the aerial part were separated, and the leaf dry matter (LDM), stalk dry matter (SDM) and dry matter of the aerial part (DMAP) were analyzed. The productivity of stalks (PS) was determined by weighing all stalks present in the useful area of each plot. In the plant cane cycle, AN resulted in greater gains in the SDM and PS of sugarcane than did U. In the first ratoon cycle, a residual effect was observed in response to N application, which showed an increase in SDM and PS. Under the conditions of this study, to achieve a higher PS in both cycles, the application of 180 kg N ha-1 is recommended