Maximum efficiency of nitrogen (N) is attained when fertilizer is accompanied by silicon (Si). Therefore, the objective of this study was to evaluate the chemical attributes of the soil, the nutritional status, the yield of stalks, and the accumulation of N and Si by a fourth ratoon sugarcane (Saccharum sp.) crop, and the influence of N doses in the presence and absence of Si and lime. The study was carried out at the experimental farm of the UNESP Jaboticabal campus, state of São Paulo, Brazil. The experimental design was in a completely randomized block with a 5x2 factorial scheme: five doses of N (0, 40, 80, 120, and 160 kg ha-1), and two corrective materials, silicate and lime; with four replications per treatment. The soil was characterized as distrophic Red Latosol, and the sugarcane variety was RB855156. During the experiment, the N (N-NH4+ and N-NO3-) and Si content in the soil, the N and Si content in the leaf, production of stalks, and the accumulation of N and Si in the leaves and stalks were measured. Nitrogen fertilization associated with silicate and limestone increased the levels of N-NO3- and Si in the soil, and improved nutritional status and accumulation of N and Si in leaves and stalks of sugarcane; but, stalk production was lower when using silicate as compared to lime.

La eficiencia máxima de nitrógeno (N) se alcanza cuando el fertilizante de N se usa con silicio (Si). Por tanto, el objetivo de este estudio fue evaluar los atributos químicos del suelo, el estado nutricional, la producción de tallos y la acumulación de N y Si en el cuarto cultivo de soca de caña (Saccharum sp.), y la influencia de la dosis de N en presencia y ausencia de Si y cal. El estudio se realizó en la granja experimental del campus UNESP-Jaboticabal, estado de São Paulo, Brasil. El diseño experimental fue de bloques completos al azar con un arreglo factorial de 5x2: cinco dosis de N (0, 40, 80, 120 y 160 kg ha-1), y dos materiales correctivos, silicato y cal; con cuatro repeticiones por tratamiento. El suelo se clasificó como Latosol Rojo distrófico y la variedad de caña de azúcar fue RB855156. Durante el experimento se midieron el contenido de N (N-NH4+ y N-NO3-) y Si en el suelo, el contenido de N y Si en la hoja, la producción de tallos y la acumulación de N y Si en las hojas y tallos. La fertilización con N asociada con silicato y caliza aumentó los niveles de N-NO3- y Si en el suelo, lo cual mejoró el estado nutricional y la acumulación de N y Si en las hojas y tallos de la caña de azúcar, pero la producción de tallos fue menor al usar silicato, comparado con cal.

Na colheita mecanizada sem o uso de fogo ocorre deposição de palhada na superfície do solo, a qual pode ser reciclada e reduzir a adubação potássica para a cana-de-açúcar, em relação à cana queimada, o que pode refletir em menor custo de produção. Objetivou-se avaliar o efeito da aplicação de potássio no desenvolvimento inicial da soqueira de primeiro corte da cana-de-açúcar (variedade SP 89-1115), em sistema de colheita sem despalha a fogo. O experimento foi instalado em uma área de primeira soqueira de cana-de-açúcar, cultivada em Latossolo Vermelho, textura argilosa. Os tratamentos foram constituídos por cinco doses de K2O (0 kg ha-1; 32,5 kg ha-1; 65,0 kg ha-1; 130,0 kg ha-1; e 195,0 kg ha-1), na forma de KCl, aplicado em 2009, dispostos em blocos casualizados e com cinco repetições. As variáveis de crescimento avaliadas foram: número de perfilhos, altura de planta e diâmetro de colmo, aos 120 dias após o brotamento. A aplicação de potássio proporcionou incremento com ajuste linear do teor de potássio no solo, nas camadas 0-0,20 m e 0,20-0,40 m de profundidade, atingindo 0,18 cmol c dm-3 e 0,12 cmol c dm-3, respectivamente, para a maior dose de K. A aplicação de K não afetou o número de perfilhos e diâmetro de colmo, mas influenciou a altura, atingindo maior valor na dose de 195,0 kg ha-1 de K2O.

In the mechanized harvesting without the use of fire, there is deposition of straw on the soil surface, which may be recycled and reduce the potassium fertilization for sugarcane, if compared to the burned sugarcane, what may reflect in a lower production cost. This study aimed to evaluate the potassium application effect in the early development of first cutting sugarcane ratoon (SP 89-1115), in an unburned harvesting system. The experiment was installed in a first sugarcane ratoon area, in a clay Oxisol. The treatments consisted of five K2O doses (0 kg ha-1, 32.5 kg ha-1, 65.0 kg ha-1, 130.0 kg ha-1, and 195.0 kg ha-1), as KCl, applied in 2009, in a randomized blocks design with five replications. The growth variables measured were number of tillers, plant height, and stem diameter, 120 days after budding. The potassium application provided a linear increase in the soil potassium content, at the 0-0.20 m and 0.20-0.40 m depth layers, reaching, respectively, 0.18 cmol c dm-3 and 0.12 cmol c dm-3, for the highest K dose. The K fertilization did not affect the number of tillers and stem diameter, but it affected plant height, which reached its highest value at 195.0 kg ha-1 of K2O.