RESUMO Adubações com fósforo (P) apresentam baixa eficiência devido à adsorção de P na superfície da argila em solos tropicais. O superfosfato complexado com ácido húmico (SSP+HA) é apresentado como uma alternativa para melhorar a eficiência do uso do P e a produtividade das culturas. Nesse sentido, o objetivo deste estudo foi investigar o desempenho do SSP+HA na produção de cana-de-açúcar com incrementos da matéria seca (MS) e conteúdo de P nas plantas. O experimento foi conduzido com duas fontes de P (superfosfato simples-SSP; SSP+HA) e cinco doses (0; 45; 90; 135 e 180 kg ha-1 de P2O5). A dose de 135 kg ha-1 foi usada para explicar o efeito residual do P, coletando solo na cana-planta e primeiro corte. Amostras de caules, ponteiras e raízes foram coletadas para determinar MS e conteúdo de P; ambas variáveis foram usadas para calcular a eficiência de assimilação de fósforo (EaP). Os resultados mostraram que a aplicação de SSP aumentou MS e conteúdo de P nas plantas, com desempenho superior ao SSP+HA. A EaP foi maior no SSP+HA, indicando que o P foi metabolizado de forma mais eficiente, mas não refletiu no aumento de MS. As doses de P aumentaram a produtividade da cana-planta, mas não houve efeito do P aplicado em soqueira, devido ao efeito residual do P aplicado no plantio. O SSP apresentou desempenho superior ao SSP+SH no plantio da cana-de-açúcar. Mais pesquisas são necessárias para melhor ilustrar o efeito do SSP+HA na absorção e translocação do P.

ABSTRACT In tropical soils, the efficiency of phosphorus (P) fertilization is low, due to P adsorption on the surface of the clay. Superphosphate complexed with humic acid (SSP+HA) is presented as an alternative for improving P use efficiency and crop yields. The aim of this study was to investigate SSP+HA performance in sugarcane production including increases in plant dry matter (DM) and P content. The experiment was conducted with two sources of P (simple superphosphate - SSP, SSP+HA) and five doses (0, 45, 90, 135 and 180 kg ha-1 P2O5). The dose of 135 kg ha-1 P2O5 was used to explain the residual effect of P, collecting soil samples from the plant cane and first ratoon. Stalk, top and root samples were collected to determine DM and P content; both variables were used to calculate the P assimilation efficiency (PaE). Results showed that the application of SSP increased the DM and P content of the plants, with superior performance compared to SSP+HA. PaE was greater under SSP+HA, indicating that P was metabolized more efficiently; however this did not reflect in an increase in DM. AThe P rates increased the sugarcane yield in cane plant, but there was no effect of P applied in the first ratoon due to the residual effect of P applied in planting. SSP presented superior performance compared to SSP + SH in sugarcane planting. Further research is needed to better demonstrate the effect of SSP+HA on the absorption and translocation of P.

ABSTRACT: Mechanical sugarcane harvesting increases soil compaction due to the intense traffic of agricultural machinery, reducing longevity of sugarcane crops. In order to mitigate the harmful effects caused by agricultural traffic on the soil structure in sugarcane fields, this study evaluated impacts of mechanical sugarcane harvesting on traffic lane under two soil tillage systems based on load bearing capacity models. The experiment was carried out in the region of Piracicaba, state of São Paulo, Brazil, on a Rhodic Nitisol, under conventional tillage (CT) and deep strip-tillage (DST). For CT soil tillage was applied to the entire area with a heavy disk harrow, at operating depths from 0.20 to 0.30 m followed by a leveling harrow at a depth of 0.15 m. For DST, soil tillage was performed in part of the area at a depth of 0.80 m, forming strip beds for sugarcane planting, while the traffic lanes were not disturbed. Undisturbed soil samples from traffic lanes were used in the uniaxial compression test to quantify preconsolidation pressure and to model the soil load bearing capacity. The surface layer (0.00-0.10 m) was most susceptible to compaction, regardless of the tillage system (CT or DST) used. In the DST, the traffic lane maintained the previous soil stress history and presented higher load bearing capacity (LBC) than the traffic lane in the CT. As in CT the soil was tilled, the stress history was discontinued. This larger LBC in DTS minimized the impacts of the sugarcane harvest. Under CT, additional soil compaction due to mechanical sugarcane harvesting in the traffic lane was observed after the second sugarcane harvest. There was a reduction in load bearing capacity from 165 kPa to 68 kPa under CT and from 230 kPa to 108 kPa under DST, from the first to the second harvest at surface layer. Water content at mechanical harvesting was the most relevant factor to maximize impacts on the soil structure in traffic lanes, for both tillage systems.

ABSTRACT: Sugarcane (saccharum spp.) in Brazil is managed on the basis of “production environments”. These “production environments” are used for many purposes, such as variety allocation, application of fertilizers and definition of the planting and harvesting periods. A quality classification is essential to ensure high economic returns. However, the classification is carried out by few and, most of the time, non-representative soil samples, showing unreal local conditions of soil spatial variability and resulting in classifications that are imprecise. One of the important tools in the precision agriculture technological package is the apparent electrical conductivity (ECa) sensors that can quickly map soil spatial variability with high-resolution and at low-cost. The aim of the present work was to show that soil ECa maps are able to assist classification of the “production environments” in sugarcane fields and rapidly and accurately reflect the yield potential. Two sugarcane fields (35 and 100 ha) were mapped with an electromagnetic induction sensor to measure soil ECa and were sampled by a dense sampling grid. The results showed that the ECa technique was able to reflect mainly the spatial variability of the clay content, evidencing regions with different yield potentials, guiding soil sampling to soil classification that is both more secure and more accurate. Furthermore, ECa allowed for more precise classification, where new “production environments”, different from those previously defined by the traditional sampling methods, were revealed. Thus, sugarcane growers will be able to allocate suitable varieties and fertilize their agricultural fields in a coherent way with higher quality, guaranteeing greater sustainability and economic return on their production.

O objetivo deste trabalho foi avaliar a produtividade agroindustrial de cana-de-açúcar (produtividades de colmos e sacarose) após sucessivas adubações nitrogenadas de cana-planta e soqueiras, em sistema de preparo reduzido. O experimento foi conduzido em Jaboticabal, SP, em um Latossolo Vermelho eutrófico durante quatro ciclos agrícolas consecutivos (março de 2005 a julho de 2009). Os tratamentos de cana-planta consistiram de doses de N-ureia (controle, 40, 80 e 120 kg ha-1 de N + 120 kg ha-1 de P2O5 e K2O no sulco de plantio). Na primeira e na segunda soqueiras, as parcelas de cana-planta foram subdivididas em tratamentos de N-nitrato de amônio (controle, 50, 100 e 150 kg ha-1 de N + 150 kg ha-1 de K2O, sobre as fileiras de cana). Na terceira soqueira, a adubação com N foi de 100 kg ha-1 em todas as parcelas, inclusive nos controles, para detectar efeitos residuais das fertilizações anteriores na produtividade do último ciclo. Os colmos de cana foram colhidos mecanicamente. Utilizou-se caminhão instrumentado com balança para avaliação da produtividade de colmos (TCH), e amostras retiradas no campo para análise da quantidade de açúcar dos colmos (TSH). As doses crescentes de N e as condições meteorológicas proporcionam respostas significativas na TCH e na TSH da cana-planta e das soqueiras, na média e na produção acumulada dos ciclos agrícolas consecutivos.

The objective of this work was to evaluate the agroindustrial production of sugarcane (millable stalks and sucrose yield) after successive nitrogen fertilizations of plant cane and ratoons in a reduced tillage system. The experiment was carried out at Jaboticabal, SP, Brazil, on a Rhodic Eutrustox soil, during four consecutive crop cycles (March 2005 to July 2009). Plant cane treatments consisted of N-urea levels (control, 40, 80, and 120 kg ha-1 N + 120 kg ha-1 P2O5 and K2O in furrow application). In the first and second ratoons, the plant cane plots were subdivided in N-ammonium nitrate treatments (control, 50, 100, and 150 kg ha-1 N + 150 kg ha-1 K2O as top dressing over rows). In the third ratoon, N fertilization was leveled to 100 kg ha-1 in all plots, including controls, to detect residual effects of previous fertilizations on the last crop's cycle. Sugarcane ratoon was mechanically harvested. A weighing truck was used to evaluate stalk yield (TCH), and samples were collected in the field for analysis of sugar content (TSH). Increasing N doses and meteorological conditions promote significant responses in TCH and TSH in cane plant and ratoons, in the average and accumulated yield of the consecutive crop cycles.

O objetivo deste trabalho foi avaliar a eficiência agronômica das fontes nitrogenadas ureia (U), nitrato de amônio (NA), sulfato de amônio (SA) e cloreto de amônio (CA) em soqueira de cana-de-açúcar colhida sem queima, bem como determinar o efeito residual dessas fontes sobre a produtividade da cultura no ano agrícola subsequente. Utilizou-se o delineamento experimental de blocos ao acaso, com quatro repetições. Os tratamentos consistiram da aplicação de 120 kg ha-1 de N a um Latossolo Vermelho distrófico, coberto por palhada resultante da colheita sem queima da primeira soqueira. Incluiu-se um tratamento de controle sem adição de N fertilizante. Para avaliar o efeito residual dos adubos nitrogenados, aplicaram-se 450 kg ha-1 do formulado 20-5-19 após o corte da cana-soca. A maior produção de colmos e de açúcar na safra 2006/2007 foi obtida com a fonte SA. Na safra 2007/2008, não foi verificado efeito residual da adubação nitrogenada e houve queda de produtividade do tratamento CA em comparação ao controle. A fonte CA, à dose de 120 kg ha-1 de N em adubação de soqueira de segundo corte, é agronomicamente tão eficiente quanto as demais fontes de N utilizadas, mas tem menor eficiência no ano agrícola subsequente.

The objective of this work was to evaluate the agronomic efficiency of the nitrogen sources urea (U), ammonium nitrate (AN), ammonium sulfate (AS), and ammonium chloride (AC) on green harvesting sugarcane ratoon, as well as the residual effect of these sources on crop productivity in the subsequent crop year. A randomized block design was used with four replicates. Treatments consisted of applying 120 kg ha-1 of N fertilizer on a Typic Hapludox covered by straw residues resulting from the harvest without burning of the first ratoon. A control treatment was included with no N fertilizer. To evaluate the residual effect of the nitrogen fertilizers, 450 kg ha-1 of a 20-5-19 formulation was applied to soil after sugarcane ratoon harvest. The highest production of stalks and sugar, in the 2006/2007 season, was obtained with the source AS. In the 2007/2008 harvest season, no residual effect of N fertilization was observed and there was a productivity decrease in the AC treatment in comparison to the control. The AC source, at a dose of 120 kg ha-1 N in the fertilization of the second ratoon, is agronomically as efficient as the other N sources used, but shows less efficiency in the subsequent crop year.

No agrossistema da cana-de-açúcar a resposta à aplicação de B é ainda uma questão não esclarecida, porém é um procedimento que vem sendo utilizado com certa frequência. O uso de fertilizantes marcados com 10B pode auxiliar no entendimento dessa prática. Com o objetivo de avaliar o aproveitamento do B (10B) proveniente do fertilizante (ácido bórico) pela cana-de-açúcar, realizou-se um experimento em campo, na safra de 2005/2006, que consistiu na instalação de microparcelas (2 m de comprimento por 1,5 de largura), que, após 90 dias do plantio (maio de 2005), receberam 4 kg ha-1 de B (ácido bórico com 85,95 % em átomos de 10B) dissolvidos em água. A solução foi aplicada ao solo nos dois lados da linha de plantio, a uma distância de 20 cm. Após a colheita (junho de 2006), foram determinados o teor de B e a abundância de 10B em átomos % em todas as partes das plantas de cana-de-açúcar (colmos, folhas secas, ponteiros e raízes). Os resultados mostraram que o acúmulo total de B foi de 471 g ha-1, e, dessa quantidade, 35 % estavam nos colmos, 22 % nas folhas secas, 9 % nos ponteiros e 34 % nas raízes. O aproveitamento do 10B-fertilizante pela cana-de-açúcar representou em média 14 % do boro total acumulado na parte aérea (44 g ha-1), 11 % nas raízes (19 g ha-1) e 13 % na planta inteira (63 g ha-1). A recuperação do 10B-fertilizante pela cana-planta foi baixa, em torno de 2 % do total aplicado.

The response to B in agricultural systems of sugar cane is still an unexplored issue; B application has however recently been widely publicized and used with a certain degree of frequency. The use of 10B-labeled fertilizers may further contribute to clarify this practice. With the objective of evaluating sugar cane use of B (10B) derived from fertilizer (boric acid), an experiment was conducted under field conditions in the 2005/2006 growing season. The experiment consisted of the installation of microplots (2 x 1.5 m) where 4 kg ha-1 B (boric acid with 85.95 % in 10B atoms) dissolved in water was applied 90 days after planting (May 2005). The solution was applied to the soil on both sides of the plant row at a distance of 20 cm. After harvest (June 2006) the B content and 10B abundance in % atoms in all parts of the sugar cane plants (stalks, dry leaves, tips and roots) were determined. Results showed that the total B accumulated was 471 g ha-1 in the entire plant (35 % in the stalks, 22 % in the dry leaves, 9 % in the tips and 34 % in the roots). The sugar cane plants used on average 14 % of the total accumulated B in the above-ground part (44 g ha-1) and 11 % in the roots (19 g ha-1), totaling 13 % in the entire plant (63 g ha-1). The recovery of 10B-fertilizer by sugar cane plants was low, around 2 % of the total applied amount.

O objetivo deste trabalho foi avaliar o desenvolvimento de raízes e da parte aérea da cana-de-açúcar (Saccharum spp.), no ciclo cana-planta, em resposta à aplicação de nitrogênio (N) no sulco de plantio. Dois experimentos, um em Latossolo Vermelho-Amarelo eutrófico e outro em Latossolo Vermelho distrófico, foram realizados em delineamento de blocos ao acaso, com quatro repetições, com um tratamento sem N (controle) e os tratamentos com 40, 80 e 120 kg ha-1 de N na forma de ureia, aplicados no sulco de plantio. A massa de raízes e da parte aérea foi quantificada em três épocas (outubro de 2005, fevereiro de 2006 e em junho/julho de 2006). A parte aérea foi coletada em 2 m da linha, e as raízes foram coletadas com uma sonda de 0,055 m de diâmetro interno, até 0,6 m de profundidade. A adubação nitrogenada de plantio incrementou o crescimento de raízes e da parte aérea da cana-de-açúcar no Latossolo Vermelho-Amarelo. Entretanto, não houve incremento desse crescimento no Latossolo Vermelho onde grande quantidade de N orgânico foi incorporada ao solo por meio de resíduos culturais. A fase de maior desenvolvimento de raízes, em cana-planta de ano e meio, foi de outubro a fevereiro, com diminuição da massa de raízes de fevereiro a julho.

This work evaluated the root and shoot sugarcane (Saccharum spp.) development in plant cane cycle, related to nitrogen (N) rates applied at planting. Two experiments were carried out using randomized block designs, one in a Typic Eutrustox and other in an Arenic Kandiustults. Treatments were a control without N, and 40, 80 and 120 kg ha-1 N applied in furrow at planting, with four replicates. The root and shoot masses were evaluated in three periods (October 2005, February 2006 and June/July 2006). Shoots were collected in 2 m of furrow, and the roots were collected using a probe (internal diameter of 0.055 m) until 0.6 m depth. The nitrogen fertilization at planting increased the development of cane roots and shoots in Typic Eutrustox. However, there was no growth increase of sugarcane roots and shoots in the Arenic Kandiustults where a large amount of organic N from cultural residues had been incorporated into the soil. The phase of larger root development of one and half year old plant cane was from October to February, with decrease of the root mass from February to July.

O objetivo deste trabalho foi comparar três métodos de aplicação de solução de uréia marcada com15N (15N-uréia ): pulverização foliar, injeção na base do colmo e imersão radicular, a fim de se definir qual seria o mais eficiente na marcação de fitomassa de cana-de-açúcar. O experimento foi instalado na Estação Experimental Apta - Pólo Regional Centro Sul, em Piracicaba, SP. A cana-de-açúcar, variedade SP80 3280, foi plantada em vasos preenchidos com aproximadamente 120 dm³ de Neossolo Quartzarênico de textura arenosa. O delineamento experimental foi inteiramente casualizado, com quatro repetições. A fitomassa de cana-de-açúcar dos três tratamentos, no 11º mês de desenvolvimento, não diferiu estatisticamente, e suas abundâncias de 15N foram superiores à natural, tendo-se verificado a seguinte ordem decrescente de marcação com 15N: parte aérea > rizoma > rizomas+raízes na camada de 0,0-0,2 m > raízes na camada de 0,2-0,4 m > raízes em profundidade maior que 0,4 m. Entre os métodos de aplicação de 15N-uréia, a injeção na base de colmos é o de mais fácil execução, o mais efetivo na marcação da fitomassa e o que apresentou a maior recuperação do traçador (96%). A aplicação foliar é comparável à injeção, somente na marcação e na recuperação do traçador no sistema radicular.

The objective of this research was to compare three methods of 15N-urea solutions application: spray on leaf, injection in the plant base stem and root immersion, in order to define the most efficient labeling sugarcane phytomass with 15N method. The experiment was carried out at APTA - Pólo Regional Centro Sul, in Piracicaba, SP, Brazil, and the sugarcane variety SP80 3280 was planted in pots filled out with approximately 120 dm³ of a Typic Quartzipsamment soil. The experiment was conducted in a completely randomized design with four replicates. There were no difference between the methods in the plant parts dry mass, in 11º development month, and their 15N abundances were superior to the natural one, being verified the following decreasing labeling order: aerial part > rhizome > rhizome + roots in the layer 0.0-0.2 m > roots in the layer 0.2--0.4 m > roots in the layer deeper than 0.4 m. Among the 15N-urea solution application methods, the injection in the base stem is the easiest to apply, the most effective in dry mass labeling and the one wich presented the largest 15N tracer recovery (96%). The spray on leaf method is comparable to the injection in the base stem only for the labeling with 15N and tracer recovery for root system.