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The area under mechanized sugarcane (Saccharum spp.) harvesting is expanding in Brazil, increasing the return of trash to the soil. The main questions regarding this management are: (i) after adopting unburned mechanical harvesting, how long will it take to observe decreases in fertilizer requirements, (ii) what will be the magnitude of this decrease and, (iii) the impact in the short run of removing trash for energy purposes in the nutrient cycling? This study aimed to build an N prediction model for long term assessment of the contribution of sugarcane crop residues to sugarcane nutrition and to evaluate the cycling of other nutrients derived from crop residues. Keeping crop residues over the soil will increase soil N stock and N recovery by sugarcane, reaching equilibrium after 40 years with recovery of approximately 40 kg ha -1 year -1 of N. Removing trash for energy production will decrease the potential reduction in N fertilizer requirement. Of the total nutrients in the trash, 75 % of the K 2 O (81 kg ha -1 year -1 ) and 50 % of the N (31 kg ha -1 year -1 ) are in the tops, indicating the importance of maintaining tops in the soil to sustain soil fertility. Because the input data employed in the simulations are representative of the conditions in Southeast Brazil, these results might not be definitive for situations not represented in the experiments used in the study, but the model produced is useful to forecast changes that occur in the soil under different trash management.

RESUMOA pesquisa tecnológica para suporte do setor sucroalcooleiro nacional mostra que são esporádicos os trabalhos desenvolvidos com cana-de-açúcar irrigada envolvendo a exigência nutricional. Nesse contexto, objetivou-se quantificar, durante o ciclo de cana-planta de 11 variedades de cana-de-açúcar (SP79-1011, RB813804, RB863129, RB872552, RB943365, RB72454, RB763710, SP78-4764, SP81-3250, RB867515 e RB92579) cultivadas sob irrigação plena, a capacidade de extração e exportação de N, P, K, Ca e Mg, bem como a exigência nutricional para produção de uma tonelada de colmo por hectare (TCH) .

RESUMOA análise de crescimento é considerada o método padrão para medir a produtividade biológica em espécies vegetais. Neste contexto objetivou-se avaliar, em onze variedades de cana-de-açúcar (SP79-1011, RB813804, RB863129, RB872552, RB943365, RB72454, RB763710, SP78-4764, SP81-3250, RB867515, RB92579) cultivadas sob irrigação plena, o crescimento e a produção de matéria seca no ciclo de cana planta. O experimento foi instalado em condições de campo no município de Carpina, PE. Utilizou-se o delineamento estatístico de blocos ao acaso, com quatro repetições. A análise de crescimento correspondeu à quantificação dos números de perfilhos e à, na mensuração da altura e diâmetro dos colmos, avaliados mensalmente em onze períodos de cultivo, os quais se estenderam dos 60 aos 360 dias após o plantio (DAP). A produção de matéria seca foi quantificada a partir dos 120 DAP, com intervalos de amostragem a cada dois meses. Observou-se que as variedades RB92579 e SP81-3250 apresentaram o maior perfilhamento e produção de maté-ria seca e as variedades RB813804 e RB72454 às maiores médias de altura, enquanto as variedades RB867515 e RB72454 obtiveram os maiores diâmetros do colmo. Palavras-chave:Saccharum spp, perfilhamento, altura, diâmetro, produção biológica Growth and dry matter production in sugarcane varieties grown under full irrigation ABSTRACT Growth analysis is considered as a standard method for measuring the biological productivity of plant species. The objective of this research was to evaluate the growth and dry matter production of eleven sugarcane varieties (SP79-1011, RB813804, RB863129, RB872552, RB943365, RB72454, RB763710, SP78-4764, SP81-3250, RB867515, RB92579), grown under full irrigation, in the planted cane cycle. The experiment was conducted in field conditions in the municipality of Carpina, PE. A randomized block design with four replications was used. The varieties' growth analysis was represented by the quantification of the tillers numbers, stalk height and diameter, measured monthly, in eleven periods of cultivation that extended from 60 to 360 days after planting (DAP). The dry matter production was measured from 120 DAP, with sampling intervals of every two months. It was observed that, at 360 DAP, the RB92579 and SP81-3250 varieties showed the highest tillering and dry matter production. The RB813804 and RB72454 varieties had the highest average for height, while the RB72454 and RB867515 varieties presented the largest stalk diameters.

Resumo -O objetivo deste trabalho foi avaliar a produtividade de colmos e de açúcar, a eficiência de uso da água e os atributos tecnológicos de cinco variedades de cana-de-açúcar de maturação precoce e seis de maturação média à tardia, submetidas ao regime de sequeiro (1.141,4 mm) e à irrigação plena (1.396,6 mm). Utilizou-se o delineamento experimental de blocos ao acaso, com quatro repetições. A produtividade de colmos das variedades RB92579, RB72454 e SP81-3250 apresentou ganhos superiores a 180%, com uso da irrigação. A irrigação promoveu aumentos na produtividade de açúcar superiores a 200%, nas variedades RB92579 e RB943365. A irrigação plena proporcionou maior eficiência de uso da água, com produção média de 70,2 kg ha -1 mm -1 de colmos a mais em comparação ao regime de sequeiro. Com exceção das variedades RB72454, RB763710 e RB943365, não houve diferença nos atributos tecnológicos entre a irrigação plena e o regime de sequeiro. As variedades RB92579 e SP81-3250 de maturação média à tardia se destacam quanto à produtividade de colmos e de açúcar e à eficiência de uso da água, e são recomendadas para estudos de resposta à irrigação pela cana-de-açúcar.Termos para indexação: Saccharum, cana-planta, irrigação plena, sequeiro. Productivity, water use efficiency, and technological quality of sugarcane subjected to differents water regimesAbstract -The objective of this work was to assess stalk and sugar yield, water use efficiency, and technological attributes of five early maturing and six medium to late maturing sugarcane varieties with no irrigation (1,141.4 mm) and under full irrigation (1,396.6 mm). A randomized complete block design, with four replicates, was used. Stalk yield for varieties RB92579, RB72454, and SP81-3250 showed gains above 180% with irrigation. Irrigation increased sugar yield in more than 200% in the RB92579 and RB943365 varieties. Full irrigation provided greater water use efficiency, producing, in average, 70.2 kg ha -1 mm -1 more stalks than under no irrigation. Except for the varieties RB72454, RB763710, and RB943365, there were no differences regarding technological attributes between full irrigation and no irrigation. The medium to late maturing varieties RB92579 and SP81-3250 have higher stalk and sugar yield and better water use efficiency, and are recommended for studies on sugarcane response to irrigation.

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Most commercially grown cacti can be easily propagated by seed and/or cuttings. A group of rare and endangered species does not fit into this category and is therefore a good candidate for in vitro propagation productions as a tool to overcome habitat and plant-destruction. The number of rare and endangered species of Cacti goes into about 100. Many show a low production and germination of seeds and plantlets are prone to damping-off, making the in vitro propagation a feasible alternative for the multiplication and conservation of their germplasm. The aim of the present investigation is to establish a protocol for the in vitro culture and plant regeneration of Notocactus magnificus, the blue cactus, a highly ornamental species, native to Brazil. The surface sterilization of the explants was achieved with immersion for 10 min in sodium hypochlorite solution for either seeds (0