Emídio Cantídio Almeida de Oliveira

Impact of sugarcane trash on fertilizer requirements for São Paulo, Brazil

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 K2O (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.

Produtividade, eficiência de uso da água e qualidade tecnológica de cana‑de‑açúcar submetida a diferentes regimes hídricos

O objetivo deste trabalho foi avaliar a produtividade de colmos e de acucar, a eficiencia de uso da agua e os atributos tecnologicos de cinco variedades de cana-de-acucar de maturacao precoce e seis de maturacao media a tardia, submetidas ao regime de sequeiro (1.141,4 mm) e a irrigacao plena (1.396,6 mm). Utilizou-se o delineamento experimental de blocos ao acaso, com quatro repeticoes. A produtividade de colmos das variedades RB92579, RB72454 e SP81-3250 apresentou ganhos superiores a 180%, com uso da irrigacao. A irrigacao promoveu aumentos na produtividade de acucar superiores a 200%, nas variedades RB92579 e RB943365. A irrigacao plena proporcionou maior eficiencia de uso da agua, com producao media de 70,2 kg ha-1 mm-1 de colmos a mais em comparacao ao regime de sequeiro. Com excecao das variedades RB72454, RB763710 e RB943365, nao houve diferenca nos atributos tecnologicos entre a irrigacao plena e o regime de sequeiro. As variedades RB92579 e SP81-3250 de maturacao media a tardia se destacam quanto a produtividade de colmos e de acucar e a eficiencia de uso da agua, e sao recomendadas para estudos de resposta a irrigacao pela cana-de-acucar.

Acúmulo e alocação de nutrientes em cana-de-açúcar

The objective of this study was to evaluate, along the first cycle of sugar cane, the capacity of eleven varieties of sugar cane (SP79-1011; RB813804; RB863129; RB872552; RB943365; RB72454; RB763710; SP78-4764; SP81-3250; RB867515 and RB92579), cultivated under full irrigation,the accumulation of the nutrients N, P, K, Ca and Mg in the plants aerial parts (stem, leaf and pointer). The research was carried through under field conditions, during the agricultural season 2006/2007, in the Sugar Cane Agricultural Station of the Federal Rural University of Pernambuco, in Carpina County, PE/Brazil. The experimental set was a complete randomized block design, with four replications. The accumulation of nutrients in the components of the aerial part was evaluated at 120; 180; 240; 300 and 360 days after plant (DAP). It was observed along the cycle of the sugar cane, mobilization of nutrients N, P and K from the leaves to the points and stems. At 360 DAP the accumulation of N, P and K in the aerial part was higher than the amount added by fertilizers. The varieties RB92579 and SP81-3250 were detached by the highest nutrients accumulation in stems, while RB867515 and RB943365 were the varieties that allocated more nutrients in leaf, which identifies them as the varieties of larger capacity of cycling of those nutrients.

Rock biofertilizer and earthworm compost on sugarcane performance and soil attributes in two consecutive years

The deployment of soluble fertilizers has been one of the most commonly applied agricultural practices in the bid to increase crop yield. However, the production of soluble fertilizers has a considerable economic cost and consumes a substantial amount of energy. In general, soil organic matter provides the nutrients needed for plant growth in organic agriculture. However, these nutrients are not sufficient if the best yield is to be obtained. The aim of our field experiment was to evaluate the effectiveness of phosphate and potassic sources (rocks, bio-fertilizers and soluble fertilizers) based on several sugarcane characteristics and soil attributes. Our experiment was conducted over two consecutive years, and we assessed the effect of using sugarcane filter mud cake (SFMC). In addition, we mixed the phosphate and potassic sources with earthworm compost enriched in N by inoculation with diazotrophic bacteria (OM) and applied at 50, 100 and 150 % of the recommended dosage rate (RDR). The PK biofertilizer with OM enriched in N positively affected sugarcane height, yield, and industrial characteristics. The application of SFMC greatly increased available P and K in the soil and plant characteristics with residual effect in the two consecutive harvests. We conclude that the biofertilizer has the potential to increase sugarcane characteristics and may represent an alternative to soluble fertilizers.

Adubação fosfatada para cana-de-açúcar em solos representativos para o cultivo da espécie no Nordeste brasileiro

The objective of this work was to evaluate P availability in representative soils for plant cane cultivation in the Brazilian Northeast region, and to establish a new P‑fertilizing recommendation for this crop in these soils. The study was done in five soil types, in Zona da Mata of Pernambuco: Argissolo Amarelo distrocoeso (Ultisol), Argissolo Amarelo distrofico (Ultisol), Latossolo Amarelo distrofico (Oxisol), Gleissolo Haplico eutrofico (Gleisol), and Espodossolo Humiluvico ortico (Spodosol). Seven P doses were evaluated for maximum P adsorption capacity of each soil (solution equilibrium phosphorus, P‑rem). Thirty days after soil fertilization, P contents in soils were determined with the extractors Mehlich‑1, Mehlich‑3, Bray‑1, and anion exchange resin. P critical levels were calculated for each soil and extractor. From P availability ranges, five fertility classes were defined for different clay contents in the soils: very low, low, medium, high, and very high. Mehlich‑1 and anion exchange resin are able extractors to adequately represent soil‑P availability for plant cane cultivation in the evaluated soils.

Sampling of Sugarcane Leaves in Field Experiments to Determine the Activity of Nitrate Reductase

ABSTRACT Nitrogen (N) assimilation depends on nitrate reductase activity (NRA). Leaf sampling methods in field experimentation with sugarcane and analytical procedures are essential for the determination of the maximum activity (MA) of the enzyme. Thus, in five tests, it was possible to determine which period of the crop cycle should be used for leaf collection, the most adequate leaf for collection, the ideal number of leaves to be collected, the period of the day in which the enzyme has MA and which analytical procedures can be optimized. The evaluation of NRA in sugarcane should occur between 95 and 100 days after planting (DAP) and can be performed in any green leaf. In field experiments, it is recommended the collection of 15 leaves, which must occur between 12:00 and 12:30 h, with later incubation of the leaf tissues for 430 min, without vacuum application.