Willian Pereira

Avaliação agronômica de variedades de cana‑de‑açúcar inoculadas com bactérias diazotróficas e adubadas com nitrogênio

O objetivo deste trabalho foi avaliar a eficiencia da inoculacao de bacterias diazotroficas e da adubacao nitrogenada, em duas variedades de cana-de-acucar, cultivadas nas mesmas condicoes edafoclimaticas. O experimento foi conduzido durante os anos agricolas de 2006/2007 e 2008/2009, em delineamento experimental de blocos ao acaso, com quatro repeticoes, instalado em marco de 2006 em area de cultivo comercial, no Municipio de Campos dos Goytacazes, RJ. Os tratamentos foram: inoculacao com bacterias diazotroficas, adubacao com 120 kg ha-1 de N, e o controle sem inoculacao e sem adubacao com nitrogenio. As variedades de cana-de-acucar avaliadas foram RB72454 e RB867515. O inoculante continha estirpes de cinco especies de bacterias diazotroficas. Foram feitas avaliacoes quanto a produtividade de colmos frescos, ao acumulo de materia seca total, ao N total da parte aerea e quanto a abundância natural de 15N do N disponivel no solo e na cana-de-acucar. As variedades apresentaram comportamentos distintos com os tratamentos, em que a RB867515 foi responsiva e a RB72454 nao responsiva a inoculacao e a adubacao nitrogenada. Na variedade RB867515, o crescimento e o acumulo de N total na parte aerea das plantas, promovidos pela inoculacao, foram similares aos do tratamento com adubacao nitrogenada.

Inoculation of sugarcane with diazotrophic bacteria

The sugarcane industry, a strategic crop in Brazil, requires technological improvements in production efficiency to increase the crop energy balance. Among the various currently studied alternatives, inoculation with diazotrophic bacteria proved to be a technology with great potential. In this context, the efficiency of a mixture of bacterial inoculant was evaluated with regard to the agronomic performance and N nutrition of sugarcane. The experiment was carried out on an experimental field of Embrapa Agrobiologia, in Seropedica, Rio de Janeiro, using a randomized block, 2 × 3 factorial design (two varieties and three treatments) with four replications, totaling 24 plots. The varieties RB867515 and RB72454 were tested in treatments consisting of: inoculation with diazotrophic bacteria, N-fertilized control with 120 kg ha-1 N and absolute control (no inoculation and no N fertilizer). The inoculum was composed of five strains of five diazotrophic species. The yield, dry matter accumulation, total N in the shoot dry matter and the contribution of N by biological fixation were evaluated, using the natural 15N abundance in non-inoculated sugarcane as reference. The bacterial inoculant increased the stalk yield of variety RB72454 similarly to fertilization with 120 kg ha-1 N in the harvests of plant-cane and first ratoon crops, however the contribution of biological N fixation was unchanged by inoculation, indicating that the benefits of the inoculant in sugarcane may have resulted from plant growth promotion.

Acúmulo de biomassa em variedades de cana-de-açúcar inoculadas com diferentes estirpes de bactérias diazotróficas

RESUMO - O objetivo do estudo foi avaliar a contribuicao da inoculacao com bacterias diazotroficas, aplicadas individualmente e em mistura, em variedades comerciais de cana-de-acucar. O experimento foi conduzido no Campo Experimental da Embrapa Agrobiologia, em Seropedica-RJ, Brasil. O delineamento experimental foi em blocos casualizados, com parcelas subdivididas e com seis repeticoes. Foram utilizadas seis variedades de cana-de-acuca r e seis tratamentos: controle absoluto, controle nitrogenado, inoculacao individual das estipes: BR 11512, BR 11724 e BR 11411; alem de inoculacao com um coquetel composto por cinco estirpes de bacterias diazotroficas. Foi observada diferenca entre variedades, entre tratamentos e uma interacao entre tratamentos e variedades. Para todos os parâmetros avaliados nao foi observado resposta nas variedades de cana-de-acucar RB855536 e RB92606. Na variedade RB918639, houve apenas diferenca no acumulo de biomassa verde. Nao foi observada nenhuma diferenca entre tratamentos no acumulo de nitrogenio total do ponteiro. A variedade mais responsiva a inoculacao foi a RB867515, diferenciando no acumulo de biomassa seca e fresca. Este estudo mostrou que a inoculacao promove o acumulo de biomassa, sendo a contribuicao diferente entre variedades e estirpes de bacterias, sugerindo uma interacao entre os fatores estudados. A variedade RB867515 e promissora para os estudos de inoculacao com bacterias diazotroficas. Palavras-chave: Cana-de-acucar. Crescimento (plantas). Plantas-inoculacao.

Development and nitrate reductase activity of sugarcane inoculated with five diazotrophic strains

Diazotrophs are able to stimulate plant growth. This study aimed at evaluating the effect of inoculation of five diazotrophic strains on growth promotion and nitrate reductase (NR, EC 1.7.1.1) activity in sugarcane. An experiment was carried out from three stages of cultivation: sprouting, tubes, and in hydroponics. On the first two stages, seven treatments were adopted: uninoculated control; mixed inoculation with five strains; and individual inoculation with Gluconacetobacter diazotrophicus (Gd), Herbaspirillum rubrisubalbicans (Hr), Herbaspirillum seropedicae (Hs), Nitrospirillum amazonense (Na), and Paraburkholderia tropica (Pt). The four treatments showing the best performance were transferred to the hydroponic system for analysis of NR activity. Hs, Pt, and the mixture of all strains led to the highest seedling biomass in tubes, followed by Hr. In hydroponics, the mixture and the strain Hr had the highest growth-promoting effect. NR activity was influenced by inoculation only under low N supply conditions, with positive effect of Hr, Pt, and the mixture.

Agronomic performance of green cane fertilized with ammonium sulfate in a coastal tableland soil

The recent approach of eliminating the usage of fire for sugarcane harvesting resulted in managing the crop on a trashblanketed soil, to which a proper recommendation of N fertilization is lacking, a problem that remains in the coastal tablelands of the Espirito Santo State, Brazil. This study aimed at evaluating the effect of increasing N rates on stalk and sugar yields and the N use efficiency by the crop. The experimental area planted with sugarcane, at the first ratoon, is located in Linhares, Espirito Santo State. The treatments consisted of N rates varying from 80 to 160 kg N∙ha−1 as ammonium sulphate, and a control without N, in a completely randomized blocks experimental design. Stalk yield increased with the N rate, and fitting the results to a quadratic function suggests no response to fertilizer rates above 130 kg N∙ha−1. The highest margin of agricultural contribution was obtained at the rate of 100 kg N∙ha−1. The N use efficiency decreased from almost 49 to 38%, when the N rate increased from 100 to 160 kg N∙ha−1. There was no effect of increasing N rates on the sugar concentration, although the sugar yield response was positive and strongly influenced by the stalk production. Results showed the importance of reassessing the adequate N rate for maximizing yield in green cane production systems.

Yield of sugarcane varieties and their sugar quality grown in different soil types and inoculated with a diazotrophic bacteria consortium

Abstract Sugarcane is a crop of great economic, social, and environmental relevance in Brazil. The country is the largest sugar producer and the second largest bioethanol producer in the world. The goal of this study was to evaluate the efficiency of a sugarcane inoculant composed of five diazotrophic bacterial strains, as well as nitrogen fertilization of two sugarcane varieties. Two experiments were carried out on two varieties using an experimental design composed of complete randomized blocks in a factorial of two varieties and three treatments with four replicates. The treatments can be described as: inoculation with the consortium of five diazotrophic strains, or N fertilization with 120 kg ha−1, and one control treatment. The following parameters were then evaluated: stem yield, accumulation of total dry matter, nitrogen content, quality of the sugarcane juice, and 15N natural abundance on flag-leaves. Inoculation and N fertilization on the Sapucaia plantation promoted increases of stem yield equivalent to 22.3 and 26.5 Mg ha−1 in the RB867515 variety, in comparison to the control, respectively. Inoculation and N fertilizer used for the Coruripe plantation increased stem yield of 38.0 and 42.4 Mg ha−1, respectively, with the RB867515 variety, while RB72454 showed increases of 16.7 and 37.5 Mg ha−1, both compared to the control. Biological nitrogen fixation was not affected by the treatments, however, both treatments increased the total recoverable sugar yield. Benefits from inoculation appeared to promote plant growth due to the plant–bacteria interaction.