ABSTRACT The adoption of more productive and nutrient-demanding genotypes, in addition soils with low availability of nutrients of soils under forest plantations, lead high fertilizer demand and justify research that seeks to rationalize the use of these inputs. Therefore, we aimed with this research to determine classes of interpretation of soil fertility using boundary line (BL) and estimate macronutrient sufficiency ranges for eucalyptus. Fertility classes and sufficiency ranges were obtained using a database of areas cultivated with eucalyptus in the Central-East region of Minas Gerais, Brazil, totaling 689 plots, containing information on yield, leaf contents, and soil chemical properties. Scatter plots were drawn relating the mean annual increment (MAI) in trunk volume (relative) with soil organic matter (OM), phosphorus (P), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) of the 0.00-0.20 m layer. Those graphs and equations were used to estimate soil fertility classes. Leaf contents of N, P, K, Ca, and Mg were plotted with soil contents of OM, P, K+, Ca2+, and Mg2+. Using the Quadrant Diagram of the plant-soil Relationship (QDpsR) method, horizontal and vertical lines were drawn separating the cloud of points in four quadrants. With the points at the quadrants III and I, regression equations were fitted. To obtain foliar sufficiency ranges, soil values of critical and optimal levels of OM, P, K+, Ca2+, and Mg2+, obtained by BL, were substituted in the equations generated by the QDpsR method. The appropriate soil content ranges determined by BL for productivity of 47.7 m3 ha-1 yr-1 were: 24.75-38.28 g kg-1 of OM, 8.5-14.6 mg dm-3 of P, 100.0-150.35 mg dm-3 of K+, 0.77-1.47 cmolc dm-3 of Ca2+, and 0.25-0.43 cmolc dm-3 of Mg2+. Leaf content ranges determined by QDpsR are: 19.4-21.3 g kg-1 of N, 1.0-1.2 g kg-1 of P, 8.5-10.6 g kg-1 of K, 4.8-6.1 g kg-1 of Ca, and 1.9-2.4 g kg-1 of Mg. The critical levels of nutrients in the soil, obtained by the BL method, and the leaf sufficiency ranges, obtained using the QDpsR method, are similar to those existing in the literature. This indicates that this methodology is reliable in establishing standards and that the critical levels obtained can be used to improve the recommendation of fertilizers for eucalyptus.

ABSTRACT: Research focused on adequate nutrition of plants is essential in modern coffee production to increase yield and develop more efficient management strategies with greater environmental and economic sustainability. The objectives of this study were to establish critical and optimal levels of soil fertility properties for high yielding Arabica coffee crops using the Boundary Line method and, then, relate the macronutrient contents in the diagnostic leaf of coffee to the macronutrients available in the soil using the Quadrant Diagram of the Plant-Soil Relationship (QDpsR). The study made use of a soil chemical analysis database, leaf macronutrient contents, and Arabica coffee yield from five representative coffee-growing regions in Minas Gerais. An analysis of data consistency was performed, and relative fruit yield (RFY) was related to the soil organic matter (SOM), P, K, Ca, and Mg contents in the soil, establishing the boundary line (BL) in each graph. Equations were adjusted from the BL points, and the equation that best fit was selected. Using the QDpsR method, the response plane was divided into four quadrants, where the total leaf contents of N, P, K, Ca, Mg, and S were plotted as a function of the contents of SOM, P, K, Ca, and Mg in the soil, on the y and x axes of the Cartesian coordinate system. The regression equations were adjusted to the pairs of points (y, x) of quadrants III and I and were used to estimate the macronutrient sufficiency ranges from the critical and optimal levels in the soil. The BL method was used to determine the class of good soil fertility for SOM, P, K, Ca, and Mg. The QDpsR method allows determination of response curves for leaf content as a variable of soil contents, making it possible to estimate the sufficiency ranges in the diagnostic leaf of coffee: 33.4-35.8 g kg-1 of N, 1.4-1.6 g kg-1 of P, 24.4-27.0 g kg-1 of K, 11.9-13.6 g kg-1 of Ca, 3.8-4.5 g kg-1 of Mg, and 1.4-1.8 g kg-1 of S; which were consistent with the sufficiency ranges considered suitable for the crop. This study demonstrated the importance of leaf analysis as a tool for evaluation of the nutritional status of Arabica coffee since the technique is consistent with the theoretical principles underlying it.

RESUMO A cana-de-açúcar é uma cultura de grande destaque na economia, em razão da produção de açúcar, etanol e energia. Tecnologias que possam contribuir para o aumento da produtividade e qualidade da cultura com mínimos danos ao meio ambiente são necessárias. Objetivou-se avaliar a produção de ácido indol acético de cinco estirpes de bactérias diazotróficas e o efeito da inoculação delas na brotação de duas variedades de cana-de-açúcar, RB867515 e IACSP95-5000. A produção de auxina foi determinada pelo teste colorimétrico, usando o reagente de Salkowski. Para avaliar a germinação, foi conduzido um experimento em casa de vegetação, utilizando-se delineamento experimental em blocos ao acaso com quatro repetições e sete tratamentos: controle não inoculado; inoculação mista com as cinco estirpes e inoculação individual com Gluconacetobacter diazotrophicus (Gd) estirpe BR11281T(PAL-5T), Herbaspirillum seropedicae (Hs - BR11335 = HRC54), Herbaspirillum rubrisubalbicans (Hr - BR11504 = HCC103), Burkholderia tropica (Bt - BR11366T = PPe 8 T) e Azospirillum amazonense (Aa - BR11145 = CBAMc). As bactérias mais eficientes na produção de auxina foram Hs e Hr, declinando 48 h após o crescimento. Hr, Aa e Bt aumentaram o índice de velocidade de germinação e o número de brotações nas duas variedades. Na var. RB867515, a velocidade de germinação ainda foi positivamente influenciada pela inoculação mista, sendo o mesmo observado pela inoculação de Gd na var. IACSP95-5000.

ABSTRACT Sugarcane is one of the most important crops in the economy due to production of sugar, ethanol, and energy. Technologies are necessary to improve its yield and quality with minimum damage to the environment. We evaluated the indole acetic acid production and germination in the sugarcane varieties RB867515 and IACSP95-5000 after inoculation with five strains of diazotrophic bacteria. The production of indole acetic acid was assayed through the colorimetric method using the Salkowski reagent. To evaluate germination, an experiment was conducted in a greenhouse using a randomized block experimental design with four replications and seven treatments: uninoculated control; mixed inoculation with the five strains; and individual inoculation with Gluconacetobacter diazotrophicus (Gd) estirpe BR11281T (PAL-5T), Herbaspirillum seropedicae (Hs - BR11335 = HRC54), Herbaspirillum rubrisubalbicans (Hr - BR11504 = HCC103), Burkholderia tropica (Bt - BR11366T = PPe 8 T) e Azospirillum amazonense (Aa - BR11145 = CBAMc). The most efficient bacteria for production of indol acetic acid were Hs and Hr, and production declined after 48 h of growth. Hr, Aa, and Bt also improved the germination speed index and number of stalks sprouted in both varieties. Furthermore, in the var. RB867515, germination speed was positively affected by the mixed inoculation, and the same effect was observed from Gd in the var. IACSP95-5000.

O aumento da eficiência produtiva da cana-de-açúcar com tecnologias que possibilitem aumentar seu balanço energético é uma necessidade do setor sucroenergético, por se tratar de uma cultura estratégica para o país. Entre as diversas alternativas atualmente estudadas, o inoculante com bactérias diazotróficas vem se evidenciando uma tecnologia com elevado potencial. Diante desse contexto, este estudo teve como objetivo avaliar a eficiência do inoculante bacteriano no desempenho agronômico e na nutrição nitrogenada da cana-de-açúcar. O ensaio foi realizado no campo experimental da Embrapa Agrobiologia, em Seropédica, RJ. O delineamento experimental foi em bloco ao acaso, em esquema fatorial 2 × 3 (duas variedades e três tratamentos), com quatro repetições, totalizando 24 parcelas. As variedades utilizadas foram a RB867515 e RB72454. Os tratamentos foram: inoculação com bactérias diazotróficas, controle nitrogenado com 120 kg ha-1 de N e controle absoluto (sem inoculação e sem N). O inoculante foi composto por cinco estirpes de cinco espécies de bactérias diazotróficas. As variáveis avaliadas foram a produtividade de colmos, o acúmulo de matéria seca e N total da parte aérea das plantas e a contribuição da fixação biológica de N (FBN), utilizando como referência a abundância natural de 15N da própria cana-de-açúcar não inoculada. O inoculante bacteriano aumentou a produtividade de colmos na variedade RB72454 de maneira similar à adubação com 120 kg ha-1 de N, nas colheitas de cana-planta e primeira soqueira; no entanto, não houve modificação na contribuição da FBN advinda da inoculação, dando evidências de que os benefícios do inoculante para a cana-de-açúcar podem ser provenientes do efeito da promoção de crescimento de plantas.

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 Seropédica, 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.