Nutrição do feijoeiro e intensidade da antracnose em função da aplicação de silício e cobre

The objective of this work was to evaluate the effect of calcium silicate and copper sulfate on anthracnose intensity and nutrition of bean plants. The experiment was conducted using an experimental design in randomized blocks following a 4 x 4 factorial arrangement, (four levels of calcium silicate and four levels of copper sulfate) and two additional treatments (plants without inoculation and plants sprinkled with Benomyl). Four evaluations of the incidence and severity of anthracnose were done, in addition to measuring total leaf area. At the end of the evaluations, incidence and severity data were integrated over time, obtaining the area under disease progress curve (AUDPC). Contents of N, P, K, Ca, Mg, B, Cu, Fe, Mn, Zn, Si and lignin were determined in the aerial part. A linear decrease of the intensity AUDPC was observed with the increase of the doses of calcium silicate. The severity AUDPC was influenced by the doses of copper, obtaining a reduction of 35% on the higher dosage. The supply of silicon and copper altered the content of the K, Mg, S, Zn, Ca and Si in the aerial part of the bean plants.

Estudo da influencia do potássio e do cálcio na reprodução do nematoide do cisto da soja

The objective of this work was to evaluate the reproduction of the soybean cyst nematode (SCN) in soybean plants in substract with different potassium (K) and calcium (Ca) doses. The experiment was conducted in a completely randomized block design, with 25 treatments and six replicates. A factorial scheme (5 x 5) was used with five K doses (0; 150; 300; 450; and 600 mg / dm3 ) and five Ca doses (0; 75; 150; 225; and 300 mg / dm3 ). Eighteen days after sowing, plants were inoculated with 4,000 H. glycines race 3 eggs. Thirty days after inoculation a total of three weekly evaluations were performed measuring plant height and stem diameter. Seventy days after inoculation, the following variables were analyzed: measurement of leaf blade, numbers of eggs / pot, cysts / pot, eggs / cyst, females and cysts / root system, eggs / female and the reproduction factor of H. glycines. Root and shoot dry matter were weighed. Then, K and Ca shoot contents of each sample was obtained. There was a significant interaction between K and Ca doses only for number of eggs / female. The K doses significatively influenced the numbers of cysts / pot, eggs / cyst, eggs / pot, females and cysts / root system and reproduction factor. The Ca doses did not influence significatively the nematologic variables analyzed. The K-Ca interaction affected all crop-related variables analyzed. A significative K-Ca interaction was observed for Ca contents in shoot dry matter. The K contents were only influenced by potassium doses amended to the soil.

Eficiência agronômica da ureia estabilizada com inibidores de urease e nitrificação na cultura do milho

Nitrogen (N) is the most required nutrient for corn plants and, in order to supply this demand in highly productive crops, mineral fertilizers are used, especially urea. The disadvantage of urea is the loss of N-NH3 to atmosphere. To reverse this situation, some technologies have been developed, such as nitrification and urease inhibitors, which are used as additives to urea. This work aimed at evaluating the agronomic efficiency of urea stabilized with urease and nitrification inhibitors applied to cover the 2013/2014 corn crop. We evaluated 11 nitrogen fertilizer applied in coverage: urea + PA (41.6% N, 3% Cu); urea + PA (41.6% N, 1.5% Cu); urea + PA (41.6% N, 3% Zn); urea + PA (41.6% N, 1.5% Zn); urea + PA (41.6% N, 0.34% Cu, 0.94% B); urea + PA (41.6% N, 0.25% Cu, 0.68% B); urea + PA (41.6% N); urea (44.3% N, 0.15% Cu, 0.4% B); urea (43% N, 0.1% Cu, 0.3% B, 0.05% Mo); pearled urea (46% N); urea + 0,8% DMPP (45% N) and the control, which did not receive nitrogen topdressing. The evaluations were: Nitrogen losses through volatilization, content and accumulation of N, boron (B), copper (Cu) and zinc (Zn) to the dry matter of aerial parts, grains, and in straw and grain productivity. Fertilizers stabilized with urease and nitrification inhibitors did not reduce the volatilization of ammonia volatilization, when compared to pearled urea. Urea with 0.8% of DMPP nitrification inhibitor (3,4-dimethylpyrazole phosphate) provided higher loss by volatilization, lower productivity and agronomic efficiency compared to pearled urea. The coating of urea with Cu, B and Zn did not increase the accumulation of these nutrients in grains and MSPA plants. The use of fertilizers stabilized and coated with micronutrients did not increase the productivity and agronomic efficiency compared to conventional urea.

Aspectos nutricionais do baru (Dipteryx alata Vog.) em casa de vegetação e em campo

With the objective of evaluating the response of baru (Dipteryx alata Vog.) to nutrient limitation and to the different levels of fertilization, seven experiments were conducted. Experiment 1: Nutritional limitation in greenhouse. We employed 12 treatments in a completely randomized design with eight replicates. Experiment 2: Levels of liming and P in greenhouse. The experimental design was completely randomized in a factorial scheme with four levels of liming (V23.2% (natural soil), V45%, V65% and V85%) and four doses of P (0, 100, 300 and 500 mg kg -1 of P). Experiment 3: Doses of N in greenhouse. We used seven treatments (0, 75, 150, 225, 300, 375 and 450 mg kg -1 of N) in a completely randomized design. Experiment 4: Doses of K in greenhouse. We used seven treatments (0, 75, 150, 225, 300, 375 and 450 mg kg -1 ) in a completely randomized design. Experiment 5: Levels of liming under field conditions. We used four treatments (V6.7% (natural soil), V35%, V55% and V75%) in a randomized blocks design. Experiment 6: doses of P under field conditions. We used five treatments (0, 23.67, 53.34, 106.67 and 213.36 kg ha -1 of P 2O5) in a randomized blocks design. Experiment 7: Doses of N under field conditions. We used five treatments (0, 30, 60, 120 and 240 kg ha -1 of N) in Latin square. In greenhouse, the evaluations were conducted at eight months (for experiments 1 and 2) and 12 months (for experiments 3 and 4) after seeding, when the measurements of height and root collar diameter of the seedlings. Subsequently, the plants were harvested and separated into shoot and root system, for weighing and evaluating dry biomass gain. In the field, the evaluations were conducted at six, 12, 18, 24 and 30 months (for experiments 5 and 6) and at six, 12 and 18 months (for experiment 7). In these experiments, we evaluated the survival of the seedlings, height of the plants and diameter of the stem at soil height. The data obtained were submitted to analysis of variance, mean tests and regression analysis. In conclusion, during the phase of seedling formation, the species is little demanding in S and B, negatively responds to liming, positively responds to phosphate fertilization and does not respond to nitrogen and potassium fertilization. In the field, in general, the species does not respond to the application of P or to liming, and is negatively influenced by the application of elevated doses of nitrogen.

Influência do etileno na regulação do florescimento de Coffea arabica L.

Coffee is one of the most valuable exported agricultural product worldwide as well as the second most traded commodity after oil. This crop represents a source of employment and considerably accounts for the revenue of the country, besides its undeniable importance for local and world socioeconomical scenery. The quality of the coffee drink is directly related to the fruit ripening stage, which is found in different stages at harvesting due to the sequential flowering, increasing costs with the production and generating a lower-quality beverage. The asynchronous flowering of the coffee tree comes from the uneven development of buds, which can be influenced by environmental factors, taking into account that the anthesis takes place after a water deficit period, followed by precipitation. Changes in the hormone balance have been observed after water deficit and rehydration cycles, and such oscillation on the water status of the plant increased the level of ethylene in some species. This finding led to the association between the requirements at the flowering stage of the coffee tree and the involvement of the ethylene in promoting anthesis. The application of 1- MCP (ethylene action inhibitor) triggered the anthesis in coffee trees. And, in coffee seedlings in greenhouse conditions after a period of water shortage followed by irrigation, the profile of gene expression of the biosynthesis route and signaling of ethylene are changed in leaves and roots. The increased levels of the ethylene precursor (ACC) in roots throughout the dry season and the transportation of this compound into shoots may be the signal to trigger the anthesis in coffee tree after rehydration. Thus, in order to better understand the role of the ethylene in regulation of flowering, we analyzed the effects of the exogenous application of 1-MCP in different physiological characteristics and in the expression of genes related to the ethylene biosynthesis and signaling pathways in coffee leaves and bud from plants under field conditions. The evaluations and tissue sampling were carried out in different times treatments implementation: T1 – control, T2 – 1-MCP+Break-Thru, and T3 – Break-Thru. There was influence of 1-MCP and Break-Thru in gas exchange parameters and of 1-MCP contributed to the increase in relative water content. RT-qPCR analyses showed a different behavior in relation to the profile of gene expression in leaves and buds analyzed in the present study (CaACS1 – like, CaACO1 – like, CaACO4 – like, CaETR4 – like) and the expression levels were changed a few hours (2h) after applying the products. However, there was flowering only in plants treated with 1-MCP, in the absence of rain and irrigation.

Avaliação do potencial de uso agrícola da fluorita com óxido silício (AgroSiCa), derivado da fabricação de fertilizantes fosfatados

Phosphate fertilizers are critical for crop production in tropical soils, which are known for having high phosphate-fixing capacity and aluminium saturation, as well as low pH and calcium contents. Fluorine is a component of many phosphate rocks used to make phosphate fertilizers, via a process that generates hexafluorosilicic acid (H2SiF6). While many treatment technologies have been proposed for removal of fluorine in industrial facilities, little attention has been given to a process of neutralizing H2SiF6 with calcium oxide aiming to find out an alternative and sustainable use of a by-product with a great potential for beneficial use in tropical agriculture. This study evaluated the effect of a by-product of phosphoric acid production (fluorite with silicon oxide, hereafter called AgroSiCa) in levels of phosphorus (P), calcium (Ca), silicon (Si), aluminum (Al) and fluorine (F) and some others parameters in soils as on growth of soybean and corn. Experiments were conducted in a greenhouse condition at the Federal University of Lavras (UFLA), Lavras, Minas Gerais, using different types of soils in tropical regions and different doses of AgroSiCa. The application of AgroSiCa resulted in a slight increase in soil pH and significant increases in calcium, phosphorus and silicon in the soil solution and the shoots of corn and soybeans. We also found very low levels of fluoride in all soil leachates. A significant reduction of labile aluminum levels found in all soils after the cultivation of corn and soybeans. In sum, AgroSiCa improved soil properties and contributed to better growth of both cultures. In sum, AgroSiCa improved soil properties and contributed to a better growth of both crops. Our results show that reacting H2SiF6 derived from the wet-process phosphoric acid production with calcium oxide leads to a by-product with potential for agricultural use, especially when applied in highly-weathered soils. Besides providing calcium and silicon to plants, the use of such by-product in soils with high phosphate-fixing capacity and high aluminium saturation delivers additional benefits, since fluoride and silicon can play an important role in improving soil conditions due to the formation of less plant-toxic forms of aluminium, as well as upon decreasing phosphate fixation, thus improving root development and making fertilizer-derived phosphate more available for plant growth.

Compartimentos de K, Ca e Mg em solos e sua relação com o crescimento inicial, fisiologia e produtividade do eucalipto

Forestry has grown in a continuous and accelerated manner in Brazil, constituting a strategic activity for the generation of employment, income and tributes, favoring social and economic development of Brazilian agribusiness. The objectives of this study were: (1) evaluate the contents of K, Ca and Mg in the reserve compartments, non-interchangeable, interchangeable, available and the speed of its release, its correlations and its effects over productivity (annual average increment – AAI) of eucalyptus plantations, in forest sites cultivated in soils of the state of Rio Grande do Sul; (2) evaluate the initial growth, nutrition and physiological aspects of eucalyptus plants, cultivated with and without the addition of mineral sources of potassium (K), calcium (Ca) and magnesium (MG), in soils obtained from forest sites in the state of Rio Grande do Sul. In the first study, contents of K, Ca and Mg were evaluated in sulfuric digestion extract, boiling nitric acid, ammonium chloride, Mehlich-1 (only K), potassium chloride (Ca and Mg), as well as the release speed of these nutrients in the soil. In the second study, growth variables, nutritional aspects, photosynthetic rate (A) and transpiration rate of the plants (E) grown in distinct soils were evaluated under controlled conditions. The contents of K, Ca and Mg varied between compartments and depths in the studied soil classes, with the highest proportions found in the reserve compartment, indicating the importance of this compartment for the supplement of these nutrients at average and long terms. The great majority of K, Ca and Mg compartments presented significant correlations between each other, showing the dependence between them and the importance of evaluating the contents of these nutrients in the different compartments to adapt the nutritional management of the plants to each soil class, and to obtain continuous productions, minimizing the negative effects to the environment. Plants cultivated in soils that present larger reserves, availability and K, Ca and Mg release kinetics, presented similar height (H), stem diameter (SD) and shoot dry mass (SDM), with or without fertilization with K, Ca and Mg. The plants presented higher leaf content and accumulation of K in all soils fertilized with K, Ca and Mg.