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.

Processo infeccioso de Pseudocercospora musae e severidade da Sigatoka Amarela da bananeira em função do silício, potássio e cálcio em solução nutritiva

Yellow Sigatoka leaf spot, caused by Pseudocercospora musae (Mycosphaerella musicola), is one of main threats to banana production around the world. However, information regarding the infection process of P. musae and the influence of mineral nutrition on the disease severity could help with cultural control strategies and increase the fruit yield. Therefore, this work aimed to characterize the infectious process of P. musae in banana leaves, to study the effect of silicon (Si) and the interaction between potassium (K) and calcium (Ca) on the Yellow Sigatoka leaf spot severity. In the first study, samples were inoculated on the abaxial leaf surface with P. musae and analyzed at 12, 24, 36, 48, 72, 96, 120, 144, and 168 hours after inoculation (HAI) as well as 36 and 50 days after inoculation (DAI). The conidia germinated between 24 and 36 HAI and penetrated through the stomata between 96 and 120 HAI, or usually from 144 HAI. P. musae colonized intercellularly the spongy parenchyma at 36 DAI and inter- and intracellularly the palisade parenchyma at 50 DAI. The sporulation occurred at 50 DAI on the adaxial leaf surfaces. In the second study, banana plants grown in nutrient solution with 0; 0.5; 1.0; 1.8 and 3.6 mmol L -1 of silicic acid (H 4SiO 4) were inoculated with conidial suspension. The disease severity was assessed and data were integrated in the area under the disease severity progress curve (AUDSPC). The lower AUDSPC was 49.27% for the concentration of 3.05 mmol L -1 of H 4SiO 4 compared to plants grown without Si addition. Regarding silicon accumulation, at 3.6 mmol L -1 H4SiO 4, leaf Si content was 23.53% higher compared to the control. In the third study, plants grown in nutrient solution with 5 K concentrations (1, 2, 4, 6, and, 8 mmol L -1 ) combined with 5 Ca concentrations (1, 3, 5, 7, and, 9 mmol L -1 ), forming 25 treatments, were inoculated with conidial suspension. The disease severity was assessed and the data were integrated in the AUDSPC. There was no interaction between concentrations of K and Ca for AUDSPC, although the AUDSPC increased with the increase of K concentrations from 1 to 6 mmol L -1 . The K increase led to a reduction in chlorophyll a and b contents and in the N, P, Mg, B, Cu, Zn, and, Mn nutrients as well as increased the total plant dry weight.

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.

Estabilidade da fitase e sua utilização na alimentação de frangos de corte

This work was designed to evaluate the effect of storage forms and conditions upon the enzyme activity of phytase and bioavaibility of calcium and phosphorus in broiler diets. The work was accomplished in two steps. The first step, made in the laboratory measured the activity of the phytase enzyme along the storage period. In this step, two experiments were performed: Experiment 1, constituted of 5 treatments (pure phytase stored at 0 °C, 4 °C and environmental temperature and mixed to vitamin and mineral supplement, stored at environmental temperature) in CRD and split plot scheme. The activities were evaluated every 14 days for 112 days of storage, being verified that the phytase storage in the pure form at 0o C was superior to the other treatments. Experiment 2, made up of 4 treatments (phytase mixed to the ration directly, directly and afterwards pelleted, via mineral supplement and via vitamin supplement),all the treatments being stored at environmental temperature, in CRD and split plot scheme. The activities were evaluated every 7 days for 56 days' storage, being verified that the storage of the phytase mixed to the ration via vitamin supplement and directly with the ration pelleted later, provoked a fall in phytase activity when compared with the other treatments. In the second step, the effect of phytase on the bioavaibility of calcium and phytic phosphorus was evaluated, 2 experiments being accomplished (3 and 4); in both experiments were utilized 576 broiler line chicks, housed in an array of heated batteries, receiving practical diets on the basis of corn and soybean meal (basal) for 21days. At the end of 27 days of age,96 birds were slaughtered for evaluation of the mineral contents (Ca and P) in the tíbias and plasma phosphorus. The excretae were collected from 22 to 27 days of age of the birds. Experiment 3: A CRD with the treatments in 2 x 3 x 2 +4 factorial arrangement was utilized, namely, two levels of total phosphorus (0.35 and 0.45% of total phosphorus), three leveis of phytase (500, 750 and 1,000 FTU) and four additional treatments with levels of 0.35 and 0.45 % of available phosphorus for each sex, with three replicates per treatment. There was significant interaction among levels of phosphorus and phytase (P< 0.05) for weight gain, ration consumption and feed conversion. Phytase did not indicate significant differences when the level 0.45% was utilized, nevertheless, at the level 0.35% as phytase was supplemented, weight gain, ration consumption and feed conversion were improved, chiefly with 1,000 FTU/Kg, in both sexes. The males presented greater weight gain. The ration consumption and feed conversion were equal to those of females. The contrast 0.45% did not affect the performance of males and females, the same not occurring with the level 0.35%,at which the available phosphorus was superior in both the sexes. The highest contents of ashes, phosphorus and calcium in the tíbias and plasma phosphorus were obtained with the levels of 750 and 1,000 FTU/Kg of phytase and 0.45% of total phosphorus. The males presented higher contents of ashes in the tibias. The level 0.45% of available phosphorus presented the greatest contents of ashes, calcium and phosphorus in the tibias, and phosphorus in the plasma. The lowest excretions of phosphorus occurred at the levels 0.35% of total phosphorus and 1,000FTU/kg of phytase. The lowest contents of ashes and calcium in the excretae were obtained with 0.35% and 1,000FTU/Kg of phytase. The females excreted smallest amounts of ashes, calcium and phosphorus than the males. Experiment 4: a CRD with the treatments in 3 x 4 x 2 factorial arrangement, namely, three levels of phytase (0, 500 and 1,000 FTU), four levels of calcium (0.7, 0.8, 0.9 and 1.0%) with four replicates per treatment. The performance was not affected by the treatments utilized, the males being superior to the females in weight gain, feed consumption and conversion. The contents of ashes in the tibias were not affected by the levels of phytase but as calcium levels raised, the ash contents increased. The contents of calcium and phosphorus in the tibias increased with the supplementation of 500 and 1,000 FTU/kg of phytase and with calcium levels. The utilization of phytase did not decrease the excretion of ashes, calcium and phosphorus.

Caracterização mineralógica, química e solubilização do potássio de glauconita modificada

Demand for potassium in Brazil is large and is constantly increasing, but only about 5% of all consumed potassium is produced in the country. This low domestic production implies high rate of potassium imports, leaving the country vulnerable in the event of any difficulty to import this product and currency fluctuations. The modified glauconite is a rock that has a high potential for potassium exploration, found in Minas Gerais state, its extraction is relatively cheap and the prospected rock volume is high. The difficulty for its use as a direct source of potassium is in its low solubility. Thus, the objective of this study was to perform a chemical and mineralogical characterization of the modified glauconite and evaluate the effectiveness of techniques and treatments in the potassium solubilization contained in the rock. For this study, it was used characterization techniques such as X-ray diffraction, scanning electron microscopy, diffraction by Synchrotron Light and chemical analysis of high and low power of potassium extraction. Also granulometric testing and thermal treatments with different forms of calcination were carried out. Overall, it was found that the modified glauconite is a compound of minerals, of the mica groups K-feldspar and quartz and calcination substantially alter the crystal structure of these minerals, increasing the potassium availability. While the natural solubility of glauconite modified be very low, rock calcination added with high fluxes of calcium and low magnesium content at 1200 °C led to potassium solubility increase in order of 100 times compared to that observed in the glauconite natural modified.

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.