ABSTRACT: Determining nutrient uptake and accumulation rates by cotton crops is important to define management strategies, especially for transgenic varieties, which are cultivated using high-technology approaches that require substantial investment to maximize yield. Currently in Brazil, the states of Bahia and Mato Grosso are responsible for 84.4 % of the total cotton growing area. In the present study, two trials were conducted in 2013, one that involved planting FM 940 GLT, FM 980 GLT, and FM 913 GLT varieties in the state of Bahia and the other which involved FM 940 GLT and FM 980 GLT varieties in the state of Mato Grosso. The aim of the two trials was to represent the two regions that currently encompass the largest areas of cotton cultivation. Tissue samples, consisting of leaves, stems, and reproductive components, were collected eleven times during the crop cycle for determination of nutrient content and shoot dry matter. After weighing, plant tissue samples were dried and ground to determine nutrient contents. Because there were no overall differences in nutrient contents and biomass accumulation of the varieties during the crop cycle, we undertook joint analysis of the data from all varieties at each site. Favorable climatic conditions in Bahia promoted plant biomass production that was twice as much as plants grown in Mato Grosso, with cotton yields of 6.2 and 3.8 t ha−1 of lint and seed, respectively. The maximum nutrient accumulation occurred between 137-150 days after emergence (DAE) for N; 143-148 for P; 172-185 for K; 100 for Ca; 144-149 for Mg; and 153-158 for S. Maximum uptake ranged from 218-362 kg ha−1 N; 26-53 kg ha−1 P; 233-506 kg ha−1 K; 91-202 kg ha−1 Ca; 28-44 kg ha−1 Mg; and 19-61 kg ha−1 S. On average, the sites revealed nutrient export of 14, 2, 23, 3, 2, and 2 kg t−1 of lint and seed for N, P, K, Ca, Mg, and S, respectively, with little variation among sites. Extraction of nutrients per area by cotton vary among sites, but nutritional requirement of cotton per unit of lint and seeds is similar independently of yield potential.

Uma das maneiras de aumentar a eficiência dos fertilizantes nitrogenados, visando, por exemplo, à redução de perdas de amônia por volatilização, é o revestimento desses com polímeros. Objetivou-se avaliar o efeito da aplicação de ureia revestida com polímeros no controle da volatilização de amônia e a sua influência nos componentes da produção na cultura do milho. O experimento foi instalado na safra 2009/10 no município de Uberlândia, MG, em um Latossolo Vermelho-Amarelo (LVA) distrófico textura argilosa. Os tratamentos consistiram na aplicação, em cobertura no milho, de ureia revestida com polímeros e ureia convencional nas doses de 45; 67,5; e 90 kg ha-1 de N, mais um tratamento-controle (sem N), dispostos em blocos casualizados. A aplicação de N influenciou positivamente o teor do nutriente nas folhas e nos grãos, a leitura SPAD e a produtividade de grãos, porém a ureia revestida não alterou as taxas de volatilização de amônia, a leitura SPAD e o teor de N nas folhas e grãos, assim como a produtividade de grãos em relação à aplicação do fertilizante convencional.

A form of increasing the efficiency of N fertilizer is by coating urea with polymers to reduce ammonia volatilization. The aim of this study was to evaluate the effect of polymer-coated urea on the control of ammonia volatilization, yield and nutritional characteristics of maize. The experiment was carried out during one maize growing cycle in 2009/10 on a Geric Ferralsol, inUberlândia, MG, Brazil. Nitrogen fertilizers were applied as topdressing on the soil surface in the following urea treatments: polymer-coated urea at rates of 45, 67.5 and 90 kg ha-1 N and one control treatment (no N), in randomized blocks with four replications. Nitrogen application had a favorable effect on N concentrations in leaves and grains, Soil Plant Analysis Development (SPAD) chlorophyll meter readings and on grain yield, where as coated urea had no effect on the volatilization rates, SPAD readings and N leaf and grain concentration, nor on grain yield in comparison to conventional fertilization.

O aquecimento de rochas e solos em indústrias de fundição, siderúrgicas, fertilizantes, vidro e cerâmica liberam compostos contendo flúor (F) na atmosfera. Em área cultivada com duas variedades de cana-de-açúcar no município de Cordeirópolis (SP), adjacente à indústria produtora de cerâmica, foram diagnosticadas queda na produtividade e sintomas de toxidez comparados ao canavial distante da fonte emissora de F. Para a variedade SP80 1816, os teores de F variaram de 56 a 3 mg kg-1 em amostras de folhas coletadas pela técnica da diagnose foliar, ao lado e a 13.000 m da cerâmica, respectivamente. Para a variedade RB83 5089 o teor de F nas folhas foi de 26 mg kg-1 a 80 m da cerâmica. Esses teores estão acima dos considerados normais, de 10 mg kg-1 (ou menor) em áreas sem influência de emissão de F. A produtividade média foi de 54 Mg ha-1 na cana planta (1.º corte) nas duas variedades e na soqueira (2.º corte) de 50 Mg ha-1 para SP80 1816 (mais sensível ao F) e 60 Mg ha-1 para a RB83 5089 (menos sensível ao F). Na área distante 13.000 m da fonte emissora de F não se observou sintomas de toxidez e a produtividade atingiu 82 Mg ha-1 na cana-planta e 100 Mg ha-1 na soqueira para a variedade SP80 1816. O F emitido por indústria de cerâmica sem uso adequado de filtro parece limitar a produtividade da cana-de-açúcar, fato revelado pela diagnose visual, foliar e queda na produção de colmos. Constatou-se, também, na cana-de-açúcar sensibilidade aos efeitos causados pelo excesso de F.

Heating minerals, roctks, clays and soils in aluminum and iron smelters, and in ceramic, glass, and fertilizer industries release gaseous forms of fluorine into the atmosphere. In an area grown with two varieties of sugar cane (Saccharum officinarum L.) in Cordeirópolis, SP (Brazil) toxicity symptoms and abnormally low yields were observed in areas nearby as compared with those far from a ceramic industry. For the SP80 1816 sugarcane variety the leaf contents of F varied from 56 mg kg-1 of F in the dry matter of leaves collected according to recommended diagnostic techniques near the ceramic industry to 3 mg kg-1 F in samples obtained 13.000 m away. Fluorine content in the RB83 5089 variety was 26 mg kg-1 in samples collected about 80 m from the ceramic industry. These values are higher than the 10 mg kg-1 F (or less) that is considered normal for plants grown in areas not affected by atmospheric F emissions. Average sugar cane yields of the first cut of the plant cycle were 54 Mg ha-1 for both varieties in the area close to the ceramic industry. Average yields of the second cut (first ratoon) were 50 Mg ha-1 for the SP 80 1816 variety (more sensitive to F) and 60 Mg ha-1 for the RB 83 5089 variety (less sensitive to F). In the area about 13.000 m from the industry, where no foliar symptoms of toxicity were observed, yields reached 82 Mg ha-1 in the first cut and 100 Mg ha-1 in the ratoon. Fluorine released by the ceramic industry without adequate gas emission filters seems to limit sugar cane yields as shown by visual symptoms, F concentration in leaves, and yield reduction in the vicinity of the source of F. The sugar cane varieties evaluated showed to be sensitive to the effects of excess F accumulation.