Marcha de absorção de macronutrientes na cultura do girassol.

RESUMO: Este trabalho teve como objetivo estabelecer curvas de acúmulo de macronutrientes na cultura do girassol. Para isso, foi instalado um experimento em campo sobre Latossolo Vermelho distroférrico de textura muito argilosa, localizado na fazenda experimental da Embrapa Soja, em Londrina/PR. As parcelas foram constituídas de 14 linhas com 25 m de comprimento cada e espaçamento entrelinhas de 0,70 m, resultando em área total de 245 m2. Cada parcela foi repetida quatro vezes. A adubação de semeadura foi de 300 kg ha-1 da fórmula 5?20?20, aplicada a lanço, antes do plantio. A adubação de cobertura foi parcelada em duas aplicações: 25 e 1 kg ha-1 de N e B, respectivamente, sendo a primeira aos 21 e a segunda aos 35 dias após a semeadura. O híbrido utilizado foi o BRS-191, e a densidade final de plantas foi de 40.000 plantas ha-1. Amostras de plantas foram coletadas em intervalos de 14 dias após a emergência e separadas em pecíolos, folhas, caules e, quando existentes, em capítulo e em aquênios. Após secagem, cada parte da planta foi pesada e moída para, em seguida, determinarem-se os teores de N, P, K, Ca, Mg e S. A partir desses nutrientes e da matéria seca de cada parte da planta, foram obtidas as curvas de acúmulo. Verificou-se que, para obtenção de produtividades superiores a 3.000 kg ha-1, o híbrido BRS 191 extrai aproximadamente 150, 24, 286, 116, 42 e 24 kg ha-1 de N, P, K, Ca, Mg e S, respectivamente, resultando na seguinte ordem de extração: K > N > Ca > Mg > P =S. Em relação à exportação, a ordem dos nutrientes foi a seguinte: N > P = K > Mg=S > Ca. Portanto, atenção especial deve ser dada à manutenção da adequada disponibilidade de N, K e Ca, devido à alta demanda da cultura por esses nutrientes. ABSTRACT: This study aimed to establish curves of macronutrient accumulation in sunflower. The experiment was conducted in the field on a Typic Hapludox, at the experimental station of Embrapa Soja in Londrina, State of Paraná. The plots consisted of 14 25 m long rows spaced 0.70 m apart, resulting in a total area of 245 m2, with four replications. Prior to sowing a fertilization seeding of 300 kg ha-1 of 05?20?20 NPK fertilizer was applied. Fertilization was split in two applications of 25 + 1 kg ha-1 N and B, which were applied 21 and 35 days after sowing, respectively. The hybrid BRS 191 and a final plant density of 40,000 plants ha were used. Plant samples were collected every two weeks after emergence and separated in the different parts (petioles, leaves, stems and, when applicable, capitula and achenes). After drying, each plant part was weighed and ground to determine the N, P, K, Ca, Mg, and S content. From the contents of these nutrients and dry mass of each plant, the accumulation curve was obtained. It was found that for yields > 3,000 kg ha-1, BRS 191 extracted about 150, 24, 286, 116, 42, and 24 kg ha-1 of N, P, K, Ca, Mg, and S, respectively, in the following order of extraction: K> N> Ca> P = S. In addition to the relation to exportation, the nutrientorder was: N> P = K> S = Mg> Ca. Therefore, special attention should be paid to the maintenance of an adequate supply of N, K and Ca, due to the high demand of sunflower

Curva de crescimento, estado nutricional, teor de óleo e produtividade do girassol híbrido BRS 191 cultivado no Estado do Paraná.

No Estado do Paraná, o interesse pelo cultivo do girassol está crescendo consideravelmente, principalmente em virtude do aumento da demanda interna de óleos vegetais comestíveis e também da sua ampla aptidão de cultivo. Entretanto, existem poucas informações sobre o acúmulo de massa seca nas diversas fases da planta do girassol. Dessa forma, objetivou-se estabelecer a curva de acúmulo de massa seca dos diversos órgãos da planta, a altura de plantas, o número de folhas, a área foliar e o teor de óleo na planta em um híbrido nas condições atuais do Brasil. O experimento foi realizado em Latossolo Vermelho Eutroférrico, em Londrina, PR. O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições. As unidades experimentais foram constituídas de 14 linhas, com espaçamento de 0,70 m entre linhas e com 25 m de comprimento, com densidade final de 42.858 plantas ha-1. As amostras das plantas foram coletadas em intervalos de 14 dias após a emergência e divididas em pecíolo, folha, caule, capítulo e aquênios, a fim de determinar a massa seca. Além disso, foram feitas a contagem do número de folhas e a da altura de plantas. A matéria seca da parte aérea (MSPA) e de aquênios estimada foi de 10.400 kg ha-1 e 3.758 kg ha-1, respectivamente, apresentando ponto máximo de 2,12 m de altura, 35 folhas, 0,80 m2 de área foliar e teor de óleo de 49,53%

Effect of glyphosate on nutrient contents in glyphosate-resistant soybeans.

Although GR soybean technology is spread all over the countries involved in soybean production, there is no particular fertilizing recommendation under glyphosate use and not much has been reported in the influence of glyphosate on GR soybean status. The objective of this work was to evaluate the mineral status of GR soybeans and their non-GR parental lines under glyphosate use. Considering different soil types and cultivar maturity groups, a significative decrease in macro and micronutrients leaf contents and in photosynthetic parameters (chlorophyll, photosynthetic rate, transpiration and stomatal conductance) was observed under glyphosate use (single or sequential application), both when compared to their respective non GR parental lines and GR soybeans not submitted to glyphosate use. Shoot and root dry biomass productions were affected by glyphosate presence for all cultivars evaluated in both soils, probably because of a sum of effects: decrease of photosynthetic parameters, nutrient uptake and content into the plants

Effect of increasing doses of glyphosate on water use efficiency and photosynthesis in glyphosate-resistant soybeans.

The increase cultivated area of GR soybeans across different regions of the world have raised questions not yet answered as related secondary effects of glyphosate on physiology of GR soybeans. In this work, we attempted to measure the effect of increasing glyphosate doses on water absorption and photosynthetic parameters of soybean, cv. BRS 242 GR. Plants were grown in completed nutrient solution (Hoagland & Arnon, 1950) in a greenhouse equipped with an evaporative cooling system (25?35 : 20?22C day/night) under natural daylight. The commercially formulated isopropylamine salts of glyphosate was sprayed on foliar doses of 450, 675, 900, 1350 and 1800 g. e.a ha-1 either in single application at four leaf stage (24 DAE) and in sequential application (24 and 36 DAE) (50%-50%) at four and five leaf stages, respectively. Using an infrared gas analyzer (IRGA), fluorometer (pulse-modulated) and chlorophylometer, before and after herbicide application net photosynthesis (A), transpiration rate (E), stomatal conductance (gs), sub-stomatal CO2 (Ci), carboxilation efficiency (A/Ci), fluorescence (Fs), maximal fluorescence (Fms); yield of quantum efficiency (Y=Fm-Fs/Fms) and chlorophyll contents were monitored. In addition, water absorption was measured daily and biomass yield and water use efficiency (WUE) were estimated by harvesting plants at R1 stage. All measures of photosynthetic parameters (A, E, gs, Ci) and Fs, Fms and Y were affected by increasing glyphosate doses. Chlorophyll contents were reduced right after glyphosate use, however with decreased in chlorophyll content and carboxilation efficiency, (A/Ci) the values suggest that glyphosate might have interfering, in some way, in the synthesis of chlorophyll and/or in carboxilative metabolism of photosynthesis (Calvin cycle), which contributed to dry biomass reductions. Total amount of water absorbed and biomass production by plants were also decreased as glyphosate doses increased, with a more intense effect of single application, as compared to sequential. WUE was also significantly reduced with increasing glyphosate doses. Under single and sequential application, soybean plants need 13 to 20% and 8 to 14% more water to produce the same amount of biomass, respectively

Effect of glyphosate on nodule formation and its interrelation with nickel content in glyphosate-resistant soybeans.

Recent research has demonstrated that glyphosate can decrease biological nitrogen fixation in glyphosate-resistant (GR) soybeans, however this reduction has been attributed directly to the effect of glyphosate on the microorganisms or indirectly through its intermediates that are also toxic to these microorganisms. This work aims to demonstrate that glyphosate can influence the symbiotic N2 fixation by lowering nickel content available to the microorganisms. The experiment was conducted in the greenhouse at the State University of Maringá, PR, Brazil during the summer cropping season, 2008. The experimental design was a completely randomized blocks in a factorial scheme 4 x 3 x 2 where the first factor was: (T1 - single application of glyphosate (900 g a.e. ha-1) at the four-leaf stage; T2 - sequential application (450 + 450 g a.e. ha-1) at the four-leaf and five-leaf stage; T3 - without glyphosate; T4 - non-GR parental line]; the second factor, maturity group (early, medium and late;) and third factor soil type. Under glyphosate use, GR soybeans showed reduced photosynthetic parameters, nickel contents, and nodule, shoot and root dry biomass

Paraquat resistance of sumatran fleabane (Conyza sumatrensis).

Título em português: Buva (Conyza sumatrensis) resistente a Paraquat