Days After Emergence Research Articles

Drought tolerance mechanisms for yield responses to pre-flowering drought stress of peanut genotypes with different drought tolerant levels

A better understanding of the mechanisms of peanut adaptation to pre-flowering drought is important for improving pod yield productivity. Nevertheless, the mechanisms of drought tolerance are under different genetic controls, and pod yield is a complex trait. Therefore, the aim of this study was to investigate the mechanism for drought tolerance of peanut genotypes with different pod yield responses under pre-flowering drought conditions. Field experiments were conducted during February to July, 2007 and during February to July, 2009. A split-plot experiment in a randomized complete block design was used. Two water management treatments were assigned as the main plots, i.e. field capacity (F.C.) and pre-flowering stress (PFD), and six peanut genotypes as the sub-plots. Relative water content (RWC) and stomatal conductance were recorded at 5, 10, 15, 20, 25, 30, 35 and 40 days after emergence (DAE). Leaf area index was measured at 25 DAE, R5 and R7. Total dry matter samples, including shoots, roots and pods, were obtained at 25 DAE, R5, R7 and harvest. Shoot growth rate, root growth rate and pod growth rate were then calculated. Major finding, the first mechanism is explained by high water uptake of the root systems that provide sufficient water for normal transpiration, as the response of ICGV 98305 to PFD. It may induce the improvement of peanut pod growth rate in pod filling stage due to the change of assimilate proportion, resulting in increasing pod yield to PDF comparing with adequate water conditions. In contrast, such as the response of ICGV 98330, pre-flowering drought can increase the ability of peanut to save more water by reduction of transpiration, but rooting traits are not changed. This could conserve more water by reducing transpiration to maintain high RWC. Nevertheless, the ability to reduce transpiration did not support the improvement of peanut pod yield under these conditions. The increasing peanut productivity to pre-flowering drought was contributed by the improvement of assimilate proportion to economic part in reproductive phase. This knowledge will be useful for breeding of peanut for pre-flowering drought environment.

Performance of rice seeds treated with zinc, boron, and molybdenum

The objective of this study was to assess physiological quality of seeds and the initial growth of lowland rice seedlings, cv. PUITA INTA-CL, treated with a product based on Zinc, Boron and Molybdenum. The following dosages of product were used: 0 (control), 50, 100, 150 and 200 mL.100 kg-1 seed. A completely randomized experimental design was used, with 10 treatments and four replications. Physiological quality of seeds was assessed by following tests: germination; first count of germination; and length and dry phytomass of seedlings. The initial growth was assessed at 7, 14, 21, 35, and 42 days after emergence (DAE) through plant height, leaf area and dry phytomass of aerial parts and roots. It was concluded that the treatment of rice seeds with the product containing Zinc, Boron and Molybdenum up to the dosage tested of 200 mL.100 kg-1 seed does not influence germination, first count of germination, and the dry phytomass of aerial parts and roots; however, negatively influences seedling length. In addition, it also promotes greater plant height, higher leaf area, higher production of dry phytomass of seedlings, and increase on the growth rate, until 42 DAE.

Physiological performance of wheat seeds coated with micronutrients

The objective of this study was to evaluate the physiological performance of wheat seeds coated with micronutrients. The treatments were combinations of two products based on micronutrients, product "A": 780.0 g.L-1 of zinc and product "B": 182.4, 7.6 and 45.6 g.L-1 of zinc, boron and molybdenum, respectively, with five dosages of the products: 0, 1, 2, 3 and 4 mL. kg-1 seed, totaling 10 treatments with four replications. Physiological quality of the treated seed was evaluated from germination and vigor tests and the early plant growth from determinations of shoot dry weight, plant height and leaf area at 10, 20 and 30 days after emergence (DAE), as well as the rate of crop growth, relative and net assimilation. Seed yield and physiological quality were determined after harvest. It was concluded that coating wheat seeds with the product "A" , based on zinc and "B", consisting of zinc, boron and molybdenum, respectively, up to a dosage of 4 mL.kg-1 seed, did not adversely affect the physiological quality of the treated seeds or those produced. Both products tested resulted in increases in leaf area, plant height and shoot dry weight up to 30 DAE, as well as a higher seed yield.

Nutrients extraction and exportation by Savana castor bean hybrid: I – Macronutrients

Low height castor bean hybrids and highly productive possibly need larger quantity of macronutients during its development cycle. However, in Brazil there is little information on extraction and exportation of macronutrients by low height castor bean hybrids, as on season as out-of-season growing. This study aimed to evaluate the nutrients extraction and exportation by Savana hybrid castor bean on season and out-of-season growing. The experiments were conducted during the season of 2005/2006 and out-ofseason of 2006 in an Oxisol. The experimental design was a randomized block with four replications. The plots were consisted by harvest times of plants, which were composed by six plant rows to 5 m, spaced 0.45 m between rows. Samples were collected at 17, 31, 45, 59, 73, 97 and 120 days after emergence (DAE) during the season and at 17, 31, 45, 59, 80; 100 and 120 DAE in the out-of-season. The nutrients accumulation by Savana hybrid was small until the flowering (30 DAE), but intensified after this period. The period of greatest nutrient absorption occurred at 65 and 90 DAE for N, 70 and 80 DAE for P, 60 DAE for K and Mg, 55 and 60 DAE for Ca and S. The amounts absorbed per hectare by hybrid Savana ranged 155 to 31 kg of N, 17 to 3 kg of P, 71 to 13 kg of K, 56 to 12 kg of Ca, 28 to 4 kg of Mg and 29,5 to 7 kg of S in season and out-of-season, respectively. The yield was higher in growing season, but the nutrients extraction and exportation per ton of grain were similar among the seasons. Among 40% and 50% of N and S and most part of Mg, K and Ca accumulated in the plants returned to soil with crop residues, but less than 35% of P remained in the residues.

Extração e exportação de nutrientes pelo híbrido de mamona Savana: II – Micronutrientes

Information about micronutrients extraction and exportation by castor bean hybrids of short stature, and the periods of highest demand for each micronutrient, are most importance for correct management to fertilization. This study aimed to evaluate the micronutrients extraction and exportation by Savana hybrid castor bean, on season and out-of-season growing. The experiments were conducted during season of 2005/2006 and out-of-season of 2006 in an Oxisol. The experimental design was a randomized block with four replications. The plots were consisted by harvest times of plants, which were carried out at 17, 31, 45, 59, 73, 97 and 120 days after emergence (DAE) during the season and at 17, 31, 45, 59, 80; 100 and 120 DAE in the out-of-season. In both seasons the order of micronutrients extraction by hybrid Savanna is: Fe> Mn> Zn> B> Cu> Mo, but with larger amounts of season cultivation. The time of greatest Zn and Mo absorption during the season and the Fe in out-ofseason occurs at 80 DAE, although the other micronutrients are absorbed at higher rates between 50 and 65 DAE. In season the yield, nutrients extraction and exportation to soil are higher than out-of-season, but the nutrients extraction and exportation per ton show less variation between growing seasons. On average 50% of zinc uptake over the cycle and 60% of Cu absorbed in out-of-season is exported with grains, but for the other micronutrients the proportion exported with grains is less than 40%.

Índices fisiológicos de soja hortaliça em duas épocas de semeadura no Recôncavo Sul Baiano

The objective of the present work was to evaluate the performance of four vegetable soybean genotypes and one vegetable soybean cultivar in two sowing periods (April / 2009 and August / 2009) under South Reconcavo Baiano Region environmental conditions. The experiments were installed in the field at the Federal University in the county of Cruz das Almas – BA. The experimental design was in random blocks, with five treatments (genotypes: JLM 17, JLM 18, JLM 19, BR 94 and the BRS 155 cultivar) and five replicates. The experimental plots were made up by eight rows of 5.0 m in length: spacing of 50 cm between rows and 12 seeds per meter, with three side borders, three for yield data and two for growth analysis. Samplings of five plants per plot taken at random were carried out every fifteen days from 21 days after emergence (DAE) until physiological plant maturity in order to quantify dry matter mass (g plant -1 ) and plant leaf area (dm²). These characteristics were used to determine the following physiological indices: crop growth rate (CGR), relative growth rate (RGR), net assimilatory rate (NAR) and leaf area ratio (LAR). NAR and LAR were the most efficient physiological indices to indicate the performance and growth of the materials evaluated. However, vegetative and yield performance of the plant should be measured by the combined response of the physiological indices since they are interconnected, leading to compensation effects between them.

Índices fisiológicos de soja hortaliça em duas épocas de semeadura no Recôncavo Sul Baiano

The objective of the present work was to evaluate the performance of four vegetable soybean genotypes and one vegetable soybean cultivar in two sowing periods (April / 2009 and August / 2009) under South Reconcavo Baiano Region environmental conditions. The experiments were installed in the field at the Federal University in the county of Cruz das Almas – BA. The experimental design was in random blocks, with five treatments (genotypes: JLM 17, JLM 18, JLM 19, BR 94 and the BRS 155 cultivar) and five replicates. The experimental plots were made up by eight rows of 5.0 m in length: spacing of 50 cm between rows and 12 seeds per meter, with three side borders, three for yield data and two for growth analysis. Samplings of five plants per plot taken at random were carried out every fifteen days from 21 days after emergence (DAE) until physiological plant maturity in order to quantify dry matter mass (g plant -1 ) and plant leaf area (dm²). These characteristics were used to determine the following physiological indices: crop growth rate (CGR), relative growth rate (RGR), net assimilatory rate (NAR) and leaf area ratio (LAR). NAR and LAR were the most efficient physiological indices to indicate the performance and growth of the materials evaluated. However, vegetative and yield performance of the plant should be measured by the combined response of the physiological indices since they are interconnected, leading to compensation effects between them.

Influence of Time of Emergence on the Growth and Development of Wild Oat (Avena fatua)

Successful control of wild oat in cereal crops requires an accurate prediction of the developmental stages of wild oat plants that emerged during the growing season. The main objective of this research was to evaluate wild oat growth and to predict the phyllochron of wild oat plants that emerge at various times in the Red River Valley region of Minnesota and North Dakota. Field experiments were conducted in 2002 and 2003 in Crookston, MN, and Fargo, ND. Four emergence cohorts were established in 4 successive wk. Research plots were arranged in randomized complete blocks with six replications. From the naturally emerged wild oat population, 10 randomly selected plants per plot were evaluated for plant height, leaves on main stem, tillers per plant, total leaves per plant, days to flag leaf emergence and to heading, biomass per plant, and seeds per plant. Haun's numerical cereal development scale was regressed on days after emergence (DAE), day length (DL), growing degree days (GDD), or photothermal units (PTU). Wild oats that emerged first required more time for flag leaf emergence and heading, were taller, and had more biomass, leaves, tillers, and seed production than wild oat plants that emerged later. Wild oat phyllochron intervals were 5.3 d, 94 GDD, or 1,468 PTU, regardless of emergence timing. These data suggest that wild oat phyllochron is primarily driven by air temperature and is relatively stable during the extended emergence period. Later-emerging wild oat plants, although not as competitive as earlier emerging ones, still have the potential to contribute to the seed bank if left uncontrolled.

Herbicidas inibidores da ALS aplicados em pós-emergência no arroz de terras altas

Este trabalho teve por objetivo avaliar a seletividade de herbicidas inibidores da ALS recomendados para arroz irrigado, quando aplicados em diferentes estádios de desenvolvimento do arroz de terras altas. O experimento foi conduzido em campo, no município de Nova Xavantina-MT, no período de novembro de 2009 a abril de 2010. O delineamento experimental foi o de blocos ao acaso, em esquema fatorial 5 x 3, composto pelos tratamentos herbicidas penoxsulam (36 g ha-1), bispyribac-Na (50 g ha-1), pirazosulfuron-ethyl (20 g ha-1) e 2,4-D (670 g ha-1) e pela testemunha capinada. Os herbicidas foram aplicados em três épocas: 15, 30 e 45 dias após a emergência (DAE), perfazendo 15 tratamentos, com quatro repetições. Aos 7, 14 e 28 dias após a aplicação (DAA) dos herbicidas foram realizadas as seguintes avaliações: fitotoxicidade à cultura, altura de plantas, fitomassa, quantidade de panículas por metro quadrado, grãos por panícula e produtividade. Os maiores índices de fitotoxicidade foram observados nas plantas tratadas com bispyribac-Na, aplicado aos 15 e 30 DAE. As plantas de arroz conseguiram se recuperar quanto à altura de plantas provocada pelos herbicidas a partir de 28 DAA. No que se refere aos herbicidas inibidores da ALS, o penoxsulam, aplicado aos 30 DAE, apresentou potencialidade para ser utilizado no arroz de terras altas, por não reduzir a produtividade de grãos.

Produção de mudas de baru (Dipteryx alata Vog.) sob três níveis de sombreamento e quatro classes texturais de solo

Foi avaliado o desenvolvimento de mudas de baru (Dipteryx alata Vog.) em vasos, sob três níveis de sombreamento e quatro classes texturais do solo, no período de março a outubro de 2010, em Campo Grande-MS. Os tratamentos consistiram em 0%, 30% e 50% de sombreamento e solos de textura arenosa, média, argilosa e muito argilosa. O delineamento experimental foi em blocos ao acaso, em parcelas subdivididas, com medidas repetidas no tempo. Foram utilizadas três repetições e dez plantas por subparcela. Os níveis de sombreamento corresponderam aos tratamentos, e as diferentes classes texturais do solo, aos subtratamentos. As plantas foram avaliadas em intervalos de 15 dias após a emergência (DAE) até 195 DAE, sendo avaliadas quanto à altura (cm) de plantas, número de folhas e diâmetro do coleto (mm). Aos 195 DAE, também foram avaliadas a percentagem de sobrevivência, a área foliar e a massa seca de folha, caule e das raízes das plantas. Sob sombreamento, foram observados maiores valores de altura e área foliar. A altura de plantas foi de 32,09 cm e 31,21 cm planta-1 , e a área foliar foi de 639,24 cm² e 580,49 cm² planta-1 para os níveis de sombreamento de 50% e 30%, respectivamente. No solo de textura argilosa, os valores foram superiores na maioria das características avaliadas, seguido do solo com textura muito argilosa. A maior produção de massa seca de folha foi no solo com textura argilosa, com média de 7,28 g planta-1. A percentagem de sobrevivência das mudas no solo com textura arenosa foi inferior aos demais. Houve interação entre níveis de sombreamento e classes texturais do solo na massa seca de raízes, que foi maior (1,43 g kg-1 de solo) no solo de textura muito argilosa, no nível de 50% de sombreamento. As mudas de baru atingiram medidas de altura e diâmetro de coleto adequadas em todos os níveis de sombreamento e classes texturais do solo.

Seeds enriched with phosphorus and molybdenum as a strategy for improving grain yield of common bean crop

Sowing seeds with high concentrations of P or Mo can improve growth and nodulation of common bean (Phaseolus vulgaris) plants. However, the performance of the bean crop originating from seeds enriched with P and Mo has not yet been assessed under field conditions. This study aimed to evaluate the effect of sowing seeds enriched with P and Mo, harvested from plants that received foliar sprayings of P or Mo or both, on growth and yield of common bean crop. Seeds with contrasting concentrations of P and Mo were sown in three field experiments in Brazil (in 2006 and 2008 in Rio de Janeiro State, and in 2009 in Goiás State) with different N sources (control without N, seed with rhizobia inoculation, rhizobia inoculation plus 40kgNha−1 side-dressed, mineral N with 60kgNha−1). In 2006, seeds enriched with P and Mo increased nodule mass at 32 days after emergence (DAE), shoot N and biomass at 48 DAE, and grain yield and N content, for most combinations of the three cultivars and N sources evaluated. In 2008, the highest shoot growth at 57 DAE and grain yield were obtained with low-P high-Mo seeds, which was partially due to the higher Mo concentration of these seeds. In 2009, seeds enriched with P and Mo increased nodule mass at 34 DAE and grain yield but only for plants receiving inoculation plus side-dressed N. The results demonstrate the benefits of seeds with high concentrations of P and Mo for improving bean yield, although such yield increases were more effective for plants inoculated with rhizobia than amended with N. Sowing enriched seeds, associated with rhizobia inoculation and side-dressed N, provided grain yields much higher than the average common bean yields in Brazil.

Uso de nitrogênio e fósforo e seus efeitos na nutrição do algodoeiro irrigado

Water and nutrients management in cotton crop is very important to achieve high yields. Therefore, it is necessary to understand the fertilization effect on the nutritional status of cotton plants submitted to irrigated conditions. The objective of this study was to evaluate nitrogen and phosphorus fertilization on N, P, K, Ca, Mg and S leaf contents of in semiarid conditions. Treatments were arranged in a factorial scheme of four N doses (0, 90, 180 and 270 kg ha-1) and four P doses (0, 120, 240 and 360 kg ha-1) in a randomized block design with three replicates. P and 1/3 of N were applied at sowing and the remaining nitrogen at 38 days after emergence (DAE). At 80 DAE, the leaf contents of the macronutrients were determined. The application of 215 kg ha-1 of N provided sufficiency for N and K leaf contents to achieve high yield and nutrition. In the semiarid regions, supplying sulfur (S) to soil, or using fertilizers containing it, is necessary in order to meet the S needs for cotton crop.

Agronomic Traits of Corn Fertilized with Sewage Sludge

Although research on the environmental impacts of using waste as a fertilizer is of great importance, the basic principle for using a product as fertilizer is that it should provide nutrients for plants without causing any harm to them. The objective of this study was to evaluate the agronomic traits (number of nodes, plant height, leaf number, yield, and protein content of grains) and the nutritional status of corn treated with sewage sludge. The experiment was conducted in the municipality of Jaboticabal in a Red Latosol. A randomized block design with four treatments (0, 55, 110, and 167.5 Mg ha−1 of sewage sludge) and five repetitions was used. At 30 days after emergence (DAE), the dose of 110 Mg ha−1 dry weight presented greater values for plant height, leaf number and stem diameter. At 60 DAE, the treatments did not affect the agronomic traits. No influence from the treatments tested was observed for protein content of grains and yield. The dose of 167.5 Mg ha−1 showed greater weight of 100 seeds. All treatments showed nutritional imbalances. This study confirmed the agricultural potential of sewage sludge as a source of nutrients.

Performance of lowland rice seeds coated with dolomitic limestone and aluminum silicate

The objective of this study was to evaluate the performance of seeds of two cultivars of lowland rice (Oryza sativa L.), coated with dolomitic limestone and aluminum silicate. It was used a completely randomized experimental design, with the treatments arranged in a 4 X 2 factorial scheme [4 treatments: dolomitic limestone; dolomitic limestone + aluminum silicate; aluminum silicate, at the dosages of 50 g/100 kg of seeds; and control (without the products) X 2 cultivars: IRGA424 and IRGA 422 CL], totaling eight treatments with four replications each. The variables analyzed were: fresh and dry weights of aerial biomass; plant height; leaf area at 10, 20, and 30 days after emergence (DAE). The physiological quality of seeds was also assessed using tests of: seed emergence; first count of germination; emergence speed index; and field emergence. It was concluded that the coating of rice seeds with dolomitic limestone and aluminum silicate does not affect seed germination and field seedling emergence. Aluminum silicate used via seed coating on cultivar IRGA 424 promoted greater leaf area, after 20 DAE. The dolomitic limestone and the aluminum silicate used via seed coating generated plants with larger dry biomass, after 20 DAE, for the cultivar IRGA 422 CL.

Capacidade nodulatória e características agronômicas de feijoeiros comuns submetidos à adubação molíbdica parcelada e nitrogenada

The aim of this study was to evaluate the nodular ability and agronomic characteristics of three cultivars of common bean plants subjected to fragmented fertilization with molybdenum and nitrogen. The experimental design was of randomized blocks in a 3 x 7 factorial scheme, corresponding to the three cultivars (Carioca precoce, Rosinha and Ouro negro), and seven molybdic fertilization schemes, with three replications. The Ouro Negro cultivar showed a higher number of nodules and shoot dry-matter compared to Carioca precoce and Rosinha, and the Carioca and Ouro Negro cultivars achieved the highest number of grains per pod, hundred-grain weight and yield, than the Rosinha cultivar after fertilization with molybdenum and nitrogen. Nitrogen fertilization reduced the formation of nodules in the Carioca precoce and Rosinha cultivars, but increased most agronomic characteristics and yield in comparison to molybdic fertilization. However, the fragmented application of molybdenum between 15 and 30 days after emergence (DAE), positively influenced the formation of nodules, leaf-nitrogen levels, the number of grains per pod, hundred-grain weight and yield, compared to molybdenum application by seed, or the absence of fertilization, for the three cultivars studied, indicating that molybdic foliar fertilization is considered essential for increasing the productivity of bean cultivars.

Initial Growth of Soybean Plants from Seeds of High and Low Vigor Subjected to Water Stress

This study intends to evaluate responses on the growth of soybeans plants from seeds with high and low vigor in different drought periods. Experimental design was completely randomized in factorial AXB (Factor A: variables 0, 2, 3, 4 and 5 water stress; Factor B: level of seed vigor, high and low). Evaluations of fresh matter, plant height, leaf area and dry weight of shoots, 10, 20, 30 and 40 days after emergence (DAE). Soybean plants originated from seeds with high physiological quality perform better than the plants originated from seeds of low vigor, until 40 DAE. Water stress reduces the initial growth of soybean plants originated from seeds of both high and low force, until 40 DAE. Soybean seeds of high vigor generate plants with higher growth rate of the culture until 30 DAE, besides generating plants with greater capacity for growth after returning water stress.

Determinação dos períodos de interferência de plantas daninhas na cultura do girassol

O objetivo deste estudo foi determinar o período anterior à interferência e o período total de prevenção à interferência da comunidade infestante sobre a cultura do girassol (híbrido M 734). O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições. Os tratamentos foram compostos por parcelas constituídas por períodos de controle e de presença de plantas daninhas. Para os períodos de controle, o girassol foi mantido livre das plantas daninhas pelos períodos crescentes de 7, 14, 21, 28, 35, 42, 49 e 125 dias após a sua emergência (DAE). Quanto a convivência, a cultura foi mantida na presença da comunidade infestante pelos mesmos períodos. Foram avaliados a densidade e o peso da matéria seca das plantas daninhas e, no girassol, a altura de plantas, o diâmetro de capítulos e a produtividade de aquênios e de óleo. Para a produtividade de aquênios, o período anterior à interferência foi de 15 DAE da cultura, e o período total de prevenção à interferência, de 39 DAE. O período crítico de prevenção à interferência abrangeu 24 dias do ciclo da cultura. Quanto à produtividade de óleo, o período anterior à interferência foi de 32 DAE, e o período total de prevenção à interferência, de 28 DAE.

Avaliação de resistência de cultivares de amendoim de hábito de crescimento rasteiro a Enneothrips flavens Moulton (Thysanoptera: Thripidae)

Devido a sua ampla distribuição e aos danos acarretados, Enneothrips flavens Moulton destaca-se como a principal praga do amendoim no Brasil. O objetivo do presente trabalho foi avaliar, em condições de campo, o comportamento de quatro cultivares de amendoim de hábito de crescimento rasteiro sob infestação natural de E. flavens. Os experimentos foram desenvolvidos na área experimental do Departamento de Fitossanidade da FCAV/UNESP - Campus de Jaboticabal, SP. O delineamento experimental utilizado foi em blocos ao acaso, com quatro tratamentos em seis repetições. Foram utilizadas os cultivares IAC Caiapó, IAC 125, IAC 147 e IAC Runner-886. Foram avaliados o número de ninfas e adultos de E. flavens, porcentagem de folíolos atacados, sintomas de intensidade de ataque, número de brotos apicais por planta, massa seca das plantas, produção de grãos em casca (kg ha-1) e a massa seca de 100 sementes (g). Os cultivares não diferiram quanto ao nível de infestação de ninfas e adultos de E. flavens. O período de maior infestação de ninfas ocorreu entre 15 e 41 DAE, e de adultos entre 15 e 48 DAE. Analisando-se a produção, o cultivar IAC Caiapó comportou-se como portador de resistência do tipo tolerância ao ataque de E. flavens.

Parcelamento de fósforo em algodoeiro irrigado

A maioria das regiões de cultivo de algodoeiro no Brasil apresenta baixa fertilidade dos solos, especialmente com relação ao fósforo (P) disponível. Objetivou-se avaliar a aplicação parcelada de doses de P em algodoeiro irrigado, visando a uma maior eficiência da adubação fosfatada, em comparação com a aplicação tradicional, em semeadura. O experimento foi desenvolvido em Neossolo Quartzarênico com 22 mg dm-3 de P (disponibilidade média), no norte de Minas Gerais. Utilizou-se delineamento em blocos ao acaso, em arranjo fatorial (4x3) + 3, com três repetições. Os fatores estudados foram doses de P2O5 (0 kg ha-1, 30 kg ha-1, 60 kg ha-1, 120 kg ha-1 e 180 kg ha-1) e três formas de aplicação parcelada (80% e 20%; 60% e 40%; 40% e 60% da dose do fertilizante aplicada em semeadura e aos 35 dias após a emergência (DAE), respectivamente), além da aplicação de 0 kg ha-1, 60 kg ha-1 e 120 kg ha-1 de P2O5 na semeadura. A fonte de P foi o superfosfato triplo granulado e houve aumento no conteúdo de P, na parte aérea, em função das doses aplicadas. Os teores de nutrientes na folha índice, exceto P, não foram influenciados pelas doses de P e pelos parcelamentos. O teor de P na folha índice e o número de capulhos por planta aumentaram com o incremento das doses de P, mas não foram influenciados pelo parcelamento do fertilizante fosfatado. A aplicação de 40% da dose de P em semeadura e do restante parcelado aos 35 DAE reduziu a produtividade de algodão em caroço, não havendo efeito significativo nos demais parcelamentos.

Influência da nutrição mineral foliar sobre doenças da parte aérea da cultura do trigo

A utilização de fungicida para o controle de doenças foliares na cultura do trigo é prática comum entre os triticultores. Contudo, devido ao impacto ambiental provocado pelo seu uso generalizado, buscam-se alternativas para controle dos fitopatógenos. Sendo assim, este trabalho teve como objetivo avaliar o efeito da nutrição mineral foliar sobre as doenças foliares do trigo, bem como seu efeito sobre o desenvolvimento da planta. O delineamento experimental foi em blocos casualizados com quatro repetições e quatro tratamentos: 1- testemunha; 2- adubação foliar aos 30 dias após a emergência (DAE) e aos 75 DAE; 3- fungicida aos 30 e 75 DAE; e 4- adubação foliar aos 30 DAE e adubação foliar mais fungicida aos 75 DAE. Foram realizadas nove avaliações da incidência e da severidade do oídio, cujos dados foram utilizados para o cálculo das áreas abaixo das curvas de progresso da doença; três avaliações da severidade da ferrugem e da mancha da gluma; e duas avaliações da mancha amarela. Foram determinadas a massa de matéria fresca e seca da parte aérea e do sistema radicular e a produtividade da cultura. Foi observada redução da incidência e da severidade de oídio em função da adubação foliar, apenas na primeira avaliação de incidência e nas segunda e quinta avaliações de severidade da doença. O efeito complementar dos nutrientes com o fungicida para redução das doenças foi observado apenas para a mancha amarela, com redução de aproximadamente 11,16 % da severidade. Os maiores valores de produtividade foram observados para os tratamentos apenas com fungicida e, com fungicida mais nutrientes. A adubação foliar proporcionou aumento da massa fresca de raízes e massa seca de raízes. Apesar disso, não houve aumento da massa fresca da parte aérea em função da adubação foliar.