ABSTRACT Peanuts are mainly grown in sandy soils with low boron content, which may limit the crop yield, especially runner-type cultivars that have high-yields. Boron deficiency causes hollow heart in peanut seeds, reducing yield and seed quality, but the best strategy to supply boron to peanut is still not known. This study aimed to evaluate peanuts nutrition, yield, and seed quality as a function of boron rate, source, and application form. The study was conducted for two years in sandy soils with low boron in southeastern Brazil. Treatments included application of boron via soil: control (boron unfertilized), boric acid at 1.5 kg ha-1 of B, Ulexite (1.5 and 3.0 kg ha-1 of B), and sodium tetraborate (1.5 and 3.0 kg ha-1 of B) combined with foliar fertilization (sub-plots): 0, 400, 800 and 1200 g ha-1 of B (boric acid) with four replicates. Boron fertilization via soil and foliar increased peanuts yield by 20 % (1100 kg ha-1) and 14 % (700 kg ha-1) - the average of the two crops, respectively. Combined use of soil and foliar fertilizer was justified only in years with water deficit and when the rate applied via soil was low (<3.0 kg ha-1). Boron application via soil or application of 400 g ha-1 of B via foliar fertilization increased seed germination rate by 10 to 13 %. Boron fertilization increased the percentage of normal seedlings, seedling weight, and length and reduced the germination time. Foliar and soil boron applications efficiently improved peanut seed nutrition, yield, and quality. However, soil application performed better, showing a higher percentage of yield increase. content runnertype runner type highyields. highyields high yields. yields high-yields seeds known nutrition source form Brazil unfertilized, unfertilized , unfertilized) 15 1 5 1. ha1 ha ha- (1. 30 3 0 3. subplots sub plots (sub-plots) 80 120 replicates 2 1100 (110 700 (70 crops respectively <3.0 (<3. ha1. . 40 seedlings weight time However better increase (1 (sub-plots 8 12 110 (11 70 (7 <3. (<3 4 ( 11 7 <3 (< <

ABSTRACT Reduced stability and structural resilience expose sandy soils to physical degradation under intensive production systems. This study aimed to evaluate the influence of different cover crops (CC) under no-tillage system (NTS) cotton cropping, grown either individually or in combination, on the soil physical quality (SPQ) of a sandy loam Oxisol (Latossolo) in southeastern Brazil. To quantify the effects of CC on soil physical quality indicators, an experiment in randomized blocks design was implemented with the treatments: CC1: single cultivation of Ruzi grass; CC2: Intercropping of Pearl Millet + Ruzigrass; CC3: Intercropping of Pearl Millet + Velvet bean; CCMixture: Intercropping of Ruzi grass, Pearl Millet and Velvet bean; and Control: maintenance of spontaneous plants. Undisturbed samples were taken from layers 0.00-0.10, 0.10-0.20, 0.20-0.40 and 0.40-0.60 m, in which were determined the soil bulk density (Bd), total porosity (TP), available water (AW), soil penetration resistance (PR) and the least limiting water range (LLWR). According to the multivariate analyses, the CC2 treatment resulted in better SPQ compared to the other treatments. The LLWR, air-filled porosity (θAFP), and AW were responsible for differentiating the CC2 treatment compared to the other treatments evaluated. Regardless of treatments, values of Bd> 1.75 Mg m-3 result in loss of SPQ due to the significant increase in PR and decreases in AW and LLWR. In the CC3 and Control, there was a physical impediment caused by the increase in Bd in the 0.10-0.20 m layer, which could result in the confinement of cotton roots to the surface, making them more susceptible to water stress. Soil PR reached values greater than 2.5 MPa for water contents lower than the θPWP in most treatments. In treatment CC3, for water contents equivalent to the θPWP, the PR did not exceed 6 MPa, while for the other treatments, the PR reached values greater than 10 MPa. Only the PR was influenced using CC. Soil moisture is considered crucial to maintain PR below impeding values, determining the control of the physical quality of this sandy soil. systems (CC notillage no tillage NTS (NTS cropping combination (SPQ Latossolo (Latossolo Brazil indicators CC1 grass Ruzigrass bean CCMixture Control plants 0.000.10, 000010 0.00 0.10, 0 00 0.00-0.10 0.100.20, 010020 0.10 0.20, 20 0.200.40 020040 0.20 0.40 40 0.20-0.4 0.400.60 040060 0.60 60 0.40-0.6 Bd, , (Bd) TP, TP (TP) AW, (AW) (PR LLWR . (LLWR) analyses airfilled air filled θAFP, θAFP (θAFP) evaluated 175 1 75 1.7 m3 3 m- 0.100.20 0.10-0.2 layer surface stress 25 2 5 2. 000 0.000.10 00001 0.0 010 0.00-0.1 100 01002 0.1 020 200 0.200.4 02004 0.2 040 0.4 4 0.20-0. 400 0.400.6 04006 060 0.6 0.40-0. (Bd (TP (AW (LLWR (θAFP 17 7 1. 0.100.2 0.10-0. 0.000.1 0000 0. 01 0.00-0. 0100 02 0.200. 0200 04 0.20-0 0.400. 0400 06 0.40-0 0.100. 0.10-0 0.000. 0.00-0 0.200 0.20- 0.400 0.40- 0.100 0.10- 0.000 0.00-

ABSTRACT Sandy soil often has low nitrogen (N) stock. Thus, crops grown in sandy soil rely on high levels of N fertilization. The use of cover crops and efficient fertilizers can increase N stock in the soil and N availability in the topsoil, and reduce overall fertilizer costs. The objective of this study was to evaluate the effects of cover crops (fallow, a single grass species (ruzigrass), two grass species (ruzigrass + millet), one grass species (millet) with legumes [lime-yellow pea (2018) and velvet bean (2019)], and a mixture of three cover crops [two grass species (ruzigrass + millet) and one legume (lime-yellow pea (2018)] and velvet bean (2019), N sources (conventional urea and controlled-release urea) and N doses (70, 100 and 130 kg ha-1) on N dynamics in an Oxisol (Latossolo) with sandy texture in Brazil cultivated with cotton. Systems with the cover crops (average) had 17 % more total N stock in the soil than fallow systems. Inorganic N increased only in systems with legumes. The systems with cover crop mixtures had 70 % more ammonium than fallow systems. Systems only with grass species had low percentages of inorganic N in relation to total N in the soil. The increase in N-fertilizer rates augmented the N stock in the soil (total and inorganic). In the first year, controlled-release urea reduced the availability of inorganic N in cotton flowering, except for the system with mixed cover crops. After the cotton harvest, areas of controlled-release urea application had 12 % more inorganic N than the areas with conventional urea. Our findings show that the combined use of cover crops with high biomass production, moderate dose of N and controlled-release N can increase the availability of inorganic nitrogen in the upper layers of the soil in tropical areas with sandy soil and this can reduce nitrogen fertilizer consumption in the medium and long term in cotton fields.

RESUMO: O cultivo do algodoeiro no Brasil está concentrado no período chuvoso, e no momento do estabelecimento da lavoura frequentemente há períodos prolongados de baixa radiação solar. O objetivo deste trabalho foi avaliar o desenvolvimento radicular de cultivares de algodoeiro submetidos ao sombreamento na fase inicial da cultura. O experimento foi realizado em ambiente controlado, em rizotrons. O delineamento experimental foi um fatorial 2x2 em blocos ao acaso com cinco repetições. Os tratamentos foram as cultivares de algodão TMG 11WS (precoce) e TMG 81WS (tardia) e as condições de sombra: sem sombra e com sombra (50% de redução da luminosidade). Não houve interação entre os fatores “sombra” e “cultivares estudadas” para nenhum parâmetro avaliado. A sombra reduziu o crescimento radicular total e das raízes laterais a partir dos 21 dias de emergência (DAE) e da raiz principal aos 24DAE. O sombreamento reduziu o comprimento (60%), a superfície (65%), o diâmetro médio (15%), o comprimento por volume (60%), o volume radicular (69%), a massa de matéria de seca da raiz (83%) e da parte aérea (64%), o teor (36%) e o acúmulo de carboidratos na parte aérea (73%). Em conclusão, o sombreamento na fase inicial de desenvolvimento do algodoeiro reduz a produção de carboidratos da parte aérea, afetando o acúmulo de matéria seca e o crescimento radicular, sendo que essa resposta independe da cultivar.

ABSTRACT: Cotton cultivation in Brazil tends to occur mostly in the rainy season, and at the time of developing the crop there are often prolonged periods of low solar radiation. The objective of this work was to evaluate the root development of cotton cultivars subjected to shading in the initial phase. The experiment was carried out in a greenhouse, using rhizotrons. The experimental design was a 2x2 factorial in randomized blocks with five replications. The treatments were composed of cotton cultivars TMG 1WS (early) and TMG 8WS (late) and luminosity conditions: non-shaded and shaded (50% reduction of luminosity). There were no interactions between the factors “shading” and “cultivars” for any parameter evaluated. Shading reduced total and lateral root growth from the 21 days after emergence (DAE) and the main root at 24DAE. Shading caused reductions in length (60%), surface (65%), mean diameter (15%), root volume (69%), root dry matter mass (83%) and shoot (64%), as well as decreasing the content (36%) and the accumulation of carbohydrates in the shoot (73%). Shading at early cotton development reduces the shoot carbohydrates production, affecting dry matter accumulation and root growth, and this response is independent of the cultivar.

RESUMO O manejo de reguladores de crescimento tem sido um desafio para cotonicultores, devido ao aumento da instabilidade climática e adoção de cultivares precoces, em segunda safra. Objetivou-se propor um novo método, denominado Taxa de Crescimento da Cultura, para definir doses de cloreto de mepiquate em lavouras de algodão, bem como compará-lo com práticas de manejo tradicionais. Exceto para micronaire, não houve diferença nos parâmetros de crescimento do algodoeiro e nem na produtividade e qualidade de fibra, entre o novo método e o tradicional. As doses de cloreto de mepiquate foram, em média, 24 % maiores e 43 % menores em cultivares tardias e precoces, respectivamente, no novo método. O número de capulhos em plantas tratadas com cloreto de mepiquate foi menor do que nas plantas não tratadas, nas cultivares IMA5672B2RF e IMA5675B2RF, mas o peso médio do capulho foi maior nestes genótipos. O novo método é eficiente na definição da dose de regulador de crescimento para evitar crescimento excessivo em cultivares de algodão e resulta em menos cloreto de mepiquate aplicado a cultivares precoces, preservando-se a produtividade e a qualidade da fibra.

ABSTRACT Plant growth regulator management has been a challenge for cotton growers, due to the increased weather instability and the adoption of early cultivars, in off-season crops. This study aimed at proposing a new method, called Crop Growth Rate, to define mepiquat chloride rates in cotton crops, as well as to compare it with traditional management practices. Except for micronaire, there was no difference in cotton growth parameters, neither in yield nor fiber quality, between the new method and the traditional one. The mepiquat chloride rates were, on average, 24 % higher and 43 % lower in late and early maturity cultivars, respectively, for the new method. The number of bolls in plants treated with mepiquat chloride was lower than in non-treated plants, for the IMA5672B2RF and IMA5675B2RF cultivars, but a higher average weight of bolls was observed for these genotypes. The new method is efficient in defining the plant growth regulator rate to avoid an excessive growth and results in less mepiquat chloride applied to early cycle cultivars, preserving lint yield and fiber quality.

Nas maiores regiões algodoeiras no Brasil, chove mais de 1.500mm anuais, existindo risco de ocorrer lavagem de reguladores de crescimento aplicados às folhas do algodoeiro, antes que sejam absorvidos. O objetivo deste trabalho foi avaliar a lavagem dos reguladores de crescimento cloreto de mepiquat e cloreto de chlormequat de folhas de algodoeiro por chuva, ocorrendo em diferentes momentos após a aplicação. O trabalho foi realizado em casa de vegetação. Ambos os reguladores foram aplicados no aparecimento do primeiro botão floral, na dose de 15g ha-1 de i.a. com e sem adjuvante siliconado, e chuva simulada foi aplicada aos 0, 0,75; 1,5; 3,0; 6,0; 12,0 e 24 horas após a aplicação dos reguladores, mais um tratamento sem chuva. A adição de adjuvante siliconado melhorou a absorção dos produtos. A ocorrência de chuva até mesmo 24 horas após a aplicação dos reguladores pode lavar parte dos produtos das plantas de algodoeiro, com maior intensidade para o tratamento sem adjuvante. A redução da absorção do produto leva à necessidade de reaplicá-lo para que possa haver a sua ação, sem comprometer sua função.

Most of Brazilian cotton is produced in regions where annual rainfall exceeds 1,500mm, hence plant growth regulators (PGR) may be washed from the leaves before being absorbed. The objective of this research was to evaluate mepiquat chloride and chlormequat chloride washing from cotton leaves by rains occurring at different moments post spraying. The experiment was conducted in a greenhouse. Both PGR were sprayed to cotton at pin-head square at 15g ha-1 a.i. with and without a silicon-based adjuvant, and simulated rains were applied at 0, 0.75, 1.5, 3.0, 6.0, 12.0 and 24 hours after spraying, plus a control without rainfall. Addition of silicon adjuvant increased PGR uptake. Rainfall occurring up to 24 hours after spraying resulted in some PGR loss from cotton leaves, mainly in the absence of the adjuvant. The decreased uptake implies that in order to achieve the desired level of growth reduction, at least a fraction of the original PGR rate should be reapplied.

O adensamento da cultura do algodão aumenta a competição entre plantas por recursos, como luz, nutrientes e água; logo, o período de florescimento é reduzido e, consequentemente, a marcha de acúmulo de matéria seca é alterada. O objetivo deste trabalho foi determinar a marcha de absorção de N, P e K pelo algodoeiro, identificando a época de maior absorção e a quantidade absorvida e exportada em espaçamentos adensado (48 cm - 20,58 plantas m-2), intermediário (75 cm - 13,30 plantas m-2) e convencional (96 cm - 10,39 plantas m-2). Foram amostradas três plantas úteis por parcela aos 46, 69, 99, 139, 148 e 166 dias após a emergência (DAE), em que foram determinados o acúmulo de matéria seca, N, P e K. O acúmulo de matéria seca nas plantas cultivadas no espaçamento de 48 cm foi maior no início do desenvolvimento, igualando-se às demais ao final do ciclo, o que resultou em maior acúmulo de N entre os 69 e 99 DAE, no menor espaçamento. O adensamento antecipa o pico de absorção de nutrientes, sugerindo a antecipação das adubações de cobertura com N e K no algodoeiro cultivado nesse sistema. Para condições de fertilidade média/alta, a dose de nutrientes a ser aplicada não precisaria ser alterada em função do aumento da densidade de plantas, pois não há variação nas quantidades de N, P e K exportados por kg de algodão produzido, em fibra ou em caroço.

An increase in plant density of cotton (Gossypium hirsutum L., cv. FM 966 LL) results in increased interplant competition for resources, and consequently the flowering period is shortened and the rate of dry matter accumulation changed. The purpose of this study was to determine the N, P and K uptake rates by cotton plants, identifying the time of greatest absorption and the total uptake and export in narrow spacing (48 cm - 20.58 plants m-2), intermediate (75 cm - 13.30 plants m-2 ) and conventional spacing (96 cm - 10.39 plants m-2). Three competitive plants were sampled per plot 46, 69, 99, 139, 148, and 166 days after plant emergence, when dry matter accumulation, and N, P and K contents were determined. Dry matter accumulation was faster in the beginning in the narrower spacing of 48 cm, but in the end equal to the other densities; N accumulation was highest in the narrower spacing, between 69 and 99 DAE. High plant density results in an earlier absorption peak of nutrients, suggesting an anticipated sidedressing with N and K in cotton grown in this system. For medium or highly fertile soils, the nutrient rates to be applied would not have to be changed at a higher plant density, because the amounts of N, P and K exported per kg in cotton fiber or cotton seed were not significantly different.

Este trabalho teve por objetivo avaliar os efeitos causados pela deficiência hídrica induzida por manitol no crescimento inicial de plântulas de algodão. O experimento foi conduzido em dezembro de 2007 em Presidente Prudente - SP. Utilizou-se o delineamento inteiramente casualizado, em esquema fatorial 4x5, com 3 repetições. Os tratamentos foram gerados da combinação de quatro 4 cultivares de algodão (LD CV Frego; LD CV 02; FMT 701 e IAC 25) e cinco níveis de deficiência hídrica (0; -0,3; -0,6, -0,9 e -1,2 MPa) obtidos a partir de soluções de manitol. Potenciais hídricos da ordem de -0,9 MPa diminuíram significativamente a taxa de crescimento das plântulas de algodão. A diminuição do potencial hídrico reduziu a produção de massa seca da parte aérea de todos os cultivares e, aumentou a produção de massa seca da raiz até o potencial de -0,6 MPa. O cultivar LD CV 02 foi o que melhor se desenvolveu sob deficiência hídrica.

The main goal of this work was to evaluate the effects induced by mannitol- water stress in the initial growing of cotton plants. The experiment was conducted as a completely randomized design, in factorial design 4 x 5, with 3 replications. Treatments were generated by the combination of four cotton cultivars (LD CV Frego; LD CV 02; FMT 701 and IAC 25) and five levels of water stress (0; -0.3; -0.6, -0.9 and -1.2MPa), obtained with mannitol solutions. Water potentials of -0.9 MPa reduced significantly the rate of cotton plants growth. The decrease of the water potential reduced the production of dry mass of the aerial part of all cultivars and increased the production of root dry mass on -0.6MPa potential. LD CV 02 cultivar exhibited a superior performance under water stress.