Intercropping is a production system that can reduce the production cost and increase the profitability of vegetable producers, since it permits more efficient land and agricultural inputs use. In order to evaluate the effect of lettuce plant density on the economic feasibility of lettuce-rocket intercropping system over two growing seasons (winter and summer), two experiments were conducted in the field at São Paulo State University “Júlio de Mesquita Filho” (UNESP), Jaboticabal, São Paulo, Brazil. The treatments consisted of five lettuce-rocket intercrops with spacing between lettuce rows of: 0.20; 0.25; 0.30; 0.35 and 0.40 m, five sole crop of lettuce in the same spacing between rows adopted in the intercropping system, and a sole cropping of rocket with spacing between rows of 0.20 m. The statistical design adopted was the complete randomized block with four replicates. During winter, higher profitability was achieved with the highest population density. Highest profitability of the crops in both seasons was obtained in summer.
In intensive vegetable production systems, it is natural to increase nutrient contents in the soil due to the frequent fertiliser applications, especially phosphorus (P). There are few studies on the response of vegetables to phosphate fertilisation under such conditions. In this context, the objective of this study was to evaluate the agronomic performance of rocket as a function of phosphorus fertilisation in a P-rich Rhodic Eutrudox soil. Five P doses (0, 50, 100, 200, and 300 kg ha-1 P2O5) were evaluated in a randomised complete block design with four replicates. Maximum soil P content and shoot P content at harvest were obtained at a dose of 300 kg ha-1 P2O5. Rocket responded negatively to P fertilisation. The increase of P doses promoted the decrease of height and yield of the crop.
Arugula is a short-cycle species with a high demand for nutrients. In the plant, each nutrient performs one or more specific functions, so its deficiency will negatively impact the crop growth and development, being important to recognize the nutritional symptoms to help in decision making. In this context, the objective of this study was to describe the evolution of N, K, and Mg deficiencies symptoms and their effect on the growth of arugula plants. One at a time, the nutrients were omitted from the nutrient solution. At 13, 16, 18, and 20 days after transplanting (DAT) the seedlings to the - Nutrient Film Technique (NFT) system, plants were collected, symptoms characterized, and leaves were scanned in JPEG (1.200 pixels). At 10 DAT of arugula, plants grew in a nutrient solution N-depleted shown the initial visual symptoms of N deficiency and at 16 DAT was recorded the first symptoms of K and Mg depletion in nutrient solution. At 20 DAT, the plants showed severe N deficiency symptoms, the old leaves presented intense and generalized chlorosis, followed by necrosis. Deficient plants in K exhibited chlorosis at the edge of old leaves advancing to the center of the leaves and small white dots. For Mg, the older leaves developed interveinal chlorosis from the leaf tip towards the central vein. The omission of nitrogen resulted in plants with lower height, leaf area, and number of leaves when compared to arugula plants grown in a complete nutrient solution.
Sintomas de deficiências de macronutrientes em melancieiraResumo O manejo inadequado de corretivos e fertilizantes pode desencadear desordens nutricionais. Objetivou-se descrever e retratar a evolução dos sintomas de deficiências de nutrientes em melancieira quando induzidos no estádio de frutificação, e determinar o teor foliar no órgão e no momento em que foi visualizado o sintoma. O experimento foi instalado em hidroponia. Os sintomas de deficiências N e Ca foram os primeiros a serem observados. A deficiência de N causou cessação do crescimento, inibição de hastes laterais, clorose generalizada e necrose em folhas velhas. Os sintomas da deficiência de P apareceram inicialmente em folhas velhas, com áreas cloróticas e enrugadas, que posteriormente progrediram para necrose. A deficiência de K causou clorose marginal em folhas velhas, progredindo para todo o limbo e evoluindo para necrose. Com a deficiência de Ca, as folhas novas ficaram deformadas, com clorose e necrose marginal, margens encurvadas para baixo, limbo foliar grosso, enrugado e com necrose nos meristemas. A omissão de Mg inicialmente provocou sintomas de clorose internerval nas folhas velhas, com evolução para tecidos esbranquiçados e necróticos. Os teores de N, P, K, Ca e Mg na folha e por ocasião de deficiência foram 9,7; 1,4; 7,1; 1,8 e 1,8 g kg -1 , respectivamente. Palavras-chave: Citrullus lanatus, diagnóstico nutricional, nutrição mineral Symptoms of deficiencies macronutrients in watermelon AbstractImproper handling of lime and fertilizer can trigger nutritional disorders. This study aimed at describing and depicting the evolution of the symptoms of nutrient deficiencies in watermelon when induced in the fruiting stage, and determining the leaf content in the organ and at the time the symptom was visualized. The experiment was in hydroponics. The symptoms of N and Ca deficiencies were the first to be observed. Nitrogen deficiency caused cessation of growth, inhibition of lateral rods, general chlorosis and necrosis in older leaves. Symptoms of P deficiency first appeared in old leaves with chlorotic and wrinkled areas, which later progressed to necrosis. K deficiency caused marginal chlorosis in older leaves, progressing to the entire limb and evolving to necrosis. With calcium deficiency, the new leaves were deformed, with marginal chlorosis and necrosis, curved edges down, thick leaf blade, wrinkled and necrosis in meristems. The Mg omission initially caused symptoms of internerval chlorosis in old leaves, progressing to off-white and necrotic tissues. The levels of N, P, K, Ca and Mg in the leaf and on the occasion of deficiency were 9.7; 1.4; 7.1; 1.8 to 1.8 g kg-1, respectively.
Nitrogen (N) is the second most accumulated nutrient in rocket. This nutrient greatly affects growth, productivity and quality of the vegetable. Rocket is the second most widely grown leafy vegetable in hydroponic system; however, no studies on how N concentration in nutrient solution affects this crop can be found in literature. We studied four concentrations (79.2; 118.8; 158.4 and 237.6 mg L-1 of N) in a randomized block design with five replicates. Maximum number of leaves, leaf area, dry mass and productivity of rocket cv. ‘Folha larga’ were obtained with the highest N concentration. The rocket quality, evaluated by the nitrate content, was maximum with 210.2 mg L-1 of N and its value in the concentration which maximized productivity is in the acceptable range for vegetables; so, it is recommended to grow rocket with 237.6 mg L-1 of N in the nutrient solution.
Selenium (Se) is an essential micronutrient for humans, but most foods are Se deficient, mainly because of its low content in the soil. A Se-deficient diet results in increased susceptibility to cardiovascular disease, cancer, and hyperthyroidism. Agronomic biofortification is a good alternative to increase Se in food. This study investigated the effect of Se on the growth, yield, and biofortification of the rocket. Plants were grown in a hydroponic system. Seven Se concentrations (0, 10, 20, 30, 40, 50, and 60 µM) were evaluated using sodium selenate. Growth, yield, lipid peroxidation, hydrogen peroxide content, and the enzymatic activity of catalase and ascorbate peroxidase were influenced by the Se concentration. Considering the evaluated parameters, 10–30 µM Se promoted the best results, and with 20 µM, the higher yield. Rocket plants treated with Se in the nutrient solution were biofortified, showing Se contents of 598.96 to 1437.56 mg kg−1 in the dry mass, higher than plants cultivated in a nutrient solution without Se, which presented 167.84 mg kg−1 of Se. Se concentrations of 10–30 µM in the nutrient solution were beneficial for rocket plants, while concentrations above 50 µM were toxic to the plants.
The aim of this study was to evaluate the efficiency of the porous ceramic cup extractors, associated with ion meters, for the determination of nutrients availability for bell pepper and melon crops in substrate. Substrate solution was acquired using aqueous extract 1:1.5 (v/v) and also the porous ceramic cup extractor. Electrical conductivity (EC), pH and macronutrient contents were determined for the substrate solution through analytical method. The concentrations of NO- and K+ in the solutions obtained with porous ceramic cup extractors, and the N and K contents in the diagnostic leaf for nutritional evaluation were also determined. The concentrations of NO3- and K+ using the porous ceramic cup extractors have strong correlation (r=0.96 and 0.92, respectively) with the ones obtained using the standard method, as well as a moderate correlation (r=0.65) and a strong one (r=0.71) with contents of N and K, respectively, in the melon diagnostic leaf; and a weak correlation (r=0.36 and 0.26, respectively) in the bell pepper diagnostic leaf. The use of porous ceramic cup extractors for obtaining the substrate solution and the determination of the N-NO- and K+ contents by means of specific ion meters are a fast method of evaluating nutrients availability in soilless cultures.
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