INTRODUÇÃOO arroz é importante fonte de calorias e proteínas, na dieta alimentar do povo brasileiro. No entanto, por conta da oscilação na sua produção, eventualmente, a importação deste cereal tem sido necessária, para suprir a demanda do País (Arf et al. 2001). Neste sentido, esforços com o intuito de elevar a produção de arroz, no Brasil, são importantes. Den- ABSTRACT RESUMOtre os fatores que podem afetar, significativamente, a produção de arroz de terras altas, o preparo do solo tem despertado atenção. A despeito das vantagens do sistema plantio direto, frequentemente a produção de arroz de terras altas sob este sistema tem ficado abaixo da obtida com o sistema convencional. Isto tem sido atribuído, principalmente, ao menor desenvolvimento das raízes das plantas cultivadas neste sistema, acarretando , and 125 kg ha -1 ), with four replications. The leaf N concentration, plant height, yield components, milled grain yield, and grain yield were evaluated. The scarifier + leveling disc harrow system provided the highest grain yield for both cultivars, while the topdressing nitrogen fertilization just affected the IAC 202 cultivar yield, without affecting the milled grains yield. KEY-WORDS:Oryza sativa L.; nitrogen fertilization; no-till system.

SUMMARYThe current high price of KCl and great dependence on importation to satisfy the Brazilian demand indicate the need for studies that evaluate the efficiency of other K sources, particularly those based on domestic raw material. For this purpose, a greenhouse experiment was conducted with samples of a sandy clay loam Typic Haplustox, in a completely randomized 4 x 3 x 2 factorial design: four K rates (0, 60, 120, and 180 mg kg -1 ), three sources (potassium chloride (KCl), fused magnesium potassium phosphate (FMPP) and a mixture of 70 % FMPP + 30 % KCl) and two particle sizes (100 and 60 mesh), with three replications. Potassium fertilization resulted in significant increases in shoot dry matter production and in K concentrations, both in soil and plants. The K source and particle size had no significant effect on the evaluated characteristics. Potassium critical levels in the soil and the shoots were 1.53 mmol c dm -3 and 19.1 g kg -1 , respectively.

O objetivo deste trabalho foi avaliar a influência de doses e fontes de nitrogênio nas concentrações foliares e na produtividade de grãos de milho, cultivado em sistema semeadura direta, num solo argiloso (Latossolo Vermelho distroférrico) com baixo teor de enxofre. As doses de N (0, 50, 100, 150 e 200 kg ha -1 ) foram aplicadas na forma de uréia e sulfato de amônio. A adubação nitrogenada aumentou significativamente as concentrações de N nas folhas e a produtividade de grãos de milho. Para essas variáveis, a uréia e o sulfato de amônio apresentaram um comportamento semelhante. Sintomas de deficiência de N foram observados quando as plantas apresentavam concentrações desse nutriente inferiores a 23,0 g kg -1 . As concentrações de N nas folhas, consideradas adequadas, estiveram dentro dos limites de 28,0 a 31,9 g kg -1 .

Biostimulants currently available on the market include those containing seaweed extract. There is sufficient scientific evidence to conclude that applying biostimulants to agricultural crops can positively impact plant growth and yield. However, results differ between plants species and environmental conditions. As such, the present study aimed to assess the effects of doses and application times of a biostimulant based on seaweed (Ecklonia maxima) extract on the morphology and yield of soybean crops. The experiment was conducted in a field in the municipality of Uberaba, Minas Gerais state (MG), Brazil, in dystrophic red latosol. A randomized block design was used, with four repetitions, in a 3 x 5 factorial scheme consisting of three application times (phenological growth stages: V4, R1 and V4+R1) and five doses of foliar -applied biostimulant (0, 250, 500, 750 and 1000 mL ha-1). In general, biostimulant application influenced the number of branches, nodes, flowers, and pods on the soybean plants and, consequently, crop yield. A dose of 607 mL ha-1 promoted a 6.1% greater grain yield (5379 kg ha-1) than that obtained without biostimulant spraying (5070 kg ha-1). Application in stage R1 resulted in plants with more flowers and pods.

Intensive conventional tillage cultivation of both green and sweet corn can contribute to soil degradation when compared to no-till systems. This study aimed to assess the agronomic characteristics and physicochemical quality of green and sweet corn grains grown under succession planting using different cover crops. Two experiments were conducted, one with green corn and the other sweet corn, using a randomized block design consisting of seven treatments: brachiaria (B); Pearl millet (PM); showy crotalaria (SC); SC+B; PM+B; PM+SC and PM+SC+B, with four repetitions. The fresh (FW) and dry weight (DW) of the cover crops and decomposition of their residue were assessed, in addition to the agronomic performance and bromatological quality of green and sweet corn grains. Brachiaria showed the lowest FW and DW production, highest residue decomposition rate and shortest half-life when compared to the other soil covers assessed. Productivity and yield for sweet corn grains and green corn ears were not statistically affected by the different cover crop residues. The cover crop residues influenced moisture content, total titratable acidity and total soluble solids in green corn, and lipids, proteins, total soluble solids, pH and ascorbic acid in sweet corn.

El rendimiento industrial de frutos de tomate (Solanum lycopersicon) depende de factores cualitativos y cuantitativos que pueden ser influenciados por la disponibilidad de fósforo (P) y potasio (K) para las plantas. El experimento fue conducido en la región de Janaúba, Minas Gerais, Brasil, en un Oxisol con textura arcillosa, con el objetivo de evaluar los efectos de la fertilización con P y K sobre el estado nutricional de la planta, la producción y algunas variables cualitativas de los frutos de tomate (cv. IPA-5). El diseño experimental fue en bloques al azar, en un arreglo factorial de cuatro por cuatro (cuatro dosis de fósforo y cuatro dosis de potasio), con cuatro repeticiones. Se utilizaron los siguientes niveles de P: 0, 150, 300 y 600 kg ha-1 de P2 O5 (superfosfato triple); los niveles de potasio (2/3 de la dosis en la siembra y 1/3 de la dosis en cobertura) fueron: 0, 50, 100 y 200 kg ha-1 de K2 O (cloruro de potasio). La fertilización fosfatada aumentó el contenido de P foliar y la producción de frutos. Por otra parte, ni el pH ni el contenido de sólidos solubles de los frutos fueron afectados por la fertilización fosfatada. La máxima producción de frutos comerciales fue obtenida con la aplicación (estimada) de 293 kg ha-1 de P2 O5 . El nivel crítico de P en las hojas fue 3,1 g kg-1. La fertilización potásica no influyó en las características analizadas.

The study aimed to assess application efficiency of Mo doses through leaves in two sowing dates and different phenological stages on agronomic characteristics of two peanut cultivars. The experimental design was a randomized block with four replications, with the treatments arranged in a factorial design 2 x 2 x 6 x 2, being two cultivars (IAC Tatu and IAC 886), two sowing dates, six Mo doses applied to the leaves (0, 50, 100, 200, 400 and 800 g ha-1) and two application times (early flowering and early seed formation). Were evaluated the number of pods/plant, the number of grains/pod, the weight of 100 grains, the yield of grain, the pod production and protein, lipids and the Mo contents in the grains. The highest pod yields were obtained with sowing in November, for both cultivars. The IAC 886 presents a significantly higher production than IAC Tatu when sown in November. When the seeds were sown in March, the cultivars showed similar productions. Foliar application of Mo at flowering and pod formation did not affect the agronomic characteristics, protein and lipid contents in peanut grains. The increase in Mo doses increased the content of this micronutrient in the grains.

O objetivo deste estudo foi avaliar o efeito de doses e modos de aplicação de N, fornecido por meio de ureia revestida, no estado nutricional e produção de alface americana. Utilizou-se o delineamento em blocos ao acaso em arranjo fatorial 6x4 + 1, sendo seis doses de N (28,75; 57,50; 115,00; 172,50; 230,00; 287,50 kg ha-1 de N), como fonte a ureia revestida, e quatro modos de aplicação do nutriente (100% da dose no transplante; 50% no transplante + 50% aos 10 dias após o transplante (DAT); 25% no transplante + 75% aos 10 dias DAT; 25% no transplante + 25% a cada cobertura, aos 10, 20 e 30 DAT). No tratamento adicional utilizou-se a ureia convencional. Foram determinados os teores foliares de N, P, K, Ca e Mg, a massa fresca total e comercial da cabeça, o diâmetro do caule, a altura da planta e o diâmetro da cabeça aos 30 e 60 dias após o transplante. Verificou-se que a adubação nitrogenada aumentou os teores foliares de N, Ca e Mg, e reduziu os teores foliares de K e P. Não houve influência das doses de N proveniente de ureia revestida com polímero e dos modos de aplicação nos atributos morfológicos e produtivos da cultura. Palavras-chave: Lactuca sativa L.; nitrogênio; fertilizante de liberação lenta; fertilizante de liberação controlada.   RATES AND APPLICATIONS WAYS OF POLYMER-COATED UREA IN CRISPHEAD LETTUCE CULTIVATION   ABSTRACT: The aim of this study was to evaluate the effect of N rates (using a polymer-coated urea) and N application ways in nutritional status and yield of crisphead lettuce. The randomized block design in a 6 x 4 + 1 factorial arrangement was used, with six N rates (28.75, 57.50, 115.00, 172.50, 230.00, 287.50 kg ha-1 of N), with the use of polymer-coated urea, and four nutrient application ways (100% of the transplant rate, 50% at the transplant + 50% at the 10 days after the transplant (DAT), 25% at the transplant + 75% at 10 days DAT, 25% at transplant + 25% at each side dressing fertilization at 10, 20 and 30 DAT). The additional treatment was related to the recommended N fertilization using conventional urea. N, P, K, Ca and Mg, total and commercial yield, stem diameter, plant height and head diameter were determined at 30 and 60 days after transplant. Nitrogen fertilization increased the N, Ca and Mg foliar levels, independently of the application way. However, in general, it reduced the leaf levels of K and P. There was no influence of N rates from polymer-coated urea and application way on the morphological attributes and yield of the crop. Keywords: Lactuca sativa L.; nitrogen; slow-release fertilizer; controlled-release fertilizer.