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.

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 presente estudo objetivou avaliar os efeitos de doses de K em atributos morfológicos, produtivos e qualitativos do sorgo sacarino. O experimento foi conduzido em campo em Latossolo Vermelho com teor inicial de 0,6 mmolc dm-3 de K. Adotou-se o delineamento em blocos casualizados com cinco tratamentos (0, 50, 100, 150 e 200 kg ha-1 de K2O) e quatro repetições. Avaliaram-se: diâmetro de colmos, altura de plantas, teor de K na folha e no caldo, produção de colmos e de caldo e concentração de açúcar total no caldo. Os dados foram submetidos à análise de variância e de regressão polinomial. O fornecimento de K incrementou linearmente o diâmetro do colmo e aumentou a altura de plantas até a dose de 152 kg ha-1 de K2O. O maior diâmetro e altura foi, respectivamente, 18,1 mm e 2,73 m. A adubação potássica não afetou o teor de K nas folhas, mas elevou a produção de colmos até 32.454 kg ha-1 com aplicação de 132 kg ha-1 de K2O. Houve incremento linear na produção de caldo, chegando-se a 7.322 L ha-1. A dose de, aproximadamente, 100 kg ha-1 de K2O proporcionou as maiores concentrações de açúcar total (62,7 mg L-1) e K no caldo (1.144 mg L-1).Palavras-chave: Sorghum bicolor, biocombustível, adubação potássica. POTASSIUM RATES FOR SWEET SORGHUM CULTIVATED FOR ETHANOL PRODUCTION ABSTRACT: The objective of this study was to evaluate the effects of K rates on morphological, productive and qualitative attributes of sweet sorghum cultivated for ethanol production. The experiment was conducted in field conditions in a cerrado soil with 0.6 mmolc dm-3 of K. The randomized block design with five treatments (0, 50, 100, 150 and 200 kg ha-1 of K2O) and four replicate was adopted. The following variables were evaluated: stem diameter, plant height, leaf and juice K content, stem and juice yield, and total sugar concentration in the juice. Data were submitted to analysis of variance and polynomial regression. The K supply linearly increased stem diameter and increased plant height up to the 152 kg ha-1 of K2O rate. The largest diameter and height were, respectively, 18.1 mm and 2.73 m. Potassium fertilization did not affect the leaves K content, but increased stem yield up to 32,454 kg ha-1 with application of 132 kg ha-1of K2O. There was a linear increase in juice yield, reaching 7,322 L ha-1. The rate of approximately 100 kg ha-1 of K2O provided the highest total sugar (62.7 mg L-1) and K concentrations in the juice (1,144 mg L-1).Keywords: Sorghum bicolor, biofuel, potassium fertilization.

Potassium chloride (KCl) is the most widely used potassium source to meet crops requirements. However, Brazil’s dependence on imports to meet the national demand demonstrates the need to assess the efficiency of other sources of this nutrient. The present study aimed to assess the agronomic efficiency of phonolite in natura and its mixture with a water-soluble source (KCl), for Paiaguás palisadegrass. The experiment was conducted in a greenhouse, with a sandy clay loam typic Hapludox. A completely randomized block design was used, in a 3 x 5 factorial scheme, consisting of three K sources (KCl, phonolite and a 30 % of KCl + 70 % of phonolite blend) and five doses of the nutrient (0, 50, 100, 150 and 200 mg kg-1), with four replications. The phonolite doses promoted a linear increase in the dry weight production, albeit inferior to KCl for all the cuttings, whereas the KCl (30 %) and phonolite (70 %) blend showed a better fertilization efficiency than phonolite alone, which exhibited an intermediate effect. The agronomic efficiency was 29 % for the phonolite alone and 63 % for the blend, and the critical K levels in the soil and shoots were, respectively, 1.4 mmolc dm-3 and 8.7 g kg-1.