ABSTRACT No study has investigated the fertilization of beet with manganese (Mn) in the Brazilian semi-arid region. In this study, we evaluated the agronomic performance of manganese fertigated beet in Mossoró, Rio Grande do Norte. The experiments were conducted at Fazenda Experimental Rafael Fernandes in 2019 and 2021, and the study had a complete randomized block design with five treatments (0, 3, 6, 9, and 12 kg ha-1 Mn) and four replications. The Mn content increased in foliar diagnosis with fertilization. The accumulation of dry mass and the number of leaves did not differ significantly as a function of the dose. The highest total (21.59 t ha-1) and commercial (20.55 t ha-1) yields of tuberous roots were obtained with 6 kg ha-1 Mn. The adverse effects of excess Mn were expressed in the lower total and commercial productivity of beet fertilized with more than 6 kg ha-1 Mn. The accumulation of Mn in the tuberous roots was not affected by fertilization. In the leaves and the whole plant, the maximum accumulation occurred when 12 kg ha-1 Mn was applied. Although Mn did not influence the content of soluble solids, the pH of the tuberous roots of plants fertilized with 6 kg ha-1 Mn decreased, and the dose with the highest total and commercial productivity had a lower content of soluble sugars. Our findings suggest that treatment with 6 kg ha-1 Mn is optimum for the beet crop.

RESUMO Não há na literatura recomendações de adubação com manganês (Mn) para beterraba estabelecidas no semiárido brasileiro. Objetivou-se avaliar o desempenho agronômico de beterraba fertirrigada manganês em Mossoró, RN. Foram desenvolvidos experimentos na Fazenda Experimental Rafael Fernandes nos anos de 2019 e 2021, delineados em blocos casualizados completos com cinco tratamentos (0, 3,0, 6,0, 9,0 e 12,0 kg ha-1 de Mn) e quatro repetições. Houve aumento no teor de Mn na diagnose foliar com a adubação. O acúmulo de massa seca e o número de folhas não diferiram estatisticamente em função das doses. A maior produtividade total (21,59 t ha-1) e comercial (20,55 t ha-1) de raiz tuberosa foi obtida com 6,0 kg ha-1 de Mn. O efeito deletério do excesso de Mn foi expresso na menor produtividade total e comercial de beterraba adubada com mais que 6,0 kg ha-1 de Mn. O Mn acumulado na raiz tuberosa não foi influenciado pela adubação. Nas folhas e na planta inteira, o acúmulo máximo ocorreu na dose 12,0 kg ha-1 de Mn. O Mn não influenciou no conteúdo de sólidos solúveis, mas reduziu o pH e, a raiz tuberosa das plantas adubadas com 6,0 kg ha-1 de Mn, dose com maior produtividade total e comercial, tiveram menor teor de açúcares solúveis. Recomenda-se adubação com 6,0 kg ha-1 de Mn para a cultura da beterraba.

RESUMO O objetivo deste trabalho foi avaliar a eficiência de extratores de cápsula porosa, associados a medidores de íons específicos, para determinar a disponibilidade de nutrientes em pimentão e melão cultivados em substrato. A solução de substrato foi obtida utilizando o extrator aquoso 1:1,5 (v/v) e o extrator de cápsula porosa. A condutividade elétrica (CE), o pH e a concentração dos macronutrientes na solução do substrato foram determinados por meio do método analítico. Além disso, foram determinadas as concentrações de NO ‑ e K+ nas soluções obtidas com os extratores de cápsula porosa, bem como as concentrações de N e K na folha diagnose do estado nutricional. As concentrações de NO- e K+ obtidas por extratores de cápsula porosa apresentam forte correlação (r=0,96 e 0,92, respectivamente) com as obtidas pelo método padrão, bem como correlação moderada (r=0,65) e forte (r=0,71) com as concentrações de N e K, respectivamente, na folha diagnose do estado nutricional do melão e, correlação fraca (r=0,36 e 0,26, respectivamente) na folha diagnose do estado nutricional do pimentão. A utilização de extratores de cápsula porosa para a obtenção da solução do substrato e, a determinação das concentrações de N-NO3- e K+ por medidores de íons específicos, é um método rápido para avaliar a disponibilidade de nutrientes em cultivos sem solo.

ABSTRACT 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.

The objective of this work was to evaluate the effects of N and K2O doses, applied by a drip fertigation system, and of distances between plants on the productivity of the Shadow hybrid of seedless watermelon. The experiment was carried out from August to October 2008, at Tupã, SP, Brazil. Four doses of N + K2O (79.8 + 106.7, 106.4 + 142.2, 133.0 + 177.7, and 159.6 + 213.2 kg ha-1) and four spacings between plants (0.5, 1.0, 1.5, and 2.0 m) were evaluated in 2.0-m spaced rows. A randomized complete block design with split plots and three replicates was used. Evaluated variables were: N and K foliar content, mean fruit weight, number of fruit and total and commercial productivity; and number of fruit from classes 3 to 5 kg, 5 to 7 kg, 7 to 9 kg, and above 9 kg per plant and per hectare. Nitrogen and potassium doses significantly affected K foliar content, and total and commercial productivity of the hybrid Shadow decreased linearly with the increase in spacing between plants. However, there was no effect of the interaction between factors or from the factors themselves on the other evaluated variables.

El objetivo de este trabajo fue evaluar los efectos de dosis de N y K2O, vía fertirrigación por goteo, y de la distancia entre plantas sobre la productividad del híbrido Shadow de sandía sin semillas. El experimento se realizó de agosto a octubre de 2008 en el Município de Tupã, SP, Brazil. Se avaluaran cuatro dosis de N + K2O (79,8 + 106,7, 106,4 + 142,2, 133,0 + 177,7, y 159,6 + 213,2 kg ha-1, respectivamente), y cuatro distancias entre plantas (0,5, 1,0, 1,5 y 2,0 m), en hileras espaciadas de 2,0 m. Se utilizó el diseño experimental de bloques al azar, en parcelas subdivididas, con tres repeticiones. Las variables evaluadas fueron: concentración foliar de N y K, peso medio de frutos, número de frutos y productividad total y comercial; y número de frutos en las clases de 3 a 5, 5 a 7, 7 a 9 kg y con más de 9 kg, por planta y por hectárea. Hubo efecto del factor dosis de N + K2O sobre la concentración foliar de K, y la productividad total y comercial de la sandía híbrido Shadow disminuyó linealmente con el aumento de la distancia entre plantas. Sin embargo, no hubo efecto significativo de la interacción ni efecto individual de los factores sobre las otras variables avaliadas.