RESUMO A goiabeira é uma frutífera cultivada mundialmente, destacando-se pela grande aceitação no mercado consumidor. Entretanto, para que a cultura explore o seu máximo potencial produtivo e mantenha a qualidade dos frutos, é necessária a adequada adubação mineral para elevar a disponibilidade de nutrientes no solo e aumentar sua absorção pelas plantas. Objetivou-se, com este trabalho, avaliar os efeitos da adubação com doses de potássio, na presença e na ausência de cálcio, no estado nutricional e na produção da goiabeira 'Paluma'. O experimento foi desenvolvido de agosto de 2015 a maio de 2016, no município de Remígio, Paraíba. As variáveis analisadas foram: teores foliares de macro e de micronutrientes, número de frutos por planta, massa média de frutos, produção de frutos por planta e produtividade. As plantas da goiabeira estavam adequadamente supridas em nitrogênio, fósforo, potássio, cálcio, magnésio, boro, ferro, manganês e deficientes em enxofre, cobre e zinco. A adubação com cálcio incrementou os teores foliares de P, K, Ca, S, B, Mn e Zn e reduziu o número de frutos por planta e a produtividade da goiabeira 'Paluma'. A adubação potássica sem adição de cálcio, nas doses entre 101 e 143 g planta-1 ano-1 de K2O, aos 16 meses de idade, proporcionou a maior produtividade da goiabeira 'Paluma'.

ABSTRACT The guava is a fruit cultivated worldwide, distinguished by the great acceptance in the consumer market. However, so that the crop exploits its maximum productive potential and maintains the quality of the fruits it is necessary an adequate mineral fertilization to raise the availability of nutrients in the soil and to increase the absorption by plants. The objective of the work was to evaluate the effects of fertilization with potassium doses, in the presence and absence of calcium, on the nutritional status and on the production of 'Paluma' guava. The experiment was carried out from August 2015 to May 2016, in the municipality of Remígio-PB, Brazil. The variables analyzed were: macro and micronutrient leaf contents, number of fruits per plant, average fruit mass, fruit yield per plant and productivity. Guava plants were adequately supplied with nitrogen, phosphorus, potassium, calcium, magnesium, boron, iron and manganese, and deficient in sulfur, copper and zinc. Calcium fertilization increased the leaf content of P, K, Ca, S, B, Mn and Zn, but reduced the number of fruits per plant and the yield of 'Paluma' guava. Potassium fertilization without calcium addition at doses between 101 and 143 g plant-1 year-1 K2O at 16 months of age provides the highest productivity of 'Paluma' guava.

ABSTRACT Guava is a perennial fruit, highly preferred by the Brazilian consumer and in increasing commercial exploitation in almost all the national territory. The most required nutrients are nitrogen, followed by potassium and calcium with great participation in the growth and physiology of guava. The objective of this study was to evaluate the effects of potassium doses in the soil without and with calcium in the physiology of Paluma guava plants. The experiment was carried out in a randomized complete block design in a 5 × 2 factorial arrangement, with K2O of 0, 45, 90, 135 and 180 g plant-1 year-1, without and with 120 g plant-1 year-1 calcium from calcium nitrate. The variables analyzed were chlorophyll indices (a, b and total), chlorophyll fluorescence and gas exchange. The results were submitted to analysis of variance by the “F” test and the potassium doses were submitted to regression analysis, using SAS© software version 9.3. Guava plants fertilized with only potassium in the soil had higher photosynthetic rate, water use efficiency and instantaneous carboxylation efficiency. The addition of calcium and potassium to the soil increased chlorophyll a, b, total, variable fluorescence, maximum fluorescence, quantum efficiency, stomatal conductance, transpiration rate and internal carbon concentration in guava.

RESUMEN La guayaba es una planta perenne, de alta preferencia por los consumidores brasileños y generando esto un crecimiento operacional en su comercio en casi todo el territorio nacional. Nutricionalmente, los nutrientes más necesarios son nitrógeno, potasio y calcio, con gran participación en el crecimiento y fisiología de la guayaba. Teniendo en cuenta lo anterior, el objetivo fue evaluar los efectos de dosis de potasio en el suelo con y sin calcio en la fisiología de la guayaba con la variedad Paluma. El experimento se realizó en un bloque completamente aleatorizado con arreglo factorial 5 × 2, relativo al suelo con dosis de K2O de 0, 45, 90, 135 y 180 g planta-1 año-1 y sin y con 120 g planta-1 año-1 de calcio derivado del nitrato de calcio. Las variables analizadas fueron las tasas de clorofila (a, b, y total) fluorescencia de la clorofila y el intercambio gaseoso. Los resultados fueron sometidos a la prueba por análisis de varianza “F” y las doses de potasio fueron sometidos a análisis de regresión, utilizando el software SAS versión 9.3 ©. Las plantas de guayaba fertilizados solamente con el potasio en el suelo, mostraron una mayor tasa de fotosíntesis, el uso eficiente del agua y la eficiencia instantánea de carboxilación. La adición de calcio y potasio en el suelo aumentó los índices de clorofila a, b, total, fluorescencia variable, el máximo rendimiento cuántico de fluorescencia, conductancia estomática, tasa de transpiración e concentración interna de carbono en la planta de guayaba.