ABSTRACT Foliar fertilization can be recommended to treat boron (B) deficiency in coffee and cotton. Considering that B foliar fertilizers with polyol-boron complexes can affect B uptake and mobility differently within the plant, and coffee and cotton have different cuticles and stomata density, a differential response would be expected. We aimed to study the foliar application of boric acid combined with sorbitol on B uptake and translocation in cotton and coffee. Green-house grown plants received B as boric acid and a sorbitol-monoethanolamine complex and were sampled up to 96 h after application. Boron absorption was fast, reaching 60 and 80 % in cotton and coffee 96 h after application, respectively. Uptake rates and total B absorption were similar for the fertilizers. The proportion of B taken up by coffee is greater than by cotton likely because of the greater stomata density in coffee and less likely due to the higher amount of wax in cotton cuticle. Boron remobilization is higher in coffee as compared with cotton. Sorbitol seems to increase B transport in the transpiratory stream of cotton, but impairs remobilization in the phloem since B translocation to roots is decreased in both cotton and coffee.

Resumo: O objetivo deste trabalho foi avaliar o teor nutricional e a produtividade de grãos de três cultivos de milho (Zea mays) em resposta à adubação fosfatada com fertilizante organomineral à base de cama de aves ou mineral, quando cultivado em Nitossolo Vermelho Distroférrico com elevado teor inicial de fósforo. O experimento foi conduzido em campo, em delineamento de blocos ao acaso, em arranjo fatorial 2×4+1 (fertilizantes organomineral ou mineral × 20, 40, 60 ou 80 kg ha-1 de P + controle sem adubação fosfatada), com quatro repetições cada um. Foram determinados os teores de P disponível e carbono orgânico total (COT) no solo ao final do ciclo da cultura, os teores de P no tecido vegetal e a produtividade de grãos. O índice de eficiência agronômica (IEA) foi estimado com base na produtividade de grãos. Após três safras, os teores de P disponível e COT no solo não aumentaram significativa com uso dos fertilizantes, mas apresentaram relação direta com as doses de P. Em um Nitossolo Vermelho Distroférrico com elevado teor inicial de P, o uso de fertilizante organomineral à base de cama de aves proporciona maior produtividade de milho, com IEA 20% superior ao do fertilizante mineral.

Abstract: The objective of this work was to evaluate the nutritional content and grain yield of three corn (Zea mays) crops in response to phosphate fertilization with an organomineral fertilizer based on poultry litter or a mineral fertilizer, when cultivated on a Rhodic Khandiudox with a high initial phosphorus content. The experiment was carried out in the field in a randomized complete block design in a 2×4+1 factorial arrangement (organomineral or mineral fertilizer × 20, 40, 60, or 80 kg ha-1 P + control treatment with no phosphate fertilization), with four replicates each. Available P and total organic carbon (TOC) contents in the soil at the end of the crop cycle, plant tissue P contents, and grain yield were determined. The agronomic efficiency index (AEI) was estimated based on corn grain yield. After three harvests, soil available P and TOC contents did not increase significantly due to fertilizer use, but were directly related to P doses. In a Rhodic Khandiudox with a high initial P content, the use of an organomineral fertilizer based on poultry litter promotes higher corn crop yield, with an AEI 20% higher than that of the mineral fertilizer.