ABSTRACT Management of boron fertilization depends on the magnitude of B leaching in the soil profile, which varies proportionally with the concentration of B in the soil solution, which, in turn, decreases as the soil pH increases due to the higher sorption of B on soil solid surfaces. The objective of this study was to quantify the effect of liming and rates of B applied to the soil on B leaching. The experiment was carried out in the laboratory in 2012, and treatments consisted of a factorial combination of two rates of liming (without and with lime to raise the soil pH to 6.0) and five rates of B (0, 10, 20, 50 and 100 mg kg-1, as boric acid). A Typic Rhodudalf was used, containing 790 g kg-1 clay and 23 g kg-1 organic matter; the pH(H2O) was 4.6. Experimental units were composed of PVC leaching columns (0.10 m in diameter) containing 1.42 kg of soil (dry base). Boron was manually mixed with the top 0.15 m of the soil. After that, every seven days for 15 weeks, 300 mL of distilled water were added to the top of each column. In the percolated solution, both the volume and concentration of B were measured. Leaching of B decreased with increased soil pH and, averaged across the B rates applied, was 58 % higher from unlimed (pH 4.6) than from limed (pH 6.6) samples as a result of the increase in B sorption with higher soil pH. In spite of its high vertical mobility, the residual effect of B was high in this oxisol, mainly in the limed samples where 80 % of B applied at the two highest rates remained in the soil, even after 15 water percolations. Total recovery of applied B, including leached B plus B extracted from the soil after all percolations, was less than 50 %, showing that not all sorbed B was quantified by the hot water extraction method.

O boro (B) é aplicado na maioria dos pomares brasileiros de maçã, porém sem fundamentação experimental regional. Este trabalho teve por objetivo avaliar o efeito de formas, doses e épocas de aplicação de B no rendimento e na qualidade de maçãs. O experimento foi instalado em São Joaquim-SC, em 2002, com as cultivares Imperial Gala e Fuji Suprema conduzidas em áreas diferentes, cujas avaliações foram realizadas nas safras de 2009/2010 e 2010/2011. Os tratamentos consistiram em um fatorial envolvendo doses de B aplicadas ao solo, a cada dois anos, e épocas de pulverização na planta, feitas anualmente. Utilizou-se de delineamento experimental de blocos ao acaso, com três repetições, cujos tratamentos foram arranjados em parcelas subdividas: na parcela principal, foram alocadas as épocas de aplicação foliar de ácido bórico (sem pulverização, 0,3% pulverizado na fase de botão rosado e 0,6% em pós-colheita) e nas subparcelas, as doses de bórax no solo (0; 2,5 e 5,0 kg ha-1 de B). A aplicação de B no solo foi mais eficiente do que a pulverização foliar para aumentar o teor de B na polpa, na folha e no solo; no entanto, não afetou nenhum dos atributos relacionados com a qualidade dos frutos, nas duas cultivares. A pulverização com B diminuiu o teor de amido e a acidez titulável, e não afetou o teor de sólidos solúveis e a firmeza da polpa dos frutos. A pulverização na floração diminuiu a germinação de grãos de pólen na cultivar Imperial Gala e a frutificação efetiva na cultivar Fuji Suprema. O rendimento de frutos não foi afetado pela adição de B, independentemente da época, da forma de aplicação ou dose, nas duas cultivares. Assim, não há necessidade de aplicar B nessas cultivares em pomares cultivados em solos com altos teores de matéria orgânica, com o objetivo de incrementar a produção e a qualidade dos frutos.

Boron (B) is normally applied at Brazilian apple orchards, but without any regional experimental support. The aim of this study was to evaluate the effect of forms of B addition on apple yield and quality. The experiment was set up in São Joaquim, Southern of Brazil, using two apple cultivars (Imperial Gala and Fuji Suprema). Treatments consisted of a factorial combination of rates of B applied to the soil, biannually, and time of B sprayed to the plants, annually, from 2002. It was used a randomized block with treatments arranged in a split-plot design. Boron sprays were allocated in the main plots (only water or acid boric solutions applied at 0.3% at the pink stage or at 0.6% just after harvest) and rates of soil B (0, 2.5 and 5.0 kg ha-1 of B as borax) were allocated in the split-plots. Determinations were performed in the seasons of 2009/2010 and 2010/2011. Application of B to the soil was more effective than foliar B sprays for increasing B concentration inthe fruits, leaves and in the soil, however it did not affect any of the fruit attributes related to the physiological quality, regardless of cultivar. Foliar B sprays decreased starch content and titratable acidity, and did not affect soluble solids content and flesh firmness. Sprays of B applied at bloom decreased pollen grain germination in 'Imperial Gala' and fruit set in 'Fuji Suprema'. Fruit yield was not affected by the application of B, regardless of time, form or rate in any cultivar. Thus, there is no need to apply B in orchards containing these cultivars when grown in high organic matter soils in order to increase yield or fruit quality.

O gesso agrícola não altera as cargas negativas do solo e mantém o sulfato na solução, razão pela qual é uma das fontes mais baratas para aumentar a atividade do Ca, principalmente nas camadas mais profundas do solo. O maior teor de Ca na solução do solo pode aumentar a absorção desse nutriente pela macieira, reduzindo o risco de distúrbios fisiológicos causados pela deficiência de Ca. O objetivo deste trabalho foi avaliar a influência da aplicação de gesso sobre alguns atributos químicos do solo e sobre a composição química de folhas e frutos de uma cultivar de macieira sensível à deficiência de Ca. O experimento foi conduzido durante o período de 2001 a 2009, em São Joaquim, SC, num pomar de macieira implantado em 1997 com a cultivar Catarina. Os tratamentos consistiram de aplicações anuais de gesso agrícola nas doses de 0; 1,0; 2,0; e 3,0 t ha-1 sobre a superfície do solo, sem incorporação. A aplicação de gesso por oito anos consecutivos na superfície do solo não influenciou os teores trocáveis de K, tampouco de Al. Os teores de Ca trocável foram incrementados pelas doses de gesso nas diferentes camadas de solo amostradas (0-10, 10-20, 40-60 e 60-80 cm de profundidade), enquanto os de Mg diminuíram somente nas camadas superficiais (0-20 cm). A adição de gesso não alterou a concentração de Ca e dos demais nutrientes nos frutos; com exceção do Mg, que teve suas concentrações diminuídas com as doses de gesso. Embora o gesso agrícola tenha aumentado os teores trocáveis de Ca até 80 cm de profundidade, ele não foi eficiente em aumentar as concentrações de Ca nas folhas e nos frutos de uma cultivar de macieira sensível à deficiência de Ca quando cultivada em solo adequadamente calcariado.

Gypsum does not affect the soil negative charges and maintains sulfate in the soil solution, making it one of the cheapest products to increase Ca activity in soil solution, especially in the deeper soil layers. Higher Ca levels in the soil solution can increase the uptake of this nutrient by apple trees, reducing the risk of physiological disorders caused by Ca deficiency. This study assessed the effect of long-term gypsum application on some soil properties and on the chemical composition of leaves and fruits of an apple cultivar susceptible to fruit disorders associated with low Ca. The experiment was conducted in São Joaquim, in the South of Brazil, from 2001 to 2009. Gypsum rates of 0, 1.0, 2.0 and 3.0 t ha-1 were annually broadcast over the soil surface, without incorporation, in an apple orchard with cultivar ´Catarina´, planted in 1997. Gypsum application over eight consecutive years had no effect on soil exchangeable K and Al to a depth of 80 cm, but increased exchangeable Ca in the sampled layers (0-10, 10-20, 40-60 and 60-80 cm), while exchangeable Mg decreased only in the surface layer (0-20 cm). Gypsum did not affect the concentration of any nutrient in the fruits, including Ca. The same was verified in the leaves, except for Mg which decreased with increased gypsum rate. Despite increasing the availability of Ca in the soil profile to a depth of 80 cm, gypsum was not effective to increase the Ca content in leaves and fruits of an apple cultivar susceptible to Ca deficiency grown in an appropriately limed soil.