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ABSTRACT. The custard apple (Annona squamosa L.), also known as the sugar apple, is a fruit species native to Brazil that has been poorly studied, especially in relation to the effect of humic substances on its fruit quality and yield. An experiment was conducted from December 2010 to November 2011 to evaluate the fruit quality and yield of the custard apple as a function of nitrogen fertilising and the use of humic substances. The experimental design consisted of randomised blocks, with treatments distributed in a factorial arrangement (4 x 2), using four nitrogen doses (0, 100, 175 and 250 g of N plant -1 ) and two humic substance applications (with and without humic substances), with four replications. The fruit yield and fruit characteristics, such as fruit mass, titratable acidity (TA), soluble solids (SS), pulp pH and SS/TA ratio, were recorded. The humic substances and the nitrogen levels significantly affected the soluble solids, titratable acidity and SS/TA ratio, while the pH pulp was only influenced by the humic substances. The humic substances promoted a quantitative increase in the fruit yield of 0.63 ton ha -1 . The fruit quality and yield of the custard apple depend on the nitrogen fertiliser and the interaction of the humic substances. Nitrogen fertilising of 100 g per plant, associated with humic substances, could be recommended for use in the production of custard apples.

Yellow passion fruit is the most cultivated species in Brazil and requires high amounts of nitrogen and an adequate nutritional status to express its entire productive potential. In this sense, this study aimed to evaluate the effect of different sources and doses of nitrogen via fertigation on nutritional status and leaf chlorophyll of yellow passion fruit. The experiment was conducted from June 2013 to August 2014 in Gurgueia Valley, Cristino Castro county, Piaui State, Brazil. The experimental design was randomized blocks with four replications, in a 2 x 5 factorial design related to the application of two nitrogen sources (urea and ammonium sulfate) and five N levels (100, 200, 300, 400 and 500 kg ha-1 year-1). Six plants per replication were considered, totaling 240 plants, spaced 3 m between rows and 3 m between plants, and covering an area of 2,160 m2. At pre-flourishing, it was evaluated leaf chlorophyll index and leaf nitrogen, phosphorus, potassium, calcium, magnesium and sulfur contents. Urea increases Ca and Mg leaf contents and reduces leaf S content in relation to ammonium sulfate. The increase in nitrogen fertilizing levels enhances leaf N and Mg concentrations. For Ca, the optimal ammonium sulfate dose is 296.30 kg ha-1.

The melon has little boron deficiency tolerance and supply as seed treatment can meet the need of the plant and improve its development especially in the seedling stage. The objective of this study was to evaluate the initial development of muskmelon seedlings 'Imperial' on the basis of boron application in seeds. The experiment was conducted under greenhouse conditions (50% brightness) in Bom Jesus-PI in the period April-May 2011. It was adopted a randomized block design, with treatments: 0.0; 4.24; 8.50; 17.00; 34.00 g kg -1 B seeds, with five replications, and experimental unit consisting of five seedlings. Tubes were used as containers for up to 50 cm -3 , filled with a substrate composed of soil (Oxisol), washed sand and manure in the ratio (1: 1: 2) respectively. At the end of the experiment were evaluated: i) plant height; ii) stem diameter and iii) dry matter of root and shoot. There was an effect of boron rates applied to melon seed, with increased production of dry matter of shoots and roots, recommending the dose 11 g B per kg of seed for increased production of dry tissue.Additional keywords: boric acid; Cucumis melo L.; seed fertilization. ResumoO meloeiro apresenta pouca tolerância à deficiência de boro, e seu fornecimento via tratamento de sementes pode atender à necessidade da planta e melhorar seu desenvolvimento, especialmente na fase de mudas. Objetivou-se com este trabalho avaliar o desenvolvimento inicial de mudas de meloeiro 'Imperial' em função da aplicação de boro nas sementes. O experimento foi realizado em abrigo telado (50% de luminosidade), em Bom Jesus-PI, no período de abril a maio de 2011. Adotou-se delineamento em blocos casualizados, com os tratamentos: 0,0; 4,24; 8,50; 17,00 e 34,00 gramas de B por quilograma de sementes, com cinco repetições, e parcela experimental constituída por cinco plântulas. Foram utilizados como recipientes tubetes com capacidade para 50 cm -3 , preenchidos com substrato constituído de solo (Latossolo Vermelho), areia lavada e esterco bovino, na proporção (1:1:2), respectivamente. No final do experimento, avaliaram-se: i) altura da planta; ii) diâmetro do caule, e iii) matéria seca de raiz e da parte aérea. Houve efeito das doses de boro aplicadas via semente de melão, com aumento na produção de matéria seca da parte aérea e radicular, recomendando-se a dose de 11 g de B por kg de semente para maior produção de matéria seca das mudas.Palavras-chave adicionais: ácido bórico; adubação via semente; Cucumis melo L.

Apple tree has been experimentally grown Brazilian tropical semiarid. In these new regions, fertilizing management research for N and K is crucial to reach apple high yields. Therefore, an experiment was conducted to evaluate the effect of N and K fertilizing on fruit production, leaf chlorophyll and N and K nutritional status of apple cv. ‘Julieta’ grown in Brazilian tropical semiarid. The experimental design used was randomized blocks with treatments disposed in a factorial arrangement (4 x 4) referring to nitrogen doses (30, 60, 90, and 120 g of N plant-1) and potassium doses (30, 60, 90, and 120 g of K2O plant-1), with three replications and three plants in each parcel. ‘Julieta’ apple trees propagated by grafting (with ‘M9 filter and Maruba rootstock) and transplanted in 2013 were used in this study. The following variables were evaluated: i) fruit production (kg plant-1); ii) number of fruits (in a plant); iii) leaf chlorophyll index (‘a’, ‘b’, and total); and iv) leaf N and K concentrations (g kg-1). N and K doses effects depend on the consecutive production cycles of apple cv. ‘Julieta’ grown in tropical semiarid. An adequate N supply is very important for the subsequent production cycle. K fertilization until 120 g plant-1 of K2O is not enough to supply K demand of apple cv. ‘Julieta’ grown in tropical semiarid. In tropical semiarid, 60-90 g plant-1 of N through fertirrigation is enough for ‘Julieta’ apple production.