L. F. Sobral

Fertigation of banana cv Prata Anã with N and K in an ultisol

The Brazilian Northeast is the main producing area, being responsible for about 35,80% of bananas national production. In spite of the favorable conditions to its cultivation, the average national yield has been a lot below its potential, due mainly to water and nutrients supply. Among all nutrients, nitrogen (N) and potassium (K) are the ones required in larger amounts by the banana. With the objective of studying the effect of four rates of N (0, 117, 235 and 352 kg ha-1 of N), and of four rates K (0, 157, 313 and 470 kg ha-1 of K2O) applied by fertirrigation in the 2o cycle of cultivation of the cv. Prata Ana, data was collected in an factorial experiment in randomized blocks, in an Ultisol of the coastal tableland, of the northeast of Brazil. There was not response to N but a linear one was observed for K. Soil K by Mehlich-1 critical level at 0,20- 0,40 m was 0,71 mmolc kg-1.

Crescimento, produção de biomassa e eficiência fotossintética da bananeira sob fertirrigação com nitrogênio e potássio

de K 2 O. Palavras-chave - Plantas-nutricao. Plantas-efeito do potassio. Plantas-efeito do nitrogenio. Biomassa vegetal. Abstract - The objective of this study was to evaluate effects of nitrogen and potassium applied trough water irrigation on physiological characteristcs of banana cv Prata Ana in the coastal tablelands of Sergipe State. The experiment was carried out in the Sergipe Federal University Experiment Station, as 4x4 factorial, in randomized blocks with four repplications. Doses of nitrogen as ureia were (0; 250; 500 e 750 kg ha -1 ) and doses of potassium as potassium chloride were (0; 290; 580

Resposta da laranjeira-pêra à adubação com nitrogênio, fósforo e potássio em um Latossolo Amarelo dos Tabuleiros Costeiros

The effects of N, P, and K applications on yield and fruit quality of orange (Citrus sinensis (L.) Osbeck) was studied in a factorial experiment carried out in a Yellow Latosol, of the Coastal Plateau of the Northeast of Brazil. Zero, 150 e 300 kg ha-1 N as urea; 0, 26 and 52 kg ha-1 of P as concentrated superfosfate and 0, 96 and 192 kg ha-1 of K as KCl were used. A linear yield response to N was observed in one, out of four years of observation. Nitrogen decreased fruit size and had no influence on fruit quality measured by percentage of juice, total soluble solids, acidity and ratio total soluble solids/acidity. Yield was highly responsive to P in each year observed. The nutrient increased percentage of juice and the total soluble solids/acidity ratio. Potassium increased yield and fruit size, but decreased the total soluble solids/acidity ratio.

Influência de nitrogênio e potássio, via fertirrigação, em atributos do solo, níveis críticos foliares e produção do coqueiro-anão

Irrigated plantations of dwarf coconut for the production of coconut water have expanded considerably in Brazil. Higher yields obtained under irrigation affect the amount of N and K required by dwarf coconut, influencing the relationships between yield and soil and leaf contents of these nutrients. An experiment was set up on an Ultissol in the Brazilian Northeast coastal tablelands, following a Pan Puebla III experimental matrix in a randomized block design. Ten combinations of urea and potassium chloride were weekly injected during 52 months. Soil samples were collected in the irrigated area and leaf samples taken from the leaves 9 and 14. Soil pH, Ca and Mg contents decreased as urea doses increased. The highest electrical conductivity value was 0.65 dS m-1 in the 0_5 cm layer and it decreased with depth. Correlation coefficients between leaf K and soil K in the layers 0_5, 0_20 and 20_40 cm were very similar, indicating that layer 0_20 cm can be sampled for fertility purposes in irrigated coconut. Highest fruit weight and coconut water volume were obtained with the lowest N level, due to the lower number of nuts per tree. Nitrogen and K combinations did not influence the coconut water pH, but increased coconut water brix. The K content in the coconut water increased along the K doses; leaf K and K in the coconut water were directly related. Nitrogen and K critical levels for leaves 9 and 14 were 19.2 and 20.5 g kg-1 and 12.1 and 9.4 g kg-1, respectively. The critical level of soil K by Mehlich-1 in the 0-20 cm layer was 45 mg dm-3.

EFICIÊNCIA AGRONÔMICA DE FOSFATOS DE ROCHA EM SOLO COM ELEVADO TEOR DE CÁLCIO TROCÁVEL

No Brasil, a maioria dos trabalhos sobre a aplicacao de fosfatos de rocha foi realizada em solos do Cerrado com pH menor que 5,5 e baixos teores de Ca trocavel. Estudos em condicoes diferentes dessa, alem de raros, tem sido desestimulados, pois esses solos podem apresentar-se restritivos a dissolucao dessas fontes, a depender da especie cultivada e da natureza geologica do fosfato aplicado. Um experimento para estudar a eficiencia agronomica dos fosfatos de Bayovar e Itafos, aplicados por meio da adubacao corretiva, foi implantado em um Cambissolo Haplico Ta eutrofico vertissolico de elevado teor de Ca trocavel e pH 6. O delineamento experimental utilizado foi em blocos ao acaso com parcelas subdivididas em faixas e quatro repeticoes. As parcelas consistiam de tres tratamentos de fosfatagem, na dose de 200 kg ha-1 de P2O5, com o Fosfato Natural Reativo de Bayovar, o Fosfato de Rocha Itafos e o superfosfato triplo (fonte de referencia), alem de um tratamento-padrao sem correcao de P. As subparcelas correspondiam aos tres niveis de adubacao de manutencao (0, 60 e 120 kg ha-1 de P2O5) aplicados anualmente no sulco de semeadura, utilizando superfosfato triplo. Cultivou-se milho nos dois anos em que o experimento foi conduzido (2011 e 2012). No periodo avaliado, a produtividade de graos e o teor de P foliar do milho indicaram menores necessidades de reposicao de P, por meio das doses de manutencao, conforme maior era a solubilidade da fonte corretiva aplicada. Tanto Mehlich-1 quanto a Resina de Troca Ionica Mista removeram mais P dos tratamentos em que foram aplicados fosfatos de rocha em relacao ao tratamento onde foi aplicado o superfosfato triplo via adubacao corretiva. Quando aplicados de maneira isolada (dose 0 de manutencao), os indices de eficiencia agronomica dos fosfatos de rocha foram de 72,08 e 82,31% para o Bayovar e de 43,85 e 47,47% para o Itafos nos anos de 2011 e 2012, respectivamente. No periodo avaliado, os tratamentos de maior economicidade foram a fosfatagem com o superfosfato triplo nas doses de manutencao de 0 e 60 kg ha-1 de P2O5 e a com o fosfato reativo de Bayovar, nas doses de 60 e 120 kg ha-1 de P2O5.

Chlorophyll and macronutrients content in leaf tissue of Musa sp ‘Prata-Anã’ under fertigation

1 Paraiba State University, Av. das Baraunas, 351, Bodocongo, CEP 58109-753, Campina Grande-PB, Brazil. 2 Department of Agricultural Engineering, Sergipe Federal University, Av. Marechal Cândido Rondon, Jardim Rosa Elze, CEP 49100-000, Sao Cristovao-SE, Brazil. 3 Campina Grande Federal University, Academic Unit of Agricultural Sciences, Av. Jairo Vieira de Feitosa, Pereiros, CEP 58840-000, Pombal-PB, Brazil. 4 EMBRAPA, Agricultural Research Center of Tabuleiros Costeiros, Av. Beira Mar, 3250, Jardins, CEP 49025-040, Aracaju-SE, Brazil. 5 Department of Agronomy, Paulistan State University Julio de Mesquita, CEP 14884-900, Jaboticabal, SP, Brazil.

Efeito da calagem em atributos químicos do solo e na produção da laranjeira

The objective of the work was to study the behavior of the base saturation method, related to the amount of lime and its effect on chemical attributes of an Ultisol and yield and of orange crop calcium and magnesium contents in leaf. The experiment was designed in a completely randomized block with four treatments, six replications and four plants per plot. Treatments were: 1. Soil under natural condition; 2. 40%; 3. 60%; and 4. 80% base saturation, corresponding to final lime levels of 2.1; 5.5 and 9.5 Mg ha-1. The amount of lime calculated by the base saturation method was not sufficient to increase base saturation to treatments levels in 0 - 0.2 m depth and additional applications were necessary. The liming effect was more pronounced in the 0-0.1m layer. Liming increased pH, base saturation, Ca2+, Mg2+ and decreased Al3+ and (H+Al). Cation exchange capacity (CEC) at pH7, obtained by base summation plus (H+Al) decreased with lime levels. Lime increased Mg leaf content but had no influence on yield.