Fernando José Freire

Estimativa do risco de sodificação de solos de Pernambuco pelo uso de águas salinas

An experiment was carried out in permeameters provided with vertical column and constant hydraulic head in order to evaluate sodification risks of soils with contrasting characteristics and treated with solutions of different electrical conductivities (EC) and sodium adsorption ratios (SAR). The treatments consisted of nine soils and eighteen percolating solutions with three EC values (175, 500 and 1,500 μS cm -1 ) and six SAR values (0 to 30 for sandy soils, 0 to 25 for medium textured soils and 0 to 15 for clay textured soils). Initially, the adjustment of the Na:Ca ratio on the cation exchange complex of the soils was performed using solutions with concentration of 50 mmol c L -1 . Later on leaching with solutions of different EC but same SAR was maintained to reach steady state flow, when the permeameters were dismantled and the soil samples removed for chemical analysis. Exchangeable sodium and cation exchange capacity were determined to calculate exchangeable sodium ratio (ESR) and exchangeable sodium percentage (ESP). Equations were adjusted between either ESR or ESP with EC and SAR of the percolating solution, the increment of EC and SAR elevated the soil ESR and the ESP. It may be concluded that the correct assessment of the sodification hazard has to take into consideration the soil properties and the water quality.

Gafsa rock phosphate and triple superphosphate for dry matter production and P uptake by corn

Crops in general make poor use of phosphorous fertilizer and, as a result, recommended rates and production costs are very high. Phosphorus can be made more readily available to plants by proper management of phosphate fertilization, selecting both, type of fertilizer and application method. This study was carried out to evaluate the efficiency of the natural Gafsa rock phosphate and the triple superphosphate on dry matter production and P uptake by corn plants cultivated in a greenhouse. Fertilizers were applied localized and broadcast/incorporated on to two soils with contrasting phosphorus capacity factors (PCF). Rock phosphate broadcast application was as efficient as triple superphosphate in increasing corn plant dry matter in the Tropudult, with lower PCF. This effect was not observed on the Haplustox, owing to the lower P solubility due to the higher Ca concentration in this soil. Triple superphosphate rates increased plant P uptake in both soils and for both application forms. Rock phosphate resulted in higher P-content in plants, but only for broadcast application on the Ultisol.

Produtividade, eficiência de uso da água e qualidade tecnológica de cana‑de‑açúcar submetida a diferentes regimes hídricos

O objetivo deste trabalho foi avaliar a produtividade de colmos e de acucar, a eficiencia de uso da agua e os atributos tecnologicos de cinco variedades de cana-de-acucar de maturacao precoce e seis de maturacao media a tardia, submetidas ao regime de sequeiro (1.141,4 mm) e a irrigacao plena (1.396,6 mm). Utilizou-se o delineamento experimental de blocos ao acaso, com quatro repeticoes. A produtividade de colmos das variedades RB92579, RB72454 e SP81-3250 apresentou ganhos superiores a 180%, com uso da irrigacao. A irrigacao promoveu aumentos na produtividade de acucar superiores a 200%, nas variedades RB92579 e RB943365. A irrigacao plena proporcionou maior eficiencia de uso da agua, com producao media de 70,2 kg ha-1 mm-1 de colmos a mais em comparacao ao regime de sequeiro. Com excecao das variedades RB72454, RB763710 e RB943365, nao houve diferenca nos atributos tecnologicos entre a irrigacao plena e o regime de sequeiro. As variedades RB92579 e SP81-3250 de maturacao media a tardia se destacam quanto a produtividade de colmos e de acucar e a eficiencia de uso da agua, e sao recomendadas para estudos de resposta a irrigacao pela cana-de-acucar.

Condutividade hidráulica de solos de Pernambuco em resposta à condutividade elétrica e RAS da água de irrigação

An experiment was carried out in permeameters provided on vertical soil columns with constant hydraulic head in order to evaluate the hydraulic conductivity of soils with contrasting characteristics, and treated with solutions of different electrical conductivities (EC) and sodium adsorption ratios (SAR). The treatments consisted of nine soils, three EC values (175, 500 and 1.500 mS cm-1) and six SAR values of the irrigation water (0 to 30 for sandy soils, 0 to 25 for medium textured soils, and 0 to 15 for clay textured soils). Initially, an adjustment of the Na:Ca ratio in the cation exchange complex was performed with solutions at concentration of 50 mmolc L-1. The saturated hydraulic conductivity of soil (K0) was measured and the relative hydraulic conductivity (K0R) was determined, considering the maximum average K0 values of each soil as 100%. The K0R values were related to CE and SAR of the treatments, by adjusting the response surfaces. The correlation between K0 and the exchangeable sodium percentage (ESP) showed an inverse relationship between both variables in most of the studied soils. The increment in SAR resulted in the decrease of the K0R. It was not possible to define just one ESP value in order to establish a limit for sodic soils. ESP should be considered together with the EC of the irrigation water, as well as soil properties such as texture and mineralogy.

Fracionamento químico e físico do carbono orgânico total em um solo de mata submetido a diferentes usos

A materia orgânica e um importante indicador da qualidade do solo, pois esta relacionada com diversas propriedades quimicas, fisicas e biologicas, sendo importante o conhecimento do teor de C orgânico total (COT), bem como de suas fracoes. Com base nisso, realizou-se esta pesquisa objetivando caracterizar e quantificar os estoques de COT e suas fracoes como indicadores da qualidade de um solo, submetido a diferentes usos: (1) Mata Atlântica, (2) Cacau (Theobroma cacao) e (3) Pastagem (Brachiaria decumbens), em uma microbacia no sul da Bahia. Para cada uso, coletaram-se amostras nas profundidades de 0-10 e 10-20 cm e procedeu-se a caracterizacao quimica e fisica do solo, a determinacao do COT e ao seu fracionamento quimico e fisico. O teor de COT nao diferiu entre os diferentes usos do solo nas duas profundidades estudadas. A percentagem de C humificado e nas fracoes de acidos fulvicos e humina foi maior na pastagem, na camada de 0-10 cm. Houve menor percentagem de C nao-humificado nos sistemas cacau e pastagem, e maior relacao C:N no sistema pastagem na camada de 10-20 cm. O sistema cacau promoveu aumento na quantidade de C orgânico na fracao leve na camada de 10-20 cm. A substituicao da mata pelo cultivo do cacau no sistema cabruca (sub-bosque) ou pela pastagem nao alterou os teores de COT e de suas fracoes na area estudada.

Acúmulo e alocação de nutrientes em cana-de-açúcar

The objective of this study was to evaluate, along the first cycle of sugar cane, the capacity of eleven varieties of sugar cane (SP79-1011; RB813804; RB863129; RB872552; RB943365; RB72454; RB763710; SP78-4764; SP81-3250; RB867515 and RB92579), cultivated under full irrigation,the accumulation of the nutrients N, P, K, Ca and Mg in the plants aerial parts (stem, leaf and pointer). The research was carried through under field conditions, during the agricultural season 2006/2007, in the Sugar Cane Agricultural Station of the Federal Rural University of Pernambuco, in Carpina County, PE/Brazil. The experimental set was a complete randomized block design, with four replications. The accumulation of nutrients in the components of the aerial part was evaluated at 120; 180; 240; 300 and 360 days after plant (DAP). It was observed along the cycle of the sugar cane, mobilization of nutrients N, P and K from the leaves to the points and stems. At 360 DAP the accumulation of N, P and K in the aerial part was higher than the amount added by fertilizers. The varieties RB92579 and SP81-3250 were detached by the highest nutrients accumulation in stems, while RB867515 and RB943365 were the varieties that allocated more nutrients in leaf, which identifies them as the varieties of larger capacity of cycling of those nutrients.

Adsorption and chemical extraction of phosphorus as a function of soil incubation time

The objectives of this work were to evaluate the relationship between phosphate adsorption in different mineral soil constituents of the clay fraction to determine the P recovery rate by the Mehlich-1, Mehlich-3, Bray-1 and CaCl2 0.01 mol L-1 extractants as a function of incubation time of soil as well as to compare this rate with physical and chemical soil characteristics. In five soil samples five doses of P based on the maximum phosphate adsorption capacities (MPAC) of the soil, were applied, corresponding to 0, 0.2, 0.4, 0.8 and 1.0 level. The samples were incubated for 90, 60, 30, 15 and 0.5 days. The experiment consisted of a 5 x 4 x 5 factorial (five doses, four extractants and five different periods of incubation time) in five different soils, all distributed in blocks, with three replicates. The P content in soil was determined by the Mehlich-1, Mehlich-3, Bray-1 and CaCl2 0.01 mol L-1 extractants. The soil characteristics that best correlated with the recovery rate of applied P were the remaining P (rem-P) and the MPAC. Soils high in gibbsite presented the highest P adsorption. Soils possessing high MPAC and the low rem-P presented higher reversibility for the non-labile P (residual P) for smaller time periods.

Crescimento de meloeiro e acúmulo de nutrientes na planta sob irrigação com águas salinas

This study was conducted in a greenhouse at the Environmental Sciences Department of the Federal Rural University for the Semi-Arid. Four soil types, traditionally used for cantaloupe production in the Mossoro Region, were used and irrigated with solutions corresponding to eight electrical conductivities (EC = 100; 250; 500; 750; 1,250; 1,750; 2,250 and 3,000 µS cm-1) and two sodium adsorption ratios [SAR = 4 and 12 (mmol L-1)1/2], combined as salinity treatments. The experiment was a factorial arrangement of 4 x 8 x 2 (four soils, eight EC and two SAR), with three replicates, and 192 experimental units, in a randomized block design. Plant characteristics (fresh and dry matter production and mineral composition) were evaluated. Fresh and dry cantaloupe production was reduced with increased water salinity in two successive crops, leading to plant death a few days after transplanting in the second cycle. Increased water salinity elevated Ca, Mg, Na, K and Cl accumulation in the plants. Saline water use increased salinity and sodicity of all studied soils, diminishing cantaloupe growth.

Fator capacidade de fósforo em solos de pernambuco mineralogicamente diferentes e influência do pH na capacidade máxima de adsorção

O Fator Capacidade de Fosforo (FCP) e definido pela razao de equilibrio entre o fator quantidade de P (Q) e o fator intensidade (I) e representa uma medida da capacidade do solo em manter um determinado nivel de P em solucao. As caracteristicas e o teor dos constituintes minerais da fracao argila sao responsaveis por uma maior ou menor FCP, interferindo nas relacoes solo-planta. Por outro lado, o pH do solo tem, em alguns casos, mostrado-se com efeito na adsorcao e, em outros, com pequena e nao consistente alteracao na Capacidade Maxima de Adsorcao de P (CMAP). Objetivou-se, neste trabalho, determinar o FCP de solos mineralogicamente diferentes em Pernambuco; correlacionar caracteristicas fisicas e quimicas dos solos com o FCP; e avaliar o efeito do pH na CMAP. Amostras subsuperficiais de quatro solos, mineralogicamente diferentes, foram caracterizadas quimica e fisicamente e determinado o FCP. Essas amostras foram corrigidas com CaCO3 e MgCO3 na proporcao 4:1 e incubadas por 30 dias, com excecao do Vertissolo. Determinou-se a CMAP antes e apos a correcao dos solos. O experimento consistiu de um fatorial 4 x 2 (quatro solos com e sem correcao), distribuidos em blocos ao acaso, com tres repeticoes. As caracteristicas dos solos que melhor refletiram o FCP foram o P remanescente (P-rem) e a CMAP. Independentemente dos constituintes mineralogicos da fracao argila, solos com elevados teores de aluminio apresentaram aumento da CMAP com a correcao. A energia de adsorcao (EA) nos solos corrigidos foi, em media, significativamente menor, independentemente do solo.

Litter seasonality, composition and nutrient input in remnant of Atlantic Forest in the State of Pernambuco, Brazil

This research aimed to evaluate the amount of litter fall, the seasonal distribution and the influence of precipitation on the fall. It also intended to determine the nutrient contents and estimated the nutrient input according to time and plant structure. The research was carried out in an Atlantic Forest remnant in Recife-PE metropolitan region. The litter fall was equal to 10.07 tons/ha/year, and the leaf component contributed with 6.74 tons/ha/year (66.9 % of the total). Litter fall was higher during the dry season. Seasonality influenced the leaf component of the litter fall. The amount of K was low in the rainy season for the leaf and miscellaneous components. The contents of nutrients in g/kg in the litter were Ca, 15.73; K, 4.74; Mg, 2.42; and P, 0.50. The input of nutrients through the litter was 170.7; 26.4; 5.2; and 49.7 kg/ha/year for Ca, Mg, P and K, respectively.