Gerônimo Ferreira da Silva

Production, water consumption and nutrient content of Chinese cabbage grown hydroponically in brackish water

Underground water reserves in the semi-arid region of Brazil are stored in the crystal formations that in large part have high concentrations of salt. However, the scarcity of this resource makes the use of this water necessary for various activities, including agriculture. The aim of this study was to evaluate the use of brackish water on the electrical conductivity and pH of the nutrient solution, and on the production, water consumption and the uptake of nutrients in Chinese cabbage (Brassica pekinensis L.) under a hydroponic system. The experimental design was completely randomised, with four replications and six levels of water salinity (0.2, 1.2, 2.2, 3.2, 4.2 and 5.2 dS m-1), obtained by adding NaCl to the local water supply, with this water being used to prepare the nutrient solution and to make up the volume lost through evapotranspiration. The results showed that with the exception of the treatment at the lowest salinity, there was a tendency to increased electrical conductivity of the nutrient solution with the increasing salinity of the water; that the pH of the nutrient solution remained within the normal range throughout the cycle; that with the increasing salinity of the solution there was a reduction in all growth and production variables under analysis, in water consumption, and in leaf N, K, Ca and Mg, and an increase in leaf concentrations of Na and Cl. It is possible to use brackish water for the production of Chinese cabbage when grown hydroponically as an alternative for those producers who have an available supply of brackish water and a restricted supply of fresh water, however with a reduction in productivity.

NUTRIÇÃO MINERAL DE ALFACE AMERICANA EM CULTIVO HIDROPÔNICO COM ÁGUAS SALOBRAS

Water availability in the Brazilian semiarid is restricted and often the only water source available has high salt concentrations. Hydroponics allows using these waters for production of various crops, including vegetables, however, the water salinity can cause nutritional disorders. Thus, two experiments were conducted in a greenhouse at the Department of Agricultural Engineering of the Federal Rural University of Pernambuco, to evaluate the effects of salinity on the mineral nutrition of crisphead lettuce, cultivar Taina, in a hydroponic system (Nutrient Film Technique), using brackish water in the nutrient solution, which was prepared by adding NaCl to the local water (0.2 dS m). A randomized blocks experimental design was used in both experiments. The treatments consisted of water of different salinity levels (0.2, 1.2, 2.2, 3.2, 4.2 and 5.2 dS m) with four replications, totaling 24 plots for each experiment. The water added to compensate for the waterdepth loss due to evapotranspiration (WCET) was the brackish water of each treatment in Experiment I and the local water without modifications in Experiment II. The increase in the salinity of the water used for the nutrient solution preparation reduced the foliar phosphorus and potassium contents and increased the chloride and sodium contents, regardless of the WCET. Foliar nitrogen, calcium, magnesium and sulfur contents were not affected by increasing the water salinity used for the nutrient solution preparation.

CONTINUIDADE ESPACIAL DA CONDUTIVIDADE ELÉTRICA, CONTEÚDO DE ÁGUA E TEXTURA EM UMA ÁREA CULTIVADA COM CANA-DE-AÇÚCAR

Spatial variability of soil attributes affects crop development. Thus, information on its variability assists in soil and plant integrated management systems. The objective of this study was to assess the spatial variability of the soil apparent electrical conductivity (ECa), electrical conductivity of the saturation extract (ECse), water content in the soil (θ) and soil texture (clay, silt and sand) of a sugarcane crop area in the State of Pernambuco, Brazil. The study area had about 6.5 ha and its soil was classified as orthic Humiluvic Spodosol. Ninety soil samples were randomly collected and evaluated. The attributes assessed were soil apparent electrical conductivity (ECa) measured by electromagnetic induction with vertical dipole (ECa-V) in the soil layer 0.0.4 and horizontal dipole (ECa-H) in the soil layer 0.0-1.5 m; and ECse, θ and texture in the soil layers 0.0-0.2 m and 0.2-0.4 m. Spatial variability of the ECa was affected by the area relief, and had no direct correlation with the electrical conductivity of the saturation extract (ECse). The results showed overestimated mean frequency distribution, with means distant from the mode and median. The area relief affected the spatial variability maps of ECa-V, ECa-H, ECse and θ, however, the correlation matrix did not show a well-defined cause-and-effect relationship. Spatial variability of texture attributes (clay, site and sand) was high, presenting pure nugget effect.

Concentração de nutrientes em tomate cereja sob manejos de aplicação da solução nutritiva com água salobra

Objetivou-se com este trabalho avaliar a concentracao dos nutrientes no tecido foliar das plantas de tomate cereja cv. “Rita”, cultivadas em sistema hidroponico utilizando agua com crescentes niveis de salinidade no preparo da solucao nutritiva, submetendo as plantas a diferentes tempos de exposicao a salinidade e turnos de rega. O experimento foi conduzido em casa de vegetacao em sistema hidroponico em vasos com substrato. O delineamento experimental foi em blocos inteiramente casualizados em esquema fatorial 6 x 2 x 2, sendo seis niveis de salinidade da solucao nutritiva (3,01; 4,51; 5,94; 7,34; 8,71 e 10,40 dS m-1), dois tempos de exposicao das plantas a salinidade (51 e 6 dias) e dois turnos de rega (uma irrigacao por dia e uma irrigacao a cada dois dias). Foram avaliadas as concentracoes de nitrogenio, fosforo, potassio, calcio, magnesio, enxofre, sodio e cloro no tecido foliar das plantas. O uso de agua salobra no preparo da solucao nutritiva promoveu efeitos de interacoes antagonicas entre os nutrientes, afetando as concentracoes dos mesmos. O aumento da salinidade provocou aumentos nas concentracoes de sodio e cloro e reducao nas concentracoes de potassio e nitrogenio no tecido foliar. O menor tempo de exposicao das plantas a salinidade proporcionou reducoes de menores magnitudes nas concentracoes de potassio e nitrogenio e diminui as concentracoes de sodio e cloro. O turno de rega com uma irrigacao a cada dois dias afetou as concentracoes foliares de nitrogenio, calcio e magnesio.

Nitrogen and phosphate fertilizer on green corn grown in succession to the melon crop

Os produtores de melao na Chapada do Apodi, localizada entre os Estados do Ceara e do Rio Grande do Norte, tem cultivado o milho verde como cultura de sucessao ao meloeiro. Contudo, nessa sucessao de culturas ainda nao se avaliou ate que ponto o efeito residual das adubacoes nitrogenadas e fosfatadas realizadas no meloeiro pode suprir parcial ou totalmente as demandas de nitrogenio e de fosforo do milho verde. Neste trabalho objetivou-se avaliar o efeito de doses de nitrogenio (N) e de fosforo (P) na producao de milho verde, em sucessao ao cultivo de melao (Cucumis melo) irrigado, em um Cambissolo Alcalino da Chapada do Apodi. Foram comparados dez tratamentos resultantes de combinacoes entre cinco doses de N (0, 45, 90, 160 e 220 kg/ha) e quatro doses de P2O5 (0, 40, 80 e 120 kg/ha). O delineamento experimental foi de blocos ao acaso com quatro repeticoes. A cultivar utilizada para producao de milho verde foi o hibrido AG 1051 e as caracteristicas avaliadas foram numero e peso total de espigas, numero e peso de espigas comercializaveis empalhadas e teores de N e de P na planta e P no solo. Tambem foram estimados os niveis criticos de N e de P na planta e de P no solo. Nas condicoes deste experimento, e viavel produzir milho verde em sucessao ao cultivo de melao sem a aplicacao de nitrogenio e de fosforo no solo. Porem, para obtencao de uma produtividade de milho verde ainda maior, e com um gasto minimo de fertilizantes, recomenda-se a aplicacao de 45 kg/ha de N na ausencia de adubacao fosfatada, ou 40 kg/ha de P2O5 na ausencia de adubacao nitrogenada. O nivel critico medio de N e de P na planta para producao de milho verde foi de 32,29 e 4,31 g/kg, respectivamente, e para o P no solo foi de 20,7 mg/dm3.