R. D. Coelho

Regulated deficit irrigation benefits the production of container-grown citrus nursery trees

Key messageWithholding irrigation at − 15 to − 25xa0kPa water potential significantly saved water with minimal changes in plant growth, water relations, and percentage of shippable citrus trees on drought-tolerant and -sensitive rootstocks.AbstractWe evaluated the impacts of regulated deficit irrigation (RDI) on plant growth, water relations, and biochemical variables of Valencia sweet orange nursery trees grafted on drought-tolerant Rangpur lime (RL) and drought-sensitive Swingle citrumelo (SC) rootstocks in pots. Irrigation was withheld to potting mix water potential of −u200915 (mild RDI) and −u200925xa0kPa (moderate RDI), with daily irrigation as control, in three graft growth periods (20–60, 61–120, and 20–120 days after grafting, DAG). Plant growth was reduced by moderate RDI, albeit RL induced more vigor than SC. SC induced higher CO2 assimilation rates and water use efficiency (WUE), regardless of the irrigation regime, and only trees grafted on RL decreased WUE under moderate RDI. Most leaf nutrient concentrations were increased with RDI intensity, while K levels were decreased by moderate RDI. Starch reserves were drastically decreased, while reducing sugars were increased by RDI in all plant organs, most notably in the leaves; roots represented the main source of carbohydrates for both rootstocks under water deficit. Starch concentration promptly recovered in all organs after restoring irrigation. Leaf proline concentration was 20 times higher at RDI, but decreased by 50% just 1xa0day after rehydration. Mild-to-moderate RDI resulted in water savings of 54–80%, but a 0–40% reduction in the percentage of shippable trees at 120 DAG; the biological responses were mainly related to the RDI duration. The production of container-grown citrus nursery trees in greenhouses could greatly benefit from the use of RDI, without major negative effects on tree quality.

Susceptibility to clogging of different conventional drip irrigation system submitted the application of ferrous sulfate through irrigation water.

Objetivo-se com este experimento avaliar a susceptibilidade de diferentes tubos gotejadores convencionais ao entupimento por ferro soluvel na agua de irrigacao (sulfato de ferroso) via duas qualidades de agua (com e sem carga orgânica), solidos suspensos (solo) e solucao concentrada, com os emissores dos tubos gotejadores posicionados para baixo. O experimento foi realizado durante o periodo de 12 meses, com 7 modelos de tubos gotejadores. Os testes foram realizados em uma bancada de ensaios em estrutura metalica localizada no Laboratorio de Irrigacao, da Escola Superior de Agricultura “Luiz de Queiroz” - ESALQ/USP. A aplicacao de particulas de solo e elevado teor de ferro, sem passar por filtragem intensificaram o processo de entupimento. Os modelos B, F e G apresentaram entupimento total a partir das 1296, 792 e 1152 horas de funcionamento.

Distribution of solutes in soil columns with vinasse.

This study aimed to determine the retardation factors, diffusive-dispersive coefficients involved in the transport and distribution of vinasse effluent curves for the ions Calcium and Nitrate in soil columns. The Alfisol was collected in the rural municipality of Piracicaba-SP, soil samples were collected at 0-20 cm depth. For the manufacture of columns was used PVC tubing 25 cm long and 5 cm in diameter, wire mesh, and fast filter paper at one end, fastened by a cap bottomless PVC screw. The volumes of 10 mL were collected, defined in terms of pore volume and the amount required to be performed the analysis of chemical components NO3 and Ca. We used the computer program to calculate the DISP parameters of solute transport in soil miscible fluid displacement. The transport parameters showed the positive effects of adsorption and calcium ion present in the shift vinasse. For the nitrate ion, despite the breakthrough curve not have adjusted the parameters indicate low adsorption to soil may be moved to greater depths.

Drippers flow disturbances due to application of CO2 for irrigation water.

O presente trabalho avaliou a dinâmica do uso de CO 2 em gotejadores autocompensantes, com emissores posicionados tanto para baixo quanto para cima, observando a ocorrencia de histerese para curvas de vazao em funcao da pressao crescente e decrescente em diferentes modelos para diferentes concentracoes de CO 2 . O experimento foi conduzido em uma bancada de ensaios em estrutura metalica instalada no Laboratorio de Irrigacao do DER-ESALQ/USP, localizada no municipio de Piracicaba – SP. Utilizaram-se cinco modelos de gotejadores (M1 a M5) que foram expostos aos seguintes tratamentos: a) pressoes: 50, 100, 150, 200, 250, 300, 350 e 400 kPa; b) posicao dos emissores: para baixo e para cima; c) concentracao de CO 2 : zero, 50, 100, 200 e 400% da dissolucao maxima de CO 2 em agua. Foram observados altos valores de coeficiente de variacao de vazao quando se aplicou a concentracao 400% da dissolucao de CO 2 em agua.