The Influence of Nitrogen Fertilization on Growth, Yield and Nitrate and Oxalic Acid Concentration in Purslane (Portulaca oleracea)

Abstract Culinary use of purslane (Portulaca oleracea L.) is appreciated across the whole of the Mediterranean, and the interest in this plant has been increasing due to be a source of bio-protectives compounds, such as fatty acids and antioxidants. However, their use may be difficult due to the accumulation of high contents of compounds harmful to human health, such as nitrate and oxalic acid. The main objective of the present study was to evaluate the influence of nitrogen fertilization on growth and yield parameters, and on nitrate and oxalic acid concentration in leaves and stems. Plants of golden-leafed purslane of sativa subspecies were grown in styrofoam boxes with substrate and fertigated 2 times per week along 4 weeks with ammonium-nitrate solution (16.9% NO3--N and 17.6% NH4+-N), for testing 4 nitrogen levels (0, 30, 60 and 90 kg N ha-1). Plant growth, yield, nitrate and oxalic acid concentrations were significantly affected by nitrogen application. The best quantity/quality ratio was achieved in fertilization level of 60 kg N ha-1, in which the yield was 5.1 kg m-2 FW and nitrate concentration was 48.98 and 43.90 mg g-1 DW in leaf and stem, respectively, and oxalic acid concentration was 1.27 and 0.55 mg g-1 DW, in leaf and stem, respectively, values not harmful to consumer health

Desenvolvimento, Produtividade E Atributos Qualitativos De Cultivares De Cana-de-açúcar Fertirrigadas Por Gotejamento Subsuperficial

The present study aimed to evaluate the development, yield and quality of four sugarcane cultivars fertigated by subsurface drip system. The experiment was carried out in Campinas-SP, Brazil, from January 2012 to November 2013, with the cultivars SP79-1011, IACSP94-2101, IACSP94-2094 and IACSP95-5000 subjected to daily irrigations. The irrigations depths were applied to bring soil moisture to field capacity. Soil moisture was monitored using soil moisture probes. Samples were collected along the crop cycle in order to evaluate crop development and yield, at the end of the first and second ratoons. Stalk height showed good correlation for the estimation of crop yield, with R2 equal to or higher than 0.96. The cultivar IACSP95-5000 showed the highest yield in the first ratoon. In the second ratoon the highest yield was observed in IACSP94-2101, followed by IACSP95-5000 and SP79-1011. Considering the yield results associated with the technological analysis, such as soluble solids content and apparent sucrose, the cultivar IACSP95-5000 excelled the others in the cultivation under subsurface drip irrigation. © 2016, Departamento de Engenharia Agricola - UFCG/Cnpq. All rights reserved.20652553

Time-Fractional KdV Equation: Formulation and Solution using Variational Methods

In this work, the semi-inverse method has been used to derive the Lagrangian of the Korteweg-de Vries (KdV) equation. Then, the time operator of the Lagrangian of the KdV equation has been transformed into fractional domain in terms of the left-Riemann-Liouville fractional differential operator. The variational of the functional of this Lagrangian leads neatly to Euler-Lagrange equation. Via Agrawal's method, one can easily derive the time-fractional KdV equation from this Euler-Lagrange equation. Remarkably, the time-fractional term in the resulting KdV equation is obtained in Riesz fractional derivative in a direct manner. As a second step, the derived time-fractional KdV equation is solved using He's variational-iteration method. The calculations are carried out using initial condition depends on the nonlinear and dispersion coefficients of the KdV equation. We remark that more pronounced effects and deeper insight into the formation and properties of the resulting solitary wave by additionally considering the fractional order derivative beside the nonlinearity and dispersion terms.Comment: The paper has been rewritten, 12 pages, 3 figure