Acúmulo de nutrientes e resposta da alface à adubação fosfatada

Abstract

RESUMO O objetivo deste trabalho foi determinar a curva de acúmulo de nutrientes pela planta de alface destinada à produção de sementes. O experimento foi conduzido na Fazenda Experimental São Manuel, pertencente à Faculdade de Ciências Agronômicas da Universidade Estadual Paulista, no período de 25/09/03 a 19/02/04. O delineamento experimental utilizado foi em blocos ao acaso com cinco repetições e seis tratamentos (épocas de coleta das plantas: 0, 20, 34, 49, 69 e 112 dias após o transplante (DAT)). Foi utilizada a alface crespa cultivar Verônica, sendo avaliados o acúmulo da massa seca e de N, P, K, Ca, Mg, S, B, Cu, Fe, Mn e Zn na parte aérea das plantas. O maior incremento da massa seca das plantas ocorreu após o ponto comercial (34 DAT). O período de maior demanda de macronutrientes foi entre o início do pendoamento e o início do florescimento. Observa-se que para a maioria dos micronutrientes o período de maior exigência foi após o início do florescimento. A ordem decrescente de acúmulo de nutrientes foi: K>N>Ca>Mg>P>S>Fe>Mn>Zn>B>Cu. Palavras-chave: Lactuca sativa, nutriente, demanda nutricional. ABSTRACT Nutrients uptake by lettuce plants for seed production The nutrients uptake curve of lettuce plants for seed production was evaluated. The experiment was carried out from September 2003 to February 2004 at the Faculdade de Ciências Agronômicas of the Universidade Estadual Paulista, in Botucatu, São Paulo State, Brazil. A randomized block design was used, with five replicates and six treatments (periods of plant collection: 0, 20, 34, 49, 69 and 112 days after transplant (DAT)). We utilized the Verônica lettuce cultivar and evaluated the dry mass and the N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn accumulated in the aboveground part of the plants. The greatest increase in the plant dry matter occurred after the marketable point (34 DAT). The period of greatest demand for nutrients was between the beginning of the stem elongation stage and the beginning of the flowering stage. We also observed that for most micronutrients the period of highest demand was after the beginning of the flowering stage. nutrients accumulation in descending order was: K>N>Ca>Mg>P>S>Fe>Mn>Zn>B>Cu.

Effect of different substrates in aquaponic lettuce production associated with intensive tilapia farming with water recirculation systems

“…KANO et al (2012) found similar results with conventional soil system with Ca concentrations ranging from Effect of different substrates in aquaponic lettuce production associated with intensive tilapia farming ALMEIDA et al (2011) reported lower Ca concentrations in hydroponics compared to this work, with concentrations ranging from 3.6 to 12,1g kg -1 .…”

“…However, they showed no visible deficiency symptoms. KANO et al (2012) found similar results, in conventional soil system, with Mg concentrations between 3.1 to 3.6 g kg -1 , below the recommended by RAIJ et al (1996). In hydroponic culture, ALMEIDA et al (2011) also found concentrations below the appropriate, with Mg concentrations between 0.7 and 5.5 g kg -1 .…”

“…Using the cultivar Veronica in conventional system with soil, SFM and SDM of 166 g plant -1 and 11 g plant -1 were found, respectively (KANO et al, 2012), better results than the ones reported in this study. However, values similar to those seen in this study are also reported in conventional cultivation with soil SFM and SDM of 90.30 g plant -1 and 4.86 g plant -1 were found, respectively (DUARTE et al, 2012).…”

“…MARTINS et al (2009), who making a nutrient absorption curve in hydroponic lettuce obtained P concentration of 5.8 g kg -1 , being similar to our results. Moreover, KANO et al (2012) who in conventional soil cultivation found values ranging from 2.1 to 5.0 g kg -1 .…”

“…According to RAIJ et al (1996), foliar nitrogen and potassium levels were adequate for both treatments, as they were within the range between 30 and 50 g kg -1 of N and 50 to 80 g kg -1 of K. KANO et al (2012) obtained similar results, using conventional soil system these authors reported concentrations ranging from 32 to 37 g kg -1 of N and 57 to 62 g kg -1 of K. However, ALMEIDA et al (2011) obtained reduced concentrations of N in hydroponics compared to this work, with N concentrations ranging from 9.5 to 23.2 g kg -1 and K concentrations ranging from 3.2 to 58.9 g kg -1 .…”