Estado nutricional do arroz cultivado em diferentes épocas e adubações sob cobertura morta

Abstract

Com o objetivo de se avaliar o efeito de épocas de plantio e da adubação sobre o estado nutricional do arroz (Oryza sativa L. variedade "Maravilha") no final do ciclo, conduziu-se um experimento no município de Igarapé-Açu, Pará, num Latossolo Amarelo coeso típico. Testaram-se quatro épocas de plantio e duas adubações, com delineamento experimental em blocos ao acaso, com parcelas subdivididas. A avaliação do estado nutricional foi feita na palhada e nos grãos. As maiores concentrações de N, P, Ca, B e Cu, foram observadas nos grãos e as maiores concentrações de K, Mg, S, Fe, Mn e Zn, na matéria seca das plantas. As concentrações dos nutrientes foram afetadas significativamente pelas épocas de plantio 1 e 2, sem que este fato impedisse a observação de concentrações consideradas adequadas nas plantas e grãos. A adubação com mais P promoveu significativos aumentos nos teores de Cu e Zn na planta, e de P, K, Ca e Zn nos grãos. Ocorreu interação significativa entre as épocas de plantio e adubações, apenas para as concentrações de Cu na planta e de Ca e Zn nos grãos. No período de maior precipitação observaram-se as maiores concentrações de P e micronutrientes nas plantas.

Absorption of macronutrients by cassava in different harvest dates and dosages of nitrogen

“…Results for leaf N levels below such sufficiency standard level were observed by Parry et al (2005). It is possible that the sufficiency level indicated in literature is vulnerable to environmental conditions and cultivars.…”

“…Studies conducted by Parry et al (2005) in cassava subjected to two P dosages and four planting periods found that dosages and planting times had influence on the leaf P content, with concentrations ranging from 2.2 to 3.1 g kg -1…”

“…Leaf K concentration in Aciolina cultivar was maintained within the sufficiency range established by Raij (2011), of 10 to 20 g kg -1 , 120 DAE, as well as, on the other dates of assessment and for N dosages, except for the N dosage of 0 kg ha -1 at 300 DAE. The planting dates and P dosages affected the leaf K contents in the cassava cultivar Olho Verde, with concentrations varying from 15.3 to 21.3 g kg -1 (PARRY et al, 2005). Studies conducted by Rodríguez et al (2009) on the high plains of Maracaibo, Venezuela, on cultivar Tempranita, showed that the leaf was the part of the plant with the Absorption of macronutrients by cassava in different harvest dates and dosages of nitrogen Table 2 -N, P, K, Ca and Mg contents in the leaves 120 DAE and roots production 300 DAE, for Aciolina cassava, with different N dosages 1/ Estimated contents based on regression equations (Figures 2a -2g) for the 120 DAE assessment time;…”

“…Parry et al (2005), when assessing the plants' nutritional status at different times and subjected to leaf litter coverage and fertilization, found the following descending order of accumulation: K>N>Ca>Mg>P>S>Cu>Fe>Mn>Zn>B.…”

Micronutrient and Silicon Uptake and Removal by Upland Rice Cultivars with Different Plant Architecture

“…In a study carried out in pots, the cultivars BRSGO Guara and Talento had the same order of micronutrient uptake presented by the cultivars Caiapó and Maravilha (Fageria and Santos, 2013;Fageria and Knupp, 2013). However, other authors also observed a greater uptake of Mn than Fe by some rice cultivars (Fageria, 2004;Parry et al, 2005).…”