Absorção de nutrientes pela cultura do arroz

Abstract

Com a finalidade de determinar a marcha da absorção dos nutrientes essenciais pela cultura do arroz (Oryza sativa L.). conduziu-se um ensaio em casa de vegetação, em vasos de Mitscherlich. Cada 10 dias, colhiam-se plantas, para análise de N, P, K, Ca e Mg. Verificou-se que, para a produção de 4.300 kg de grãos em casca e 39.350 kg de palha e raízes por hectare, seriam absorvidos 115 kg de N, 18,5 kg de P, 142 kg de K, 35 kg de Ca e 36 kg de Mg. O nitrogênio e o potássio foram, na totalidade, absorvidos até 110 dias da germinação. O fósforo, o cálcio e o magnésio foram requeridos igualmente pela cultura, em todo o ciclo.

Macronutrient Uptake and Removal by Upland Rice Cultivars with Different Plant Architecture

“…The maximum accumulation of N in the shoots was later and occurred from 95 to 110 DAE, but with the maximum uptake rates occurring after 65 DAE (Figures 2d and 2f). Gargantini and Blanco (1965) also observed that the maximum accumulation of N in the rice shoots occurred at around 110 DAE. Phosphorus was the only nutrient to be accumulated at an increased rate in the shoots up to the end of the cycle, which shows that its uptake occurred practically throughout the crop cycle (Figure 3d), which was also observed by Gargantini and Blanco (1965).…”

“…Gargantini and Blanco (1965) also observed that the maximum accumulation of N in the rice shoots occurred at around 110 DAE. Phosphorus was the only nutrient to be accumulated at an increased rate in the shoots up to the end of the cycle, which shows that its uptake occurred practically throughout the crop cycle (Figure 3d), which was also observed by Gargantini and Blanco (1965). Nevertheless, there are periods in the cycle in which the cultivars take up P at higher rates, as may be seen in the high P uptake rates of the BRS Primavera cultivar at 70 DAE and of the cultivars Caiapó and Maravilha after 90 DAE (Figure 3f).…”

“…This shows that approximately half of the N, and most of the K, Ca, Mg, and S accumulated in plants during the cycle return to the soil with crop residues, reducing nutrient exhaustion; however, less than 30 % of the P taken up remains in the crop residues. Phosphorus is the nutrient that accumulates in the greatest proportions in the grains of the rice plant, whereas most of the N, K, Ca, and Mg return to the soil with the straw (Gargantini and Blanco, 1965). It should be noted that the BRS Primavera cultivar of the intermediate group removed relatively greater proportions of nutrients than the other cultivars, since it is higher yielding and accumulates greater amounts of macronutrients in the panicles (Table 1).…”

“…The rice plant is quite demanding of nutrients and, to avoid the limitation of grain yield, these nutrients need to be readily available at the times of greatest plant demand (Fidelis et al, 2012). The quantity of nutrients taken up and especially the time periods of greatest uptake are factors that must be considered in carrying out fertilization (Gargantini and Blanco, 1965). Studies indicate that the uptake and adequate use of nutrients by rice plants also depend on the physiological processes inherent to the cultivars used (Fageria et al, 1995a), which, depending on the type of plant, may exhibit expressive differences in biomass production and grain yield (Guimarães et al, 2008;Alvarez et al, 2012).…”

Influência de lâminas de água e adubação mineral na nutrição e produtividade de arroz de terras altas

“…Independentemente dos tratamentos utilizados, o cultivar IAC 201 apresentou, nos dois anos de cultivo, a seguinte ordem decrescente de exigência de macronutrientes no período de florescimento: N > K > Ca > Mg > P > S, bastante semelhante à observada por Gargantini & Blanco (1965), N > K > Ca > Mg > P, e diferente das seqüências relatadas por Fageria et al (1997) Crusciol et al (1999), para o cultivar IAC 201 no sistema de sequeiro, N > K > Mg > Ca > P > S.…”