Accumulation and partition of macronutrients in Pennisetum purpureum cv. Roxo managed under different growth ages and seasons

Theyson Duarte Maranhão,Wesley Do Nascimento Sousa,Ismail Soares,Magno José Duarte Cândido,Marcos Neves Lopes,Gabriela Florencio Lacerda,Roberto Cláudio Fernandes Franco Pompeu,Rafael Rodrigues Da Silva

doi:10.1590/s1519-99402018000300001

Abstract

SUMMARY The objective of this study was to evaluate the macronutrient accumulations in leaf, stem, and shoot of elephant grass cv. Roxo. The treatments consisted of seven growth ages (9, 18, 27, 36, 45, 54, and 63 days) and three growing seasons (rainy, transition, and dry). A completely randomized design and a split-plot time arrangement were used, where the ages were the plots and the seasons the subplots, with three replications. Interaction between the factors age and season of cultivation for the contents and the daily accumulation rates of N, P, K, Ca, Mg, and S in leaf, stem, and shoot fractions were calculated. The margins of daily accumulation of nutrients N, P, K, Mg, and S presented positive linear behavior in all seasons studied; however, with variation in the magnitude of the response between them. The daily accumulation rate of Ca in the canopy was adjusted to a linear model for the rainy and dry seasons and to a quadratic model for the transition season, reaching a maximum of 4.60 kg ha-1 at 59.76 days of growth. The accumulation of nutrients in elephant grass cv. Roxo showed the following decreasing order: K > N > P > Mg > Ca > S in the rainy and transition seasons, while in the dry season the following decreasing order was observed: K > P > N > Ca > Mg > S.

Highlights

An efficient management of fertilization requires knowledge of nutrient accumulation (ECHER et al, 2009)
Yields of 11,869.26, 5,550.23, and 2,692.68 kg ha-1 were estimated at age 63 days after cutting (DAC) in the rainy, transition, and dry seasons, respectively
It is worth noting that the forage was managed only up to 63 days of age in order to match the productivity and quality of the biomass produced, since harvest at later ages leads to qualitative reduction of the forage due to a lower leaf/stem ratio, an increase in the rumen undegradable fiber fraction, and a reduction in the crude protein of the forage (BHERING et al, 2008; LOPES et al, 2013a)

Summary

Introduction

An efficient management of fertilization requires knowledge of nutrient accumulation (ECHER et al, 2009). Most studies on nutrient accumulation are carried out in intensive irrigation systems, making it difficult to extend the results to plants managed on dry lands. It is worth mentioning the scarcity of studies on the partition of nutrients in forage plants. The demand for research on nutrient accumulation in tropical regions is explicit, considering the variation of rainfall, in particular regarding the requirements of macronutrients by elephant grass cv. It is worth noting that studies of this nature make it possible to generate predictive models of macronutrient accumulation by elephant grass under dry conditions. Roxo managed at different ages and seasons of growth under waterless conditions

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Conclusion