Effects of timing of nitrogen fertilizer application on responses by tropical grasses

Carlos E A Cabral,Aline M Motta,Carla H A Cabral,Alyce R M Santos,Fagner J Gomes,Bruno C Pedreira

doi:10.17138/tgft(9)182-191

Abstract

Timing of nitrogen (N) fertilizer application can influence grass regrowth, so it is important to identify how tropical grasses respond to delays in applying fertilizer after defoliation. Our objective was to identify the effects of timing of N fertilizer application after harvest on the productive, morphogenic and structural characteristics of 3 tropical grasses: ‘Xaraés’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Xaraés), ‘Marandu’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Marandu) and ‘Tanzânia’ (Megathyrsus maximus [Jacq.] cv. Tanzânia). The experiments were performed in a greenhouse, in a completely randomized design, with 5 delays in applying N after harvesting (0, 3, 6, 9 and 12 days). Delaying fertilizer application did not affect the forage mass of Xaraés and Marandu palisade grass (7.4 and 7.8 g/pot, respectively). There was a linear decrease in number of leaves per tiller and leaf appearance rate, but tiller population density and phyllochron increased linearly as fertilizer application was delayed. Grass forage mass (12.2‒10.6 g/pot), number of leaves per tiller (3.1‒2.6 leaves/tiller) and forage accumulation rate (0.47 to 0.41 g DM/d) of Tanzânia guinea decreased linearly as N application was delayed, but tiller population density was unaffected (25 tillers/pot). Based on our results, N fertilizer should be applied to Tanzânia guinea grass pastures as soon as possible after harvest and certainly before 3 days, while there is not the same urgency with Xaraés and Marandu where fertilization could be delayed up to 12 days without significant detriment. These suggestions need to be tested in a field study before being recommended widely.

Highlights

Grasslands are among the most abundant ecosystems in the world (Hewins et al 2018), where livestock production occurs in areas with native or exotic grasses
There was a linear decrease in number of leaves per tiller and leaf appearance rate, but tiller population density and phyllochron increased linearly as fertilizer application was delayed
While Individual tiller mass (ITM) in Xaraés showed a quadratic effect, with a lesser value for the 9 days delay in applying N after harvest, linear effects were observed with TPD for Xaraés and Marandu and number of leaves per tiller (NLT) and ITM for Marandu

Summary

Introduction

Grasslands are among the most abundant ecosystems in the world (Hewins et al 2018), where livestock production occurs in areas with native or exotic grasses. Periodic soil nutrient replacement is important, especially in intensified systems with high stocking rate, (Bourscheidt et al 2019) which is commonly a combination of intermittent stocking management and a grass with high potential production. Fertilizer application becomes an essential practice, especially when pastures have been established in infertile soils, such as the Oxisols (Chaves et al 2017). The N requirement of grass is greater than that of other nutrients, so applying N fertilizer should be given priority to maintain pasture productivity and persistence (Rosado et al 2017)

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Conclusion