Strategic timing of nitrogen fertilization to increase root biomass and nitrogen-use efficiency of Lolium perenne L.

H.C De Boer,N Van Eekeren,J.G.C Deru,N.J Hoekstra

doi:10.1007/s11104-016-2917-y

Abstract

Aims: During the first days after harvest of Lolium perenne L., N remobilized from roots and stubble forms the main N source for regrowth. Low N uptake from the soil during this period may lead to N loss if N fertilizer is applied too soon. Furthermore, temporary N deprivation has been found to stimulate root growth. We therefore hypothesized that a strategic delay in N application after harvest may improve N-use efficiency of L. perenne grassland by increasing root biomass and reducing N loss. Methods: In a laboratory and field experiment with L. perenne, we delayed N fertilizer application after harvest for 0, 3, 6, 9 and 12 days, repeated this for up to six harvest cycles, and determined effects on herbage yield, herbage N uptake and root biomass. Results: In both experiments, delaying N application for up to 12 days had no significant effect on root biomass or total herbage N uptake, but it significantly reduced total herbage yield in the laboratory experiment. Total yield tended to be highest when N application was delayed for 3 days. Two growth periods in the field experiment showed significantly higher N uptake when N application was delayed, possibly due to rainfall-induced N losses in the treatments with shorter delay. Conclusions: Our results do not provide evidence that delaying N application improves N-use efficiency of L. perenne grassland by increasing root biomass. However, strategic timing of N fertilizer application based on rainfall forecasts could contribute to improve N-use efficiency by reducing N losses from leaching and denitrification.

Highlights

Root characteristics, such as rooting density and rooting depth, play a critical role in the interception and uptake of nitrogen (N) by plants, including grasses (Atkinson et al 2005)
Strategic timing of N fertilizer application based on rainfall forecasts could contribute to improve N-use efficiency by reducing N losses from leaching and denitrification
Neither in the laboratory nor the field experiment a significant effect on root biomass in the deepest soil layer (30–40 cm) was detected, suggesting that delaying N application had no effect on rooting depth

Summary

Introduction

Root characteristics, such as rooting density and rooting depth, play a critical role in the interception and uptake of nitrogen (N) by plants, including grasses (Atkinson et al 2005). The N-use efficiency of inorganic fertilizers on grassland is generally assumed to be 80–100 % (www.rvo.nl) ; in reality it is often as low as 60 to 65 % on sandy soils (Schröder et al 2007; van Eekeren et al 2010a). This means that up to 40 % of applied fertilizer N can be lost. De Klein and van Logtestijn (1994) reported that denitrification losses strongly increased when fertilizer was applied on a wet soil, ranging between 6 and 9 % of N applied

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Discussion

Conclusion