The legacy effect of synthetic N fertiliser

Cumulative crop recovery of synthetic fertiliser nitrogen (N) over several cropping seasons (legacy effect) generally receives limited attention. The increment in crop N uptake after the first-season uptake from fertiliser can be expressed as a fraction (∆RE) of the annual N application rate. This study aims to quantify ∆RE using data from nine long-term experiments (LTEs). As such, ∆RE is the difference between first season (RE1st) and long-term (RELT) recovery of synthetic fertiliser N. In this study, RE1st was assessed either by the 15N isotope method or by a zero-N subplot freshly superimposed on a long-term fertilised LTE treatment plot. RELT was calculated by comparing N uptake in the total aboveground crop biomass between a long-term fertilised and long-term control (zero-N) treatment. Using a mixed linear effect model, the effects of climate, crop type, experiment duration, average N rate, and soil clay content on ∆RE were evaluated. Because the experimental setup required for the calculation of ∆RE is relatively rare, only nine suitable LTEs were found. Across these nine LTEs in Europe and North America, the mean ∆RE was 24.4% (±12.0%, 95% CI) of annual N application, with higher values for winter wheat than for maize. This result shows that fertiliser-N retained in the soil and stubble may contribute substantially to crop N uptake in subsequent years. Our results suggest that an initial recovery of 43.8% (±11%, 95% CI) of N application may increase to around 66.0% (±15%, 95% CI) on average over time. Furthermore, we found that ∆RE was not clearly related to long-term changes in topsoil total N stock. Our findings show that the—often used—first-year recovery of synthetic fertiliser N application does not express the full effect of fertiliser application on crop nutrition. The fertiliser contribution to soil N supply should be accounted for when exploring future scenarios on N cycling, including crop N requirements and N balance schemes.

Bibliographic Details

Main Authors:	Vonk, W.J., Hijbeek, R., Glendining, M.J., Powlson, D., Bhogal, A., Merbach, I., Silva, J.V., Poffenbarger, H.J., Dhillon, J., Sieling, K., Berge, H.F.M. ten
Format:	Article biblioteca
Language:	English
Published:	Wiley-Blackwell Publishing Ltd 2022
Subjects:	AGRICULTURAL SCIENCES AND BIOTECHNOLOGY, 15-N, Cereal Production, Fertilizer Requirement, Nitrogen Recovery, Nitrogen Use Efficiency, Soil N Retention, Soil N Supply, Synthetic Fertilizer N, CEREALS, FERTILIZER APPLICATION, NITROGEN, STUBBLE, TOPSOIL, WHEAT, LONG TERM EXPERIMENTS,
Online Access:	https://hdl.handle.net/10883/22128
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