Cover crop reference values : Effective organic matter and nitrogen uptake

Abstract

Cover crop reference values Slim Landgebruik 2 Colofon Dit onderzoek is uitgevoerd door de Stichting Wageningen Research (WR), business unit Open Teelten met subsidie van het ministerie van Landbouw, Natuur en Voedselkwaliteit, in het kader van het Beleidsondersteunend Programma Slim Landgebruik (BO-53-002) en de PPS Beter Bodembeheer (TKI-AF-16064/BO-56-001-005) .

Reference values for arable crop residues : Organic matter and C:N ratio

“…This might indicate that a conversion is needed from the lab environment to the field environment. The values of this experiment are also generally higher than those found by Selin-Noren et al (2021), which can possibly be explained by that these crop residues come from more mature plant material than most green manure crops, and is therefore likely to have a higher lignin content and hence a slower decomposition (Stewart et al, 2015). Another possible explanation for high HC's, is the amount of organic matter input that is incubated, as this can have a large effect on the decomposition speed, due to influences from physical protection and priming effects (Shahbaz et al, 2016).…”

“…A similarly large variation is also found in other studies where the same methodology is applied (Rietra et al, 2019). As was also found in the incubation experiments of Selin Noren et al (2021), the difference in HC between aboveground and belowground biomass (0.44 and 0.42, respectively, in the study of Selin Noren et al ( 2021)) is smaller than the difference between the current reference values of the two (0.2 and 0.35, respectively). However, known theory and literature sources conclude that belowground biomass have slower decomposition than aboveground biomass, and is hence expected to have a higher HC (Shahbaz, 2016;Katterer et al, 2011).…”

“…However, there are also studies showing that amount does not have an influence on the HC, using this method (Rietra et al, in press). In this experiment, the amount of C added was around 40% higher than in the experiments of Selin Noren et al (2021). The precise relationship between the amount of organic matter added and the decomposition speed is currently not clear, to the best of our knowing.…”

Options to improve the nitrogen use efficiency in the Dutch agriculture sector

“…They estimated that cover crops could be grown on an additional 150 kha. On average 2 ton carbon from the cover crops would be added to the soil (Selin Norén et al, 2021). Assuming an average CN ratio of 25, about 80 kg N is being sequestered in the plant material as well.…”