Marginal increase in nitrate leaching under grass–clover leys by slurry and mineral fertilizer
Open accessAbstract
On dairy farms, fertilization of grass-clover swards ensures stable grass yields but may increase the potential for nitrate leaching on light-textured soils. The aim of this study was to quantify the N use efficiency and nitrate leaching under fertilized grass-clover leys. The study was conducted over 2 years at two sites, with increasing applications of mineral fertilizer (0–480 kg available N ha−1) alone or in combination with a basic application of cattle slurry. For plots fertilized with mineral N, the N soil surface balance was independent of the application rate and in the same range as for unfertilized plots (− 11 to 51 kg N ha−1). However, when plots were fertilized with slurry N (+ mineral N), the surplus was substantially increased owing to the fraction of organic N applied in slurry (95–100 kg N ha−1) and higher biological N 2 fixation inputs (55–228 kg N ha−1). The type of fertilizer had no effect on nitrate leaching across the full range of application rates. Nitrate leaching increased quadratically as a function of application rate, with a range of 3–117 kg N ha−1 (0.33–17 mg l−1 in soil solution sampled with suction cups) in the first year and less in the second year, when clover proportion was lower due to the self-regulatory nature of grass-clover mixtures. Importantly, the rate of marginal leaching increased with fertilization level: below 150 kg N ha−1 there was no additional leaching from fertilization and at 200 kg N ha−1 around 5% of additional fertilizer-N was leached. This is less than generally found for arable crops and thus even in intensive dairy systems, grass-clover leys are an environmentally favorable crop.
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N surpluses varied widely between treatments after the grassland phase.
“Since N surpluses varied widely between treatments after the grassland phase (Fontaine et al. 2024), some differences in the legacy effect of grass-clover swards were expected in the follow-on crop.”
From Cover crops and optimal N management reduce nitrate leaching to background levels in grass-clover–barley rotations on sandy soil (2026) · cites this paper as Fontaine et al. 2024
Treatments with combinations of organic and mineral N had considerable N surpluses, up to 167 and 320 kg N ha-1 in 1st year grass-clover at SW and MW, and up to 102 and 205 kg N ha-1 in 2nd year grass-clover.
“In particular, the treatments with combinations of organic and mineral N had considerable N surpluses (Fontaine et al. 2024), with up to 167 kg N ha -1 and 320 kg N ha -1 in 1 st year grass-clover at SW and MW, respectively, and up to 102 and 205 kg N ha -1 in 2nd year grassclover.”
From Cover crops and optimal N management reduce nitrate leaching to background levels in grass-clover–barley rotations on sandy soil (2026) · cites this paper as Fontaine et al. 2024
On average across the two years of grass-clover in 2018-19 and the two annual follow-on crops in 2020-21, only the SW site showed significant grassland fertilizer treatment effects on nitrate leaching (P = 0.0002).
“On average across the two years of grass-clover in 2018-19 (reported in Fontaine et al. 2024) and the two annual follow-on crops 2020-21 (Fig. 3), only the SW site showed significant grassland fertilizer treatment effects on nitrate leaching (P = 0.0002).”
From Cover crops and optimal N management reduce nitrate leaching to background levels in grass-clover–barley rotations on sandy soil (2026) · cites this paper as Fontaine et al. 2024
It is possible to reduce nitrate leaching even at moderately high fertilization levels of mineral N and combinations of mineral and organic N, according to this study and Fontaine et al. (2024), and thus not expected to affect grass-clover yields.
“This is possible even at moderately high fertilization levels of mineral N and combinations of mineral and organic N, according to this study and Fontaine et al. (2024) and thus not expected to affect grass-clover yields.”
From Cover crops and optimal N management reduce nitrate leaching to background levels in grass-clover–barley rotations on sandy soil (2026) · cites this paper as Fontaine et al. 2024
Cites
GRASSLAND MANAGEMENT AND CONVERSION INTO GRASSLAND: EFFECTS ON SOIL CARBON
Conant, R. T., Paustian, K., & Elliott, E. T. (2001) · Ecological Applications · doi:10.1890/1051-0761(2001)011[0343:gmacig]2.0.co;2 · Cited by 1,365 · see citing works
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Eriksen, J., Jensen, J. L., Larsen, S. U., Thers, H., & Vogeler, I. (2026) · Nutrient Cycling in Agroecosystems · doi:10.1007/s10705-026-10479-z
“Nitrate concentration was analyzed, and nitrate leaching was calculated as described by Fontaine et al. (2024).”
InfluentialSelf-citation
- Authors
- Fontaine, D., Rasmussen, J., & Eriksen, J.
- Affiliations
- Aarhus University (DK)
- Corresponding author
- Eriksen, Jørgen
- Venue
- Nutrient Cycling in Agroecosystems
- Published
- 2023-11-16
- Volume
- 128
- Issue
- 1
- Pages
- 1-12
- ISSN
- 1385-1314 (ISSN-L)
- 1573-0867
- OpenAlex
- W4388733178
- Cited by
- 6
- References
- 1
- Citations by year
- 2026: 3 · 2025: 1 · 2024: 2
- FWCI
- 0.52
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Locations
- Nutrient Cycling in Agroecosystems (publishedVersion, cc-by)
- Funders
- Innovationsfonden (6159-00001B)
- Grønt Udviklings- og Demonstrations Program (34009-19-1600)
- Royal Danish Library, Aarhus University Library
- Topics
- Physical Sciences › Environmental Science › Environmental Chemistry › Soil and Water Nutrient Dynamics
- Life Sciences › Agricultural and Biological Sciences › Forestry › Pasture and Agricultural Systems
- Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil Carbon and Nitrogen Dynamics
- Keywords
- nitrate leaching, grass-clover ley, cattle slurry, mineral fertilizers, nitrogen use efficiency, nitrogen fixation, light soils, dairy farming, soil solution nitrate
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