Grassland Reseeding: Impact on Soil Surface Nutrient Accumulation and Using LiDAR-Based Image Differencing to Infer Implications for Water Quality
Date
2022-11-04
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Publisher
MDPI
Abstract
Long-term phosphorus (P) accumulation in agricultural soils presents a challenge for water
quality improvement. P is commonly elevated in soils managed for intensive livestock production
due to repeated overapplication of slurry and fertilisers. High legacy nutrient accumulations result
in poor water quality via transport pathways such as surface runoff, subsurface drainage, and
soil erosion. To achieve environmental water quality targets, improved management strategies
are required for targeting and reducing excess agricultural P sources. Reseeding of old swards is
known to improve grassland productivity and enhance overall soil health. However, soil disturbance
associated with reseeding could have positive and negative impacts on other soil functions that
affect the nutrient balance (including improved microbial activity, but also increasing the potential
for sediment and nutrient losses). This study investigates the impact of reseeding and inversion
tillage in addressing soil surface nutrient surpluses and identifies potential trade-offs between
production, environment (through soil erosion and associated sediment and nutrient losses), and
soil health. At a study site in the Blackwater catchment in Northern Ireland, we collected highresolution
(35 m) gridded soil samples pre- and post-reseeding for nutrient analyses and combined
this with GIS-based interpolation. We found that decreases in sub-field scale surface nutrient content
(0–7.5 cm depth) occurred following tillage and reseeding, but that this was spatially variable. In
addition, the magnitude of changes in nutrient content was variable between P and other sampled
nutrients. LiDAR-based image differencing indicated variability in the magnitude of soil erosion
and sediment loss also at sub-field scale. Information on the identified deposition and erosion zones
(from LiDAR analysis) was combined with mass wasting data to determine accumulation rates and
losses of nutrients in-field and confirmed some of the identified patterns in soil surface nutrient
content changes post-reseeding. We conclude that while inversion tillage and reseeding are essential
agricultural practices, environmental trade-offs exist through potential nutrient and sediment losses.
LiDAR-based image differencing was found to be a useful tool in helping to quantify these risks.
Quantifying sediment and nutrient losses as a result of inversion tillage and reseeding induced soil
erosion aids in understanding potential trends in water quality statuses.
Description
Publication history: Accepted - 2 November 2022; Published - 4 November 2022.
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Article
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Keywords
reseeding, soil erosion, sediment, phosphorus, water quality, LiDAR
Citation
Hayes, E., Higgins, S., Geris, J. and Mullan, D. (2022) ‘Grassland Reseeding: Impact on Soil Surface Nutrient Accumulation and Using LiDAR-Based Image Differencing to Infer Implications for Water Quality’, Agriculture. MDPI AG. Available at: https://doi.org/10.3390/agriculture12111854.