Grass / vegetate the edges of watercourses
Establish grass strips, or maintain spontaneous vegetation, over a width of 5 to 10 m along watercourses. In case of planting one or more species in mixture, species with rapid start and good longevity should be favored. Sowing should take place during periods of strong growth (spring, late summer) to promote rapid soil cover and limit invasion by undesirable weeds.
Technique characterization
Maintenance consists of one to two passes per year (mowing or cutting) aimed at preventing seed setting of present species and contamination of the adjacent plot. Mowing/cutting is prohibited between May 1 and July 15 for 40 consecutive days defined by prefectural order. The spreading of fertilizers and phytosanitary products is also prohibited.
Example of implementation : The establishment of a grass strip of white clover / ryegrass twice the width of the equipment park (6 or 8 meters) represents a cost of €17 to €25 per 100 linear meters, including one to two stubble cultivations for soil preparation, an additional pass aimed at reducing the seed bank of undesirable weeds, and sowing in one to two passes (breaking down sowing into one pass per species helps promote cover uniformity). Maintenance cost (2 mowings per year) is about €7-8 per 100 linear meters. The longevity of the grass strip can reach 4 years.
Implementation period On established crop
The life cycle of a grass strip is disconnected from the cycle of cultivated species.
Spatial scale of implementation Plot
Grassing a watercourse edge is done at the plot scale, but the entire watershed (angle and slope length) must be considered to define the width of the area to be grassed.
Regulations
POSITIVE influence
Since 2010, the BCAE water protection and water management standard requires the establishment of grass strips with a minimum width of 5 meters along all eligible watercourses. The grass strip must be in place from May 1 to August 31, comply with the list of authorized covers (defined by prefectural orders), and maintenance conditions (no spreading of fertilizers, phytosanitary products, no equipment storage, no mowing/cutting during the prohibited period...).
These regulatory constraints can be strengthened in vulnerable zone by departmental action plans which may notably extend the minimum width of the grass strip to 10 or 15 meters in the concerned perimeters.
BCAE water protection and management
Nitrate directive
Effects on the sustainability of the cropping system
"Environmental" criteria
Effect on air quality : Variable
GHG emission : VARIABLE
Effect on water quality : Increasing
N.P. : DECREASE
pesticides : DECREASE
Effect on fossil resource consumption : Variable
fossil energy consumption : VARIABLE
Other : No effect (neutral)
Air : Grassing or vegetating watercourse edges involves fuel consumption, thus greenhouse gas emissions for maintenance, or even establishment in case of sowing. From this fuel consumption must be deducted the amount that would have been consumed for cultivating the buffer zone. Carbon storage by vegetation on grass strips also reduces GHG emissions at the plot scale.
Water : Grassing or vegetating reduces transfers of phytosanitary products, phosphorus and nitrogen to water by limiting atmospheric drift risks and promoting water infiltration.
Fossil energy : Grassing or vegetating watercourse edges involves fuel consumption for maintenance, or even establishment in case of sowing. From this fuel consumption must be deducted the amount that would have been consumed for cultivating the buffer zone.
"Agronomic" criteria
Productivity : No effect (neutral)
The presence of grass strips has a favorable effect on the average yield of the plot by mitigating the "edge effect". However, the reduction in cultivated area implies a decrease in production.
Functional Biodiversity : Increasing
Grass or vegetated strips along watercourses provide favorable cover for epigeal fauna (insects, birds, mammals…) as well as soil fauna.
"Economic" criteria
Operational costs : Variable
Maintaining spontaneous vegetation along watercourses incurs no planting costs. Establishing a grass strip involves seed purchase costs below €5 per 100 linear meters. But operational costs related to cash crops are proportionally reduced by the grassed or vegetated area along watercourses.
Mechanization costs : Variable
Grassing or vegetating watercourse edges involves mechanization costs related to maintenance (€7 to €8 per year per 100 linear meters) and possibly establishment (€15-20 per 100 linear meters). But mechanization costs related to cash crops are proportionally reduced by the grassed or vegetated area along watercourses.
Margin : Decreasing
Grass or vegetated strips along watercourses are areas generating no income but may involve costs for establishment or maintenance. However, the average yield of the plot may improve by mitigating the edge effect.
"Social" criteria
Working time : Increasing
Even if grass or vegetated strips along watercourses reduce areas devoted to cash crops, thus the associated workload, they involve other tasks (establishment, maintenance) consuming mechanization time (20 minutes for establishing 100 linear meters and 10 minutes for annual maintenance of 100 linear meters).
Establishing and maintaining grass strips along watercourses involves additional workload. However, the presence of these strips can facilitate end-of-field maneuvers and thus improve work rate of interventions on the cultivated plot.
Observation time : Increasing
Establishing grass or vegetated strips along watercourses may require additional observation time for species choice or management of existing flora.
For more information
- Management and practices : a range of techniques serving biodiversity
- -Maillet-Mezeray J. (arvalis)
Agricultural Perspectives No. 360, pp. 34-42, Press article, 2009
- Grass strips
- -CRA Centre
IBIS Project, Technical brochure, 2010
- Diffuse pollution : Tools to maximize buffer zone efficiency
- -Le Hénaff G., Gril J.J. (Cemagref)
Agricultural Perspectives No. 379, pp. 38-42, Press article, 2011
| Etienne Gaujour | AgroSup Dijon | e.gaujour(at)agrosupdijon.fr | Dijon (21) |
|---|---|---|---|
| Florian Celette | ISARA | fcelette(at)isara.fr | Lyon (69) |
| Rémy Ballot | INRA | remy.ballot(at)grignon.inra.fr | Grignon (78) |
