Maintaining pastures in spring, harrowing and over-seeding, helps to maintain a homogeneous cover. How and why should parcels be harrowed and overseeded?
In the spring, harrowing has an aerating effect, loosening up the soil. It levels off soil that has been trampled down in the winter and aerates areas that are waterlogged during the winter.
How to harrow
Good conditions
On short grass
A well-dried soil: the first few centimetres of soil are dry with no trace of moisture
Bad conditions
Soil too wet: risk of compacting the soil further rather than aerating it
Soil too dry: the harrow will bounce back without penetrating the soil
Vegetation is already high (>10 cm), the harrow drags and damages the plants
Under these conditions it is better not to harrow than to damage the field.
Why harrow at the end of winter?
To distribute the fertilising nutrients in the manure
To re-level trampled and uneven areas in order to limit damage to the horses’ limbs, especially foals.
To spread molehills.
Harrowing in the spring is not necessarily useful. It is necessary to prepare the surfaces to be harvested in the spring in order to reduce the accumulation of soil and dung when harvesting the forages.
Warning
Harrowing in the spring leads to spreading any parasite larvae contained in the manure.
Harrowing does not improve the productivity of a field or its mineralisation. Mineralisation consists of transforming organic matter into elements which fertilise the plant. Ref: Arvalis study (Institut du Végétal)
Overseeding
This technique consists of resowing grassy species on areas devoid of vegetation (the entrance to fields, areas which are excessively trampled on in winter).
It helps to preserve the load-bearing capacity of the soil (the soil’s ability to resist the weight of the animals).
It avoids bare ground being overtaken by weeds, especially those resistant to trampling (plantain, etc.) that are not consumed by animals.
It avoids the maintenance of bare soil areas conducive to the spread of disease-causing spores (rhodococcosis)
How?
Conditions
Overseed when temperatures (no risk of frost) and humidity are favourable for germination.
Any remaining plant cover in the area to be sown should be short.
If the surface is overgrown with self-propagating plants (weeds) it is possible to treat with a herbicide beforehand. Be careful, this type of treatment will also destroy any leguminous plants, such as clover.
Use a seed drill (e.g. fertiliser drill) or broadcast sow by hand. Seeding can also be supplemented by adding soil improvers (phosphorus and potash).
Do not apply nitrogen during seeding.
Roll the soil to encourage contact between the seeds and the soil or bring the horses into the parcel. Their hooves will do this work for you, in load-bearing soil conditions. This encourages tillering (the growth of new shoots at the base of the plant).
Species to be sown
Choose fast-growing, so-called “aggressive” plant species such as Ray-Grass (perennial, hybrid or Italian) and white or purple clover. However, these are short lived (2-3 years). Avoid fescue and dactyl.
Sowing density
5-10 g/m2 for small surface areas
25-30 kg/Ha for larger surface areas
Cost
€150 to €180/Ha
Maintenance operations must be carried out regularly to maintain a firm plant cover and thus limit bare soil.
Know more about our authors
Translated from french by : Alison DRUMMOND Translator
Pauline DOLIGEZ Development engineer IFCE
Bibliography
Guide pour un diagnostic prairial, Chambres d'Agriculture Maine et Loire et Mayenne
