Direct sowing
The "nature" seeding, called "aerial seeding" in Argentina, consists of depositing seeds on the surface in a cover crop or in an existing crop. It is a particular type of broadcast seeding without soil tillage. The approach seems simple, economical, and fast but remains opportunistic and requires specific conditions to ensure good plant development.
Presentation
Argentinians are accustomed to depositing forage seeds by plane or with a pneumatic fertilizer spreader, in corn or soybean in the maturation phase to establish forage crops used to feed livestock. The seed arrives on the ground through the air, as often happens in nature.
Benefits
The technique mimics nature: when plants develop their seeds, they fall to the ground and germinate.
- Time saving: The main advantage is to be able to establish a crop or a cover crop in advance compared to post-harvest seeding:
- Establishment of a multi-species cover crop in a cereal 1 month before harvest.
- Establishment of a cover crop before the harvest of corn to ensure its establishment under good conditions.
- Economic gain: The interest is also to minimize establishment costs and optimize the development of cover crops, or even move towards a double annual harvest.
- Weed reduction: In nature seeding, the soil is not worked and is always kept covered, which tends to reduce the dormancy break of weeds. If nothing is sown at this time, weeds emerge, despite herbicides. This lever is ensured by the establishment of effective cover crops (at least 2 t/ha of biomass). “I no longer use insecticides or anti-slugs. I add rapeseed in cereal sowings; soybean, rapeseed, flax in corn sowings. These plants will provide food to pests, then disappear after herbicide application. Slugs are present, but so are the predators, creating an ecosystem balance." Noël Deneuville is a farmer in Nièvre (58), practicing no-till farming under living cover on his farm for 20 years.
Successfully performing nature seeding
A living soil
The first criterion to be able to implement this technique under good conditions is to have a soil capable of supporting this practice. Nature seeding only succeeds on a living soil, so soil cover is essential. If the soil is crusted, without residue presence, with little OM or without biological activity to incorporate the seed into the soil, there is no chance that seeds deposited on the surface will germinate.
Water
The second limiting factor is water, a recurring issue in France especially in recent years. This practice can therefore be more delicate to implement in summer, without an irrigation system.
Light
Seeding must be done when the crop lets light through. Seeding is done as soon as light reaches the soil. If you wait too long, the soil can dry out.
- In a cereal: wait until the first leaves start to yellow (about one month before harvest).
It should be clearly stated that nature seeding is an opportunistic seeding: it is done when conditions are met. One should not be dogmatic.
Seeding rate
Losses can be observed at germination. It is therefore important to increase the seeding rate by about 30 to 50%, compared to a conventional seeding to compensate for these losses.
Suitable species
Equipment constraint
Most farms are equipped with a centrifugal fertilizer spreader.
- This tool works well for heavy seeds (wheat, soybean).
- It is not efficient for small seeds (rapeseed, millet, sunflower). This problem can be overcome by a pneumatic spreader or by seed coating to weigh down the seeds. The technique consists of creating seed pellets with molasses and clay using a concrete mixer, then drying everything to facilitate distribution. Small seeds stick to the larger ones and to the clay, improving water retention near the seed. It works well on small areas, but the process is very time-consuming to implement on a larger scale.
- To seed the cover crop in corn, a row cropper can be used when the corn starts to yellow. If it is dry, seeds remain on the ground and will germinate as soon as rain arrives. In this case, it is better to avoid chopping the stalks under the header. Leaving the stalks upright facilitates their germination.
According to the period
- For pre-summer sowings: small seeds that germinate better on untilled soil are favored. Angular seeds like buckwheat tend to better penetrate soil interstices and germinate well. Grasses and large seeds are avoided.
- In autumn: rainy periods occur. Larger seeds can be sown: cereals with some legumes. When the spring crop is harvested, the cover crop is established.
Sources
Nature seeding, a full-fledged technique - with Noël Deneuville, AgroLeague
