Summer Cover
Short or summer cover crops are placed between 2 cereals. The choice of cover crops is considered based on the planned technical itinerary, the constraints of the plot, the available equipment, the price, seed availability, and the set objectives.
Description
The summer cover crop should be planted before/shortly after harvest depending on equipment and constraints. The idea is to sow immediately after the harvest of the winter cereal to take advantage of the residual soil moisture. However, the success of this technique remains dependent on summer climatic conditions. In case of persistent drought, the cover crop can fail. Investments should therefore be considered according to the local pedo-climatic conditions.
Identifying the right species mix
The choice of species is important to obtain an efficient cover crop.
For the short intercrop, a mix including legumes and species that develop quickly, have some tolerance to heat, and different root systems can be recommended.
In addition to nitrogen storage, adding legumes to the cover also helps maintain a medium/low C/N ratio of the cover (from 10 to 20), which allows a faster release of organic elements after cover destruction, without causing nitrogen hunger.
Choosing small seeds gives more chances to succeed with the cover crop because the water requirement for germination is lower:
- Phacelia (2 kg/ha);
- Radish/rape (2 kg/ha);
- Niger (1 kg/ha);
- Alexandrian clover or squarrosum (2 kg/ha);
- Flax (2 kg/ha);
- Sorghum (20 kg/ha);
- Hairy vetch (20 kg/ha);
- Mustard (variety "Green", later maturing) (3 kg/ha);
- In case of ryegrass issues: add 5 kg/ha of Italian ryegrass.
Example of a possible summer cover crop mix:
Phacelia (2 kg/ha) - sunflower (4 kg/ha) - forage pea (25 kg/ha) - common vetch (10 kg/ha).
If the following crop in the rotation is a spring crop, sowing a relay cover or double cover may be relevant to achieve maximum density and best benefit from the positive externalities of the cover. In this case, winter species are necessary: cereals (triticale/rye or oats), legumes (forage pea/fava bean/vetches) and “small seeds” in smaller proportion (phacelia/flax/crimson clover).
Benefits of the summer cover crop
Short intercrop cover crops, between 2 wheat crops for example, play a key role in yield ceiling release. Trials conducted by Arvalis between 1975 and 2016 showed an average yield gain of +2.9% for the second wheat sown after a cover crop compared to the control without cover.
According to trial results
- Grasses in cover crops bring on average +1% yield;
- Crucifers +3%;
- Legumes and cover mixes with legumes +6%.
An example with a concrete case:
- For a wheat with a yield potential of 70 q/ha, a 3% yield increase represents 2.1 q/ha more;
These figures highlight the “yield gain” aspect, often sought by producers.
Sources
Which species to plant for the summer cover crop? - AgroLeague
