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When and How to Terminate Your Green Cover Crop for Maximum Benefits
In the realm of modern agriculture, the implementation of green cover crops has emerged as a cornerstone of sustainable and environmentally friendly farming practices. These cover crops, including legumes, grasses, and other plants, serve as invaluable assets improving soil health, preventing erosion, and enhancing overall crop productivity. However, to harness their full potential, understanding the strategic timing and methods for terminating these cover crops is essential.
Timing is key
Determining the optimum timing for terminating a green cover crop involves careful assessment of several factors. One crucial consideration is the growth stage of the cover crop. Different cover crops offer varying benefits, and the timing of termination can significantly impact the subsequent crop.
There are 2 rules to respect if you want to maximise the effect of the covercrop and avoid any negative impact on the next cash crop.
Rule 1 : it is desirable to terminate the cover crop at least one month before the establishment of the cash crop. That would prevent excessive water consumption by the cover crop and enough time to have a biomass starting to decompose and soil to be ready for the seeding of next crop.
However, there are certain cases where farmers would want to keep the cover crop for longer periods of time, and that should be the case where the green cover crop biomass is used for biogas production or for breeding cattle. There, farmers need to make sure that the biomass produced is in the highest quantity possible.
Rule 2 : once a cover crop is starting to flowering, it needs to be destroyed.
Most of the species have finished their job when flowering: nitrogen fixation is seriously slowing down, roots exploration is decreasing and the CN ratio of the cover crop will significantly increase. That can lead to nitrogen fixation to decompose the cover crop and an impact on your next cash crop moreover if you bury the covercrop with a tillage.
If your cover crop is flowering too early, you might need to adapt the species or the varieties. Contact your Cargill Agronomist to discuss it with him.
Cereal cover crops, such as rye, oats, or barley should be terminated:
- For weed suppression: Consider terminating at the jointing stage
- To prevent seeding: Terminate at the heading stage
- For maximum biomass: Allow to reach full maturity before termination
Legume cover crops, such as clover or vetch, should be terminated:
- For optimal nitrogen fixation: Terminate just before flowering to prevent self-seeding
- To maximize nutrient release: End the cover crop before seed formation to release nitrogen into the soil.
Moreover, it is essential to align the termination with the needs of the following cash crop. Timing the termination well at least one month before planting the subsequent crop is vital to prevent competition for essential resources such as sunlight, water, and nutrients.
Nutrient release optimization
Another key factor is the release of nutrients by the cover crops upon termination. Legume cover crops fix nitrogen in the soil, but this nitrogen is only made available for the next crop as the cover crop decomposes. Thus, ensuring the nutrient release aligns with the nutrient demands of the following crop is critical for successful growth and yield.
Weed Management and Soil Conditions
For cover crops intended for weed suppression, timing the termination close to the planting of the cash crop can effectively control weed populations. However, this should be carefully planned so as not to lose yield on the following cash crop. By balancing the need to suppress weeds with providing a favorable environment for the new crop, farmers can mitigate weed competition.
Considering soil conditions and weather patterns is also crucial. Optimal termination might hinge on the soil’s moisture content and the ease of preparing the soil for the new crop. Moreover, extending the growth period of the cover crop before termination could be advantageous if aiming to maximize soil coverage and erosion control.
Methods of Termination
The methods of terminating cover crops are numerous and varied. Farmers often use techniques like mowing, rolling, crimping, tilling, broadcasting herbicides, or livestock grazing, depending on the cover crops and the farming system. These methods should be chosen based on the specific goals for the cover crop and the subsequent crop. Moreover, species of cover crops used also have different sensitivity degrees depending on the termination method used. Below you can find a table that comprises this:
*For 2.4 D – this product has remanence in the soil. As such, the destruction method needs to be discussed with a Cargill Agronomist, because it can have a negative impact on the emergence of the cash crop (it depends on the next crop, but 2,4 D should be used more than 2 weeks before sowing the cash crop). Moreover, the doses for glyphosate and 2,4 D need to be discussed before making the field application.
In conclusion, the termination of green cover crops is a pivotal stage in regenerative agricultural management. It is critical to consider the growth stage of the cover crops, the needs of the subsequent cash crop, nutrient release, weed suppression, soil conditions, and the desired benefits to determine the ideal timing for termination. By selecting appropriate termination methods, farmers can capitalize on the advantages of cover crops while ensuring a smooth transition for the subsequent crop, ultimately leading to improved soil health, and enhanced agricultural productivity. This strategic approach not only contributes to increased productivity but also sustains the long-term health viability of the lands, making a significant step towards a more sustainable and profitable agricultural future.
Below you can find links to valuable information on cover crop termination:
https://cropwatch.unl.edu/tags/cover-crop-termination
https://crops.extension.iastate.edu/cropnews/2014/04/cereal-rye-cover-crops-allelopathy-and-corn
https://www.canr.msu.edu/resources/cover-crop-termination
https://www.covercropstrategies.com/articles/2973-cover-crop-strategies-best-of-the-web-oct-27-2023
https://www.farmprogress.com/soil-health/terminating-cover-crops
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