AdWorld Businesses for Sale
Visit World Businesses for Sale
Thinking of selling your business? Buy or sell a business locally, nationally or worldwide. 10% off with code AWN10.
Let the weeds be your cover crop: what 6–20 years in almond orchards showed
The full story behind my Short: Ploughing twice a year and letting native plants grow, instead of keeping soil bare, more than doubled protected soil aggregates in a silty loam almond orchard, with about 50% more carbon inside them. Sandy soils responded far less (Soil and Tillage Research, 17 Oct 2026).
The short version
Letting native plants grow can build protected soil carbon, but only in the right soil. In three rainfed semiarid almond orchards studied for 6 to 20 years, ploughing just twice a year and letting native plants grow (instead of the traditional 3 to 5 passes a year to keep the soil bare) increased free macro and occluded (protected) soil aggregates by about 120% in a silty loam soil, with about 50% more organic carbon and 35% more nitrogen inside the occluded aggregates and more microbial activity. Soils with more sand strongly limited the benefit, and total carbon in the soil as a whole often changed little. Lesson: know your soil (Fernández-Soler et al., Soil and Tillage Research, online 17 Oct 2026).
~+120%free macro and occluded aggregates, silty loam soil [1]
~+50% / +35%organic carbon / nitrogen concentration inside occluded aggregates [1]
2 vs 3–5tillage passes a year (native cover vs bare soil) [1]
Sandy soilsstrongly constrained the response [1]
What they found
The team (Cristina Fernández-Soler, María Martínez-Mena and colleagues; CSIC and partners) compared reduced tillage twice a year combined with native (spontaneous) cover crops against traditional tillage, 3 to 5 passes a year to keep the soil bare, in three rainfed semiarid almond orchards with contrasting soils (Calcisol and Regosol). Practices had been in place for 6 to 20 years, and they sampled the top 15 cm, the tillage depth [1].
The clearest effect was in the silty loam soil: free macro and occluded aggregates rose by about 120%, microbial activity increased (enzyme activity, microbial biomass and mineralised carbon), and organic carbon and nitrogen moved into more physically protected pools, with about 50% more organic carbon and 35% more nitrogen concentration inside the occluded aggregates [1].
Soils with more sand strongly constrained the outcome. Plant residue quantity alone did not explain the results: residue quality and local soil conditions mattered too. And the effects were clearer in the aggregate fractions than in the bulk soil, where total soil organic carbon and nitrogen often showed limited changes [1].
Watch the Short
AI voice note: the narration in this Short is my own voice, cloned with AI.
About this page
My wording “more than double” reflects the study's ~120% increase in free macro and occluded aggregates in silty loam soil. The ~50% rise is in carbon concentration inside the protected aggregates, not total soil carbon, which often changed little. The Short uses illustrative photos from Wikimedia Commons (credited below), not photos of the study orchards.
Why it matters
- Cheap to try. Native plants need no seed, but the benefit depends on soil texture, so check your soil first [1].
- Protected carbon. Carbon inside occluded aggregates is physically protected, which is the kind of storage that tends to last [1].
- Site-specific advice. The authors call for site-specific strategies, not one rule for every orchard [1].
Full narration (transcript)
What if the weeds in your orchard are the cover crop you never paid for? I've been reading a new study of rainfed almond orchards in Spain, followed for six to twenty years. Normally, farmers there plough three to five times a year to keep the soil bare. The alternative: plough just twice, and let the native plants grow. Soil is made of tiny crumbs, and the protected ones lock carbon away like a safe. In silty soil, those protected crumbs rose about 120 percent. That's more than double. The carbon inside them went up about half, and soil microbes got busier too. And here's where it gets interesting: in sandier soils, the same change did far less. And in the soil as a whole, total carbon often barely changed. So my tip: know your soil. Check if it's silty or sandy before you change how you plough. Why it matters: the cover crop that locks away carbon might already be growing in your rows. For the full story, follow the link in the description.
Sources
- [1] Fernández-Soler, C., Garcia-Franco, N., Almagro, M., Colocho-Hurtarte, L.C., Wiesmeier, M., Díaz-Pereira, E., Sánchez-Navarro, A. & Martínez-Mena, M. (2026). “Soil texture, plant residue quality and aggregate protection determine carbon and nitrogen stabilization under reduced tillage in semiarid rainfed almond orchards.” Soil and Tillage Research 266 (Feb 2027), online 17 Oct 2026. Open access, CC BY-NC 4.0. doi.org
Credits
Photos via Wikimedia Commons (illustrative): La Vall de Laguar – almond orchard in bloom near Benimaurell.jpg (Punteador, CC BY-SA 4.0); Agricultural landscape around Casas de Tallante in Campo Nubla, Cartagena, Murcia, Spain, 2022 January.jpg (Ximonic (Simo Räsänen), CC BY-SA 4.0); Almonds plantation and farm, Alhama de Granada, Andalusia, Spain.jpg (Jebulon, CC0); Subangular Blocky Soil Aggregate in Spain.jpg (Antonio Jordán (University of Sevilla) (https://imaggeo.egu.eu/user/ajordan/), CC BY-SA 3.0); Sandy Soil Image.jpg (Ready Street, CC BY-SA 4.0); Almond cultivation in the mountains of Relleu, Alicante, Spain, 2022 January.jpg (Ximonic (Simo Räsänen), CC BY-SA 4.0). Sketches and animation: my own. Narration: AI clone of Nasper Mushonga's own voice (Chatterbox TTS by Resemble AI, MIT licence), used with his consent.