The most common mistake on a mulched cabbage bed costs the entire benefit of the operation: laying the mulch on dry, poorly weeded soil. Mulch keeps the moisture it finds, it does not create any, and a 7 cm layer laid over weeds that have already emerged shelters them from the sun instead of smothering them. The laying rule is therefore fixed: weed completely, water, lay the mulch on moist soil, then water again on top. Only then does mulching work for you, by cutting evaporation, limiting weed emergence and preventing soil splashes onto the lower leaves.
The effects measured on cabbage, in Sahelian conditions
The most directly transferable trial was published in 2025 by Masasi and co-authors in the journal Sustainability. It was run in the village of Sonsongona, near Bobo-Dioulasso, in Houet province in Burkina Faso, on three vegetable crops: cabbage of the Oxylus variety, Violet de Galmi onion and Cobra tomato. The mulch used was rice straw from the previous crop, spread about 10 cm thick, with the plots irrigated every two days based on water requirements calculated using CropWat 8.0 software.
- Yields 42 % higher on mulched cabbage and tomato, and 58 % higher on onion, compared with the non-mulched plots.
- At 30 days, mulched plants were larger by 8 % for cabbage, 32 % for onion and 27 % for tomato.
- Irrigation water productivity of 4.75 kg per cubic metre on mulched cabbage, against 1.90 on onion and 2.59 on tomato.
On the mechanism, the review by Nazar and co-authors published in 2020 in the Bulletin of the National Research Centre brings the orders of magnitude together. Straw mulch can decrease the rate of evaporation by 35 %, from the work of Russell cited in that review. A thin layer of 0.6 inches reduces erosion by about 86 % according to Borst and Woodburn, who also measure a 43 % drop in runoff. In hot and dry conditions, Martin and Poultney record a soil temperature decrease of 10 °C under mulch. Across the trials reviewed, the yield gain ranges from 7 to 47 %.
Why cabbage in particular
FAO benchmarks explain how sensitive this crop is. Head cabbage needs 380 to 500 mm of water depending on the climate and the length of the season, over a growing period running from 90 days for a cool season sowing to 200 days, with optimum production between 120 and 140 days. Its rooting is shallow: the majority of the roots are found in the top 0.4 to 0.5 m of soil, and all of the water is extracted from that layer. Uptake starts to be restricted as soon as the available soil water has been depleted by about 35 %, at an evapotranspiration of 5 to 6 mm per day.
In other words, a cabbage draws on a small volume of soil and tolerates a deficit badly. It also asks for coolness: FAO places the optimum at a mean daily temperature of about 17 °C, with a mean daily maximum of 24 °C and a minimum of 10 °C. On a West African plain where the air runs well above those values, capping soil temperature with mulch and reducing evaporation act on exactly the two constraints that limit the crop.
The crop coefficient follows canopy development: 0.4 to 0.5 at establishment over 20 to 30 days, 0.7 to 0.8 during development over 30 to 35 days, 0.95 to 1.1 at mid season over 20 to 30 days, then 0.9 to 1.0 late in the cycle and 0.8 to 0.95 at harvest. Reference density is 30,000 to 40,000 plants per hectare, with row spacing of 0.3 to 0.5 m for small heads and 0.5 to 0.9 m for larger heads. That spacing is what determines the bare soil area to cover, and therefore the quantity of mulch to plan for.
Choosing the material
| Material | Value on a cabbage bed | Point to watch |
|---|---|---|
| Rice or cereal straw | The material used in the Bobo-Dioulasso trial, light, easy to spread, breaks down into organic matter | Check the bale for weed seed |
| Dry cut grass | Available locally at the end of the rains, decomposes quickly | Dry it before laying, otherwise the layer packs down and heats up |
| Dead leaves and hedge trimmings | Free, holds up well over time | Chop the woody pieces, which break down slowly |
| Wood chips and bark | Long lasting, suited to paths and bed edges | High in lignin, better kept for perennial crops than for cabbage |
| Plastic mulch film | Immediate, even cover, total light exclusion | Adds no organic matter, needs the edges tucked in carefully |
| Mineral mulches | No use here | Not biodegradable and not suited to a vegetable bed, according to the technical sheet published by the regional directorate for food, agriculture and forestry of Auvergne-Rhône-Alpes |
What thickness to aim for
The same technical sheet gives three benchmarks usable as they stand. A layer of about 7 cm is the working thickness on an established bed. On young plants you start at 2 to 3 cm, then top up to 7 cm once the crop has gained height. And to block weed germination you need a fairly thick layer, in the order of 10 cm, which deprives the soil of light. The Burkinabè trial sits precisely on that last step, with its 10 cm of rice straw.
Plan to top up during the cycle: an organic mulch loses a few centimetres as it decomposes, and a 120 day cabbage passes through a good part of that breakdown.
Laying the mulch, step by step
- Weed the bed completely. That is the condition set by the reference technical sheet, and the reason for the most frequent failure.
- Loosen the soil and apply the base fertiliser before covering, since the soil will no longer be easy to reach.
- Water until the root layer is moist down to 40 to 50 cm, the depth from which cabbage takes all of its water.
- Spread the mulch at 7 cm on an established bed, 10 cm where weed pressure is high, avoiding days with strong wind.
- Keep the collar of each plant clear. Never cover the junction between stem and roots, or collar rot follows.
- Water again on top to settle the layer and stop it blowing away.
- Check infiltration after the next watering. If water runs off a packed, dry mulch, scratch the surface so it penetrates.
Mulch and drip, to be combined
Mulch and the dripline act on two different losses. The dripline removes losses from sprinkling and places water at the base of the plant, the mulch removes evaporation from the soil surface between two waterings. Lay the dripline first, under the mulch, so you can check it without pulling the layer apart, and mark the position of the drippers before covering. The logic of laying driplines and mulch on a bed is set out in our article on installing drip irrigation on a bed.
A crop health benefit comes on top of the water saving: the mulch layer intercepts the soil splashes that reach the lower leaves, and those splashes carry spores. It is one of the preventive measures listed in our guide on tomato late blight in tropical climates, a crop often grown in rotation with cabbage.
Mistakes to rule out
- Laying on dry soil, or on poorly weeded soil.
- Covering the collar of the plants.
- Using freshly cut grass in a thick layer, which packs down and ferments.
- Forgetting to top up the layer mid cycle.
- Mulching before the base fertiliser has been spread.
- Spreading in strong wind, which scatters the straw onto neighbouring beds.
To place cabbage among the other bed crops and their requirements, see our overview of market gardening in Africa, and for the companion crop most often used in rotation, our tomato crop management guide.
Your mulching inputs with JOGOO
JOGOO Agriculture supplies mulch films, seed, nursery trays, substrates and bed tools, and advises on the material best suited to your soil and your calendar. The Agricultural Supplies & Inputs page presents the range, and the Contact page lets you request a quote for your area.
Frequently asked questions
What mulch thickness for a cabbage bed?
About 7 cm on an established bed, and in the order of 10 cm when the aim is to block weed germination. On young plants, start at 2 to 3 cm and top up afterwards.
Should you water before or after laying the mulch?
Both. You moisten the soil before laying, since mulch keeps the moisture present without adding any, and you water on top after laying to settle the layer.
By how much does mulching reduce evaporation?
Straw mulch can decrease the rate of evaporation by 35 %, from the work of Russell taken up in the 2020 review by Nazar and co-authors.
Does mulching lower soil temperature?
Yes. In hot and dry conditions, Martin and Poultney record a decrease of 10 °C under mulch, which matters for a crop whose mean thermal optimum is about 17 °C.
Can you mulch over a dripline?
Yes, and it is the recommended combination. Lay the dripline first, mark the position of the drippers, then cover, so you can check the line without pulling the whole layer apart.
How much water does a cabbage use over its cycle?
From 380 to 500 mm depending on the climate and the length of the cycle, according to FAO data, taken almost entirely from the top 40 to 50 centimetres of soil.
Sources
- Masasi B., Aryal N., Millogo V., Masasi J., Srivastava A., Kalita P. K., 2025, Assessing the Impacts of Mulching on Vegetable Production Under Drip Irrigation in Burkina Faso, Sustainability 17(3), 916
- Nazar and co-authors, 2020, Potential agricultural and environmental benefits of mulches, a review, Bulletin of the National Research Centre
- FAO, Land and Water, crop information, Cabbage
- Regional directorate for food, agriculture and forestry of Auvergne-Rhône-Alpes, technical sheet on mulching in the vegetable garden
