Learn / Crop guides / Kale and vegetables
Kale and vegetables: feeding the soil, keeping food safe.
Kale (sukuma wiki) is the vegetable most Kenyan households grow, and it responds well to compost. This guide covers how much to apply and when. It also covers the rule that matters for every vegetable you eat: which manure and compost is safe to put on food crops.
The numbers that matter
These figures come from the Ministry of Agriculture’s SHEP PLUS kale production guide (2019 revision). Rates are per acre, as farmers use them.
From nursery to field
Soil
Kale likes fertile, well-drained loam with plenty of organic matter that holds water. The best pH range is 5.5 to 7.0. Test your soil to decide what fertiliser to use.
Water
Kale wants about 750 mm of rain over its growing period. In drier areas, irrigate.
Nursery
Sow about 50 g of seed per acre on a seedbed 1 m wide, in drills 2 cm deep and 10 to 15 cm apart. Choose a plot that has not grown cabbage-family crops for at least three years. Avoid over-watering, which causes damping-off, and harden the seedlings for 1 to 2 weeks before moving them.
Spacing
Plant 60 cm between rows and 40 to 60 cm between plants, depending on variety. That is about 11,000 to 16,700 plants per acre. Transplant in the early morning or late evening.
SOURCE: MOALF/SHEP PLUS, KALE PRODUCTION (2019)
Compost, manure and fertiliser for kale
- Before transplantingOne to two weeks ahead, spread 5 to 8 tonnes of compost or manure per acre (about 12 to 20 t per hectare) and work it into the soil, preferably with a hoe.
- At transplantingPut one to two handfuls of compost or manure in each planting hole, along with 80 kg per acre of TSP in the holes.
- First top dressingWhen the plants are 20 cm tall, apply 40 kg per acre of CAN.
- Second top dressingThree weeks later, apply 80 kg per acre of CAN. Extra CAN and irrigation shorten the picking interval and prolong the harvest.
Only well-composted manure.
The guide says to use only thoroughly composted manure, to avoid bringing pests and diseases into the field. It also says to cover your compost while it breaks down, so rain doesn’t wash the nutrients out.
The guide repeats the 5 to 8 tonne figure in its at-transplanting instruction, which looks like a printing slip. We have taken the per-acre rate as the basal dose and the handful as the planting-hole dose.
Harvest
Picking starts about six weeks after transplanting (the guide also says 45 days) and can continue for four to six months, depending on how well you manage the crop.
Pests to watch
The guide names diamondback moth, cabbage sawfly, aphids and cutworms as the main kale pests in Kenya. Check pesticide labels for the days to wait before picking.
SOURCE: MOALF/SHEP PLUS, KALE PRODUCTION (2019). HECTARE FIGURES CONVERTED FROM ACRES.
Which manure and compost is safe on food crops?
Fresh animal manure can carry harmful bacteria. The risk is highest for crops that grow in or near the soil. The rules below come from US guidance. They are widely used as a benchmark, but they are not Kenyan law, and your buyers or export market may apply their own.
| What you apply | What the guidance says |
|---|---|
| Raw manure | Never during the growing season. Work it into the soil within 72 hours. Wait at least 90 days before harvest if the edible part does not touch the soil, and 120 days if it does. US leafy-green marketing rules call for at least a year. |
| Aged manure | Ageing is not composting. Treat aged manure exactly like raw manure. |
| Properly composted manure | In a windrow, at least 55°C for 15 days with at least five turns in that period, then 45 days of curing. In an enclosed system, at least 55°C for 3 days. Keep records of temperatures and turning dates. |
| Compost tea | Tea from properly composted manure and clean water can be applied to the soil, not onto the edible part. Raw manure tea must not touch leafy greens and follows the one-year rule. |
Under US organic rules, fully treated compost and compost made only from plant material carry no waiting interval. Treating manure properly means measuring the temperature. See windrow composting for how to prove it, and heap composting for smaller scale.
SOURCES: CORNELL NATIONAL GAP PROGRAM, “SOIL AMENDMENTS” DECISION TREE; UNIVERSITY OF MINNESOTA EXTENSION, “CAN I SAFELY USE ANIMAL-BASED COMPOST?” TEMPERATURES CONVERTED FROM °F (131°F = 55°C).
Spinach, cabbage, onions and the rest
We are writing separate guides for tomatoes and other vegetables. Until then, three principles carry over from kale and from the safety rules above.
- Use finished compost. Thoroughly composted, never fresh, and covered while it matures.
- Mind the clock. Keep a gap between any manure and harvest, longer for crops that touch the soil.
- Test the soil. Fertiliser type and amount should follow a soil test, as the kale guide advises.
Planning a kitchen garden at home? Our bin and barrel composting and bokashi pages cover composting in small spaces.
Questions people ask
How much compost does kale need?
The Ministry’s guide recommends 5 to 8 tonnes per acre before transplanting, plus one to two handfuls in each planting hole.
Is it safe to use cow or chicken manure on kale?
Only if it has been properly composted. Raw or merely aged manure should be kept off a crop you pick and eat soon after. Follow the waiting intervals in the safety table.
Can I use bokashi on vegetables?
Bokashi is a pre-compost that must finish breaking down in the soil before roots reach it. See our bokashi page for timings.
How long can I keep picking kale?
Four to six months, according to the guide. Good management, extra CAN and irrigation lengthen the harvest.
Should I apply fertiliser as well as compost?
The guide recommends TSP and CAN alongside manure or compost. Let a soil test guide the amounts.
Growing vegetables for sale?
We help growers set up safe composting that meets buyer expectations, from small plots to commercial farms.