Example of an effective intercropping strategy - push-pull
|Push-pull plot during 2nd season, maize and desmodium with Striga border crop. The plot is bordered with Napier grass.
Push-Pull is a simple cropping strategy, whereby farmers use Napier grass or Bracharia grass and desmodium legume (silverleaf or greenleaf desmodium) as intercrops in maize.
Desmodium is planted in between the rows of maize. It produces a smell or odour that stemborer moths do not like. The smell 'pushes' away the stemborer moths from the maize crop. On the other hand, Napier grass (Pennisetum purpureum)/ Bracharia grass (Brachiaria cv Mulato ) is planted around the maize crop as a trap plant. Napier grass/Bracharia grass is more attractive to stemborer moths than maize and it 'pulls' the moths to lay their eggs on it. But Napier grass/Bracharia grass does not allow stemborer larvae to develop on it. When the eggs hatch and the small larvae bore into Napier grass/Bracharia grass stems, the plant produces a sticky substance like glue which traps them, and they die. So, very few stemborer larvae survive and the maize is saved because of the 'push-pull' strategy.
In addition, a ground cover of desmodium (silverleaf or greenleaf), interplanted among the maize, reduces Striga weed. Research has shown that chemicals produced by the roots of desmodium are responsible for suppressing the Striga weed. Therefore, Striga does not grow where desmodium is growing. Being a legume, desmodium also fixes nitrogen in the soil and thus acts to enrich the soil.
Desmodium is perennial and must only be planted once. As desmodium seeds may not always be available, desmodium can also be planted using vines. This can be an easy and cheap method to plant desmodium vines.
There are two types of push-pull farming systems:
- Conventional push-pull uses napier grass and silverleaf desmodium.
- Climate smart push pull uses two drought-tolerant species: Brachiaria grass (Brachiaria cv mulato II) and greenleaf desmodium (Desmodium intortum). Bracharia grass is native to Africa. Two varieties of Brachiaria known as Mulato and Mulato II, are drought tolerant, recover fast after grazing, show high plant vigour, give good quality forage and are tasty to the animals. Brachiaria does not have stinging hairs, making it easy to cut and carry.
How to plant a push-pull field
1. Plant Napier grass/Bracharia grass in a border around the maize plot.
2. Plant at least 3 rows of Napier grass/4 rows of Bracharia grassall around the maize field. Apply 2 handfuls of well decomposed farmyard manure in each hole.
3. In the first year, plant Napier grass/Bracharia grass before the rains so that is has a start on the maize. The stemborer moths will like the larger Napier grass/Bracharia grass even more than the maize.
4. Get desmodium seeds from seed companies (Kenya seed, 'Western Seed & Grain Co. Ltd.' in Kitale, Western Kenya) or your neighbour who has started growing it. For 1 acre of land 1 kg of desmodium seed is needed.
5. Alternatively, you may plant desmodium vines. In this case plant the vines when there is enough rainfall and soil is moist.
6. Prepare the soil carefully so that it is as fine and clean as possible.
7. Using a strong pointed stick, make a furrow in the middle of the rows where the maize will be planted.
8. Mix the desmodium seed with fine sand or fine soil (about 1 handful of seed and 2 handfuls of sand).
9. Plant desmodium with the rains for maximum germination.
10. Plant your maize in the field surrounded by Napier/Bracharia grass.
11. After 3 and 6 weeks, trim the desmodium so that it does not overgrow in between the maize plants.
12. Keep the field weed free so that the Napier/Bracharia has a start on the maize. The moths will like the larger Napier/Bracharia more than the maize.
Benefits of adopting a push-pull strategy
When you adopt a push-pull strategy you will:
- Increase maize yield by 25 - 30% in the areas where stemborers are the only problem. Where both stemborers and Striga are problems, you can double your maize yields.
- Increase the supply of cattle feed from harvesting Napier grass/Bracharia grass and desmodium.
- Fix nitrogen into your farm soil by desmodium legume, so you save on fertiliser costs.
- Protect your soil from erosion, as desmodium acts as a cover crop.
- Retain soil moisture, as desmodium acts as mulch.
- Earn money from the sale of desmodium seed at an attractive price of between Kshs 600 and 800 (US$ 8 to 10) per kg.
- Make more money from increased milk production and sales.
- Save on farm labour, as you do not have to manually remove Striga weed from the farm.
- Protect maize from strong winds, by surrounding it with Napier grass/Bracharia grass.
For more documents and detailled instructions on push-pull for download, please refer to publications