Sustainable Agriculture Extension Manual

Inoculating legume seeds

Legume inoculation means mixing legume seeds (soybeans, green gram, etc) with a powder containing a special type of bacteria. This is done before planting the seeds, to make nodules form on the roots of the legumes.

The inoculant increases the amount of nitrogen fixed by the legume. This increases the yield of the legume and other crops intercropped with it, or crops grown in the same field afterwards.

The bacteria in the lumps (or "nodules") on the roots of legumes naturally fix nitrogen in a form that plants can use (see the section on Green manuring). These bacteria normally live in the soil, waiting for a legume to grow near them before they can start their nitrogen-fixing work. But if there are not enough bacteria in the soil, very little nitrogen can get fixed by the legumes growing there. The nodules stay small, and so does the legume plant.

Mixing bacteria inoculant powder with the legume seeds before planting them makes sure there will be enough bacteria to produce a lot of large nodules. This will help produce healthy, vigorous legume plants, and will mean a lot of nitrogen is fixed in the soil for another crop to use.

Location

Inoculants are useful for all types of soils. They should be used in fields where the legume has not been grown before, since there may be very few of the right kind of bacteria in the soil there. They should be used especially with soybeans and for green manures: in many situations, velvetbeans and sunn hemp will not fix nitrogen unless they are inoculated.

Advantages

• Inoculating legume seeds raises the yield of the legume and the fertility of the soil in which it grows.

Disadvantages

• Inoculants can be expensive and hard to obtain.
• Each species of legume needs a different type of inoculant.

Requirements

• Legume seeds.
• Inoculant (of the right type for the legume species).
• A bowl and a little water.
• For silver-leaf desmodium (a type of fodder legume), you also need a little sugar to mix with the inoculant.

Procedure

1. Obtain the right type of inoculant for the legume you want to plant. You can get inoculant from seed companies, universities and government research institutes. 2. On the day you want to plant the legume, put the legume seed into a bowl (Picture 1). 3. Sprinkle the inoculant over the seed. You need only a small amount of inoculant: about 5 g (1 teaspoonful) for every 100 g of seed. See the instructions on the packet for how much inoculant to use (Picture 2). 4. Sprinkle a little water over the seeds, enough to make the powder stick to the seeds, but not enough to make them wet (Picture 3). 5. Carefully mix the powder with the seeds until all the seeds are evenly covered (Picture 4). 6. Plant the legume seed on the same day by broadcasting or dibbling it in rows (Picture 5). Using soil as inoculant Since the nitrogen-fixing bacteria live in the soil, you can use soil instead of inoculant. 1. Find a field where the same legume as you want to plant is growing and where the plants are flowering. Make sure the plants are healthy. 2. Pull up several plants from different places in the field, and break open the nodules on the roots with your fingers. If the nodules are pink inside, there are

bacteria inside them that are fixing nitrogen. If there no nodules on the roots, or the nodules are not pink inside, there are no nitrogen-fixing bacteria, and you need to find another legume field.

3. Take a small amount of soil from this field (about the same amount as the seed you want to plant).

4. Mix this soil with your seeds before planting them.

You may be able to get soil from neighbours who have inoculated their legume seeds in a previous season.

Do's Before you go to the expense of buying inoculant for a large amount of seed, obtain a small amount to test. Plant a plot of treated legume seeds next to another plot of untreated seeds. Measure the amount yielded by each plot. You will then be able to tell whether the inoculant has improved the yield, and you can use inoculant for a larger area in the next season. Make sure you get the right inoculant for your legume species. If you are not sure, ask an experienced farmer or an extension worker. You can also ask to your neighbours if they have had experience with inoculant. Follow the instructions on the inoculant package carefully. Before using it, keep the inoculant in a cool, dark, dry place, away from children. Wash your hands after handling the inoculant, as it is poisonous.

Don'ts Don't use too much water to moisten the seeds. Don't use inoculant with crops that are not legumes (such as maize or other cereals), as it will not work. You do not need to use inoculant year after year for the same legume crop in the same field. Once you have grown this crop in a field, the soil will contain the bacteria, so it is not necessary to inoculate the seeds again.

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Sustainable Agriculture Extension Manual

Cattle-manure ash

Cattle-manure ash is an indigenous technology used in vegetable gardens to enhance the availability of plant nutrients. Cattle manure is either burnt directly on beds (with heavy clay soil types) or elsewhere if the soils are sandy or loamy.

The ash also improves soil pH and the soil's ability to hold moisture. It repels pests found in the soil, and lowers the cost of weeding by destroying weed seeds. It is used for vegetables in both nurseries and the main beds.

Advantages

• Uniform, rapid germination of vegetable seeds due to improved soil moisture management and enhanced release of nutrients (the effect can last for a season). This in turn helps farmers establish their vegetable gardens quickly, leading to quicker cash returns.
• Improved soil moisture retention. The ash reduces waterlogging and helps conserve soil moisture by acting as a mulch.
• Control of pests of both leaf and root crops, such as nematodes.
• Weed control: weed seeds in the manure are killed by burning.
• Cattle manure is readily available and light, so transport is not a problem.
• Vegetables grown with cattle-ash manure taste sweeter than ones where chemical fertilizer has been used.

Requirements

• Hoe.
• An adequate amount of dry, loose cattle manure, at least 1 month old. The manure must not go through a rainy season as it tends to harden, making it difficult to burn.

Procedure

1. If your soil is a heavy clay, pile the manure in heaps in the seedling bed or main beds: about 5-10 kg of manure per square metre. Set fire to the manure in the evening, and leave it to burn overnight.

On sandy and loamy soils, burn the manure on a separate piece of land, then carry the ash to the vegetable beds.

2. In the morning, spread the ash evenly and incorporate it into the soil using a hoe. Keep the ash close to the surface—less than 5 cm (2 inches) deep. Leave some on top, so that when you water the beds, a crust of ash forms to help retain soil moisture.

3. Lightly water the bed.

4. Plant vegetable seeds either in lines or by broadcasting.

5. To kill aphids, sprinkle ash on the leaves of already established vegetables.

Alternative method: burn the manure somewhere else, then put the ash in small planting holes after mixing with the soil.

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