Organic fertilisers: from compost to home-made ferments

Organic fertilisers range from bulky materials you dig in once a season to liquid ferments you make in a bucket within days. Start with the bulky ones, which are the foundation, and use the liquid ones as a boost.

The bulky materials

• Compost and farmyard manure: the base of everything. It must be well-rotted: fresh manure burns roots.
• Poultry manure: the strongest and cheapest, rich in nitrogen, but also salty and "hot". Compost it for at least a month, and use a small handful per plant, away from the stem.
• Vermicompost (worm castings): gentle and full of microbes, and can be used generously.
• Bio-fertilisers (Pseudomonas, Azotobacter and others): live bacterial cultures sold in nurseries that help roots take up nutrients and protect against some diseases. They are not plant food; they work in compost-rich soil and survive poorly in hot dry sand, so apply them at the root zone in the cool months.

Rules for making ferments

Ferments make gas. Use a bucket or bottle with a loose lid, never a sealed one, stir daily, and keep it away from sun, children and pets — it smells. Use the finished liquid diluted, and test it on one plant first. The sugar that feeds the microbes is jaggery; molasses or date syrup (dibs) works as a substitute.

The recipes

• Fish amino acid: 1 kg sardines (or fish waste) and 1 kg jaggery, layered in a container. Ready in 30–40 days. A nitrogen-rich growth tonic. The recipe gives no dilution; a common range is 2–5 ml per litre of water, sprayed or watered in.
• Egg amino acid: 3 eggs, 5 lemons and 75 g jaggery in a jar with a loose lid, out of the sun. Ready in about 20 days. A calcium-rich tonic for flowering and fruiting, at the same dilution.
• Vegetable-waste fertiliser: 500 ml paste of vegetable scraps, 1 cup soured rice-cooking water (kanji vellam), 50 g jaggery and 1½ tbsp curd. Ready in 3 days. Dilute in 7 litres of water and apply to the soil.
• Fermented fruit-and-pulse tonic: 250 g each of powdered mung bean, papaya, pumpkin, banana and jaggery (dissolved in 1 litre of water), plus 3 eggs. Ready in 2–3 weeks. Use 100 ml in 1 litre of water on the soil. This is a home ferment, not true Effective Microorganisms (EM), which is a commercial culture sold in nurseries.
• Flowering booster: 1 banana peel, 8 tsp used tea leaves, 4 egg shells and 250 ml water, blended. Make it fresh and use it at once — do not store it. The peel gives potassium and the shells calcium. Apply directly to the soil.
• Asafoetida and curd foliar spray: 5 g asafoetida (hing; Arabic: حلتيت), 100 ml curd and 1 litre of water. Dilute and spray on the leaves. A traditional tonic whose smell deters some insects. Asafoetida is sold at spice shops and nurseries.
• Onion-peel mix: dry onion peel, egg shell and used tea completely in the sun, grind to a powder, store it and mix it into the soil. Or soak onion peel in water for three days, strain it, and apply the water.

How and when to apply

• Water first, then apply liquid fertiliser to the soil, so it soaks in rather than draining straight through the sand.
• Foliar spraying works faster than feeding the soil, so cover both sides of the leaf. Spray at first light or after sunset, never in midday sun or wind, which burn the leaves.
• Never put fertiliser right against the stem; apply it in a ring beyond the spread of the leaves.
• Cut back nitrogen once a plant starts to flower: too much gives you leaves instead of fruit.
• Little and often beats one big dose, especially in sand.