Green Manure: Replanting After Garlic and Onions
She can provide a second harvest
Irina Sadi, a gardener with 20 years of experience, shared tips with UFA1.RU on getting a second harvest from a single bed. The following is a first-person account.
Onions and garlic have been harvested
Green Manure
In mid-July, my vegetable garden begins to noticeably empty out. After removing early potatoes, garlic, and onions, I see empty beds and understand: leaving bare soil under the scorching sun for several months is a bad idea. The soil will quickly dry out, become compacted after the first downpour, or become overgrown with weeds, which will be the first to sprout. After onions and garlic, the soil may need restoration, as pathogens could have accumulated in it. If you want a harvest this summer, you can, of course, plant other crops in that spot: greens, radishes, daikon, or Chinese cabbage. If the goal is to improve soil health, or the bed is being prepared for demanding crops next year (for example, tomatoes or strawberries), then the best choice is green manure. Green manure quickly builds up green mass, suppresses weeds, improves soil structure, and some (for example, mustard) also release substances that inhibit fungal infections and certain pests.
I long ago stopped sowing the first mustard I found everywhere. To avoid harming the soil, I always check which crop grew there before and what will grow there next spring. If I make a mistake with the family selection, I could repeat the same diseases in the soil and only make the situation worse.
How I Choose a Crop
We follow the simple rule of botanical kinship:
after garlic and onions: there are almost no restrictions. These crops do not overlap with any of the popular green manures, so phacelia, oats, buckwheat, or a mix of oats and vetch work great here;
after radishes, turnips, or early cabbage: mustard, rapeseed, and oilseed radish are out. They are also cruciferous, need the same micronutrients, and suffer from the same diseases. For such beds, I take phacelia or oats;
after peas or beans, I do not plant green manure, as they themselves serve this role. It is better to sow greens (dill, lettuce) here: peas and beans enrich the soil with nitrogen, which is exactly what greens need. Nitrogen helps them build mass;
after early potatoes: I most often use phacelia, mustard, or rye if I plan to leave this soil to rest until late autumn;
phacelia has generally become my «universal soldier» for me. It is not related to the main vegetables, quickly covers the soil with a soft carpet, and rarely disrupts crop rotation. As for mustard, I value it because it germinates quickly, but it needs to be planted away from cabbage beds.
My Sowing Algorithm
First, I remove the vegetable remains. Healthy tops go into the compost, and suspicious ones are burned or discarded.
There is no need to dig deep; it is enough to lightly loosen the top layer with a flat hoe.
I add 5–7 kilograms of compost or 4 kilograms of rotted manure per square meter, water it, and let the bed «rest» for seven days. This will restore the soil«s nutrients for the next crop.
If the soil is dry, I always water the bed before scattering the seeds.
I scatter the green manure seeds in a fan pattern, lightly cover them with a rake, and water again gently. They cannot be buried deeply—a couple of centimeters is enough for most crops.
In the first few days, it is especially important to monitor moisture. While the roots are small, even one hot day without water can kill all the seedlings. You can cover them with a thin layer of dry grass, but do not pile it on thickly so the sprouts get enough light.
When to Mow and What to Do with the Greens
I never wait for a specific calendar date. The main guide is the condition of the stems. I cut the green manure while it is young and tender, usually after 4–6 weeks, but well before mass flowering. Overgrown, tough stems take a very long time to decompose, and if the plants have managed to produce seeds, they will sprout in the same bed as stubborn weeds.
The cut greens can be used in different ways. Most often, I leave them on top as mulch—this saves the soil from overheating in August. If the bed is currently resting, I can lightly mix the mass into the top layer of soil. The main rule is not to bury fresh grass deep into wet clay, as it will simply sour there without air access. And if I plan to plant vegetables in just a couple of weeks, it is better to remove the green mass to the compost bin and wait at least two weeks before planting, so the roots of the seedlings do not get burned by the decomposing fresh organic matter.
July green manure does not work miracles and does not turn sand into chernozem in one season. But it does the main thing: covers my soil, retains moisture, and returns a bit of life to it, allowing the bed to calmly reach the autumn rains.
A Few General Tips
Do not leave the bed empty. As soon as you have removed the vegetables, immediately sow green manure or other vegetables—open soil quickly dries out, becomes overgrown with weeds, and becomes compacted.
Do not plant alliums again. After garlic and onions, you should not return other alliums (onions, shallots, leeks, ornamental onions) to the bed for at least 3–4 years. Specific pathogens (causative agents of fusarium, white rot) and pests (nematodes, onion fly) accumulate in the soil and will inhibit new plantings.
Do not sow cruciferous green manures (mustard, rapeseed, oilseed radish) after cruciferous vegetables and vice versa.
Do not let green manures go to seed. Otherwise, they will turn into weeds.
