Garlic Soils

Garlic growing in loamy soil


Perfect Soil

In general, garlic prefers sandy loam soils that drain well during wet periods and hold moisture during dry periods. Soils with high organic matter and good fertility are also ideal.

Garlic does not perform well in wet conditions and can rot easily if the soil remains saturated. It also does not perform well in very dry conditions found in sandy soils with low organic matter. 

Low fertility, moisture deficiencies or excesses can all cause weak plants that form small stunted bulbs. The good news, however, is that garlic is a versatile plant that can be grown in almost any soil and all of these problems can be managed if soil improvements are made.

Clay Soil

In clay soils that drain poorly, adding very large amounts of organic matter (peat moss, manure, compost, etc.) and growing the garlic on raised beds, garden boxes or on a slope can make a huge difference. Also, growing deep rooted cover crops prior to the garlic crop can help with internal drainage of the soil.

Garlic does not tolerate wet conditions for very long, so a lot of planning must take place before planting to ensure that good drainage exists. Garlic can do very well on clay soils as long as excess moisture conditions are managed during wet periods. Some of the largest garlic bulbs are grown on well managed clay soils.

Sandy Soil

In Sandy soils that drain quickly and have poor fertility, adding large amounts of organic matter to help with water retention and fertility can improve plant growth tremendously. Garlic can do very well on sandy soils as long as it receives enough supplemental fertility and it receives enough water through rain and/or irrigation.

John Boy Farms On our farm, we are located in a river valley floodplain with soils that range from river silt with high organic matter, to pure clay with medium organic matter. Although this means that our soils are naturally high in fertility, it also means that they have poor internal drainage and can become water logged very easily if not managed properly.

In order for us to grow good garlic crops, we grow all our garlic on raised beds in fields that have a slight slope and have had a large amount of organic matter added. Although the heavier soils are a challenge in wet years, they have amazing fertility and allow us to grow large, healthy bulbs consistently.
 

Soil Fertility

Garlic requires high soil fertility to perform best. When nutrients are at optimum levels, plant growth is healthy and bulb size is maximized. Soil testing is always recommended no matter how large or small your garlic garden or field is.

Often growers who use organic or natural methods feel that they don't need soil tests. This is not a good philosophy and can often lead to deficiencies in certain nutrients or even over fertilization without realizing it.

These are general fertility guidelines that can be used when determining the fertility levels before the growing season starts. They could be lower or higher for you depending on where you live and the type of soils you have, but they can serve as a good starting point. The following amounts are the recommended levels of nutrients in the 0 to 24-inch depth portion of the soil:

Nutrient

Pounds per Acre

Pounds per 1000 ft2

Nitrogen

120 lbs (55 kg)

3 lbs (1.3 kg)

Phosphorus

160 lbs (73 kg)

4 lbs (1.8 kg)

Potassium

150 lbs (68 kg)

4 lbs (1.8 kg)

Sulphur

30 lbs (14 kg)

1 lb (0.5 kg)

Fertility recommendations for growing garlic. 


Phosphorus, potassium and sulphur should be applied and incorporated before planting. Nitrogen should be split into several applications with 1/3 being applied at planting and 2/3 during the growing season starting in spring. After the first spring application, nitrogen should be applied every 2 to 3 weeks until the scapes emerge.

It is also important to not over fertilize the garlic with Nitrogen as this can cause a lot of top growth. Similar to other vegetable crops, too much top growth often leads to small bulbs because the plants are too focused on producing leaves and not storing energy below ground. The goal of fertilizing is to apply just enough nutrients to grow health plants without causing excess leaf production.

Soils that have low nutrient levels can have their fertility increased by adding either organic amendments such as manure and compost, or with commercial fertilizer such as granular and liquid soluble products. No matter what the method of fertilizing is (organic or synthetic), the same overall fertility goals are the same.

When using organic sources to correct fertility deficiencies, they should be added in the late summer or early fall before planting the garlic cloves. This will ensure that the organic materials will have a chance to be incorporated into the soil and begin releasing their nutrients before the garlic starts growing.

It's important to note that all soils, regardless of fertility levels, benefit from adding large amounts of organic matter, especially when growing garlic. Organic matter holds onto excess nutrients and slowly releases them over a number of growing seasons.

As well, organic matter is extremely effective at improving soil structure and tilth. Garlic tends to respond to high organic levels in soil better than most vegetable crops. 

John Boy Farms On our farm, the fertility levels in our soils tend to be on the high side to begin with, however we do sometimes have issues with low nitrogen. This is a common problem for a lot of growers as nitrogen is not naturally high in most soils and has often been depleted over previous years when the farming practices were not replenishing the nutrients. 

When nitrogen is needed, we try to incorporate compost in the year prior to growing a garlic crop or use pelletized manure to try and raise the fertility levels. We notice a huge difference in plant and bulb size between areas that are nitrogen deficient versus nitrogen sufficient, especially in wet or cold years. 

Next → Planting Garlic

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