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Growing potatoes in your backyard is a great way to ensure you have access to quality French fries anytime. However, growing potatoes is a soil-intensive endeavor that could drain your plot of land of all its nutrients.
Gardening forums recommend using fertilizer or natural compost when planting potatoes. After hearing about the wonders of mushroom compost, you may be wondering about using it for your potatoes.
While you can use mushroom compost for potatoes, it’s not always recommended. The contents of mushroom compost often cause potatoes to develop scab, a common disease that affects root vegetables. However, scab does not affect the taste of potatoes, just the appearance, and it isn’t guaranteed when using mushroom compost, so you can still use it sparingly.
Read on to learn more about mushroom compost and potatoes, including the situations where you can use this compost or not.
Why Does Mushroom Compost Cause Potatoes to Develop Scab?
Before weighing the risk of using mushroom compost on your potatoes, you need to understand what scab is, how it forms, and how mushroom compost contributes to its formation.
Scab is a common disease affecting mostly potatoes and other root vegetables such as carrots, parsnips, and radishes. It is caused by the bacteria Streptomyces scabies, which is most common in soils with lots of organic material or fast-drying. Potatoes infected with this bacteria have raised or slightly sunken rough patches or deep craters.
While you can still eat potatoes with scab, you have to put in extra effort to peel and prepare them for eating. They look unsightly, so they won’t sell as well and are more prone to rotting if you don’t store them in a dry enough place.
While potatoes can develop scab with too much organic material, mushroom compost causes more of this bacterium to develop due to its composition. Mushroom compost is not compost made out of mushrooms but compost made from the material that commercial mushroom farmers use to grow their fungi. The composition varies from farmer to farmer, but it usually contains materials such as:
- Animal manure
- Corn cobs
- Peat moss
- Soybean meal
The last “ingredient” is the most common culprit for potatoes developing scab. Many farmers add lime to their mushroom compost, which makes the mixture very alkaline. The bacteria that causes scab can survive indefinitely in alkaline soils (but die easily in acidic soils), so keep that in mind when adding mushroom compost to your plant beds when planting potatoes.
Tips for Using Mushroom Compost with Potatoes
If you want beautiful, easy-to-peel potatoes, you should probably avoid using mushroom compost because it will cause the potatoes to develop scab. However, you can still use mushroom compost if you are careful about the growing conditions of your potatoes or if you have no alternative.
One suggestion is to carefully monitor the pH levels of your soil. Since Streptomyces scabies thrives in very alkaline soil, you’ll have better results using mushroom compost on potato beds that are already slightly acidic. Avoid using it in soil that is already alkaline because the combination of alkaline fertilizer and alkaline soil will make it a breeding ground for bacteria.
The potato type also matters when covering your plant bed with mushroom compost. Early potatoes will do best with mushroom compost because they spend the least amount of time in the plant bed and will not have time to develop scab.
Finally, be sure to time how you spread your mushroom compost. This organic fertilizer works best if you spread it months ahead of time so that it will give it time to break down into the soil and balance out the pH. Let it sit, mixed in properly, over winter, and that will make better growing conditions for all crops, including potatoes.
What Are the Best Growing Conditions for Potatoes?
Potatoes are not a very finicky vegetable, but there are still some things to consider when choosing their growing conditions. Potatoes do best in well-drained soil that is a bit on the sandy side (another reason why mushroom compost is not the best idea—it retains water too well). They need slightly acidic soil in a sunny location.
Tips on Growing Potatoes
For growing the best tubers, here are some tips.
- Potatoes require plenty of fertilizer, so start fertilizing the soil at least a month before you actually plant your potatoes. Gardeners recommend side-dressing or distributing manure or compost along the side of the row where you will plant the potatoes. Use nitrogen-rich fertilizer or compost but avoid commercial fertilizer that also has weed-killing properties so that it doesn’t damage your plants by accident.
- When choosing your potato varieties, ensure that you use healthy potatoes if you are planting from whole plants. Diseased tubers will cause your new crop to have a disease as well.
- Potatoes are an early crop, so plant them as soon as the soil starts warming in early spring. Some potatoes, nicknamed “earlies,” will be ready for harvesting in just a few weeks, while most will take all spring and summer to mature.
- To help the potatoes grow properly, form soil hills along the stems as they shoot up and water thoroughly, soaking the soil completely, at least once a week.
- Rotate your crops and never plant potatoes in the same spot two years in a row because they are very nutrient-intensive crops.
Potatoes require lots of nutrients to grow, so gardeners recommend adding additional fertilizer or compost to the soil. However, avoid using mushroom compost if you can because it is too alkaline for potatoes, which do best in slightly acidic soil.
Alkaline soil can cause potatoes to develop scab, which doesn’t make them inedible, but it makes them ugly.
However, there are a few conditions under which you can still use mushroom compost: for example, if your soil is highly acidic, you are planting early potatoes, or you have no choice.