If you’re looking for the best fertilizer for sweet potatoes you’ve come to the right place. Growing sweet potato vines is easy, but if you want your plants to produce a bountiful harvest you’ll need to get a low nitrogen fertilizer with a high potassium content.
You can continue reading this article if you want to learn more about our sweet potato fertilizer recommendations. Or if you just want to get the best fertilizer for sweet potatoes we recommend Lilly Miller Morcrop 5-10-10 Fertilizer (Buy Online).
Best Fertilizer for Sweet Potatoes
Sweet Potato Fertilizer Requirements
The best fertilizer for sweet potatoes will contain a higher percentage of potassium to encourage root development. Sweet potatoes need 150 to 200 pounds of potassium per acre (1/3 pound per 100 sq ft.)
Sweet potatoes only need half as much nitrogen and phosphorus at about 60 pounds per acre (1/7 pound per 100 sq ft).
Using too much nitrogen will cause sweet potato vines to grow vigorously, but it will reduce the final yield of sweet potato tubers.
However, using too little nitrogen will lead to stunted growth and yellowing of the leaves, which will affect the health of the whole plant.
Phosphorus is also another important nutrient that a sweet potato fertilizer should provide in slightly lesser amounts than potassium.
A lack of phosphorus can lead to stunted growth along with weak stems and roots. However, unlike nitrogen using too much phosphorus won’t lead to a massive reduction in yield.
Best Fertilizer for Sweet Potatoes
Lilly Miller Morcrop Tomato & Vegetable Food 5-10-10 16lb
Lilly Miller Morcrop (Buy Online) is a good multi-purpose fertilizer that you can use on sweet potatoes along with other vegetables. This fertilizer has a 5-10-10 NPK ratio, which makes it a good choice for growing sweet potatoes.
Lilly Miller Morcrop contains half as much nitrogen when compared to the overall potassium content. That means it has just the right amount of nitrogen to give you optimal sweet potato vine growth while providing sufficient amounts of potassium to enhance sweet potato tuber development.
This fertilizer is also safe to use on food crops since it’s made in the USA without using any potentially toxic imported ingredients. It’s also very affordable, and you can even get this Lilly Miller Morcrop Tomato & Vegetable Food in a 16-pound bag with Free Shipping.
Grow More Hawaiian Bud 5-50-17, 25-Pound
Grow More Hawaiian Bud (Buy Online) is a water-soluble fertilizer that contains growth-enhancing humic acid. This fertilizer can be mixed into water and used to fertilize the soil around your sweet potato plants, or you can even use it as a foliar spray.
While this fertilizer is primarily geared towards hydroponic growers it still does wonders for plants grown in soil. Especially with the added humic acid, which helps promote nutrient absorption in marginal sandy soils.
JR Peters 77160 Blossom Booster 10-30-20 Fertilizer, 25-Pound
JR Peters Blossom Booster Fertilizer (Buy Online) is another good fertilizer for growing sweet potatoes. This fertilizer has a 10-30-20 NPK ratio, which means it contains half as much nitrogen compared to potassium.
JR Peters Blossom Booster Fertilizer does contain slightly more phosphorus than is necessary to grow sweet potatoes. However, if you’ve tested your soil and it’s deficient in phosphorus you can use this fertilizer to help increase the phosphorus level in the soil.
MasterBlend 4-18-38 Tomato & Vegetable Fertilizer
MasterBlend Vegetable Fertilizer (Buy Online) is a low nitrogen fertilizer which is perfect for growing sweet potatoes in rich fertile soil. This fertilizer has a 4-18-38 NPK ratio, and it also contains trace minerals like magnesium, boron, copper, iron, manganese, molybdenum, and zinc.
MasterBlend Vegetable Fertilizer contains almost 10 times more potassium than nitrogen. That’s less nitrogen than the standard sweet potato fertilizer recommendations, but it’s a good amount if you’re growing sweet potatoes in soil that has been amended with nitrogen-rich compost.
MasterBlend 4-18-38 also makes a great late season fertilizer to help boost root development without promoting excessive vine growth.
Grow More 5088 Water Soluble Fertilizer 0-50-30
Grow More No Nitrogen Water Soluble Fertilizer (Buy Online) is good for growing sweet potatoes in soil that already has enough nitrogen. This fertilizer has a 0-50-30 NPK ratio, so it contains 0% nitrogen, 50% phosphorus, and 30% potassium.
This fertilizer is great if you plan on planting sweet potatoes in a freshly tilled section of your lawn. Most lawns get plenty of nitrogen fertilizer which tends to build up in the soil. However, most lawn fertilizer lacks phosphorus and potassium, but this fertilizer can help replenish any missing nutrients before you plant sweet potatoes in your backyard.
You can also use this fertilizer late in the growing season to increase the size of your harvest without suppressing sweet potato development.
Sweet Potato Soil Requirements
Sweet potatoes also need proper soil conditions for optimal growth. They prefer to grow in warm sandy soils. They are also very sensitive to frost, and you should wait until the soil temperature reaches at least 65°F before starting sweet potato slips in soil.
Sweet potatoes prefer to grow in soil with a pH between 4.5 and 7.0, but they too picky about soil pH as long as your soil isn’t extremely alkaline.
If you need to adjust the pH of your soil you can use lime to increase the pH of your soil, or you can add sulfur to reduce the pH of alkaline soils.
Just remember that it’s a good idea to test soil samples (Buy Soil Meter) before you apply any fertilizer to your garden. You can use the final results to determine what amendments you need to add so you can properly alter the pH level of your soil.
Sweet Potato Fertilizer Problems
Once you get a sweet potato growing you might think it’s going to produce a big crop if it has lots of lush foliage. But this can be a sign that you over-fertilized the plant with too much nitrogen. This can lead to lots of surface growth but little to no root development.
Using too little nitrogen can also result in weak stunted growth along with a poor harvest of sweet potatoes.
Also if your plants don’t get enough potassium the roots will grow long and skinny, and you’ll be lucky if you get a few malformed sweet potatoes.
Sweet potatoes will also exhibit poor growth if they are planted in soil that’s deficient in boron. This trace element helps keep sweet potatoes from developing blister disorder.
The signs of blister disorder will show up early with stunted plant growth, and if the deficiency isn’t rectified it will cause raised bumps to form on the surface of the sweet potato tubers.
