Choosing the Right NPK Fertiliser: When to Use 20-10-10 vs 15-15-15

Fertiliser decisions can make or break a farming season. For many Ghanaian farmers, the choice between NPK 20-10-10 and NPK 15-15-15 often feels like guesswork, but it doesn’t have to be. We believe in equipping farmers with the knowledge and confidence to boost yields, improve soil health, and grow sustainable businesses.

In this blog, we explain the difference between these two popular fertiliser formulations, guide you on how to choose the right one for your crop and growth stage, and show how Demeter Ghana can support your farm to thrive, wherever you are in Ghana.

Why the Right NPK Ratio Matters

NPK stands for Nitrogen (N), Phosphorus (P), and Potassium (K), the three essential macronutrients that every plant needs to grow. Each nutrient plays a unique role in helping crops thrive, but different crops and even the same crop at different stages of growth have different nutrient needs.

• Nitrogen (N) promotes lush, green, leafy growth, ideal for cereals and leafy vegetables in their early stages.

• Phosphorus (P) strengthens root development and helps with flowering and fruiting.

• Potassium (K) improves the resilience of plants, making them more tolerant to drought, diseases, and improving the quality of fruits and seeds.

Choosing a fertiliser with the right proportions of these nutrients can mean the difference between a mediocre harvest and a bumper crop. In fact, research by the International Fertiliser Development Centre (IFDC) shows that applying the right fertiliser blend can increase maize yields in Ghana by as much as 60% compared to fields with no fertiliser at all (IFDC Ghana, 2023). This is why making an informed choice matters so much.

What’s the Difference? 20-10-10 vs 15-15-15

One of the most common questions we hear from farmers is which of these two blends is better. The answer depends on what you are planting and when.

NPK 20-10-10 contains a higher proportion of nitrogen, 20%, with 10% phosphorus and 10% potassium. This makes it particularly effective for crops that need a strong vegetative push at the beginning, such as maize and rice. Cassava also benefits from this nitrogen-rich boost early on, as it helps the plant develop plenty of leaves to support tuber development later.

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On the other hand, NPK 15-15-15 is a more balanced blend, offering equal parts of nitrogen, phosphorus, and potassium at 15% each. This makes it versatile and suitable for many crops, especially those that need steady and balanced nutrition throughout their life cycle. Cocoa, which benefits from a healthy mix of nutrients, responds well to 15-15-15. The same goes for fruiting vegetables like tomatoes and peppers  and fruit trees like citrus and plantain, particularly when they are flowering and fruiting

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Practical Crop Recommendations

Below is a quick reference for which formulation works best for key Ghanaian crops:

Why Partner with Demeter Ghana?

At Demeter Ghana, we don’t just sell fertilisers; we deliver tailored crop nutrition solutions backed by global expertise and a deep understanding of Ghanaian soils and farming practices. As the official distributor for partners like ICL, OMEX, OMYA, etc., we bring farmers international quality standards adapted to the unique conditions in Ghana.

Our team goes beyond supply. We work alongside farmers to provide on-farm advisory services, helping you apply the right fertilisers at the right time and in the right quantities. We also offer soil testing services so you know exactly what your land needs before you invest. And because availability can make a huge difference, we ensure a consistent supply of high-quality inputs even in remote farming communities.

We encourage you to visit our Facebook page and LinkedIn to see how other Ghanaian farmers are growing with our products and advice.

Img 3. Farmers showing yield from application of Demeter Ghana input products.

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Tips for Ghanaian Farmers When Choosing NPK

When deciding which NPK blend to use, it’s important to consider your crop and its stage of growth. Overusing nitrogen-heavy fertilisers late in the season, for example, can lead to leafy crops with poor grain or fruit development. Soil testing is also highly recommended, as many Ghanaian soils, especially in the forest and savannah transition zones, are phosphorus-deficient. Without enough phosphorus, root development suffers, and plants cannot take up nutrients effectively.

You should also follow the recommended application rates to avoid wasting resources and harming your soil. Excessive fertiliser use can cause nutrient runoff, which is bad for both the environment and your pocket. For more guidance, talk to a Demeter advisor who can help you create a plan suited to your specific needs.

• Always match the NPK formulation to the crop type and growth stage

• Test your soil regularly to avoid guessing and risking yields

Research from the Council for Scientific and Industrial Research (CSIR-SARI) highlights that over 50% of Ghanaian soils are acidic and benefit from lime application alongside fertilisers to improve nutrient uptake. This is just one example of how understanding your soil makes every cedi you spend count for more.

Let’s Grow Together

As a leader in the Ghanaian agricultural space, we are passionate about helping Ghana grow, one field at a time. Choosing the right fertiliser blend can transform your harvest, and we are here to help you make the best choice for your farm.

You can call or WhatsApp us today on +233 24 529 7047 to speak directly with one of our sales agronomists. Or, if you prefer regular updates and expert tips, follow us on LinkedIn to stay informed and inspired.