Farmers hear all the time of N, P and K, and spend a significant part of their income on bags labelled ‘NPK’.
Nitrogen (N), Phosphorus (P), and Potassium (K) are the building blocks of, and essential fuel for, your crops. Let's break down what they do for the crop; how to make sure they are adequately provided; and how to use them to maximise your harvest.
Nitrogen (N): The Growth Booster
Nitrogen is the "muscle builder" for your plants. It's essential for healthy leafy growth, which is the foundation for a strong and productive plant. Think of those lush green leaves – they're powered by nitrogen.
In Ghana, where we grow a variety of annual crops like maize, rice, and vegetables, nitrogen is especially important for promoting vigorous growth, leading to higher yields.
For perennial crops like tree crops (cocoa, oil palm, cashew), then Nitrogen might not be so important because the growth of the plant is not as important as the fruiting of the crop.
- What it does: Fuels leafy and vegetative growth, promotes chlorophyll production (for photosynthesis, creating energy for the plant), and is crucial for protein formation.
- What happens if there's not enough: Plants look pale and yellow, especially older leaves. Growth is stunted, and yields are significantly reduced.
- Where to find it: Urea, SOA, NPK fertilisers like T15, 20-10-10, 23-10-5, and organic sources like manure. High levels provided by Calcium Nitrate, Potassium Nitrate. See our products page for more information
Legumes like soybean, groundnuts, and cowpea have the unique capacity to fix nitrogen from the air into nitrogen for the plant, if treated with inoculants like Demeter Rizoliq Soy
- How to make it effective: test your soil beforehand or ask your Demeter agronomist the soil pH in your area. If the soil is acidic, make sure you neutralise it before applying fertiliser to ensure that the fertiliser is more effective.
Do one thing to improve N levels on your farm: Apply Urea or SOA
Phosphorus (P): The Root and Energy Champion
Phosphorus is the "root developer" and "energy provider." It plays a vital role in root growth, especially in the early stages of a plant's life. A strong root system is crucial for absorbing water and nutrients from the soil, making your crops more resilient. Phosphorus also helps the plant convert sunlight into energy, which is essential for growth and development. In crops like cocoa, which is so important to our economy, phosphorus is crucial for healthy pod development.
One thing to note about P is that deficiency is often harder to detect, often appearing as a general stunting. Often, when you can identify the P deficiency, it is already too late to help that particular crop, so if there are stunted crops in your fields, then it may be that there is P deficiency.
- What it does: Stimulates root growth, helps with energy transfer, and promotes flowering and fruiting.
- What happens if there's not enough: Poor root development, stunted growth, and delayed maturity. You might see purplish or reddish discoloration on leaves.
- Where to find it: NPK, Ground Rock Phosphate (GRP), Diammonium phosphate (DAP), triple superphosphate (TSP), MKP, organic fertilisers and compost.
- How to make it effective: Phosphorus is the most sensitive crop to soil acidity, and where levels if acidity are high, then levels of P availability in the soil will be low, because the acidity binds the P into a form that is unavailable to plants. In situations of high acidity, neutralise the farm using Calciprill, or use GRP.
Do one thing to improve P on your farm: apply Calciprill (soil neutraliser) to make P available to your crops
Potassium (K): The Strength and Quality Guardian
Potassium is the "strength builder" and "quality enhancer." It's essential for overall plant health, making your crops strong and resistant to diseases. Potassium also plays a crucial role in fruit development and improves the quality of your harvest. For crops like yams and cassava, which are staples in our diets, potassium is vital for producing large, healthy tubers. And any crop that is producing a fruit, from tomatoes and cashews to cocoa and oil palm, will always need high levels of potassium to put into the fruit.
- What it does: Strengthens stalks, improves disease resistance, helps with water regulation, and enhances fruit production and quality.
- What happens if there's not enough: Weak stalks, making plants prone to lodging (falling over). Leaves may have yellow or brown edges. Fruit yield and quality is also affected, and you will typically see high levels of fruit abortion because the plant lacks the K to produce a healthy fruit
Plants will also be more susceptible to disease where K is deficient
- Where to find it: NPK, Muriate of potash (MOP), MKP, and Asaase Hene (Polysulphate) are the best sources of K for your farm.
Do one thing to improve K on your farm: Apply Asaase Hene (Polysulphate) to provide slow release K to your crop
Getting it Right on Your Farm
Understanding the roles of N-P-K is just the first step. To maximize your yields, you need to know the right amounts to apply. That's where soil testing comes in. A soil test tells you what nutrients your soil is lacking, allowing you to apply the correct type and amount of fertilizer. Don't just guess. Investing in a soil test is an investment in your farm's future: think about not only what the NPK do for your crops, but how the soil acidity and health affects the availability of those nutrients to your crops.
Think of your farm like a mobile money account for your crops.
- pH is like your mobile money network signal: It needs to be strong and stable for transactions to go through smoothly.
- Nutrients are the airtime or data bundles: Your crops need these "bundles" to grow and thrive.
Just like a weak signal can prevent you from topping up your airtime or data, an imbalanced pH can prevent your crops from accessing the nutrients they need.
- Ideal pH (strong signal): When the soil pH is just right (around 6.0 to 7.0), it's like having a strong, stable mobile network signal. The "airtime" (nutrients) can be transferred easily to your crops. They can "top up" (absorb) what they need without any problems.
- Acidic pH (weak signal): If the soil is too acidic (below 6.0), it's like having a very weak signal. You might have the "airtime" (nutrients) available, but the "transaction" (nutrient uptake) keeps failing. Your crops can't "top up" effectively.
- Alkaline pH (network overload): If the soil is too alkaline (above 7.0), it's like the network is overloaded. Some "transactions" (nutrient uptake) get blocked. Even if the "airtime" (nutrients) is there, your crops can't access it reliably.
Why does this matter?
- Crops need "airtime" (nutrients) to function: Just like your phone needs airtime or data, crops need a balanced diet of nutrients to grow strong and produce a good harvest.
- The network signal (pH) affects how easily you can "top up" (nutrient uptake): If the pH isn't right, your crops won't be able to "top up" (absorb) the nutrients, even if they're in the soil.
- Checking your signal strength (soil testing): A soil test is like checking your network signal strength. It tells you if your soil pH is optimal or if you need to adjust it (by adding lime or other amendments) to make sure your crops can reliably "top up" (access) the nutrients they need.
In short: Keeping your soil pH in the sweet spot is like ensuring a strong and stable mobile network signal so your crops can easily "top up" (access) the "airtime" (nutrients) they need to grow and give you a good harvest.
If you don’t believe in the results of soil testing or can’t afford the test, then contact your local Demeter agronomist today on +233 24 529 7047: we will provide, for free, a simple analysis of your soil using satellite imagery and ground-truthed data. If you care for your soil and understand why the Three Harvest Heroes are so important, you will be moving in the direction of a productive and profitable farm!
