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November 3, 2023
Rocco Falconer

What Farmers are Missing When it Comes to Fertiliser Application

What Farmers are Missing When it Comes to Fertiliser Application
It is not fertiliser usage but fertiliser use efficiency that matters.

Farmers purchase and apply fertiliser for one reason: to in crease profits. At Demeter Ghana, we are obsessed with making farmers more productive and more profitable. Sometimes, however, more fertiliser doesn’t always mean more yield. And it certainly doesn’t always mean more profit.

A much-overlooked statistic that we should pay more attention to is that of nutrient use efficiency. Nutrient use efficiency (NUE) is a measure of how efficiently plants use available nutrients to produce biomass and, importantly, grain yield. NUE depends on the plant’s ability to uptake nutrients efficiently from the soil, but also depends on internal transport, storage and remobilisation of nutrients.

Our intention is to encourage farmers to apply the economically optimum nutrient amount. Too little nutrient application will result in yield limitation, and farmers should never cut corners to compromise yield.

Multinational organisations, governments, farmers and NGOs all use an increase in fertiliser application rates per hectare as a target for sustainable development. As a company that sells more fertiliser than any other product, we wholeheartedly support this objective, and agree with the Abuja Declaration that we should target the application of [50kgs] of nitrogen fertiliser per hectare. The impact of fertilisers is well documented and hugely beneficial to food security.

However, increasing fertiliser application rates must be seen as just one part of closing the yield gap. A huge part of increasing productivity and profitability is not always to increase fertiliser application rates, but rather to increase nutrient use efficiency. Nutrient Use Efficiency, which can be measured as the amount of nutrient that is converted into harvestable yield, can be as low as 27% in Ghana, and it can be as high as 80-90% in the rest of the world. This means that the same amount of fertiliser might be 3x as effective if you pay attention to this important metric: that is a huge uptick in economic recovery and return on investment (ROI)! 

Put another way, the challenge is not putting an ever-higher number of bags of fertiliser on your crops: rather it is to increase the effectiveness of the bags you apply. If one bag of fertiliser can either be 27% efficient or 90% efficient, wouldn’t you like to get the value of three bags for the price of one?

There are several simple ways to do this, which we will discuss shortly. A useful way of thinking about it is considering what we should start, what we should stop, and what we should continue:

STOP thinking about only applying fertiliser

START thinking about soil health

CONTINUE thinking about crop nutrition

What we mean by this is: farmers sometimes think that soil is just a growing medium. This is wrong: the soil is a living and breathing organism that is host to millions of life forms, from helpful bacteria and fungus to dangerous and destructive pests. The healthier your soil, the healthier your plants will be, and the more able to defend against pest and disease attack. And, crucially, the soil will be more able to supply nutrients to the plant.

If the soil is not healthy, such as very acidic, or with limited soil flora and fauna, then the majority of nutrients that are applied will be leached: this means they are either converted into a different form, or are converted into gases which leach away, or in another way are not able to be supplied to the plants. This can cause huge losses: if nutrient use efficiency is as low as 27% then you are paying 400% for the same nutrients that someone who has neutralised their soil is paying.

On the other hand, if the soil is healthy, your soil will support a wide range of nutrients to the plants. Whatever happens, you still need to think about crop nutrition, and there is a real risk of nutrient mining. This means  the soil nutrients taken away in the form of harvestable yield are not replaced year on year, which reduces the long-term nutrient balance of the soil and can seriously degrade it. This certainly is a serious risk across Ghana, and needs to be countered through the application of fertilisers to yielding crops.

Let’s start with maize. For maize, as with many other crops, nitrogen is the most important nutrient. N is usually the costliest nutrient because it is required in the largest quantity, almost always inadequate without fertilisation, does not carryover substantially from season to season, and has the greatest impact on yield.

Increasing nitrogen use efficiency (NUE) is crucial for sustainable agricultural practices, minimizing environmental impacts, and optimizing crop productivity. Several approaches can be employed to enhance nitrogen use efficiency. Here are some effective strategies:

1.      Soil Testing and Nutrient Management: Conducting regular soil testing allows farmers to assess the nutrient content and pH levels of the soil:

Soil pH is likely to be the biggest single contributing factor to nutrient use efficiency. This is because the pH of the soil will determine the ability of the soil to supply the nutrients applied as fertiliser to the crop. When pH is low, the soil cannot supply the nutrients to the crop. The extent of this is demonstrated in the below chart:

More information on this important topic is available on our other blog here: What is Soil Conditioning and Why is it Important? - Demeter Ghana Blog - Helping Ghana Grow

The second reason we go in for soil testing is by understanding the soil's nutrient status, farmers can apply nitrogen fertilisers more precisely, matching the crop's specific requirements. This approach prevents over-fertilisation and ensures that nitrogen is supplied at the right time and in the right amounts. If you already have the correct level of nitrogen in your soil, why do you need to spend money to apply more? Remember, Nitrogen rarely builds up year on year, so if you apply nitrogen and it is not used by the crop within that cycle, it will not carry over to next year (this is not the same with other nutrients).

2.      Timing and Split Applications:

Timing is crucial for maximising nitrogen uptake by crops. Applying nitrogen fertilizers at critical growth stages, such as during active vegetative growth or just before the reproductive phase, enhances plant nitrogen utilisation. Additionally, splitting the application of nitrogen fertilizers into multiple doses throughout the growing season can improve nutrient uptake efficiency and reduce losses due to leaching or volatilisation.

The fertiliser should be applied to the crop at the time of maximum demand.

3.      This issue can also be overcome through the useof controlled release fertilisers, which release their nutrients over timerather than all in one go.

Speak to an agronomist for more specific information on crop types and nutrient regimes.

4.      Crop Rotation and Cover Crops:

Implementing crop rotation practices and incorporating cover crops into the rotation can enhance nitrogen use efficiency. Certain crops, such as legumes (e.g., soybeans, cowpeas, clover), have the ability to fix atmospheric nitrogen through symbiotic relationships with nitrogen-fixing bacteria. When these crops are included in the rotation, they can contribute nitrogen to subsequent crops, reducing the reliance on synthetic fertilizers.

5.      Enhanced Nutrient Management Practices:

Implementing best management practices, such as proper irrigation management, optimised planting density, and use of organic amendments, can improve nitrogen use efficiency. Efficient irrigation practices reduce waterlogging and leaching of nitrogen from the root zone. Optimal planting density ensures that nitrogen resources are utilized effectively, while organic amendments enhance soil organic matter content and nutrient-holding capacity.

6.      Always paying attention to soil biology, through the use of inoculants and by paying attention to soil health, and minimising tillage (where possible)
7.      Integrated Nutrient Management:

Integrated nutrient management involves combining different nutrient sources, such as organic fertilisers, crop residues, and mineral fertilisers, to meet crop nutrient requirements. By diversifying nutrient sources, farmers can optimise nutrient availability and reduce dependence on fertilisers, thereby improving nitrogen use efficiency.

It's important to note that the most effective approach to increasing nitrogen use efficiency may vary depending on factors such as crop type, local conditions, and farming practices. Farmers should consider adopting a combination of these strategies based on their specific context. Demeter Ghana Ltd can help with all of these questions and help you devise a strategy that is crop, region and season specific. Do get in touch with your local agronomist by calling 024 529 7047 now, and ensure that you are making the most of your agricultural budget.

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