Soybean is a crop that is being fast adopted in Ghana.

With fertilizer and grain prices hitting record highs, and availability being very limited due to the global price of gas and the ongoing war in Ukraine, farmers in Ghana will continue their turn towards Soybean as a great crop to grow in 2022. Land under soybean cultivation in Ghana has already been growing dramatically in previous years thanks to high prices achieved by producers, and it now is set to increase further still.

We therefore turn our attention to the best ways to get the most from your soybean crop this year. Whilst soybean offers opportunity to get good yields in the absence of Urea, it is important to remember that it is also a hungry crop and actually removes more nutrients than both groundnuts and maize:

This nutrient hunger is really important, because although there is opportunity to make money on soybeans, it is important to do that in the context of a good crop rotation that is building soil health, not depleting it.

It is therefore very important to focus on the nutritional requirements of soybean, both in season to ensure you get the best harvest, and post-harvest, to ensure the soil is ready for the next crop and subsequent yield optimization.

This article has been written with the help of the fantastic Soybean Innovation Lab, whose help we are very grateful for. We will do a subsequent follow up article about pest and disease management in soybean, as it is also very critical.

First Thing’s First: Understand your Soil and Correct Soil Acidity

The important thing about land preparation is to understand your soil and its nutrient availability. This is best done through testing the soil which can be done by contacting Demeter or your local soil lab. Click here to view Demeter Ghana’s mobile soil testing services.

Once your soil result is known, it is important to take the appropriate action. We have written on other blogs about the importance of soil pH on nutrient uptake.

Soil pH is particularly important in soybean. This is because the main way that soybean gets its Nitrogen is through nitrogen fixation in the root nodules: this is the advantage that soybean has over other crops. It can convert nitrogen from the air into nitrogen in the soil as it is a legume, like groundnut and beans. However, this process relies on bacteria infesting the root nodules, and these bacteria cannot survive at an acidic pH. As a result, it is really important to ensure that soil pH is corrected. Use Calciprill to achieve this after testing your soil.

Be Sure to Treat Your Seeds with Inoculant

One of the most important drivers of soy growth and yield is the amount of Nitrogen that the plant can take. The main source of nitrogen for the plant is the plant’s own ability to generate nitrogen from the rhizobium in its root nodules.

Plants treated with inoculant on average yield 45% higher[1] than seedlings that have not been treated with inoculant. This is because treating the seed with inoculant will dramatically increase the root nodulation and therefore the nitrogen fixation. Get in touch with Demeter Ghana Ltd to get the best inoculants for soybean, imported directly from Argentina.

Focus on Key Inputs

At a time of global highs of fertilizer prices, any farmer needs to ensure he or she is getting maximum value from inputs spend. As our other blogs make clear, the key macronutrients are Nitrogen, Phosphorous and Potassium. Let’s look at each one:

No Need for Nitrogen at yields less than 4 tons per hectare

For most farmers in Ghana we do not recommend additional nitrogen application outside of what is provided by rhizobium through inoculant. So, provided inoculant is used, there should be no need for additional Urea or Sulphate of Ammonia (SOA).

The primary reason for this is the amount of Nitrogen fixation provided by rhizobium is directly related to how much bio-available nitrogen is in the soil. So the more nitrogen fertilizer you add, the less benefit you get from inoculant. Inoculant is a much cheaper way to get the Nitrogen that the plant needs.

This relationship between nitrogen fixation and soil-borne nitrogen holds true until you start achieving soybean yields above ~4 metric tons/ hectare. At this point it’s suggested that soybean nitrogen requirements start to exceed what is provided by the soil + inoculant, and that additional nitrogen fertilizer may be beneficial. So if you are achieving more than 4 tons per hectare, you DO need to add Nitrogen. But if you are achieving less than 4 tons per hectare, just stick to inoculant for this year.

Key soybean inputs:

Phosphorus, Potassium, Inoculum and lime are the most important soybean inputs.

As we have discussed, the most effective way of achieving optimal Nitrogen fertilization is through applying inoculant to the seed.

If inoculum is applied, then you still need to focus on Phosphorus and Potassium (P and K) nutrition to ensure that the plant is not limited by nutritional deficiencies that will limit the yield of the plant.

If you have tested your soil, you will know exactly how much of each input you will need to provide to ensure that your plant is not deficient.

However, if you have not undertaken a soil test, we recommend application of DAP (Di-ammonium Phosphate) and our special Polysulphate granules to offer slow release potassium, Magnesium, Calcium and Sulphur to the plant to ensure that they are not limited by these micronutrients or the potassium required.

Reincorporate as much as possible after harvest

It is important to note that even though the plant may produce it’s own N, it will still be deficient in P and K throughout the growing cycle, and especially after harvest. After harvesting your crop, try to ensure you reincorporate the stover leftover to ensure as much nutrition as possible returns to the soil.

More information

This article is a brief summary of the nutritional requirements of growing soybean. There are many other important facts to note when it comes to soybean cultivation such as integrated pest and disease management, good seedbed preparation, and the importance of weed suppression at the early stages of crop growth. For more information read this guide and check out the work of the Soybean Innovation Lab across Africa, and be sure to check in to this website in a few weeks time to see the next instalment of soybean focus.

Get in touch today to understand more about soybean nutrition and how to get the most from your crop.

Phone: +233 24 529 7047

Email: info@demeterafrica.com  

[1] Check Soybean Nodulation to Determine Inoculant Efficacy - UNL CropWatch, Aug. 29, 2013 | CropWatch | University of Nebraska–Lincoln