Giving Clarity to the issues of fertilizer use and of soil acidity in Kenya

Questions surrounding the types and availability of fertilizers being used in Kenya have emerged over the past few years. The issues of soil acidity and reduced yields over the years has also paused a chain of questions on the credibility of the advice given to farmers on fertilizer application rate and on the use of certain fertilizer products.

In 2014, the government released a countrywide maize suitability soil survey study that revealed most of the soils in Kenya, particularly in the high productive regions of North-Rift and western Kenya were acidic. Unfortunately the narrative that come out of this, was that DAP is the main cause of acidification in our soils with farmers being discouraged from using DAP as a fertilizer. Secondly, farmers were encouraged to use either, NPK 23:23:0 or NPK 17:17:17, without considering the difference in \nutrients added compared to what DAP was providing. Not surprisingly, even upon changing to these fertilizers, the yields would many times be lower than when they would use DAP.

This has brought a lot of confusion among the farmers especially among the small and medium scale farmers. This begs the question, what is the cause of declining crop yields in these regions and secondly, why are our soils becoming more acidic over the years. Answers to these questions would then lead us to probable remedies that can be undertaken to rectify and/or reduce the rate of soil degradation.

There are so many factors that affect soil pH which is a widespread natural phenomenon worldwide especially in regions with medium to high rainfall, whereby leaching of cations slowly acidifies soil over time. Secondly, agricultural production systems can accelerate soil acidification processes through removal of agricultural produce from the land which leads to mining of some of the nutrients that cause an imbalance between cationic and anionic elements which then can lead to reduced soil pH (soil acidity). Thirdly, soil acidification can occur through perturbation of the natural cycles of nitrogen (N), phosphorus (P) and sulfur (S) in soil, through the addition of fertilizers that have the potential to acidify soil. Another issue is the inherent soil properties controlled by the parent material. If we consider the regions in Kenya with soils that have become acidic over the years, these are regions with heavy-medium rainfall and secondly, they have had high yield potential over the years which means a lot of nutrients have been mined over the years, hence the decrease in yields to a meagre to 2-3mt/ha. When it comes to fertilizer usage, the main problem lies in unbalanced fertilization which has mainly focused on only supplying N and P, (DAP, CAN, UREA) leaving out all the other macro and micro-nutrient essential for plant growth meaning all the other nutrients are then removed with the harvests.

Secondly, farmers will usually remove all the plant residues from the field for animal feed or burn them at the beginning of the next planting season. Thirdly, most of these regions also lie in inherently acidic parent material. The more nutrients are mined, the more the cause of nutrient imbalances which leads to soil pH decreases. This, we believe is the main cause of declining soil fertility and soil acidity buildup in Kenya. DAP has wrongly been criminalized for years as the cause of acidic soils while in actual sense a sudden shift to using other products without sorting out the soil nutrients imbalance linked to soil pH and nutrient mining will only accelerate the current confusion that farmers have when it comes to fertilizer usage.

While amending soil has never been an overnight venture liming of soils is the most viable and sensible solution used to rectifying soil acidity problems worldwide. Changing to other fertilizer types without rectify the soil acidity issue will only solve half the problem and will in essence make fertilizer usage more expensive as the efficiency of fertilizer decreases as soil pH reduces (with increase in soil acidity). Kenya is lucky to have a reserve of liming material available in the country and with goodwill from the government; a 3-4 year liming program in the affected regions can be initiated. This has been done in other countries including Rwanda and Brazil which has soils with a closer profile to the Kenyan soils.

In addition, we are only a food deficit because we have limited ourselves to low fertilizer usage. If we compare fertilizer application rates in Kenya and Africa to other productive regions in the world, Kenya uses only a meager fraction of fertilizer used worldwide. It is time that the private sector and government came together and updated the current fertilizer (generally farm inputs) recommendations to allow for improved yields among our farmers. We have potential as a country to improve agriculture if we had more PPPs towards improving agriculture. We should stop using ‘blanket’ recommendations and turn to more specific recommendation for input utilization within Kenya. If we can bring forth all expertise and address one subject at a time, we are bound to increase our yields and improve food security.

To purchase farm inputs and fertilizers in Kenya, buy at our online virtual agrovet in Kenya.

The article was written by Wafullah T. Nekesah and Lillian W. Mbuthia, members of the Society for Crop Agribusiness Advisors, Kenya

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