Unlocking the potential of organic fertiliser to build healthy soils and resilient food systems
Youths in Mwea, Kirinyaga County carbonising rice husks to produce biochar fertiliser, which is extremely rich in nutrients and good for rebuilding the soil.
What you need to know:
- Biofertilisers are farm inputs made using organic materials that produce beneficial microorganisms (microbes) such as bacteria, fungi, or algae, which enhance plant nutrient availability and soil health.
A new study has revealed that application of biofertilisers can compete effectively with synthetic fertilisers based on crop yields.
If produced on scale, the study affirms that biofertilisers will effectively serve as alternative input that can also improve soil health, contribute to the long-term sustainability of agricultural production and productivity, thereby building toward climate change mitigation and adaptation.
Biofertilisers are farm inputs made using organic materials that produce beneficial microorganisms (microbes) such as bacteria, fungi, or algae, which enhance plant nutrient availability and soil health, offering a sustainable alternative to chemical fertilisers that only provide nutrients directly to the plant, but leave behind depleted and acidified soils.
“The results from the participatory on-farm trials indicate that biofertilisers and farmer practices (use of farmyard manure, bokashi and intercropping) are competitive to the use of inorganic fertiliser (NPK - nitrogen, phosphorus, and potassium), as there were no noted significant differences among yield at the five locations,” said Dr David Ojwang, sector leader, Agrifood systems at SNV.
Bokashi is a biofertiliser made by fermenting organic wastes such as farmyard waste, bran, molasses, and charcoal dust, to produce an input that enriches soil with nutrients and beneficial microorganisms.
The study, which was commissioned by IKEA foundation and implemented by SNV, Great Lakes University of Kisumu and Pwani University, compared NPK – the most used fertiliser in Kenya - with the use of farmyard manure, bokashi and intercropping with leguminous plants (which aid in nitrogen fixation in the soil).
The trials were laid in a randomised complete block design (RCBD) in selected farmer fields in Kakamega, Kericho, Bungoma, Uasin Gishu and Nakuru during the 2022 and 2023 long and short rains, where Irish potatoes, Swiss chard, beans, cow peas and Black night shade vegetables were adopted as test crops.
“There was also an added advantage in application of biofertiliser, where it improved germination rate, minimised further reduction of soil pH, while increasing soil potassium levels,” said Dr Ojwang.
“The study therefore recommends promotion of biofertilisers among smallholder farmers in the region although concerted efforts need to be put on their availability,” reads part of the recommendation from the study that was presented at the second Eastern Africa Agroecology Conference in Nairobi.
This comes at a time when application of biofertilisers is rapidly gaining traction among agronomists and soil scientists, particularly in Africa, as the ecological inputs have the potential to promote sustainable agriculture for African food systems and climate resilience.
In Kericho County, for example, the management of a 50-acre Kaptepeswet Tea Estate have turned entirely to the use of biofertilisers as a replacement for NPK, and after three years, the farm is thriving with healthy organic bushes.
“We have always used the NPK fertilisers on our tea estate, but for the past three years, we started trials with organic fertilisers and soil conditioners deliberately to convert our crop into an organic estate so as to address the constantly growing global demand for organic products,” said Gilbert Korir, the farm manager at Kaptepeswet Farm.
According to the Data Bridge Market Research, the global organic tea market size was valued at USD 1.70 billion (Sh221 billion) in 2023 and is projected to reach USD 2.83 billion (Sh367.9 billion) by 2031, with a Compound Annual Growth Rate of 6.60% during the forecast period of 2024 to 2031. This exponential growth is driven by increasing consumer awareness of health and environmental issues related to organic farming.
Despite the growing demand for organically grown food, experts have observed that biofertilisers have the potential to improve soil biological characteristics as they sustain the proliferation of microorganisms and support crop growth and development by enhancing nutrient availability.
Studies have further indicated that such organic inputs have active formulations made of microorganisms such as nitrogen-fixing rhizobia, which, when applied into the soil, improves the soil ecosystem functions in the restoration and preservation of nutrient richness.
“It may take a longer period to see the results of organic fertilisers, but once the nutrients are provided, it will take a longer time rejuvenating the soil, from which the plants will continue benefiting from season to season,” said Dr George Oduor, a soil health research scientist.
In the contrary, synthetic fertilisers are water-soluble and, they provide nutrients directly to the plants without necessarily replenishing the soil, hence, the farmer must reapply the fertilisers regularly to keep the crops healthy.
Overuse of synthetic fertilisers can also change soil pH, increase the likeliness of pest infestations, accelerate soil acidification and lead to biodiversity loss.
So far, different organisations in the country are now able to produce biofertilisers and organic soil conditioners using locally available raw materials.
According to Dr Ojwang, there is need for long-term comparative cost-benefit analyses to ascertain the potential of biofertiliser, farmer practices and NPK to determine investment pathways for evidence-based promotion of sustainable agriculture in Kenya.
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