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Acidity levels in soil denying farmers good yields, scientists warn

Agriculture researchers have warned of drastic food reduction in coming years following high soil acidity levels.

The challenge is further compounded by lack of soil tests and low application of lime to replace depleted nutrients and with continuous cropping particularly because of population pressure in the medium and high rainfall areas in the country, the soil fertility has greatly declined.

Soil acidity has rapidly become a serious problem to the country, creating production problems and limiting availability of some essential plant nutrients, a major cause of poor crop performance and failure.

The scientists from Kenya Agriculture Livestock and Research Organization (KALRO) caution that acidity levels in medium and high rainfall regions currently stand at 63 per cent and this is denying farmers the ability to produce more food.

Speaking at KALRO- National Agriculture Research Laboratories (NARL) Kabete, during a farmers’ field day, Centre Director Dr. Esther Gikonyo said the acidity level in soils is worrying and it is time drastic measures are taken by all stakeholders to improve on production that will result in food sufficiency.

“The situation has not been helped by application of fertilizers and farmers have little preference of lime to boost the nature and texture of their soils and identify it with the cash crops such as coffee and tea and this has continued to deny the country enough food, ” said Gikonyo.

“There is no awareness and farmers are ignorant of the benefits of lime. It is good for improving food production and besides also human health,” she said, adding that there is a very high correlation with human health in soils that are very acidic and lack micro nutrients.

“The parameters in soil fertility are soil PH which is the alkalinity and acidity of soil that determines the availability of crop nutrients and considering that 70 percent of the high and medium areas supply food to the nation, it’s a high time that we cure the acidity issue,” she said.

Gikonyo added that the only remedy to acidity is applying lime which neutralizes and this enhances the crop nutrients, noting that if coupled with appropriate fertilizer recommendations based on the soil testing, this will not only improve the crop production fourfold but will address the issue of food sufficiency and nutrient security.

“For the high medium rainfall areas which is equivalent to 7.5 hectares, and whose PH level are below the optimal soil levels for good crop production, liming is a cheap technology as it is available in the country, can be mined also in the country and is cheap as one bag will sell between Sh 300 and Sh 600,” she said.

Another benefit of liming, Gikonyo said is that when soil is limed, the impurities in the fertilizer like the heavy metal absorption becomes less, unlike where PH is low as is in many soils, the uptake of heavy metal is high thus the likelihood of food being unhealthy as it will have heavy metal contamination.

On matters fertilizer, Gikonyo explained that when the PH of the soil is below 5.5, this indicates the possibility of aluminum toxicity which is detrimental to soil growth.

She noted that fertilizer should be provided according to the requirement of soils in the different regions, noting that there is a need for soil fertility mapping done that will indicate the deficient plant nutrient in specific areas.

In research done in 2014, she said that they established that there were many plant nutrients that are deficient in soils, constraining crop productivity but the mapping of geographical location of soil sampling sites was not incorporated into the research and that was a weakness.

“We are proposing, in future, that we need to have soil fertility maps established for different regions or counties so that the fertilizer that is specific in specific areas, based on nutritional requirement of the crop in the counties can be provided or availed by the government,” Dr. Gikonyo said.

The Centre Director also added her voice to the issue of DAP (diammonium phosphate) fertilizer and the NPK (nitrogen (N), phosphorus (P), and potassium (K) fertilizer that has brought a lot of debate in the country saying that research they conducted between 2016 and 2019 came out clearly to show that DAP gives the best yields.

“We worked in Uasin Gishu and three Counties in Central Kenya where soils are strongly acidic and the result indicated what the farmers have always believed and know that DAP is the best fertilizer and also from our findings, the DAP still gives best yields compared to NPK,” Gikonyo added.

She explained that DAP has the highest phosphate content which is inherently low in the soils and particularly so in the acidic soils and that when applied to the soils, it is converted to the insoluble form that cannot be taken up by the crop.

“The best management of acidic soils would be the application of lime to neutralize the acidity and combining it with recommended fertilizer based on soil test then we will address the food production challenge,” Dr. Gikonyo said.

According to the researchers, there is a need to prioritize liming as a sustainable integrated soil fertility management technology within National Agricultural Research and Extension Systems.

By Wangari Ndirangu

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