Soils in Nyeri County have become too acidic to sustain quality food production, researchers have noted as output from farms dwindle.
Climate change, soil infertility and emerging pests and diseases are also to blame for the low productivity seen in the last few years.
The researchers in a report by the Department of Agriculture and Kenya Agricultural Livestock and Research Organisation, said the county’s soil pH ranges mostly from moderate to strongly acidic.
Soil pH in Tetu, Othaya and Mukurwe-ini constituencies is strongly acidic with the pH ranging from between 4.1 to 4.4 and it is moderately acidic in Mathira, where the pH stands at soil PH 5.4.
In Kieni constituency, the county’s food basket, the soil is slightly acidic to a few moderately alkaline with a pH of 7.1 to 8.1, which is not suitable for both food and industrial crops.
Agriculture is the main economic mainstay in Nyeri with maize, beans and potatoes being commonly grown for subsistence while coffee, tea and horticulture are the main cash crops.
In the report dated last month, some soils tested had a low pH of 3.6 to 4.2 for growing food crops in the case of Tetu.
Soils tested for coffee in Mathira East and Mukurwe-ini are extremely acidic with an average pH of 4, according to the report.
Soil infertility is attributed to soils that are strongly acidic, which renders soil nutrients unavailable for crop use.
The report blamed the acidity to inadequate application of manure resulting to poor soil structure, texture and water retention capacity, and inadequate inorganic fertiliser use and poor or lack of soil conservation.
Emerging pests and diseases have also taken a toll on the main cash crop, which is coffee.
MAKE USE OF ORGANIC MANURES
The fall armyworm and maize lethal necrosis diseases are also a major threat to food security in the country.
The report projects a decline in coffee, maize, beans, wheat and potato production if corrective measures are not taken.
“The soils get acidic due to poor farming practices and aggregated use of acidifying chemical fertiliser, continuous mining without replenishment and furrowing,” said Robert Thuo, the Agriculture county executive.
Farmers have been urged to shun the use of conventional fertilisers that have been excessively used taking a toll on their output, Instead, they are asked to use organic fertilisers to boost soil health.
The report further noted there is low soil organic carbon matter content in the soils, a situation prevails across the entire county.
Low soil organic matter content results in low water-holding capacity and encourages soil erosion by water and wind.
Most of the limited nutrients in the soils are nitrogen, phosphorus and calcium which are below adequate levels across the county while potassium and magnesium are also below to acute adequate level.
“Micro nutrient zinc and copper are low in most soils across the county and boron in coffee growing zones,” read the report.
Thuo said farmers in the entire county should make use of organic manures and agricultural lime to modify acidic soils.
He also encouraged crop rotation or mixed cropping especially with nitrogen fixing crops.
Dr Patrick Gicheru, centre director Kalro in Embu said it is important for county governments to provide subsidised fertilisers depending on sub-county particulars.
“Different sub counties have different soil pH, the government should distribute fertilisers that suit particular sub-counties as opposed to uniform use,” he said.
Application of manure the way to boost soils
Well-rotten manure or compost improves the organic matter content, supplement the soil nutrients, improves soil structure, water retention capacity and soil microbial activities.
Farmers are also encouraged farmers to adopt conservation agriculture where minimum tillage is highly recommended.
Most farms have poor soils compromising nutrient uptake and water retention and this challenge can be tackled through conservation agriculture.