Fake fertiliser has flooded Kisii markets with farmers being advised to be alert this planting season.
Authorities have consequently launched a crackdown with a view to impounding counterfeits and those behind them.
Cartels in the agricultural industry are suspected to be behind the trade with cereals farmers in the region being their main target.
The result has been declining yields blamed on low quality manure and other inputs.
The main crops produced in the region are maize, bananas and beans. Other are potatoes, tea, sugarcane, coffee and horticultural crops.
Kisii County Executive for Agriculture Esman Onsarigo said the region produces all kinds of crops but regretted that counterfeit farm inputs had turned the soil acidic.
“Farmers in this region are practising agribusiness despite the small sizes of land. They produce a lot of maize even challenging Trans Nzoia where the crop is grown on a large scale,” he said.
The current acreage under cash crops in Kisii is approximated at 17,800 acres while the area under food crops is about 72,500 acres.
However, land tenure is small with residents forced to practise small-scale farming.
“Many of our animals have also died as the drugs and chemicals are ineffective. If the situation persists, some of us may abandon livestock farming," said Ms Mercy Kemunto, a farmer.
Farmers in the region have also been asked to watch out for desert locusts as a majority of them were confusing them with grasshoppers.
“We have trained groups on how to counter locusts in case they invade our farms. We are on standby in case of anything but, so far, no case has been reported,” said Onsarigo.