Growing Onion in Kirinyaga

Soil suitability analysis based on Kirinyaga's nutrient profile

Onion can be grown in Kirinyaga County, but the soil scores 57/100 and needs targeted management to reach full potential. At an average pH of 5.31 the soil is moderately acidic, below Onion's preferred 6–7 range; agricultural lime will lift pH and unlock phosphorus the crop cannot otherwise access. The main gap is phosphorus — measured at N 1.36 g/kg, P 12.5 mg/kg, K 177 mg/kg against this crop's high/high/medium demand — so the fertilizer plan below prioritises closing that deficit. Onion prefers sandy loam soils, while Kirinyaga is largely clay, so drainage and organic-matter management matter more here. At current prices (about KES 45/kg) and a typical 3,500 kg/acre yield, a well-managed Onion crop here can gross roughly KES 157,500 per acre.