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. Onion's full potential is about 6,000 kg/acre (~KES 420,000/acre at KES 70/kg), but at Kirinyaga's 57/100 suitability a realistic target here is closer to 4,275 kg/acre (~KES 299,250/acre) unless the constraints above are addressed.