Effects of rates of organic fertiliser on growth, yield and nutrient content of cabbage (Brassica oleracea var. capitata) grown under shelter

This study investigated the effects of various rates of an organic fertiliser (processed poultry manure) on the growth, yield and nutrient content of cabbage grown under shelter on a clay soil, in the lowlands. Treatments consisted of varying rates (0, 15, 30, 45 and 60 t/ha) of processed poultry manure (PPM). The control treatment was an inorganic fertiliser (N:P2 05 :K2 0: MgO = 12:12:17:2) applied at 2 t/ha. Canopy diameter increased significantly from 32.0-59.5 cm when PPM was increased from 0-15 t/ha, while the corresponding values for head diameter were from 13.8-15.2 cm. A quadratic yield response to rates of organic fertiliser, represented by the equation Y= 9.832 + 0.636x - 0.008x^2, where Y = yield in t/ha and x = organic fertiliser in t/ha, was obtained. The optimum rate of organic fertiliser was 39.75 t/ha. Yield obtained at this rate was 22.47 t/ha. Organic fertiliser rates had significant effects on P and K contents in the outer leaves and, K and Ca contents in the head. Nitrate contents did not differ significantly. Organic fertiliser improved soil chemical properties compared to the inorganic fertiliser. It is concluded that about 40 t/ha of processed poultry manure as the sole source of nutrient, can be used as a guide for organic cultivation of lowland cabbage grown on clay soils under shelter.