Effect of organic based Soil fertility management strategies on soil nutrient status and marketable quality of Kales (Brassica Oleracea Var. Acephala) in Kabete, Kenya
Demand for uncontaminated and safe agricultural products in Kenya for the last two decades has created a major shift from the use of conventional farming practices to organic based techniques. However, there remains a challenge of poor quality and yield of vegetables. This study aimed to enhance the quality and yield of kale ((Brassica oleracea var. acephala) in Kabete - Kenya, through use of organic inputs and integration of chickpea (Cicer arietinum) either as an intercrop or in rotation with kale. The experimental layout was a randomized complete block design with a split plot arrangement. The main plots were cropping systems; crop rotation (Chickpea – Kale), monocropping (sole Kale) and intercropping (chickpea/Kale). The split plots were organic inputs (FYM and Minjingu rock phosphate). The preferred kale quality attributes were also assessed during the study through a survey targeting 70 farmers. To ascertain the sustainability of the imposed treatments, partial and full nutrient balances (N, P and K) were determined using NUTMON. Parameters collected for the survey included the major vegetable produced by the farmers and the quality attributes they aim for in production, challenges that they face and coping strategies adopted. Organic carbon, N, P, K and kale yield were measured for the on station experiments. About 78% of farmers produced kale with the major quality attributes preferred being large size (76%) and produce free from disease and pest signs (52%) such as black rot and diamond back moth. The production challenges were; unpredictable rains (85%), lack of standardized input application rates (66%) and lack of irrigation equipment (43%). Organic C (3.2%), N (0.45%) and K (1.5 mg/kg) were significantly (P<0.05) higher in the rotation system with application of FYM. P content was significantly (P<0.05) higher in the intercropping systems with application of Rock P (32 mg/kg). The kale yields followed a similar trend as for the nutrients C, N and K with highest yield (1.62 t/ha) obtained in the rotation system with application of FYM. The control (0.45 t/ha) of the intercrop had the lowest Kale yield. Positive full N balances were realized in the crop rotation systems with application of FYM whereas the partial N balances were all negative across cropping systems and organic inputs except for the monocropping system with application of FYM. Positive full and partial P balances were realized in all the cropping systems with the application of Rock P. Negative full P balances were realized in all cropping systems with application of FYM and control. Negative full and partial K balances were realized across cropping systems and organic inputs. Kales grown in rotation with chick pea and application of FYM are a sustainable strategy for enhanced kale production in Kabete. Key Words; Chickpea; Crop Rotation; Farm Yard Manure; Intercropping; Monocropping; NUTMON; Rock Phosphate.