Integration of Biochar, Organic and Inorganic Fertilizer Amendments on Growth and Yield of Carrot (Daucus carota).

Abstract

Two field experiments were carried out at the Multipurpose Crop Nursery of AAMUSTED, Mampong campus, in two seasons: the minor rainy season (September to December 2021) and the major rainy season (April to July 2022). The study aimed to assess the impact of integrating biochar, organic, and inorganic fertilizer amendments on the growth and yield of carrots. The experimental design followed a 2 x 6 factorial arrangement, implemented in a Randomized Complete Block Design (RCBD) with four replications. The treatments included two carrot varieties (Technisen and Tokita) and five different soil amendment rates: (i) 10 t/ha chicken manure (CM), (ii) 250 kg/ha NPK fertilizer, (iii) 10 t/ha Leucaena biochar (LB), (iv) 5 t/ha CM + 5 t/ha LB, (v) 5 t/ha LB + 125 kg/ha NPK, and (vi) a control with no fertilizer. The findings indicated that soil amendment with 10 t/ha CM and 5 t/ha CM + 5 t/ha LB improved soil chemical properties (organic carbon, organic matter, nitrogen, phosphorus, potassium, calcium) compared to the other amended treatments and the control. Tokita variety showed significantly greater plant height and wider canopy spread than Technisen in both seasons. Carrot plants treated with 10 t/ha CM and 5 t/ha CM + 5 t/ha LB exhibited significantly better vegetative growth—such as taller plants, more leaves per plant, wider canopy, and higher dry matter accumulation—compared to the unamended control plots. Tokita, along with 10 t/ha CM, and their interactions, produced significantly longer and thicker roots, as well as higher marketable root weight, root weight per plot, and root tuber yield, especially in the 2021 minor season. Across both seasons, the amended plots showed significantly higher root length, plant biomass at harvest, carrot root yield, marketable root yield, and harvest index compared to the control. Based on the improved soil chemical properties and higher carrot yields, it is recommended that farmers use 10 t/ha CM and/or 5 t/ha CM + 5 t/ha LB for optimal carrot (Tokita variety) production.