Effects of Integrated Nutrient Management on Growth, Yield and Nutritional Quality of Carrots (Daucus carota L.).

Abstract

Two experiments were conducted from September to December 2021 and from April to July 2022 at the Multipurpose Crop Nursery Field of Akenten Appiah-Menka University of Skills Training and Entrepreneurial Development (AAMUSTED), Mampong Campus. The objective was to assess the effects of combining inorganic fertilizer with chicken manure on the growth, yield, nutritional qualities, and profitability of carrot production. The study was conducted using a Randomized Complete Block Design (RCBD) with six treatment options, each replicated four times. The treatments included: (i) 300 kg/ha of NPK (15-15-15) fertilizer (Full NPK), (ii) 20 t/ha of poultry manure (Full PM), (iii) 225 kg/ha NPK combined with 5 t/ha PM (¾ NPK + ¼ PM), (iv) 150 kg/ha NPK plus 10 t/ha PM (½ NPK + ½ PM), (v) 75 kg/ha NPK with 15 t/ha PM (¼ NPK + ¾ PM), (vi) Control treatment with no fertilizer applied. The results showed that vegetative growth parameters of the carrots such as plant height, canopy width, and number of leaves per plant were significantly improved with the application of full chicken manure (CM) and full NPK compared to the control. Additionally, dry shoot weight, fresh root weight, and dry root weight were higher in treatments with full CM, full NPK, ¾ NPK + ¼ CM, and ¼ NPK + ¾ CM than in the control group. Application of full chicken manure (CM), ¼ NPK + ¾ CM, and ½ NPK + ½ CM resulted in increased root diameter, root length, number of plants harvested, number of marketable roots, and total root yield compared to the control. Root yield in these treatments was 14–41% higher than that of the control. The nutritional qualities of carrots including crude protein, iron, calcium, reducing sugars, total oxalates, total carotenoids, carbohydrates, and moisture content were generally higher in treatments with full chicken manure (CM) and full NPK compared to the control. The economic analysis revealed that applying 20 t/ha of poultry manure (PM) was the most profitable option in 2021, yielding the highest benefit-cost ratio (2.56) and marginal rate of return (MRR) of 641.57%. In 2022, the combination of 75 kg/ha NPK + 15 t/ha PM proved more profitable, recording the highest MRR of 708.44%. During the minor season, 20 t/ha PM produced the highest yield (4.06 t/ha), along with the best benefit-cost ratio and MRR, and is therefore recommended to farmers for improved yield and profitability in carrot production during that season. In contrast, the application of 75 kg/ha NPK combined with 15 t/ha poultry manure resulted in the highest yield (14.37 t/ha) and marginal rate of return (MRR) of 708.44% during the major season. This treatment is therefore recommended for farmers to adopt in order to achieve higher yields and increased profitability in carrot production during the major season.