Comparing the effectiveness and performance of semi-organic fertilizers to inorganic fertilizers in terms of the growth, yield and quality of potato crops

The aim of this study was to compare the effectiveness and performance of semi-organic fertilizers to inorganic fertilizers in terms of the growth, yield and quality of potato crops. The study was conducted as two field trials during the 2023-2024 growing seasons at the Innovation Africa Campus of the University of Pretoria. Each trial consisted of seven different fertilizer treatments and three replicates, arranged in a randomized complete block design. The crop was grown under irrigated conditions and baseline fertilization for each treatment was set at 240 kg ha⁻¹ N; 110 kg ha⁻¹ P and 200 kg ha⁻¹ K. Canopy cover and leaf N content were measured during the growing season, the harvest index, yield and nutrient use efficiency (NUE) were calculated, and the tuber specific gravity (SG) and dry matter (DM) content were determined after harvest. The average yield obtained in Trials 1 and 2 were 46 081 kg ha⁻¹ and 23 402 kg ha⁻¹, respectively. Two semi-organic fertilizer treatments consistently achieved higher yields compared to the inorganic fertilizer treatment, and also obtained better NUE values. No significant differences were observed in the tuber quality traits between the different fertilizer treatments. The results of the present study suggest that semi-organic fertilizers had a positive impact on the growth and yield of potatoes, compared to inorganic fertilizers, however, it did not have a positive impact on the harvest index or tuber quality of potatoes. In general, semi-organic fertilizers can be recommended to optimize potato production, however, its performance will depend on the specific fertilizer source that is used.