Pruning and Organic Fertilization Influence Growth, Yield, and Fruit Quality of Blackberry (Rubus fruticosus L.) Grown Under Greenhouse Conditions

Abstract

Blackberry is one of the most popular berry fruit species. This study investigated the effects of pruning and organic fertilization on the growth, yield, and fruit quality parameters of ‘P45’ blackberry plants grown under greenhouse conditions in Riyadh, Saudi Arabia. The experiment included two pruning levels (pruned and nonpruned) and three organic fertilizer rates (NPK60, NPK80, and NPK100) along with control (inorganic-fertilization). Pruning improved physiological traits of blackberry plants such as chlorophyll content, net CO 2 assimilation, stomatal conductance, and transpiration rate. Pruning also significantly promoted plant growth, increased leaf area and biomass, stem diameter, and fruit yield, with pruned plants yielding 2442.8 g per plant as compared with 2011.1 g for nonpruned plants, while elevating fruit quality parameters and fruit texture profile analysis, including total soluble solids (TSS), vitamin C, sugar content, and fruit firmness. Among different fertilization treatments, the NPK100 organic fertilizer rate resulted in the highest values of most parameters, including plant growth, fruit quality, and yield (2653.9 g per plant as compared with 2049.3 g for inorganic-fertilized plant). The combination treatment of pruning with the 100% organic fertilizer rate (NPK100-P) recorded the most significant results, producing the highest fruit yield (2853.7 g per plant), superior fruit size, and elevated fruit quality parameters, including TSS and vitamin C. These findings demonstrate the importance of integrating pruning with high organic fertilization for maximizing fruit yield and quality of blackberry under greenhouse conditions.