The Effect of Biochar and Plant Growth-Promoting Microorganisms on Strawberry (Fragaria × ananassa) Growth and Fruit Quality

Abstract

Strawberry production in Alabama has increased substantially in recent years; however, the industry continues to face challenges from disease pressure, limited cultivar options, and environmental conditions that affect plant growth and fruit quality. Sustainable production practices that improve crop performance while reducing reliance on synthetic inputs are therefore needed. Biochar and plant growth-promoting microorganisms (PGPM) have been proposed as potential tools to improve soil and plant health and fruit quality. The objective of this study was to evaluate the effects of different rates of biochar and a PGPM consortium, applied individually and in combination, on strawberry growth, substrate properties, and fruit quality. A greenhouse study was conducted at the Paterson Greenhouse Complex at Auburn University. Pine-derived biochar produced through pyrolysis at 700°C was incorporated into a substrate consisting of 40% sand and 60% ProMix General Purpose potting mix at rates of 0%, 5%, 10%, and 20% (v/v). A consortium of PGPM strains from the Auburn University PGPM library was applied at transplanting. Treatments were arranged in a factorial combination of biochar and PGPM in a completely randomized design with three replications. ‘Florida Radiance’ and ‘Camarosa’ cultivars were used in the first and second years, respectively. Growth measurements included vegetative and reproductive parameters, root and shoot biomass, substrate parameters such as electrical conductivity (EC), and pH. Fruit quality evaluations included fruit size, average weight, color, firmness, total soluble solids (TSS), titratable acidity (TA), and pH. No significant interactions were detected between biochar and PGPM, and PGPM did not significantly affect the strawberry growth, substrate properties, or fruit quality parameters measured. In contrast, biochar significantly influenced several plant growth, substrate, and fruit quality characteristics. The highest biochar inclusion rate (20%) reduced plant height in both years and decreased plant width in the second year, and reduced bud and flower development in the first year. Biochar increased root biomass and significantly increased substrate pH, particularly at the highest application rate. Fruit firmness increased with increasing biochar rates, while the 20% biochar treatment reduced fruit weight and fruit length. Overall, the results indicate that the effects of biochar on strawberry performance are rate-dependent and may vary among cultivars. While high biochar inclusion rates negatively affected some growth and fruit size parameters, low-to-moderate rates did not. Under these greenhouse conditions, the biochar, particularly at a 5% inclusion rate, showed some promising effects on strawberry growth and fruit quality. Further research is needed to validate these findings across cultivars and production systems. The PGPM consortium evaluated in this study provided limited benefits under the conditions tested.