Impacts of Biofumigation and Anaerobic Soil Disinfestation on Strawberry Plant Nutrition and Fruit Quality

Anaerobic soil disinfestation and biofumigation are two non-chemical methods for controlling soilborne plant pathogens of strawberry. Due to their high mineral contents, both treatments could potentially increase mineral content in strawberry plants and thus impact fruit quality, but research in this area is limited. A trial was conducted with 11 pre-plant soil-incorporated treatments arranged in a randomized complete-block design with six rows (blocks). Biofumigation treatments consisted of deactivated mustard meal, deoiled mustard meal, mustard pellets, and Biofence mustard seed meal. Other treatments included dried molasses as a carbon source for an anaerobic treatment and a Basamid® chemical treatment. Additional combination treatments of deactivated mustard meal combined with molasses, deoiled mustard meal combined with molasses, and molasses combined with soybean meal (to lower amendment C:N ratio) were also applied, as well as an untreated control. Harvested strawberry fruit were analyzed for sugars (fructose, glucose, sucrose), organic acids (malic and citric), and mineral content (B, Na, Mg, P, S, K, Ca, Fe, Cu, Mn, and Zn). Harvested leaves were analyzed for mineral content. Data were analyzed using mixed model analysis of variance (Glimmix procedure, SAS Institute, Cary, NC) and least squares means were compared with ten orthogonal contrasts of scientific interest. There were no differences among treatments for glucose and fructose. However, fruit from the plots treated with the combination treatment of molasses with deoiled mustard meal did have significantly more sucrose than the control (P < 0.05). Fruit citric and malic acid contents were greater in the anaerobic disinfestation plots treated with the combination of molasses and soybean meal than in the plot treated with  Basamid^® (P < 0.05). However, fruit sugar and organic acid content did not consistently differ among most treatments. Likewise, there were no consistent patterns of differences among treatments in mineral content of either fruit or leaf tissues (P < 0.05).  However, plants in Basamid^® treated plots had a greater concentration of Ca than those treated with molasses and soybean meal (P < 0.05). In general, the alternative methods of biofumigation and soil anaerobic disinfestation produced fruit of equal quality to that produced using the Basamid^® chemical treatment.