No Effect of Biostimulants on the Growth, Yield and Nutritional Value of Shallots Grown for Bunch Harvest

Abstract

Shallots (Allium cepa L. Aggregatum group) are cultivated on small areas, mostly to harvest mature bulbs with dry scales. Due to their exceptional taste and nutritional value, and a short growing season, they can also be grown for early bunch harvest. New shallot cultivation strategies are being sought to meet consumers’ growing expectations regarding the quality of vegetables, and their increasing awareness of global food safety. Therefore, the aim of this study was to evaluate the effect of selected biostimulants on the biometric parameters, yield and nutritional value of shallot bulbs and leaves. The experimental factors were as follows: two biostimulant types—Effective Microorganisms (EM) and Goëmar Goteo (GG), two shallot cultivars—Bonilla F1 and Matador F1, grown for bunch harvest, and year of the study. Shallot leaves had a higher content of L-ascorbic acid, reducing sugars and nitrates than bulbs. Young bulbs had a higher content of DM and total sugars than leaves. The leaves and bulbs of shallot plants treated with EM accumulated the highest amounts of minerals. Macronutrient ratios were closer to optimal in shallot leaves than bulbs. The nitrate content of bulbs was inversely proportional to the nitrate content of leaves. Therefore, an increase in the nitrate content of leaves by around 330% led to an approximately 40% decrease in the nitrate content of bulbs. The correlations between the parameters of the chemical composition of shallots and shallot leaves show that the increase in the dry matter content of the bulbs (by approx. 60%) was accompanied by an increase in the L-ascorbic acid content in the leaves (by approx. 240%). The use of biostimulants in the cultivation of A. cepa L. Aggregatum group contributed to the reduction of L-ascorbic acid content in bulbs and had no positive effect on the leaves. Moreover, no positive effect of biostimulants on the reduction of nitrate content in shallot leaves and bulbs was observed, which is undesirable from the consumer’s point of view. After the use of biopreparations, the yield of shallots was lower than that of the control—by approx. 14% (EM) and approx. 4% (GG). Therefore, the measurable benefits of biostimulants in the cultivation of shallots grown for early bunch harvest do not balance the costs of their purchase and use.