The paper deals with the effects of boron topdressing and Effective Microorganism (EM) treatments on the growth, yield and quality of broccoli harvested in summer. EM is a microbial inoculant promoted to stimulate plant growth and soil fertility in agriculture. Boron (B) is one of eight micronutrients needed for proper plant growth. Different combinations of Effective Microorganism were applied: added to the nursery substrate before planting seeds (EM1); added to the nursery substrate before planting seeds and as topdressing in a form of spray after seedlings were planted out (EM2); as pre-planting treatment in the field, just before the seedlings were transplanted (EM3); as pre-planting treatment in the field, followed by topdressing as a spray (EM4); control (without EM). Boron was applied as mineral fertilizer three weeks after broccoli seedlings had been planted out in the field. The experiment was carried out between 2014 and 2015, at the Experimental Station of Siedlce University of Natural Sciences and Humanities, located in central-eastern Poland. Compared to the control, each method of Effective Microorganisms application to broccoli significantly increased its marketable curd yield, average curd weight and leaf greenness index (SPAD). Plants had the longest arc of curd and the largest L-Ascorbic acid content when EM were added to the substrate and then applied in the field in the form of spray. Effective Microorganisms applied as EM1, EM2, and EM3 combinations increased the potassium and calcium content in broccoli. However, there was no significant effect of EM application on dry matter, sugar and protein content in broccoli curds. Boron application to broccoli resulted in an increase in the marketable curd yield, the weight of marketable curds, the length of arc of curd, and dry matter, phosphorus and potassium content.  

24.4.2019