A Preliminary Assessment of the Combined Effects of a Novel Microbial Biostimulant Product, Fertilizers, and Herbicides on the Growth and Yield of Field Crops in Greece

Abstract

Field trials were conducted (2022–2023) in a randomized complete block design to evaluate the combined use of a microbial biostimulant, P-K Stim, which contains phosphate and potassium solubilizing bacteria (109 Colony Forming Units mL−1), various fertilization rates, and herbicide use on weed growth and the productivity of alfalfa (Medicago sativa L.), oilseed rape (Brassica napus L.), and durum wheat (Triticum durum Desf.). The following treatment list was the same on all trial fields: (1) 100% basal fertilization (100N), (2) 20% basal fertilization and application of microbial biostimulant P-K Stim (20N + PK), (3) 100% basal fertilization and post-emergence herbicide treatment (100N + H), (4) 20% basal fertilization together with the application of P-K Stim and a post-emergence herbicide treatment (20N + PK + H), and (5) 50% basal fertilization together with the application of P-K Stim and a post-emergence herbicide treatment (50N + PK + H). The combined use of fertilization, biostimulants, and herbicides significantly affected crop yield, its components and weed biomass (p ≤ 0.05). The concentrations for potassium and phosphorus were higher in the 20N + PK + H and 50N + PK + H treatments for all crops compared to other treatments. Nutrient concentrations were remarkably high across all crops, closely approximating the values of the recommended nitrogen fertilization. Crop yield and its components were positively influenced by the 20N + PK + H and 50N + PK + H treatments. Weed biomass was significantly lower in these plots compared to other treatments.