The Effect of Organic Biostimulants on Beneficial Soil Microorganism Activity

Organic biostimulants and organic fertilizers can improve soil health for various horticultural crops. The objectives of these experiments were to determine if biostimulants beneficially increase soil microorganism activity in soilless medium, and additionally measure the impact of synthetic and organic fertilizers with blackstrap molasses on plant nutrient uptake nutrient runoff. It was hypothesized that the addition of biostimulants will increase soil microbe activity. Evolution of soil carbon dioxide was measured by comparing different rates (0, 15, 30, and 45 mL/3.8 L of water) of blackstrap molasses using a randomized block design with 3 replications in nursery containers. Also, a second study using St. Augustinegrass and tomatoes fertilized with organic and synthetic fertilizers was evaluated with and without a biostimulant rate (30 mL/3.8 L of water). The plants were arranged in randomized complete block design with 6 replications. Soil biostimulants did significantly increase the microorganism activity at the 0.05 level. The highest rate of blackstrap molasses improved soil biological activity over a 4-week period. Additionally, fertilizer combined with molasses did show significant increases in soil microbiology for over 5 weeks for both tomatoes and St. Augustinegrass. Molasses increased soil microbial activity but not plant nutrition. Organic fertilizer though resulted in higher levels of phosphorus, calcium, magnesium, and sulfur in plant tissue. Further research is being conducted to measure the influence of biostimulants on the breakdown of composting plant matter. Organic fertilizer slightly increased soil water pH but reduced nutrient load pollution based on a 7-day nutrient effluent study. Total nutrients (nitrates, P, Ca, Mg, and S) runoff was significantly less than synthetic fertilizer. Organic fertilizer reduced nutrient dumping in waste effluent. Organic fertilizers can improve nutrient use efficiency.