Plant Growth and Yield Response of Maize to in-Furrow Biological and Plant Growth Regulator Products.

In-furrow biological (BIO) and plant growth regulator (PGR) products are increasingly available and promoted for use in U.S. maize production. Marketing claims imply these products stimulate plant growth, enhance nutrient uptake, and increase grain yield. The goal of our research was to evaluate the impact of four in-furrow products (three BIO and one PGR) on maize early-season growth, nutrient concentrations, and grain yield in five field scale trials varying in soil type, management practices, and weather. The BIO products (BIO-A, B, & C) each contained different combinations of bacteria and/or fungi belonging to the Bacillus, Rhodopseudomonas, Streptomyces, Lactobacillus, and/or Trichoderma genera. The PGR product was a combination of cytokinin, gibberellic acid, and indole-3-butyric acid. At planting, each product was applied with water in the seed furrow at recommended label rates. Each treatment also included liquid starter fertilizer (rates and formulations varied by location) applied in a 5x5 cm band below and to the side of the seed. Plant growth and yield parameters measured in each BIO and PGR treatment were compared to a starter fertilizer-only control treatment. At four locations, BIO and PGR had little effect on total plant biomass at V6, development rate, and total number of leaves per plant. At one location, the BIO-B treatment increased plant biomass 20% at V6 and accelerated the rate of leaf appearance relative to the starter-only treatment, however did not affect yield. At another location, the BIO-B treatment yielded 314 kg ha^-1 greater than the starter-only treatment, even though no early season growth differences were detected. The BIO-A, BIO-C, and PGR treatments did not affect yield at any location. Whole plant nutrient concentrations at V6 and earleaf nutrient concentrations at R1 were unaffected by any of the in-furrow treatments.