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Title: Effect of microbial-based inoculants on nutrient concentrations and early root morphology of corn (Zea mays)

Author
item CALVO, PAMELA - Auburn University
item Watts, Dexter
item KLOEPPER, JOSEPH - Auburn University
item Torbert, Henry - Allen

Submitted to: Journal of Plant Nutrition and Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2016
Publication Date: 2/17/2017
Publication URL: http://handle.nal.usda.gov/10113/5879525
Citation: Calvo, P., Watts, D.B., Kloepper, J.W., Torbert III, H.A. 2017. Effect of microbial-based inoculants on nutrient concentrations and early root morphology of corn (Zea mays). Journal of Plant Nutrition and Soil Science. 180:56-70.

Interpretive Summary: Addition of certain microbes to the rooting zone of plants has been shown to increase production and nutrient uptake but interactions with different fertilizer types have not been well studied. This study tested the use of soil microbes known to improve plant growth on the development of corn plants and nutrient uptake at four different growth stages using three different fertilizer sources. The microbial based treatments were SoilBuilder (SB), a metabolite extract of SoilBuilder (SBF), and a mixture of four Bacillus spp (BM). The three fertilizer sources consisted of urea 46% N, urea-ammonium nitrate 32% N (UAN) and calcium-ammonium nitrate 17% N (CAN ). Early root development was improved and plant growth was enhanced by all three microbial treatments. The microbial treatments greatest effect on plant growth occurred during the late stages of vegetative growth (the start of tasseling). Plant nutrient uptake of N, P, and K was also increased by the addition of microbial treatments at tasseling. Therefore to maximize growth and N, P, and K used by plants microbial treatments should to be considered.

Technical Abstract: Microbial-based inoculants have been reported to stimulate plant growth and nutrient uptake. However, their effect may vary depending on the growth stage when evaluated and on the chemical fertilizer applied. Thus, the objective of this study was to test the hypothesis that microbial-based inoculants known to promote root growth and nutrient uptake will promote plant growth, enhanced early root development and increased nutrient uptake of corn. Plants were evaluated at 4 different growth stages and in the presence of three different N fertilizers. The microbial-based treatments evaluated were SoilBuilder (SB), a metabolite extract of SoilBuilder (SBF), and a mixture of four strains of plant growth-promoting Bacillus spp (BM). Experiments included three different N fertilizers: urea, urea- ammonium nitrate (UAN-32) and calcium- ammonium nitrate (CAN-17) And an unfertilized control. Corn plants were evaluated at V2, V4, V6 and VT stages. Plant growth parameters such as plant fresh and dry biomass, plant height and SPAD readings were enhanced by the three microbial-based treatments. A greater effect of microbial-based treatments was observed when plants were evaluated at V6 and VT stages. Early root development parameters such as total root length (TRL), root surface area (RSA), and length of fine roots were enhanced when microbial-based treatments were applied. Nutrient uptake of N, P, and K was also increased by microbial-based treatments compare to the non-inoculated control. Increases on plant N uptake by microbial-based treatments were on average 72% for CAN-17, 61% for UAN-32, 72% for urea, and 54% in the unfertilized control. Phosphorus uptake was increased the most (138%) when BM was applied with CAN-17. In the same way, when CAN-17 was present K uptake was increased by 95% with BM and on average 65% when SB and SBF were applied. Overall, the results demonstrated that microbial-based inoculants can positive impact corn growth and nutrient uptake, especially during the at late vegetative stages. Furthermore, results indicate that nutrient uptake enhancement is related to the capacity of microbial-based treatments to impact root morphology at early stages of corn growth.