The fate and biostimulant potential of metal lactates in silt loam soil

Authors: OPDAHL, LEE - Washington State University; Hansen, Jeremy; STRAWN, DANIEL - University Of Idaho; SANGUINET, KAREN - Washington State University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Micronutrient deficiencies are becoming more common in agricultural soils due, in part, to conventional farming practices as well as the introduction of nutrient-demanding, high-yielding crop cultivars. The objective of this study was to investigate the ability of metal lactates to provide readily available micronutrients, Zn, Cu, Mn, Ni, and Co in lactate and chloride salt, as well as their potential as a biostimulant for soil microbes. Results show a similar distribution of Zn, Cu, Ni, and Co when supplied in lactate and mineral chloride form; however, Zn, Cu, and Ni delivered as chlorides appeared to have significantly greater availability than lactate forms of each metal. Additionally, microbial PLFA analysis revealed a significant increase in bacterial and protozoan biomass in soil treated with metal lactates. Metal lactates may be an effective and sustainable alternative to conventional, inorganic fertilizer forms by providing readily available micronutrients while also stimulating microbial populations. These results are of particular interest to agricultural producers, the agribusiness and fertilizer industries, and researchers who support producers and agricultural industry.

Technical Abstract: Conventional farming practices have negatively impacted micronutrient fertility and overall soil health. Metal lactates are an organic micronutrient amendment that provide labile carbon substrate and mineral nutrition for plant and microbial growth, but their effects in soil have not been studied. To determine the ability of metal lactates to provide readily available micronutrients, Zn, Cu, Mn, Ni, and Co in lactate and chloride salt form were amended to soils and incubated for 28 days. Operationally defined speciation was determined using sequential extraction on samples incubated for different times (1, 5, and 28 days). Additionally, microbial phospholipid fatty acids (PLFA) were quantified to determine the effect of metal lactates on microbial communities. Results show a comparable distribution of metals in chloride and lactate form; however, slight differences were detected in water soluble and exchangeable Ni and Zn at each sample collection timepoint, where absolute percent of the total metal supplied in lactate form was 2.58-2.88% less for Ni and 0.17-0.25% less for Zn. Furthermore, carbonate-bound Ni when supplied in lactate form averaged 4.06% and 3.59% less than metal chloride treatment on days 1 and 5, respectively, and Cu in lactate form decreased 2.93-3.29% during the treatment period. Microbial PLFA analysis confirmed a stimulatory effect of metal lactates on bacterial biomass, yielding PLFA concentrations that were 12.2-17.5% greater than metal chloride treatment. Results from this study support the use of metal lactates as a sustainable alternative to conventional fertilizers by providing rapidly available micronutrients for plant nutrition while also stimulating microbial populations.