Evaluation of Mehlich-3 as a Multi-Element Extractant of Micronutrients and Sulfur in a Soil–Ryegrass System Amended with Varying Biochar Rates from Two Feedstocks

Abstract

Mehlich-3 (M-3) is used as a universal nutrient extractant due to its ability to simultaneously extract multiple elements. This study aimed to assess M-3 for the simultaneous determination of plant-available zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), boron (B), and sulfate (SO4-S) in a soil amended with switchgrass- (SGB) and poultry litter-derived biochars (PLB), which were used to vary soil pH values (5.7–7.6) and organic carbon (OC) content (2.0–5.5%) in the short-term. Soil and ryegrass (Lolium perenne) were sampled from a growth chamber experiment and analyzed for plant-available and tissue phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), micronutrients (B, Cu, Fe, Mn, and Zn), and sulfur contents. The commonly accepted extractants diethylenetriaminepentaacetic acid (DTPA), for micronutrients, and 0.008 M monocalcium phosphate (MCP), for SO4-S, were used for the evaluation. Relationships between M-3 and DTPA were not reliable for micronutrient availability, although highly significant relationships for Zn and Cu were found. However, M-3-extractable S was highly correlated with S contents in ryegrass tissues regardless of the treatments and provided a 1:1 relationship between MCP and M-3. This offers the potential to eliminate MCP by simply adding S determination after extraction with M-3. Although this research evaluated the d-index for an easier linear relationship between the traditional and proposed methods, more research using several soil samples is needed to establish models and find conversion equations for micronutrients and SO4-S between DTPA-sorbitol, MCP, and M-3.

Comparative analysis and prediction of cation exchange capacity via summation: influence of biochar type and nutrient ratios

“…In contrast, the 100% sufficiency K levels (125 mg kg −1 ) had already been attained with PLB application at rates as low as 0.5 to 1%. Inversely, the decline in yield observed as PLB rates increased beyond the (Ca+Mg)/K ratio of 82.4 (M3) and 69 (AA) can be attributed to an imbalanced nutrient relationship in the soil and elevated electrical conductivity for ryegrass production (17). Therefore, in our study, maintaining a harmonious balance of Ca : Mg:K holds paramount significance in achieving optimal crop yields.…”

“…Biochar was produced via high-temperature slow pyrolysis (700°C ) using two feedstocks: switchgrass (Panicum virgatum) and poultry litter, as detailed in Antonangelo and Zhang (17). The coarse biochar materials were subsequently ground evenly and gently, then sieved through 1-and 0.25-mm screens for physicochemical analyses and experimentation, as outlined by Antonangelo et al (18).…”

“…In a subsequent trial with ryegrass (experiment 2), plastic pots were filled with 1.2 kg of dried, sieved soil, and a lower range of five SGB and PLB rates (0.0%, 0.5%, 1.0%, 2.0%, and 4.0% w/w) were applied to the soil. Using higher rates up to 8.0% as in the first experiment was unfeasible for ryegrass, as growth was compromised at 4% biochar application (17). The soil-biochar mixes were incubated for 30 days at 75% field capacity before ryegrass sowing, with each pot receiving a seeding rate of 30 kg ha −1 .…”

Biochar amendment of a metal contaminated soil partially immobilized Zn, Pb, and Cd and reduced ryegrass uptake

“…Boxplot was plotted after normalizing the whole dataset of measurements (n = 15 for each biochar) to show soil chemical attributes (Antonangelo et al, 2022) affected by switchgrass and poultry litter-derived biochar application rates. The effects of Biochar, Rate, and the interaction Biochar × Rate were tested and a 2-way ANOVA was performed to compare treatment means using the Tukey test (p < 0.05).…”