Pyrolysis Temperature and Application Rate of Sugarcane Straw Biochar Influence Sorption and Desorption of Metribuzin and Soil Chemical Properties

Abstract

Pyrolysis temperature and application rate of biochar to soil can influence herbicide behavior and soil fertility. The objective was to investigate the effect of soil amendments with application rates of sugarcane straw biochar, produced at different pyrolysis temperatures, on the sorption–desorption of metribuzin in soil. The analysis was performed using high-performance liquid chromatography (HPLC). The treatments were three pyrolysis temperatures (BC350, BC550 and BC750 °C) and seven application rates (0, 0.1, 0.5, 1, 1.5, 5 and 10% w w−1). Amended soil with different application rates decreased H + Al and increased pH, OC, P, K, Ca, Mg, Fe, Mn, CEC and BS contents. Kf values of sorption and desorption of metribuzin were 1.42 and 0.78 mg(1−1/n) L1/n Kg−1, respectively, in the unamended soil. Application rates < 1% of biochar sorbed ~23% and desorbed ~15% of metribuzin, similar to unamended soil, for all pyrolysis temperatures. Amended soil with 10% of BC350, BC550 and BC750 sorbed 63.8, 75.5 and 89.4% and desorbed 8.3, 5.8 and 3.7% of metribuzin, respectively. High pyrolysis temperature and application rates of sugarcane straw biochar show an ability to immobilize metribuzin and improve soil fertility, which may influence the effectiveness in weed control.

Availability of Metribuzin-Loaded Polymeric Nanoparticles in Different Soil Systems: An Important Study on the Development of Safe Nanoherbicides

“…Metribuzin presented a greater desorption process than sorption rates, becoming available for absorption and transport processes. This was also found by Mielke et al [ 41 ], although availability is dependent on different biochar rates. Mendes et al [ 33 ] indicate deep profile transport for metribuzin (distributed in 30 cm of soil profile), even with the application of organic material on top of the soil.…”

“…Humic substances, from the organic matter degradation portion, have high reactivity, a large surface area, and variable composition, interacting with neutral or ionizable molecules [ 49 , 50 ], such as MTZ formulations. Even stable SOM compounds, which increase hydrophobicity in the soil, can sorb triazines and soluble herbicides such as metribuzin [ 41 , 51 , 52 ]. Therefore, despite the low sorption, soils with consolidated SOM can retain more metribuzin in the soil, in both formulations, reducing the risk of loss.…”

Pyrolysis Temperature vs. Application Rate of Biochar Amendments: Impacts on Soil Microbiota and Metribuzin Degradation

“…Herbicide sorption is directly influenced by characteristics such as porosity, SSA, aromatic structures, carbon contents, surface functional groups, pH, and the elemental composition of the soil [ 35 ]. The biochar produced at 750 °C (BC750 °C) showed a higher C/N ratio, ash content, lower number of surface functional groups, and a 13-fold higher surface area than the biochar produced at 350 °C (BC350 °C), which increases the sorption capacity of BC750 °C [ 24 ].…”

“…The results showed that biochar produced at low temperatures (BC350 °C) negatively influenced the degradation of metribuzin in the soil. The greater degradation of metribuzin in soils amended with BC550 °C and BC750 °C may be related to the physicochemical characteristics of the biochar, as high pyrolysis temperatures produced a material with high pH (9.7), ash content (11%), OC (1.4%), and high nutrient content [ 24 ]. These factors can favor chemical degradation through increased pH, active groups, and generation of free radicals [ 36 ], and the level of C and ash content can affect soil microbial activities due to the presence of nutrient-rich materials (N, S, P, among others).…”

“…Metribuzin [4-amino-6-tert-butyl-3-methylsulfanyl-1,2,4-triazin-5-one] is a strong acid herbicide with high water solubility ( S w = 10.700 mg L −1 at 20 °C), high mobility in soil (coefficient of sorption normalized by OC, K oc = 38 mg L −1 ), high leaching index (groundwater ubiquity score = 2.96), and low persistence in soil (DT 50 = ~20 days) [ 20 , 21 , 22 ]. This herbicide showed high sorption in carbonaceous materials produced at different pyrolysis temperatures [ 13 , 23 , 24 ]. The addition of biochar and organic compost decreased the DT 50 of metribuzin by 4 days when compared to the unamended soil (DT 50 = 34 days) [ 25 ].…”