Field dissipation and leaching potential of indaziflam in soil columns from coffee-cultivated areas with different soil cover materials

Abstract

Background  Pre-emergence (PRE) herbicides, such as indaziflam, are commonly used in coffee crops for weed control. However, the influence of soil cover materials on herbicide dissipation and leaching remains unclear.

Objective  This study evaluated indaziflam dissipation and leaching in two coffee-cultivated areas with different soil cover materials to determine their compatibility with indaziflam.

Methods  The field dissipation study was performed in a sandy clay Oxisol (OXI_sc) and clay Oxisol (OXI_cl) using a recommended indaziflam dose (75 g a.i. ha⁻¹) with three soil cover materials (crop debris, organic compost, bare soil) applied at 5 t ha⁻¹. Indaziflam residues were measured at eight intervals (0–210 days after application—DAA) using high-performance liquid chromatography. Dissipation time (DT₅₀) was estimated. Leaching potential was assessed in a greenhouse using PVC columns and simulated rainfall (100 mm). Soybean was used as a bioindicator to measure injury and biomass reduction at various soil depths.

Results  Indaziflam DT₅₀ ranged from 95–119 days in OXI_sc and 135–161 days in OXI_cl. Soil cover materials did not affect dissipation, indicating prolonged herbicide activity. Indaziflam remained in the 0–5 cm soil layer, proving minimal soybean injury and biomass reduction below this depth. Injury in the 0–5 cm layer decreased from 85–90% at 0 DAE to 70–85% at 21 DAE in OXI_sc, and from 88–95% to 70–80% in OXI_cl.

Conclusion  Organic compost and crop debris did not alter Indaziflam dissipation or leaching, making these soil covers compatible with indaziflam applications under the study conditions.

Herbicide; Pre-emergence; Transport; Degradation

1.Introduction

Brazil is the leading global producer and exporter of coffee. This sustained dominance in coffee production has lasted for over 150 years, with Brazil currently accounting for one-third of the world’s coffee supply (Fontes et al., 2022). The slow initial growth of coffee plants and their high susceptibility to weed competition, especially during the first two years of cultivation, make effective weed control with herbicides essential in coffee farming (DaMatta et al., 2007; Ronchi, Silva, 2018).

Pre-emergence (PRE) herbicides are widely used in coffee crops to provide selective and residual weed control. Among these, indaziflam, registered for use in Brazilian coffee crops since 2016, stands out due to its unique mode of action inhibiting cellulose biosynthesis. This herbicide belongs to the alkylazine chemical group (Tompkins, 2010). Known for its broad-spectrum efficacy, indaziflam controls both monocotyledonous and dicotyledonous species, even at low doses (Brosnan et al., 2011; 2012).

Indaziflam is classified as an herbicide with low solubility in water (S_w = 2.8 mg L⁻¹ at 20 °C), an octanol-water partition coefficient (K_ow) of 6.31 x 10⁻² (pH 7, 20 °C), high sorption (K_oc = 1,000 L kg⁻¹), moderate mobility, and high soil persistence (DT₅₀ = 150 days) (University of Hertfordshire, 2024). These properties contribute to its prolonged residual effect, making it a valuable tool for weed management. Indaziflam is applied directly to the soil and must remain available for weed absorption to be effective.

The interaction between herbicides and the soil matrix is complex, leading to a dynamic and site-specific dissipation process for each herbicide-soil combination (Rocha et al., 2013). Environmental conditions and agricultural practices significantly impact herbicide dissipation, leaching potential, and overall fate in the soil (Mendes et al., 2013).

The time required for a substance’s concentration to decrease by half from its initial value, known as its DT₅₀ (dissipation or degradation time), is also referred to as t_1/2. While DT₅₀ is primarily a physicochemical property, biological factors in the soil also have a significant impact. The DT₅₀ value is calculated as ln(2)/k, where k is the rate constant per day, and it is typically determined in controlled laboratory settings to estimate the time needed for the substance’s concentration to decrease by 50% during the incubation period (Mendes et al., 2024). Persistence is critical for the efficacy of PRE herbicides, as they must be long enough to control weed emergence over time. Excessive persistence, however, can cause injury to the crop if the herbicide reaches the roots and may also affect subsequent crops, a phenomenon known as carryover (Mendes et al., 2024).

Leaching potential refers to the downward movement of herbicides through the soil matrix or with soil water, influenced by the herbicides’ physicochemical properties, soil characteristics, and climate conditions. In practice, herbicide mobility within the soil can have a significant impact on its effectiveness. Controlled leaching can enhance herbicide efficiency by moving it to areas of high weed seed concentration, but excessive leaching can lead to groundwater contamination (Mendes et al., 2024).

Coffee cultivation commonly uses vegetative cover to complement chemical control method. Common organic materials for soil cover include coffee straw, cattle and chicken manure, crop debris from mechanized harvesting, and organic compost.

However, vegetative cover can influence herbicide leaching potential and dissipation processes (Silva et al., 2020). Thus, understanding indaziflam’s persistence and transport under different field conditions is essential to minimize the risk of off-target plant injury (Jeffries et al., 2014). Despite its importance, there is limited information on the behavior of indaziflam in coffee cultivation, especially in field conditions. Such studies are crucial to helping coffee producers select soil management practices that are compatible with indaziflam applications.

This study aimed to evaluate indaziflam’s dissipation and leaching potential in two coffee-cultivated areas with different soil cover materials to assess their compatibility with indaziflam application.

2.Material and Methods

2.1 Dissipation in the field of indaziflam

2.1.1 Study local

This study was carried out at two farms in Rio Paranaíba, Minas Gerais, Brazil (Figure 1). 1) Glória farm (19°10’11” S, 46°12’49” W, 1,100 m above sea level) cultivated the Catucaí 2 SL variety of Coffea arabica in 4 m between rows and 0.5 m between plants, which was planted in December 2001 on a clay Oxisol (OXI_cl) (Table 1), and 2) IPACER farm (19°10’35” S, 46°06’09” W, 990 m above sea level) with the Catucaí 144 variety of C. arabica, planted in December 2018 with 3.8 m in rows and 0.6 m between plants, on a sand clay Oxisol (OXI_sc) (Table 1). Both farms were situated in a Cwb climate zone according to the Köppen classification, characterized by temperate, humid conditions with dry winters, average temperatures ranging from 16 to 23 °C , and annual precipitation below 2,000 mm.

Figure 1
Study sites cultivated with coffee (Coffee arabica) - cultivar Catucaí 2 SL and Catuaí 144 in the experimental units of the Glória and IPACER farms, respectively. Rio Paranaíba, MG, Brazil

Table 1
Physical-chemical properties of soils in the study areas. Rio Paranaíba, MG, Brazil

Properties	Unity	Farm
		IPACER	Glória
pH	CaCl2	4.9	5.3
pH	H2O	5.5	5.9
H+Al	cmolc dm-3	3.8	2.6
Aluminum	cmolc dm-3	0.0	0.0
Calcium	cmolc dm-3	2.6	2.9
Magnesium	cmolc dm-3	0.6	0.5
Potassium	cmolc dm-3	0.2	0.0
Phosphorus (Mehlich)	mg dm-3	10.0	3.0
Phosphorus (Resin)	mg dm-3	17.0	7.0
Organic carbon	%	2.3	1.4
Organic matter	%	4.0	2.4
Sum of bases	cmolc dm-3	3.4	3.5
Cation exchange capacity	cmolc dm-3	7.2	6.0
Base saturation	%	47.2	57.0
Sulfur	mg dm-3	15.4	7.1
Sodium	mg dm-3	2.0	2.4
Borum	mg dm-3	0.3	0.3
Iron	mg dm-3	19.8	13.4
Manganese	mg dm-3	12.8	2.2
Cooper	mg dm-3	2.7	1.1
Zinc	mg dm-3	10.2	2.6
Gravel	%	0	0
Coarse sand	%	15.6	6.0
Fine sand	%	14.1	6.0
Clay	%	45.0	73.0
Silt	%	25.3	15.0
Bulk density	g cm-3	1.2	1.1
Real density	g cm-3	2.9	3.0
Textural class		sand clay	clay

• pH: hydrogen potential; H+Al: hydrogen + aluminum
• Source: Unithal Laboratory, Rio Paranaíba, MG, Brazil

2.1.2 Experimental Design

The experiments were performed using a randomized block design at each farm, organized in a factorial arrangement of 2x3x8, with 3 repetitions. The first factor was the application of indaziflam (recommended field dose in coffee, 75 g a.i. ha^-1) and no application, the second factor consisted of three soil cover materials (crop debris, organic compost, and bare soil), and the third factor was eight evaluation times (0, 30, 60, 90, 120, 150, 180, and 210 days after application – DAA). Each experimental unit measured 10 m in length and 1 m in width, totaling an area of 10 m². To ensure consistency, a 1 m border was maintained at each end, resulting in a total useful area of 8 m².

2.1.3 Soil cover materials

Crop debris (5 t ha^-1 of vegetative residues from between coffee rows) and organic compost (2 t ha^-1 of crop debris combined with 3 t ha^-1 of chicken manure) were used, sourced from IPACER farm in Rio Paranaíba, MG, Brazil. A control treatment with bare soil was included. The chemical properties of these materials are detailed in Table 2.

Table 2
Chemical properties of organic compost and crop debris materials

Properties	Unity	Crop debris	Organic compost
Nitrogen	%	1.1	2.15
Phosphorus		0.6	3.4
Potassium		0.0	2.9
Calcium		0.8	6.8
Magnesium		0.2	0.4
Sulfur		2.0	0.9
Iron		7.3	1.6
Sodium		0.0	0.3
Manganese	ppm	286.0	284.0
Copper		76.0	52.0
Zinc		107.0	218.0
Borum		196.0	196.0
Organic matter	%	30.1	43.5
Ashes		69.9	56.5
Humidity		4.9	13.4
pH (CaCl2)		6.9	7.6
Carbon/Nitrogen		15/1	11/1

• pH: potential of hydrogen; ppm: parts per million
• Source: Unithal Laboratory, Rio Paranaíba, MG, Brazil

Before the experiments, weeds were desiccated along a 1-m-wide coffee row using glyphosate isopropylamine salt (1,440 g a.e. ha^-1). The soil cover materials were applied to the coffee row using a tractor-mounted Minami M 535-D fertilizer spreader.

2.1.4 Indaziflam application

Indaziflam (commercial product Alion®) was applied one week after applying the soil cover materials. A 1-m-wide strip on both sides of the coffee row was treated using a tractor-mounted PH 400 Jacto sprayer with a Jacto XR110.02 fan-type nozzle. The spray volume was set to 200 L ha^-1and the working pressure to 0.2942 MPa, spraying from a height of 20 cm above the ground and 10 cm from the coffee plant stems. On the time of application, the relative humidity was 80%, the air temperature was 25 °C, and the wind speed was 4 km h^-1. Throughout the study, meteorological data was monitored, including maximum and minimum temperatures and precipitation, provided by the Regional Cooperative of Coffee Growers of Guaxupé (Cooxupé), Rio Paranaíba Branch (Figure 2).

Figure 2
Precipitation and maximum and minimum temperatures in Rio Paranaíba, MG, Brazil, between October 2021 and August 2022, application of indaziflam on October 11, 2021, and November 16, 2021, at the Glória and Ipacer farms, respectively

2.1.5 Collection and preparation of soil samples for indaziflam analysis by HPLC

The indaziflam dissipation was evaluated using high-performance liquid chromatography (HPLC) by analysing soil samples collected at various intervals after application (0, 30, 60, 90, 120, 150, 180, and 210 DAA), as well as from control areas where indaziflam was not applied.

In the field, individual samples were collected (three replicates) to create composite soil samples with a 5 cm diameter probe auger, reaching a depth of 0–10 cm. The samples were then sieved to remove surface residues and air-dried. After drying, the samples were stored in polyethylene containers with a capacity of 250 mL for subsequent HPLC quantification.

2.1.6 Chromatographic conditions

The quantification of indaziflam was performed using a Shimadzu LC 20AT HPLC system (Kyoto, Japan), equipped with a Shimadzu SPD 20AT DAD detector and a stainless steel C18 column (Shimadzu VP-ODS Shim-pack, 250 mm x 4.6 mm i.d., 5 μm particle size). Herbicide extraction from soil samples employed the solid-liquid extraction with low-temperature partitioning (ESL-LTP) method, following Ramirez et al. (2018). Each 4 g sample was placed in a 50 mL Falcon tube, to which 14 mL of extraction solution (8 mL acetonitrile, 4.1 mL ultrapure water, and 1.9 mL ethyl acetate) was added.

The mixture was vortexed for 2 minutes using a Kasvi K45-2810 vortex mixer (São José dos Pinhais, SP, Brazil) to ensure proper homogenization. The tubes were then stored at -20°C in a Consul CHB53EB freezer (534 L, São Bernardo do Campo, SP, Brazil) for 4 hours. After cooling, the organic extract (solvents + herbicide) was filtered through paper filters into 50 mL round-bottom volumetric flasks. Anhydrous sodium sulfate (2 g) was added to the filters to remove any water, as recommended by the OECD (2002). The flasks were then subjected to rotary evaporation (Fisatom model 802, São Paulo, SP, Brazil) at 80 rpm and 50°C to evaporate the solvents, leaving only indaziflam.

Finally, the residue was rinsed with three 0.5 mL aliquots of acetonitrile and filtered through a 0.45 μm PTFE membrane filter into 1.50 mL vials for HPLC analysis.

2.1.7 Validation of chromatographic conditions

The methodology employed was validated based on parameters of selectivity, linearity, limits of detection (LoD) and quantification (LoQ), as well as precision and accuracy, following the guidelines for validation methods of chemical products by Anvisa (2017) and Inmetro (2020).

Selectivity of the ESL/LTP-HPLC-UV/Vis method was confirmed by comparing chromatograms of extracts obtained from a herbicide-free matrix with those from a matrix fortified with indaziflam, using the optimized method.

Linearity within the working range was evaluated through regression analysis of chromatographic data relative to herbicide concentration in an organic solvent, ranging from 0.01 to 4.0 mg L⁻¹. Indaziflam solutions at concentrations of 0.01, 0.05, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 mg L⁻¹ in acetonitrile were injected to establish the analytical curve. The quality of the regression was assessed by the coefficient of determination and residual analysis.

Limits of detection (LoD) and quantification (LoQ) were determined using the methodology proposed by Ribani et al. (2004). The LoD, which represents the minimum concentration of a substance detectable but not necessarily quantifiable with accuracy, was calculated by dividing the standard deviation of the analytical response of the blank by the slope (S) of the analytical curve, then multiplying by 3.3 (Equation 1):

$\text{LoD =}3.3\times \text{s s/S}$ (1)

The LoQ, representing the minimum concentration of the substance that can be quantified with acceptable precision, was determined using a 10:1 ratio of standard deviation to slope (Equation 2):

$\text{LoQ =}10\times s/S$ (2)

Accuracy, defined as the closeness between the measured value and the accepted reference value, was evaluated using recovery assays (%R) as described by Ribani et al. (2004). Soil samples with different coverages were fortified at three concentration levels (0.25, 0.50, and 1.00 mg L⁻¹), in triplicate, and analyzed using the ESL/LTP-HPLC-UV/Vis method.

Precision was assessed by the consistency of analytical results obtained from the same sample. It was expressed as repeatability and intermediate precision, and evaluated using the coefficient of variation (CV, expressed as %), also known as the relative standard deviation (RSD), calculated by Equation 3 (Inmetro, 2020):

$CV=RSD=\left(SD/MDC\right)X100$ (3)

where SD is the standard deviation and MDC is the mean determined concentration.

The results of the chromatographic method validation are presented in the supplementary material.

2.1.8. Statistical analysis of the dissipation study

The dissipation of indaziflam was assessed by calculating its half-life (DT₅₀) using first-order kinetics, as described by Mehdizadeh et al. (2017). The DT₅₀ was determined using equations 4 and 5:

$C_t=C_i{e}^{-kt}$ (4)

$D{T}_{50}=\ln 2/k$ (5)

where C_t is the herbicide concentration at time t, C_i is the initial concentration of the herbicide (Maheswari, Ramesh, 2007; Yousefi et al., 2016), and k is the dissipation rate constant in days. The DT₅₀ is subsequently calculated based on the value of k (Mendes et al., 2019).

Regression analysis, analysis of variance (ANOVA), and DT₅₀ calculations were performed using R software (version 4.2.3) with the dose response curve (DRC) package (R Core Team, 2023). Plots were generated using SigmaPlot® software (version 13.0 for Windows, Systat Software Inc., Point Richmond, CA, USA).

2.2 Leaching potential of indaziflam

2.2.1 Study site and experimental design

The leaching potential study was carried out in a greenhouse in Viçosa-MG, Brazil, using untreated soils with indaziflam from the IPACER and Glória farms. Two independent experiments in a completely randomized design with a $3\times 6+1$ layout included three soil cover materials (crop debris, organic compost, and bare soil), six depths (0–5, 5–10, 10–15, 15–20, 20–25, 25–30 cm), and a control without indaziflam.

Soil columns were constructed using 30 cm tall and 10 cm diameter PVC tubes, coated internally with paraffin to prevent runoff. Tees at the base retained soil and allowed drainage. After filling the tubes with the two soil types, soil cover materials were applied at a rate of 5 t ha⁻¹. A layer of filter paper was placed on top of each column to minimize droplet impact and ensure uniform simulated rainfall distribution. After filling, the columns were saturated with water for 24 h to remove air bubbles, then drained them vertically for 72 h to reach near-field capacity moisture.

Indaziflam (75 g a.i. ha^-1) was applied using a CO₂-pressurized sprayer at 0.1961 MPa equipped with an XR11002 fan-type nozzle, spray volume of 200 L ha^-1, 25°C, and 80% relative humidity. Twelve hours later, 100 mm of simulated rainfall was applied by manually adding 20 mm aliquots every 2 h to each column and allowed 72 h for drainage.

The tubes were then cut at specified depths (0-30 cm) using a marble saw. Soil samples were transferred to 300 mL polyethylene pots with sealed bottoms and sowed five soybean seeds per pot. Irrigation was provided daily according to the needs of each experimental unit, and fertilization was carried out using a nutrient solution containing macro and micronutrients to maintain optimal plant nutrition.

Plant injury was visually assessed at 7, 14, and 21 days after emergence (DAE), scoring from 0 (no injury) to 100 (death). At 21 DAE, the aboveground biomass was harvested and oven-dried at 65 °C until reaching a constant weight to determine dry biomass accumulation.

2.2.2 Statistical analysis of the leaching potential study

The injury levels and biomass accumulation of soybeans in the bioassay were visualized using R software (R Core Team, 2023). The means and standard deviations for each treatment were compared and analyzed descriptively.

3. Results

3.1 Validation of analytical methods by HPLC

The conditions used in this study effectively quantified indaziflam, achieving optimal peak area, peak symmetry, and reduced retention time. The validated chromatographic conditions identified the indaziflam peak in acetonitrile with a retention time of 7.3 minutes (Figure S1). The linear response across a range of indaziflam concentrations in acetonitrile (Figure S2A) demonstrated an R² value of 0.9999, exceeding the 0.99 threshold recommended by Agência Nacional de Vigilância Sanitária – Anvisa (2019) for pesticide studies in Brazil, confirming the suitability of the calibration curve for quantifying indaziflam. Regression analysis and residual plots for indaziflam (Figure S2B) indicated a strong model fit.

The method showed high selectivity, as chromatograms from both fortified and non-fortified soil extracts displayed no interfering peaks at indaziflam’s retention time. This selectivity was consistent across all tested soils and soil cover material types (Figure S3). The method achieved a limit of detection (LoD) of 0.0015 mg L⁻¹ and a limit of quantification (LoQ) of 0.0047 mg L⁻¹ (Table S1), outperforming previous values reported by Ramirez et al. (2018), which were 0.15 mg L⁻¹ and 0.44 mg L⁻¹, respectively.

The extraction method demonstrated accuracy and precision for both soil types, meeting Anvisa (2019) and Inmetro (2020) standards, which require recovery rates of 80–120% and precision coefficients of variation (CVs) below 20% (Table S2). Therefore, this chromatographic method was validated for laboratory evaluation of indaziflam dissipation in field studies.

3.2 Dissipation of indaziflam

The remaining indaziflam in OXI_cl with crop debris was 80, 67, 56, and 52% at 30, 60, 90, and 120 DAA, respectively (Figure 3). However, beyond this point, the dissipation rate slowed, with 40% of the herbicide still present at 210 DAA. Thus, the DT₅₀ of indaziflam in this scenario was estimated to be 138 days.

Figure 3
Dissipation of indaziflam (75 g a.i. ha-1) at 0, 30, 60, 90, 120, 150, 180, and 210 days after application (DAA) in a clay Oxisol (OXIcl) with crop debris, compost, and bare soil. The symbols correspond to the mean values, and bars represent the standard deviations of the means (n = 3).

ns: not significant by t-test (p<0.05)

Using an organic compost in OXI_cl, the remaining indaziflam was 71, 64, 59, 45% at 30, 60, 90, and 120 DAA (Figure 3). From 150 DAA onwards, indaziflam dissipation rate slowed, ending at 37% by 210 DAA. Thus, the DT₅₀ was estimated in 135 days.

In OXI_cl with bare soil, the remaining indaziflam was 67, 63, 52, 50 and 38% at 60, 90, 120, 180, and 210 DAA (Figure 3). The DT₅₀ in this scenario was estimated in 161 days. The soil cover material types did not affect indaziflam dissipation in OXI_cl (F = 0.524, p = 0.90), and the total dissipation at 210 DAA was similar across all soil cover materials.

In OXI_sc, the remaining indaziflam was 58% by 60 DAA in bare soil, 62% with crop debris, and 64% with organic compost (Figure 4). At 90 DAA, the remaining indaziflam was 47, 43, and 53% for bare soil, crop debris, and compost, respectively. At 210 DAA, only 16, 23, and 30% of the herbicide remained in bare soil, crop debris, and organic compost areas, respectively. The DT₅₀ for indaziflam in OXI_sc was 95 days in bare soil, 106 days with organic compost, and 119 days with crop debris.

Figure 4
Dissipation of indaziflam (75 g a.i. ha-1) at 0, 30, 60, 90, 120, 150, 180, and 210 days after application (DAA) in a sand clay Oxisol (OXIsc) with crop debris, compost, and bare soil. The symbols correspond to the mean values, and bars represent the standard deviations of the means (n = 3)

ns: not significant by t-test (p <0.05)

3.3 Leaching potential of indaziflam

3.3.1 Injury level

Indaziflam remained primarily in the 0-10 cm soil layer after 100 mm of simulated rainfall (Figure 5). No soybean injury was detected below 15 cm in any condition of soil or soil cover materials.

Figure 5
Level of injury (% relative to control) due to the application of indaziflam (75 g a.i. ha-1) in the bioindicator species - soybean (Glycine max) at different soil depths at 0, 7, 14, and 21 days after emergence (DAE), with a simulation of 100 mm of rain in a clay Oxisol (OXIcl) with crop debris (A), organic compost (B), and bare soil (C), and a sand clay Oxisol (OXIsc) with crop debris (D), organic compost (E), and bare soil (F)

The columns represent the means, and the bars represent the standard deviations of the mean (n = 3)

In OXI_cl with crop debris, the injury level in the 0–5 cm decreased from 88% at 0 DAE to 73% at 21 DAE, while the 5-10 cm layer decreased from 55 to 41% (Figure 5A). Minor injury at 10–15 cm decreased from 8 to 5%. With organic compost in OXI_cl, the injury level was 86% in the 0–5 cm layer at 0 DAE, decreasing to 70% at 21 DAE, and 41% in the 5-10 cm layer, reducing to 23% at 21 DAE, with no injury detected below 10 cm (Figure 5B). In bare soil, injury level was 95% at 0 DAE, maintaining close to 80% at 21 DAE in the 0–5 cm layer. In the 5–10 cm depth, soybean injury levels were 33% at 0 DAE and only 6% at 21 DAE.

In OXI_sc with crop debris, injury in the 0–5 cm layer remained stable, decreasing slightly from 88% at 0 DAE to 85% at 21 DAE; in the 5–10 cm layer, injury decreased from 36% at 0 DAE to 20% at 21 DAE, and minimal injury at 10–15 cm diminished from 10% at 0 DAE to 0% at 21 DAE (Figure 5D). With organic compost, injury in the 0–5 cm layer reduced from 90% at 0 DAE to 70% at 21 DAE, while the 5–10 cm layer showed no change, remaining at 20% throughout (Figure 5E). In bare soil, injury in the 0–5 cm layer stayed high, from 90% at 0 DAE to 85% at 21 DAE, with a decrease from 36% at 0 DAE to 13% at 21 DAE in the 5-10 cm layer (Figure 5F).

3.3.2 Biomass accumulation

In OXI_cl (Figure 6A), biomass accumulation in soybean plants was lower in bare soil (10%) compared to crop debris (18%) and organic compost (15%) in the 0–5 cm layer (Figures 7A, 7B, and 7C). This trend was also observed in the 5–10 cm and 10–15 cm layers, but the overlap in error bars limits any inference about the magnitude of these differences. No variation in biomass was observed below the 15–20 cm depth.

Figure 6
Biomass accumulation (% relative to control) caused by the application of indaziflam (75 g a.i. ha-1) in the bioindicator species - soybean (Glycine max) at different soil depths at 21 days after emergence (DAE), with a simulation of 100 mm of rain in a clay Oxisol (OXIcl) (A) and a sand clay Oxisol (OXIsc) (B) covered with crop debris, organic compost, and bare soil

The columns represent the means, and the bars represent the standard deviations of the mean (n = 3)

Figure 7
Images of soybean plants (Glycine max) sown in soils from different layers at 21 days after emergence (DAE) after application of indaziflam (75 g a.i. ha-1) and without application of indaziflam with a simulation of 100 mm of rain in a clay Oxisol (OXIcl) (A, B, and C) and a sand clay Oxisol (OXIsc) (D, E, and F) with three soil cover materials (crop debris, organic compost, and bare soil)

In OXI_sc (Figures 6B, 7D, 7E, and 7F), biomass accumulation in the 0–5 cm layer was lower in the bare soil (15%) compared to compost (20%), with crop debris showing intermediate values (18%). In the 5–10 cm layer, biomass was 75% for bare soil, 72% for crop debris, and 81% for compost. While differences were observed across treatments, the overlap in error bars suggests that no definitive conclusion can be drawn. Biomass increased with depth, reaching 100% in all treatments from the 20–25 cm depth onwards.

4.Discussion

4.1 Dissipation of indaziflam

Indaziflam is a herbicide with limited photodegradation, a soil DT₅₀ of about 150 days, and effective weed control at low doses compared to other pre-emergent herbicides (Sebastian et al., 2016). These characteristics contribute to its prolonged residual effect and slow dissipation in soil (Sebastian et al., 2017). The DT₅₀ values for indaziflam in OXI_cl and OXI_sc across all soil cover material types align with the reported ~150 days (Tompkins, 2010). However, indaziflam dissipation varies with environmental factors (González-Delgado et al., 2015), where residues up to 7.5 μm kg⁻¹ were detected even 365 days post-application, highlighting the herbicide’s high persistence. Variability in DT₅₀ values has been reported, ranging from 30 to 86 days (González-Delgado et al., 2017) and from 63 to 99 days depending on the applied dose (González-Delgado, Shukla, 2020). Persistence of indaziflam has been shown to range from 365 to 491 days at doses of 150 and 400 g a.i. ha⁻¹, respectively, indicating slower dissipation and increased persistence with higher doses (Blanco, 2023). In Brazilian soils, indaziflam persistence exceeded 150 days, with clay content having no significant effect on persistence (Guerra et al., 2016), suggesting a wide range of environmental persistence.

Indaziflam dissipates in the environment mainly through degradation and leaching processes (Tompkins, 2010). The herbicide does not isomerize under various environmental conditions, indicating isomeric stability, which is crucial for maintaining efficacy (Eckelmann et al., 2020). The metabolites of indaziflam—ITI, ICA, indaziflam-hydroxyethyl, indaziflam-olefin, and FDAT—exhibit varying chemical reactivity, with ITI being the most reactive (Alonso et al., 2016; Mendoza-Huizar et al., 2019). These differences in reactivity suggest variability in soil degradation rates, influenced by chemical properties and interactions with soil components (Mendoza-Huizar et al., 2019).

When establishing new coffee plantations or replanting, it is important to consider indaziflam residues, as the herbicide can inhibit seedling development by reducing root growth and dry matter accumulation (Gomes et al., 2019). While indaziflam has broad applications, its physicochemical properties and persistence necessitate careful consideration of soil effects on its bioavailability. Soil properties, such as organic matter, clay content, and pH, significantly influence persistence (Monquero, Silva, 2021). In this study, greater indaziflam dissipation was observed in OXI_sc, which had a higher organic matter content (Table 1), compared to OXI_cl. This suggests that soil characteristics, particularly the higher organic matter content in OXI_sc, may influence indaziflam dissipation. These findings provide a reference for understanding indaziflam dissipation in coffee cultivation, but further research is needed to explore the effects of soil properties in more detail.

4.2 Leaching potential of indaziflam

Indaziflam exhibits low water S_w and a high K_ow, indicating its tendency to remain near the soil surface rather than leaching through the soil profile (Sebastian et al., 2017). Studies suggest that indaziflam has a lower leaching potential compared to most pre-emergent herbicides (Guerra et al., 2016). Bioassay studies have shown that indaziflam fails to control weeds below a depth of 30 cm, even after 150 mm of precipitation (Jhala et al., 2012).

Leaching and sorption-desorption processes are interconnected; an herbicide sorbed to soil experiences reduced leaching potential. Factors such as organic matter (OM) content, soil pH, and texture significantly influence indaziflam’s sorption-desorption dynamics (Alonso et al., 2011; Gonçalves et al., 2021; Lima et al., 2023). Within a pH range of 4.9 to 7.3, OM plays a more significant role in indaziflam sorption than pH (Lima et al., 2023). At pH levels approaching neutrality or above the herbicide’s acid dissociation constant (pK_a), the dissociated (ionic) form predominates, reducing sorption and increasing availability in the soil solution (El-Nahhal, Hamdona, 2017; Souza et al., 2020; Refatti et al., 2014). Despite differences in OM content between OXI_sc (4.0%) and OXI_cl (2.4%), similar injury levels and biomass accumulation were observed in both soils. This similarity may be attributed to the small variation in pH and slightly acidic conditions (OXI_sc 4.90 and OXI_cl 5.3), which promoted sorption and minimized leaching potential. Additionally, the OXI_cl higher clay content (73%) compared to OXI_sc (45%) may reduce leaching by enhancing herbicide sorption or limiting vertical water movement in the soil.

The efficacy of indaziflam in controlling weeds in coffee crops with soil cover depends on adequate soil moisture for herbicide availability and root absorption. Indaziflam has proven effective in controlling weeds in soils with 5 t ha⁻¹ of plant residues and at least 10 mm of rainfall following herbicide application (Silva et al., 2020). Even with 10 t ha⁻¹ of cover, indaziflam remains effective if there is sufficient rainfall or irrigation to facilitate herbicide removal from the straw (Guerra et al., 2015). Thus, soil cover does not appear to reduce indaziflam’s efficacy, indicating its suitability in such scenarios. The 100 mm rainfall simulation in our study likely exceeded the requirement for removing the herbicide from the soil covers.

Moreover, the reduced leaching potential of indaziflam not only mitigates environmental contamination risks but also contributes to prolonged residual control in the soil, aiding in the reduction of the weed seed bank, as weed seeds can remain viable for extended periods (Sebastian et al., 2017).

5.Conclusions

The use of soil cover materials, such as organic compost and crop debris at a dose of 5 t ha⁻¹, did not affect the dissipation or leaching of indaziflam in either OXI_cl or OXI_sc soils. Therefore, soil covers were considered compatible with indaziflam applications under the conditions of this study.

References

• Agência Nacional de Vigilância Sanitária - Anvisa. [Program for analysis of pesticide residues in food - PARA: report on sample evaluations monitored from 2017 to 2018]. Brasília: Agência Nacional de Vigilância Sanitária; 2019[access Mar 13, 2024]. Portuguese. Available from: http://portal.anvisa.gov.br/documents/219201/2782895/Relat%C3%B3rio+PARA+Vers%C3%A3o+Final/1230de7d-306d-4249-a62c-a68708fab153
  » http://portal.anvisa.gov.br/documents/219201/2782895/Relat%C3%B3rio+PARA+Vers%C3%A3o+Final/1230de7d-306d-4249-a62c-a68708fab153
• Alonso DG, Koskinen WC, Oliveira RS, Constantin J, Mislankar S. Sorption-desorption of indaziflam in selected agricultural soils. J Agric Food Chem. 2011;59(24):13096-101. Available from: https://doi.org/10.1021/jf203014g
  » https://doi.org/10.1021/jf203014g
• Alonso DG, Oliveira RS, Hall KE, Koskinen WC, Constantin J, Mislankar S. Changes in sorption of indaziflam and three transformation products in soil with aging. Geoderma 2015;239-240:250-6. Available from: https://doi.org/10.1016/j.geoderma.2014.11.008
  » https://doi.org/10.1016/j.geoderma.2014.11.008
• Blanco FMG. Determination of the persistence in soil of the herbicide indaziflam applied on sugarcane crop under brazilian conditions. J Environ Sci Engin A. 2023;12:59-67. Available from: https://doi.org/10.17265/2162-5298/2023.02.002
  » https://doi.org/10.17265/2162-5298/2023.02.002
• Brosnan JT, Breeden GK, McCullough PE, Henry GM. PRE and POST control of annual bluegrass ( Poa annua ) with indaziflam. Weed Technol. 2012;26:48-53. Available from: https://doi.org/10.1614/wt-d-11-00088.1
  » https://doi.org/10.1614/wt-d-11-00088.1
• Brosnan JT, McCullough PE, Breeden GK. Smooth crabgrass control with indaziflam at various spring timings. Weed Technol. 2011;25(3):363-6. Available from: https://doi.org/10.1614/wt-d-11-00005.1
  » https://doi.org/10.1614/wt-d-11-00005.1
• DaMatta FM. Ecophysiology of tropical tree crops: an introduction. Braz J Plant Physiol. 2007;19(4):239-44. Available from: https://doi.org/10.1590/S1677-04202007000400001
  » https://doi.org/10.1590/S1677-04202007000400001
• Eckelmann D, Augustin T, Leake C. Isomeric stability of indaziflam and major degradation products in the environment. Sci Total Environ. 2020;737:1-8. Available from: https://doi.org/10.1016/j.scitotenv.2020.140223
  » https://doi.org/10.1016/j.scitotenv.2020.140223
• El-Nahhal Y, Hamdona N. Adsorption, leaching and phytotoxicity of some herbicides as single and mixtures to some crops. J Assoc Arab Univer Basic Appl Sci. 2017;22(1):17-25. Available from: https://doi.org/10.1016/j.jaubas.2016.01.001
  » https://doi.org/10.1016/j.jaubas.2016.01.001
• Fontes DR, Ribeiro ADP, Reis MR, Inoue MH, Mendes KF. Integrated weed management in coffee for sustainable agriculture: a practical brazilian approach. In: Mendes KF, editor. New insights in herbicide science. Rijeka: IntechOpen; 2022. Available from: https://doi.org/10.5772/intechopen.108881
  » https://doi.org/10.5772/intechopen.108881
• Gomes CA, Pucci LF, Alves DP, Leandro VA, Pereira GAM, Reis MR. Indaziflam application in newly transplanted arabica coffee seedlings. Coffee Sci. 2019;14:373. Available from: https://doi.org/10.25186/cs.v14i3.1591
  » https://doi.org/10.25186/cs.v14i3.1591
• Gonçalves VA, Ferreira LR, Teixeira MFF, Freitas FCLD, D'Antonino L. Sorption of indaziflam in brazilian soils with different ph values. Rev Caatinga. 2021;34(4):494-504. Available from: https://doi.org/10.1590/1983-21252021v34n301rc
  » https://doi.org/10.1590/1983-21252021v34n301rc
• González-Delgado AM, Ashigh J, Shukla MK, Perkins R. Mobility of indaziflam influenced by soil properties in a semi-arid area. Plos One. 2015;10(5):1-12. Available from: https://doi.org/10.1371/journal.pone.0126100
  » https://doi.org/10.1371/journal.pone.0126100
• González-Delgado AM, Shukla MK, Ashigh J, Perkins R. Effect of application rate and irrigation on the movement and dissipation of indaziflam. J Environ Sci. 2017;51:111-9. Available from: https://doi.org/10.1016/j.jes.2016.09.002
  » https://doi.org/10.1016/j.jes.2016.09.002
• González-Delgado AM, Shukla MK. Mobility, degradation, and uptake of indaziflam under greenhouse conditions. HortScience. 2020;55(8):1216-21. Available from: https://doi.org/10.21273/hortsci14966-20
  » https://doi.org/10.21273/hortsci14966-20
• Guerra N, Oliveira Júnior RS, Constantin J, Oliveira Neto AM, Gemelli A, Pereira Júnior DM. Persistence of biological activity and leaching potential of herbicides aminocyclopyrachlor and indaziflam in soils with different textures. Planta Daninha. 2016;34(2):345-56. Available from: https://doi.org/10.1590/S0100-83582016340200016
  » https://doi.org/10.1590/S0100-83582016340200016
• Guerra N, Oliveira Júnior RS, Constantin J, Oliveira Neto AM, Puton G, Garrido THP. Influence of precipitation and sugarcane straw in aminocyclopyrachlor and indaziflam control efficiency. Planta Daninha. 2015;33(3):535-42. Available from: https://doi.org/10.1590/S0100-83582015000300015
  » https://doi.org/10.1590/S0100-83582015000300015
• Instituto Nacional de Metrologia, Qualidade e Tecnologia - Inmetro. [Guidelines on the validation of chemical test methods]. Brasília: Instituto Nacional de Metrologia, Qualidade e Tecnologia; 2020[access Mar 13, 2024]. Portuguese. Available from: http://www.inmetro.gov.br/sidoq/arquivos/cgcre/doq/doq-cgcre-8_09.pdf
  » http://www.inmetro.gov.br/sidoq/arquivos/cgcre/doq/doq-cgcre-8_09.pdf
• Jeffries MD, Gannon TW. Soil organic matter content and volumetric water content affect indaziflam: soil bioavailability. Weed Sci. 2016;64:757-65. Available from: https://doi.org/10.1614/ws-d-16-00039.1
  » https://doi.org/10.1614/ws-d-16-00039.1
• Jhala AJ, Ramirez AHM, Singh M. Leaching of indaziflam applied at two rates under different rainfall situations in florida candler soil. Bull Environ Cont Toxicol. 2012;88:326-32. Available from: https://doi.org/10.1007/s00128-011-0514-6
  » https://doi.org/10.1007/s00128-011-0514-6
• Lima AC, Wei MCF, Laube AFS, La Cruz RAD, Freitas FCL, Silva AA, Mendes KF. Spatial variability mapping of indaziflam and metribuzin sorption-desorption for precision weed control. Prec Agric. 2023;25:30-50. https://doi.org/10.1007/s11119-023-10056-2
  » https://doi.org/10.1007/s11119-023-10056-2
• Mendes KF, Goulart BF, Possamai ACS, Inoue MH, Matos AKA, Tschope MC. [Leaching of hexazinone and mixture hexazinone + diuron in columns of soils with distinct textures]. Rev Agro@mbiente. 2013;7:218. Portuguese. Available from: https://doi.org/10.18227/1982-8470ragro.v7i2.972
  » https://doi.org/10.18227/1982-8470ragro.v7i2.972
• Mendes KF, Soares MB, Sousa RN, Mielke KC, Brochado MGS, Tornisielo VL. Indaziflam sorption-desorption and its three metabolites from biochars- and their raw feedstock-amended agricultural soils using radiometric technique. J Environ Sci Health Part B. 2021;56(8):731-40. Available from: https://doi.org/10.1080/03601234.2021.1941559
  » https://doi.org/10.1080/03601234.2021.1941559
• Mendes KF, Sousa RN, Lima AC, Godoi Junior M. Understanding the environmental behavior of herbicides: a systematic review of practical insights. Rijeka: IntechOpen; 2024[access Jul 15, 2024]. Available from: https://doi.org/10.5772/intechopen.1002280
  » https://doi.org/10.5772/intechopen.1002280
• Mendoza-Huizar L, Rios-Reyes C, Álvarez-Romero G, Páez-Hernánde ME. Analysis of the chemical reactivity of indaziflam herbicide and its metabolites through global and local reactivity descriptors. Quim Nova. 2019;46(4):628-37. Available from: https://doi.org/10.21577/0100-4042.20170382
  » https://doi.org/10.21577/0100-4042.20170382
• Monquero P, Silva PV. [Behavior of herbicides in the environment]. In: Barroso AA, Murata AT, editors. [Weedology]. Jaboticabal: Fábrica da Palavra; 2021. p. 253-94. Portuguese.
• R Core Team. R: a language and environment for statistical computing, version 3.6.0. Vienna: R Foundation for Statistical Computing; 2023[access July 15, 2023]. Available from: https://www.r-project.org
  » https://www.r-project.org
• Refatti JP, Avila LA, Agostinetto D, Manica-Berto R, Bundt ADC, Elgueira DB. [Effect of liming on imazethapyr and imazapyr leaching in rice paddy soil]. Cienc Rural. 2014;44(6):1008-14. Portuguese. Available from: https://doi.org/10.1590/s0103-84782014000600009
  » https://doi.org/10.1590/s0103-84782014000600009
• Ribani M, Bottoli CBG, Collins CH, Jardim ICSF, Melo LFC. [Validation for chromatographic and electrophoretic methods]. Quim Nova. 2004;27(5):771-80. Portuguese. Available from: https://doi.org/10.1590/s0100-40422004000500017
  » https://doi.org/10.1590/s0100-40422004000500017
• Rocha PRR, Faria AT, Borges LGFC, Silva LOC, Silva AA, Ferreira EA. [Sorption and desorption of diuron in four brazilian latosols]. Planta Daninha. 2013;31(1):231-8. Portuguese. Available from: https://doi.org/10.1590/s0100-83582013000100025
  » https://doi.org/10.1590/s0100-83582013000100025
• Ronchi CP, Silva AA. Sustainable weed control in coffee. In: Korres NE, Burgos NR, Duke SO, editors. Weed control sustainability, hazards and risks in cropping systems worldwide. Boca Raton: CRC; 2018. p. 425-41.
• Sebastian DJ, Nissen SJ, Sebastian JR, Meiman PJ, Beck KG. Preemergence control of nine invasive weeds with aminocyclopyrachlor, aminopyralid, and indaziflam. Invas Plant Sci Manag. 2017;10(1):99-109. Available from: https://doi.org/10.1017/inp.2017.7
  » https://doi.org/10.1017/inp.2017.7
• Sebastian DJ, Nissen SJ, Westra P, Shaner DL, Butters G. Influence of soil properties and soil moisture on the efficacy of indaziflam and flumioxazin on Kochia scoparia L. Pest Manag Sci. 2016;73(2):444-51. Available from: https://doi.org/10.1002/ps.4300
  » https://doi.org/10.1002/ps.4300
• Silva PV, Santos MJ, Tronquini SM, Giraldeli AL, Carvalho RD, Monquero PA et al. Indaziflam: leaching and control of Urochloa plantaginea in applications on coffee litter with different rainfall simulations. Coffee Sci. 2020;15:1-8. Available from: https://doi.org/10.25186/.v15i.1816
  » https://doi.org/10.25186/.v15i.1816
• Souza ADS, Leal JFL, Langaro AC, Carvalho GSD, Pinho CFD. Leaching AND Carryover for safrinha corn of the herbicides imazapyr + imazapic in soil under different water conditions. Rev Caatinga 2020;33(2):287-98. Available from: https://doi.org/10.1590/1983-21252020v33n202rc
  » https://doi.org/10.1590/1983-21252020v33n202rc
• Tompkins JP. Pesticide fact sheet: indaziflam. Washington: US Environmental Protection Agency; 2010[access Mar 13, 2024]. Available from: https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-080818_26-Jul-10.pdf
  » https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-080818_26-Jul-10.pdf
• University of Hertfordshire. Hertfordshire Pesticide Properties DataBase: indaziflam. Hatfield: University of Hertfordshire; 2024[access July 25, 2024]. Available from: http://sitem.herts.ac.uk/aeru/ppdb/en/Reports/1663.htm#none
  » http://sitem.herts.ac.uk/aeru/ppdb/en/Reports/1663.htm#none
• Yousefi M, Kamkar B, Gherekhloo J, Faez R. Sulfosulfuron persistence in soil under different cultivation systems of wheat ( Triticum aestivum ). Pedosphere. 2016;26(5):666-75. Available from: https://doi.org/10.1016/s1002-0160 (15)60075-3
  » https://doi.org/10.1016/s1002-0160 (15)60075-3

• Funding
  The present study was carried out with the support of the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Funding Code 001.

Edited by

• Editor in Chief:
  Carol Ann Mallory-Smith

• Associate Editor:
  Carol Ann Mallory-Smith

Publication Dates

• Publication in this collection
  06 Dec 2024
• Date of issue
  2024

History

• Received
  14 Mar 2024
• Accepted
  7 Oct 2024