Spatial variability mapping of indaziflam and metribuzin sorption–desorption for precision weed control

Preemergence herbicides are traditionally applied uniformly throughout the area; however, weed control may vary due to spatial variability of the soil within the same area. Precision agriculture tools such as variable rate applications of herbicides improve weed control, making it necessary to know the physicochemical characteristics of the soil. The objective of this study was to map the spatial variability of sorption–desorption and agronomic efficiency of indaziflam and metribuzin for weed management in a field of 17.5 ha of Minas Gerais, Brazil. Fifty-five soil samples were collected (0–10 cm depth) and based on their physicochemical characteristics and the sorption and desorption coefficients for indaziflam and metribuzin, determined by a batch equilibrium method, thematic maps were generated for each variable in QGIS (Quantum Geographic Information System). In addition, the bioavailability concentration of each herbicide was determined, and its efficacy was evaluated in controlling Amaranthus hybridus and Eleusine indica in a representative soil sample. The sorption coefficient (K d(s) ) of indaziflam ranged from 6.9 to 40.5 L kg −1 , the sorbed percentage (S%) from 61 to 86.6%, the desorbed percentage (D%) from 8.4 to 33.1%, and the total bioavailability (TB%) from 26 to 55.7%. The K d(s) values of metribuzin ranged from 1.1 to 4.3 L kg −1 , S% from 22.8 to 33.9%, D% from 17.2 to 22.0%, and TB% from 79.4 to 96.7%. Organic matter was highly correlated with the TB% of indaziflam (r = –0.8) and metribuzin (r = –0.7). Soil solution equilibrium concentration (Ce) of 1.9 g a.i. ha −1 of indaziflam controlled 80% of A. hybridus and E. indica . The Ce values of metribuzin were 55.2 and 111.2 g a.i. ha −1 to control 80% of A. hybridus and E. indica , respectively. Recommendations of varied doses provided reductions of 17.6% in the total application of indaziflam and 9.8% of metribuzin concerning the highest dose recommended in the field. The characterization of the soil physicochemical characteristics as well as the determination of the total bioavailability of indaziflam and metribuzin, by knowing the sorption–desorption coefficients, allowed for the recommendation of variable and precise doses of herbicides for the efficient management of A. hybridus and E. indica in preemergence, reducing potential negative environmental impacts.