Integrated Mechanical Weeding and Herbicide Application in Weed Management of Sugarcane (Saccharum officinarum L.)

Weeds are among the most important factors reducing sugarcane yield in Khuzestan province. Sugarcane has a vegetative stage susceptible to weed competition, which is about 3 to 6 weeks from the time of planting in a warm and humid season. Therefore, the control of weeds in the early part of the growing season before the canopy closure of sugarcane and covering more than half the rows of planting is very critical. In order to investigate the effect of combination of mechanized weeding and application of three herbicides including indaziflam, 2,4-D + MCPA + metribuzin, on weed control and sugarcane yield, a field experiment was conducted in Ratoon2 field in 2017-2018 growing season in Dehkhoda Sugarcane Plantation and Industry Company, Khuzestan, Iran.

The experimental design was split plot based on randomized complete block design with three replications. Mechanical weeding at three levels (sweep cultivator, rotavator, and no cultivation) was considered as the main plots. Herbicide application was considered as sub plot at three levels [indaziflam (50 ml ai ha-1), 2,4-D + MCPA + metribuzin (675 ml ai ha-1 + 1050 g ai ha-1) and no herbicide application (as weedy control)]. A weed- free check was included for comparison. Herbicide applications were made using backpack sprayer with TeeJet 11004 flat fan nozzle calibrated to deliver 250 L ha-1 at pressure of 2.5 atm. Sugarcane cultivar was CP-614. Weed sampling was carried out 60 days after treatment. Single stem weight, cane yield, final sugar yield, brix, pol, sugar purity and recoverable sugar were measured at the end of growing season and after sugarcane harvest.

The results showed that mechanical weeding treatments lead into reduced weed dry weight. As a result, weed control was more effective in rotavator treatment than cultivator. Maximum reduction weed dry weight (52.47%) was observed in integrated rotavator and indaziflam treatment. The results of the quantitative traits of sugarcane showed that using mechanized weeding and herbicide application, caused an increase in weight of single stem and yield of cane compared to the control. The greatest single stem weight was observed in cultivator treatment plus 2,4-D + MCPA + metribuzin (1.65 Kg m-2), rotavator + 2,4-D + MCPA + metribuzin (1.63 Kg m-2) and indaziflam (1.61 Kg m-2). The final sugar yield (9.79 t ha-1) in indaziflam treatment was greater than other treatments (except weed -free treatment). However, the measured values of Brix, pol, sugar purity and recoverable sugar did not differ significantly among treatments. Results showed that the use of mechanized weeding combined with herbicide applications would have an effective role in improving sugarcane yield and inhibition of sugarcane weeds.

The use of herbicides at the beginning of the sugarcane growing season led to more effective weed control; As a result, competition between sugarcane and weeds in access to food resources decreased, which led to the growth and development of sugarcane. However, the indaziflam did better than 2,4-D + MCPA + metribuzin due to its slight superiority in single-stem weight and cane yield. In general, it can be said that the use of mechanical weeding has an important role in controlling sugarcane weeds and the use of rotivator had a significant advantage over cultivator. According to the results of single stem weight, the use of combination weeding with herbicides will play an effective role in improving the weight of sugarcane.