Novel method to manage weeds in the rainfed groundnut (var. VRI 8 and TMV 14) using nano encapsulated herbicide formulations

The groundnut crop harbours heavy weed infestation due to its small stature and slow growing nature. The current weed management practices of hand weeding and use of commercial herbicides are unsuitable because of high labour cost and inadequate moisture availability to activate herbicides.  In order to release the herbicide in a smart way, this experiment aimed to study the efficacy of encapsulated herbicides . Field experiments were conducted during Kharif 2021 and late Rabi 2022 under rainfed conditions in randomised block design with three replications. The treatments consisted of sulfentrazone, oxyfluorfen, diclosulam and metolachlor in both commercial and encapsulated form using two doses, hand weeding at 20 and 40 DAS, weed free plot and weedy check. Minimum weed density (28.33 and 17.30 No./m2 at 90 DAS during Kharif and late Rabi respectively) and weed dry weight (65.33 and 61.25 g/m2 at 90 DAS during Kharif and late Rabi respectively) were observed in hand weeding at 20 and 40 DAS (T19) followed by diclosulam @ 25 g ha-1 with encapsulation (T7). Maximum weed density and weed dry weight was observed in metolachlor @ 1 kg/ha with encapsulation (T8). Higher productivity was observed in hand weeding at 20 and 40 DAS (T19) (1802 kg ha-1  and 1753 kg ha-1  pod yield during Kharif and late Rabi respectively) and higher profitability was obtained in diclosulam @ 25 g ha-1 with encapsulation (T7) (1.80 and 2.01 B:C ratio during (Kharif and late Rabi respectively). Nano-encapsulated herbicides can thus significantly improve weed control in rainfed groundnut

Effect of Glyphosate on Physiology and Biochemical Properties of Purple Nutsedge (Cyperus rotundus L.)

The study was conducted to understand the influence of herbicide on the changes in physiology and biochemical properties of purple nutsedge weed (Cyperus rotundus L.). Laboratory and pot culture study were conducted at the Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore during 2020-21. Glyphosate was tested with different concentrations (500, 600, 700, 800, 900 and 1000 ppm) and various soaking duration (6, 12, 24 and 48 hrs) with three replication. The extent of weed damage is based on the site of herbicide action, inhibition of enzymes activity and other metabolic functions. It resulted in chlorophyll content and membrane stability index of the weeds were affected. Proline level of treated weeds were found to be increased at initial stage of herbicide application and followed by declined gradually. It causes the weeds to kill by exhibiting oxidative stress. Phytotoxic effect of herbicide application was visualized until 15-20 DAHA (days after herbicide application) and thereafter weeds were died due to cessation of all the metabolic activities. The findings of the soaking experiment confirmed the negative impact of herbicide on phenol and starch content in tubers. Phenol degradation or dilution was observed to be increased with increasing duration of soaking period and however starch content decreases simultaneously. The results showed that application of glyphosate @ 1000 ppm is more effective to arrest the population of Cyperus rotundus