Weed seed bank and residual effect on succeeding crop (Sunflower) as influenced by weed control methods in maize

To study the effect of weed control methods on weed seed bank and the residual effect of different herbicides applied in maize on succeeding sunflower crop, a field experiment was conducted at Tamilnadu Agricultural University, Coimbatore during kharif seasons of 2018-19 and 2019-20. Treatments included two pre-emergence herbicides viz., atrazine 0.5 kg ha^-1 and pendimethalin 1 kg ha^-1 at 1 DAS along with two early post-emergence herbicides topramezone 25.2 g ha^-1 and tembotrione 122 g ha^-1 at 20 DAS were used. Hand weeding twice at 20 and 45 DAS and control were also included. After the maize harvest, a reduction in weed seed bank was observed with hand weeding twice at 20 and 45 DAS which was on par with pre emergence atrazine fb either early post emergence topramezone or tembotrione at 20 DAS. Residue of herbicides was noticed in early post emergence topramezone alone or tembotrione at 20 DAS alone and sequential application of pre emergence atrazine fb either topramezone or tembotrione as early post emergence were noticed above detectable level in the soil at harvest stage of maize. However, none of the herbicide treatments used in the kharif maize season showed any residual carryover effects on the subsequent sunflower crop.