Sweetpotato [<i>Ipomoea batatas</i> (L.) Lam.] Response to <i>S</i>-Metolachlor and Rainfall under Three Temperature Regimes

Abstract

The <i> S </i> -metolachlor is used to control/suppress yellow nutsedge, annual grasses, and several broadleaf weeds in sweetpotato. However, when used under adverse environmental conditions, it may lead to crop injury. Information is limited on the effect of <i> S </i>-metolachlor application followed immediately by rainfall on sweetpotato growth and development under different temperature regimes. The objective of this study was to determine sweetpotato response to <i> S </i>-metolachlor under low, optimum, and high temperatures with no rainfall and rainfall immediately after application. Sweetpotato slips were transplanted to sandy loam soil-filled pots. Half of the pots were subjected to 38 mm rainfall at 50.8 mm · h -1 intensity within the first 24 h after POST-transplant <i> S </i>-metolachlor application at 0, 0.86, 1.72, 2.58 and 3.44 kg · ha -1 . The pots were moved into sunlit, computer-controlled plant growth chambers that were maintained at their respective temperatures for 61 days. Plant growth, development and plant-component dry weights and quantity of storage roots were recorded at harvest. Storage root yield was highest at the optimum temperature and declined at low and high temperature conditions. Shoot, root, and total plant biomass yield declined with increasing concentration of <i> S </i>-metolachlor across temperature conditions. In addition, storage root yield decline was S-metolachlor rate-dependent and aggravated by a rainfall event immediately after herbicide treatment across temperatures tested. These results can be used to weigh the risk of potential crop injury against the benefits of <i> S </i>-metolachlor when making management decisions as well as considering weather forecast information to avoid herbicide application coinciding with adverse weather conditions such as excessive rainfall event.