Research Article AllelopathicEffectsofAqueousExtractsofSorghum(Sorghum bicolor L.Moench)ontheEarlySeedlingGrowthofSesame (Sesamum indicum L.)VarietiesandSelectedWeeds J.C.Murimwa , 1 J.T.Rugare , 1 S.Mabasa, 1 andR.Mandumbu 2 1 University of Zimbabwe, Faculty of Agriculture, Department of Crop Science, Mount Pleasant, Harare, Zimbabwe 2 Bindura University of Science Education, Department of Crop Science, Bindura, Zimbabwe Correspondence should be addressed to J. T. Rugare; rugarejoy@yahoo.co.uk Received 2 December 2018; Accepted 6 February 2019; Published 3 March 2019 Academic Editor: Isabel Marques Copyright©2019J.C.Murimwaetal.isisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Sesame (Sesamum indicum L.) production is lucrative to resource poor farmers in marginalised areas of Zimbabwe, although most farmers have reportedly been failing to derive maximum economic benefits from sesame production due to poor productivity. Low productivity has been attributed to several factors including challenges of weed control due to absence of registered herbicides for use in sesame in Zimbabwe. Laboratory enzyme assays were conducted using different sorghum aqueous leaf and stem extract concentrations at 0, 2.5, 5.0, 7.5, and 10.0% wv -1 to determine the effect of sorghum aqueous extracts on plant defense enzymes polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia lyase (PAL) in sesame and selected weeds. Greenhouse experiments were conducted to assess the effect of sorgaab or sorgaab-Agil postemergence sprays on the seedling growth and physiology of sesame and weeds. e exposure of sesame, black jack, and goose grass to sorghum aqueous extracts caused a significant (p < 0.05) concentration-dependent increase on the activity of antioxidant enzymes PAL, POD, and POD. Similarly, postemergence sprays of sole sorgaab, herbicide, and sorgaab-herbicide combination significantly (p < 0.05) increased sesame and black jack seedling growth, chlorophyll content, and fluorescence but not of goose grass. From this study, it could be concluded that the allelochemicals in sorghum aqueous extracts were not effective at inhibiting the growth and physiological processes of sesame and the weeds. erefore, resource-poor farmers cannot rely on sorgaab to control weeds in sesame but there is a need to integrate weed control options to form an effective integrated weed management program. 1.Introduction Sesame (Sesamum indicum L.) is one of the world’s oldest cultivated oilseed crops, and it belongs to the Pedaliaceae family [1]. e place of origin of this crop is not clearly known to one place because it is thought to be either Africa or Asia which together contribute to 96% of the total global sesame production [2]. Sesame is one of the first crops to be processed for oil, and the oil extracted from the seeds is the most important product, commonly referred to as the “Queen of oils” by virtue of high-quality oil resistant to rancidity [1, 3]. In Zimbabwe, sesame is currently grown in areas that receive low to moderate rainfall (<300to600mm) because of the plant’s drought tolerance properties which render it suitable to be grown in low rainfall areas. In Zimbabwe, most farmers in dry land areas such as Gokwe, Guruve, Chiredzi, and Nkayi have abandoned cotton (Gossypium hirsutum L.) production and have since then adopted commercial sesame production for export to Mozambique [4]. In areas such as Guruve and Chiredzi, farmers are growing sesame on contract farming arrange- ments. In 2014/15 Sidella, a company which is promoting widespread adoption of this crop, contracted 2820 small- holder famers which resulted in total production of 1,474,860 kg [5]. As is true for any other crop production system, crop yield quality and quantity is compromised by yield reducing biotic or abiotic factors [6]. Weeds are a major yield reducing factor in sesame production as they compete with crops for pho- tosynthetically active radiation, moisture, nutrients, and Hindawi International Journal of Agronomy Volume 2019, Article ID 5494756, 12 pages https://doi.org/10.1155/2019/5494756