Influence of tillage, fertiliser regime and weeding frequency on germinable weed seed bank in a subhumid environment in Zimbabwe

Abstract

Minimum tillage (MT) under conservation agriculture (CA), fertiliser application and weeding frequency influence weed seed-bank dynamics in cropping systems. A study was conducted at the Chinhoyi University of Technology farm, Zimbabwe during the 2014/15 and 2015/16 cropping seasons to investigate the influence of tillage, fertiliser and weeding on weed seed-bank dynamics. A field experiment arranged in a split-split plot randomised complete block design with three replications was used. Tillage (conventional tillage [CT] and MT), fertiliser application (zero, low, medium and high) and weeding frequency (twice, four times and clean) were the main plot, subplot and sub-subplot factors, respectively. Minimum tillage decreased Nicandra physalodes (L.) Gaertn. and Leucas martinicensis (Jacq.) R.Br. germinable seeds by up to 40% compared with CT. Germinable seeds of Amaranthus hybridus L. and Galinsoga parviflora Cav. were more frequent in high than medium fertiliser plots. Weeding four times resulted in more weed seeds than weeding twice and clean weeding. Results of this study suggest that some problem weeds, including N. physalodes, are likely to be reduced, whereas Iopmoea plebeia R.Br. may be persistent under MT. The results further suggest that weeding four times created conditions that were favourable for rapid weed seed germination, weed growth and possible seed return.

Keywords:

• basin planting
• rip-line seeding
• soil depth
• tillage