The effects of clipping and burning on the allocation of total nonstructural carbohydrates and selected mineral nutrients in Imperata cylindrica (L.) Raeuschel

Abstract

The rhizomatous grass, Imperata cylindrica, occurs in the Cape Flats Nature Reserve (CFNR), South Africa. It is recognised globally as a weed of crop plants. The response of this weed to defoliation, in the forms of clipping and burning, was studied in terms of its total nonstructural carbohydrates and mineral nutrition. This study will serve as a starting point for later studies aiming to control this weed. It was confirmed that the underground stems or rhizomes serve as the major storage tissue for total nonstructural carbohydrates and mineral nutrients. These rhizomes also make up the largest part of its biomass and hence defoliation was found not to significantly decrease stem total nonstructural carbohydrates or mineral nutrients. The burn treatment induced faster replacement of above ground material than the other defoliation treatments. The burn and basal clipping treatments induced higher leaf nitrogen and phosphorus levels following defoliation. These two treatments also led to significantly higher number of tillers after defoliation and were also the only treatments which induced flowering. The one-off defoliation which was applied at the start of this study, was found to be ineffective in taxing I. cylindrica's resources to the point where it would be vulnerable to eradication. It is hence recommended that future studies on the grass should entail multiple defoliations in order to develop a defoliation regime which will exterminate the grass.