Sweet pepper crops are characterised by a large leaf area that increases continuously throughout the growing season. Towards the end of the season the leaf area can be eight times that of the floor area on which the crop is growing.
However, are all of these leaves contributing to pepper production? Previous HDC work has shown that many lower leaves were respiring more than they were photosynthesizing, appearing to be net sinks rather than sources of food. Hence there might be no detrimental impact on yield if these leaves were removed.
There may also be implications for energy use because less heat would be needed to drive transpiration, although a balance is needed because transpiration helps cool plants in summer.
In the first year of HDC project PC 285, experiments explored how much leaf can be removed without reducing light interception and yield. Four deleafing treatments were applied to rows of the variety Special in a commercial crop. There were three levels of deleafing: 1.6m, 2m or 2.4m of leaf were left on the top of each shoot.
By the end of the season there had been no significant effect on yield or quality from any of the deleafing treatments. It would appear to be safe to deleaf peppers providing that at least 1.6m of leaf is retained, although it may beneficial to leave slightly more leaf in summer.
In the second year, deleafing experiments will quantify the benefits in terms of water and energy use and disease incidence.