Chapter 5 - Integrated Weed Management in Organic Farming

Abstract

Organic farming has a pedigree stretching back over a century, and, is now increasingly a role model for how mainstream agriculture needs to change. Integrated weed management, uses all the sciences, physics, chemistry, biology and ecology in a holistic / systems based approach manage weeds. The old idea that particular plant species are weeds, needs to be abandoned and replaced with an understanding that weeds are ‘value judgements’ and the judgement needs to be made on a case by case basis if a particular plant or population are, or are not, judged to be causing harm. A good understanding of weed biology, such as morphology, lifecycles, seed production, etc., are essential to effective organic and integrated weed management and in particular a deep understanding of the weed seed bank is essential. The hierarchy of weed management tools starts with managing weed seed rain and the seed bank, then moves through, the potential and limits of rotations, soil quality, crop and pasture choices, pre-crop emergence weeding, particularly false and stale seedbeds, crop establishment techniques, and concluding with post-crop emergence weeding, which is considered the icing on the cake of integrated weed management. The range of post-emergent weeding machinery continues to grow, with completely new machine designs still being developed, compared to the stagnation of herbicide discovery. The plethora of machines are classified first into contiguous and incontiguous, the former that weed the whole field surface, the latter have gaps for crop rows. Incontiguous are further sub-divided into interrow and intrarow weeders. The pros and cons of ‘intelligent’ computer controlled intrarow discriminatory weeders vs. simple mechanical intrarow non-discriminatory weeders are discussed. The chapter concludes with weed management options for perennial crops.