RECENT rains that most parts of the country have been receiving have renewed hope for a decent harvest in the 2023/24 cropping season.
This follows the weakening of the El-Nino phenomenon, which was expected to cause a severe drought in Southern Africa, including Zimbabwe.
While the rains have seen an improvement in crops and livestock, they have triggered a menacing weed problem. This calls for farmers to adopt proper integrated weed management practices save their crop and obtain optimum yields. Farmers risk losing up to 80% of their potential yield if they fail to effectively deal with the weed menace, especially in the first 10 weeks from germination.
Weeds are unwanted plants that compete for sunlight, water and nutrients with crops. Weeds can be distinguished according to habitat, origin, degree of harm among other many characteristics with the most common being the plant morphology and life span of weeds.
Life span of weeds is the classification of weeds by using the time or duration in which they complete their lifecyle, for example, annual, biennial and perennial weeds. Plant morphology is the physical appearance of plats – there are broad leaf weeds which have wider leaf structures like the bonongwe [Pigweed (Amaranthus thunbergia) and narrow leaf, which includes grasses and nodes.
Owing to changes in climate change, weed problem is becoming severe. One of the lesser-known consequences of climate change is its impact on weeds, which can have far-reaching consequences on yield. As global temperatures continue to rise, this is leading to extended seasons, which can lead to an increase in weed populations. Warmer temperatures can also enable weeds to reproduce more quickly, making it difficult for farmers to manage their spread.
Consequently, farmers are required to respond by adopting the most effective weed management techniques to save their crop.
Agronomist Mercy Ndebele warned that farmers that they can lose more than half of their potential yield if they fail to deal with weeds.
“As we celebrate the gift of good rains we have been receiving for the past weeks, farmers should be on the lookout for weeds. They need to employ good weed management practices. Weeds sprout and outdo crops in the fight for nutrients and sunlight, resulting in reduced yield and crop quality,” Ndebele said.
Effective weed management is essential for maintaining plant health and sustainability of farming. At the core of it, it involves a combination of traditional, mechanical, biological, and chemical control methods tailored to specific weed species and the cropping system in question.
Mechanical weed management – This involves the removal of weeds or disrupting their growth using tools and machines. The most common mechanical control methods include hand-pulling, hoeing, mowing, tilling, and mulching. Even though this method is labour-intensive, it can be effective in managing weeds, especially in areas where other methods are not feasible.
Traditional weed management – This involves incorporation of practices that create conditions that are unfavourable for weed growth while promoting the growth of preferred crops. These methods include crop rotation, intercropping, planting competitive crop varieties, adjusting planting dates, among others. By manipulating the growing environment, these traditional methods suppress weed populations. Such methods should be accompanied by others to be effective.
Biological weed management – This involves the use of natural enemies such as insects, pathogens, or animals to suppress weed populations.
Chemical weed management – Involves the use of herbicides to selectively target and control weeds. Herbicides are formulated to interfere with specific processes in plants, leading to their growth inhibition or death. However, the use of herbicides requires careful consideration as some weeds can become resistant and their impact and effects on the environment and non-target organisms.
Farmers are encouraged to adopt an integrated weed management practices where a several control tactics are combined in a coordinated and sustainable manner to achieve effective weed suppression while minimising environmental impact. Such practices consider specific cropping systems and consider factors such as weed biology, ecology, and economic considerations.
Integrated weed management, also referred to as integrated weed control, is an approach that integrates both chemical and non-chemical practices to control weeds and is meant to suppress weed populations below the economic injury level of the crop yield.
Before any method is adopted, farmers should first scout for weeds. Scouting helps farmers to identify and control weeds early, when they are in their most vulnerable state since some species become more challenging to manage as they mature. Scouting should be repeated at several times during the production cycle of crops. Timely weed scouting is meant to inform the farmer of weed species, location, and density. This helps in designing an effective integrated weed management programme.
For Zimbabwe to attain food and nutrition security, farmers should adopt good agronomic practices which include integrated weed management practices. The government has prioritised food security and has since surpassed the targeted US$8,2 billion agricultural economy initially targeted for 2025, contributing 20% of the gross domestic product underpinned by the National Development Strategy 1 as Zimbabwe moves toward an upper middle-class economy.
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