Farmers have struggled with the presence of weeds in their fields since the beginning of agriculture. Weeds can be considered a significant problem because they tend to decrease crop yields by increasing competition for water, sunlight and nutrients while serving as host plants for pests and diseases. Losses due to weeds have been one of the major limiting factors in soybean production. Most of the yield reduction due to weed competition occurs during the first six weeks after planting therefore, major emphasis on control should be given during this period. Good soybean weed control involves utilizing the following methods available and combining them in an integrated weed management system.
1. Crop rotations may be beneficial since most of the troublesome weeds in soybeans can be more easily controlled in a crop. If the full benefit of the rotation is to be achieved, weeds must be controlled throughout the growing season of the rotational crop. The main goal of the rotational crop for weed control is to reduce the number of weed seed available for germination the following season. Other benefits of crop rotation may include reduction in insects, diseases, and nematodes.
2. Crop competition is another important component of cultural weed control and an effective way to control weed growth. Use high-quality, vigorous seed, adapted varieties, uniform proper placement of the crop seed, optimal soil fertility, and plant populations that lead to vigorous crop growth and canopy closure. A vigorous growing crop is less likely to be adversely affected by weeds.
3. Cultivation or tillage is a good and economical method of weed control however, for tillage to be effective in controlling weeds in the row, the soybeans must be taller than the weeds.
4. Mulching is anything applied to the soil surface with the intent of reducing weeds, conserving soil moisture and stabilizing soil temperature is considered mulch. Applying 3 or 4 inches of straw, shredded leaves, untreated grass clippings or compost around plants and between rows keeps weed seeds in the dark and prevents them from germinating.
5. Planting to moisture is another technique similar to pre-germination. After weeds are killed by cultivation, the top 2 to 3 inches of soil are allowed to dry and form dust mulch. At planting, the dust mulch is pushed away and soybeans can be planted into the zone of soil moisture. Thus soybean seeds can germinate, grow, and provide partial shading of the soil surface without supplemental irrigations that would otherwise provide for an early flush of weeds.
The challenge of agriculture sustainability requires solving the exchange between producing satisfying levels of agricultural products, both in terms of quantity and quality, and reducing the environmental impacts and preserving non renewable resources. Weed management is a key issue, because herbicides are the most sprayed around the world and they are mostly found contaminating the surface and below-ground waters. Therefore, it is necessary to adopt correct strategies for weed management. Simple measures like choosing the correct cultivar, adopting correct tillage practices, using cover crops and crop rotation are responsible for decreasing the use of herbicides and consequently contribute for environmental sustainability.
Hannah Krujia Asangla, SMS Agronomy, KVK Phek
