Unwanted plants in crop commonly called weeds reduces the yield and the quality of a harvest. It also increases production costs. In the case of paddy, the yield drops by 15-20% and sometimes even 50%.
A harvest that is heavily infested with weeds usually fails in its entirety. Every year there is a huge loss of rice, while the quality of the products from the weed-infected fields is also inferior. These also hamper the harvest.
Weed Competition: Weeds compete with desirable plants. The contest designates a relationship between the same or different species that leads to the blossoming of one at the expense of the other or at the expense of both.
While weed control with rice does not normally lead to the death of one of the two species, this results in almost reduced yields. Weeds are known, but the extent of the problem they represent is not recognized. Farmers recognize the problem in their fields, but the high labor costs for hand washing prevent proper reaction.
The competition between weeds and rice depends on the following influences:
- Relative growth stages of rice and weeds.
- Type of orientation (transplant versus direct sowing).
iii. Density of the planting.
- Rice variety.
- Moisture and nutrient availability.
In irrigated systems, rice seedlings are transplanted in puddle soil. This gives rice a significant lead over weeds and initially the contest is minimal. The competition is increasing as growth continues, especially in direct sowing, as weeds germinate at the same time and compete with the reed seedlings for light and nutrients. Weed competition generally has three forms:
Competition for light: weeds, which during the growth period are shorter than Reisernte, compete a little or not with rice for light. However, weeds that are larger can reduce the light available for rice by up to 50 percent. Since sunlight is the main source of energy used by plants for the production of foodstuffs, the shading of high weeds can stagnate growth and reduce yields.
Competition for water: where there is abundant water, the competition between rice and weeds is minimal, but in the case of scarcity, the situation is quite different. When weeds consume a considerable portion of the water, tillering, flowering and grain filling are delayed or hindered.
Competition for nutrients: weeds have a high need for nutrients. They are large feeders and, if left unchecked, can absorb more nutrients than the crop. Fertility increases, although fertilization is generally associated with an increase in weeds, which can result in greater yield reduction.
Reduction of cereal quality: Weed seeds in cereals lower the price. Weed seeds in cereals can also result in uneven moisture in the grain resulting in quality losses due to the formation of mold and / or cracking during milling.
In addition to competition with rice for sunlight, water and nutrients, weeds pose another problem. Many weed species function as alternative hosts to insect pests and disease-causing organisms, and their presence under crops or along ramparts and peripheries can result in losses due to insect or disease attacks increase.
Why are some weeds successful?
Weeds become successful because of their properties, which give them the ability to:
- Put in seeds before the harvest is ripe.
- Produce large quantities of seeds (for example, Cyperus difformis can put 100,000 seeds per plant).
iii. Seeds survive in the soil.
- Vegetative proliferation, which promotes their proliferation and makes them difficult to control.
- Imitating the harvest (eg red rice – which can not be distinguished from the harvest in early stages, but sets seeds and then breaks down before the harvest is harvested).
- Grow vigorously, allowing them to exceed the harvest.
Integrated weed management: Integrated weed management uses a combination of different agronomic methods to control weeds, reducing dependence on a weed control method.
Reducing dependence on one or two specific weed control techniques means that these techniques or tools will be effective for future use. The goal of integrated weed management is to keep the weed densities at manageable levels and at the same time to prevent the populations from shifting into difficult-to-control populations. Weeds caused by weeds are minimized without reducing agricultural income.
Controlling with one or two techniques gives the weeds a chance to adapt to these practices. For example, the use of herbicides with the same mode of action has led to weeds that are resistant to these herbicides year after year.
Integrated management uses a variety of techniques to get weeds out of balance. Weeds are less able to adapt to a constantly changing system that uses many different control practices, as opposed to a program that needs one or two control tools. Integrated weed management practices in rice include:
Soil preparation: Thorough soil preparation can significantly reduce the incidence of weeds in rice by destroying all weeds and weeds in order to provide weed free conditions at the time of planting and to provide a good environment for rapid growth of reed seedlings.
Water Management: Many weeds can not germinate or grow in flooded soils, which makes water management a very effective tool for controlling grasses and sedges.
Once the transplanted seedlings have established (approximately one week after the transplant), they completely flood the plot to a depth of 3 to 4 inches to inhibit weed growth. When the rice grows, gradually increase the depth to 6 “. The soil must be completely and continuously submerged if the flooding is to take effect.
Hand-weeding: hand-weeding is time-consuming and lengthy. When weeds are large enough to be grasped, they are pulled out of the ground and discarded. Smaller weeds can be pulled by hand. Early hand weeding is better, since any delay can absorb the weed absorbing nutrients.
A common mistake is that small weeds do not affect the rice, but they certainly do it, as a simple jentemonstration will show.
Hand Chopping: Hand chopping is used as a method of weed control, especially during planting. Hand chopping is faster than hand washing and works well against creeping perennials.
Fruit Seed: Since each plant has its own characteristic weed, the continued cultivation of the same fruit in an action can build up these weeds. The rotation of rice with kharif cultures can lead to a reduced incidence of water-incompatible weeds in the following crops.
Fruit Seed with Allelopathic Cultures and Reiskulturen: Some crops such as sorghum, pearl millet and maize can drastically suppress the weed population and reduce their biomass. Bearded millet may have a rest herb suppression in the following crop. The inclusion of these fodder plants prior to rice harvesting in a rice-wheat rotation can provide a satisfactory control of the weeds and minimize the use of herbicides. It is obviously necessary to evaluate whether these crops can be successfully grown.
Herbicides: The importance of using herbicides is closely linked to labor costs and availability. Herbicides are one of the first labor-saving technologies that must be adopted when labor costs rise. As a result, the use of herbicides varies widely across countries. Herbicides replace weeding by hand and allow direct sowing instead of a transplantation that is less labor intensive.
The direct sowing is linked to the use of herbicides, since without its use the weeds in the stadiums in which the fields can be flooded grow so fast that manual control possibilities are often not possible.
Herbicides are also used in the transplanted systems. The costs associated with the use of herbicides should continue to be a major constraint on their widespread use. Herbicides can be classified as nonselective or selective and before and after emergence.
Most herbicides used in rice production are selective and control some or most of the weeds while they have a limited effect on the culture. The selectivity does not necessarily depend on the connections, but also on the speeds, timing, and application procedures, and therefore it is important to follow the manufacturer’s recommendations.[social_warfare]
Non-selective herbicides such as glyphosate are sometimes used prior to the establishment of rice in weed infestations such as wild rice, which is difficult to control with selective herbicides.
Pre-emergence herbicides are applied to the soil and combated weeds before they arise while they are applied after emergence onto weeds after they have been formed. The amide groups include the herbicides butachlor, pretilachlor and propanil. Butachlor can be used either in the pre-emergence or early after emergence to allow control over a wide range of one-year-old grasses and some broad-leaved weeds.