Pre emergent weed control is defined as the control of weeds before of the emergence of crop plants into the crop fields. These are the weed control measures which are applied before the emergence of the yield providing produces in the farming areas. These methods of weed control are applied before the coming out of crop plants from the soil. This method of weed control is of immense importance as it saves the crop plants from the competition of space, moisture, nutrients & sunlight which is posed to them by the weed plants. It is also a useful method for the preparation of the stale seedbed for nursery raising of different transplanting crops. Pre-Emergence weed control would also be a helpful factor in controlling the farmer from reaching the stage of being overrun by the weeds due to reaching the maturity stages from where they are very difficult to control or eradicate. Pre-emergence weed control is also a means of eradicating the weeds temporarily from the crop fields in the earlier stages of crop growth. The different benefits provided by the pre-emergence weed control are discussed in detail below:
- It will be very much helpful in increasing the crop production due to providing the weed free periods in earlier growth stages to the crop plants. The weed plants would decrease the crop yields due to providing the competition of space, sunlight, moisture & nutrients which lead to decreased crop yields.
- It is also of much economic importance as it saves the money spends on the weed control in later stages of crop production. The most of the farmer money is spend on the herbicides for the weed control which is very much reduced if the pre-emergence weed control techniques are applied.
- Pre-emergence weed control is also a step in the minimum tillage or zero tillage concepts which are the means of sustainable crop productions in saving the resources for future use as well.
- These practices of weed control would also saves the soil, air & land units from the pollution which occurs due to large or overuse of herbicides in controlling the weeds after germination or in later stages, which is very much difficult & a wastage of herbicides & also drops a residual effect on the soil, plants, beneficial insects & environment.
- It is also a helpful practice in making the weed seeds dormant by do not allow them to germinate with the crop plants or by depositing them to the lower layers of the soil with the different actions of methods used for pre-emergent weed control.
- Pre-emergence weed control is also a helpful practice in performing the crop production programs in the dry land or rain-fed areas which face shortage of moisture due to less availability of rainfall.
- The pre-emergence weed controls are also favourable for the environment as the low rate of herbicides is used for controlling weeds which do not pose any threat to the environment & helps in conserving the nature & wildlife.
There are a variety of methods which can be used for controlling the weeds as pre-emergence weed control methods. These are the combined or individual methods of physical, chemical, cultural or biological methods which are used singly or in combination for the control of weeds pre-emergence. The different methods of pre-emergence weed control are discussed below:
- Application of standing water: It is a kind of physical method of pre-emergence weed control. The application of standing water layer in the crop fields up to 4 or 5 cm is a useful means of controlling the weed problem before the crop emergence as it would not allow the weeds to respire & cut off them from the oxygen & kill them as a result. It is also a useful means of depositing the weed seeds into the lower layers of the soil where they become dormant & do not germinate for long periods.
- Application of lower dose of pre-emergent herbicides: The pre-emergent herbicides like those of Pendimethalin, Atrazine, Simazine, Tributyrin, Isoxaflutole, Diuron, 2,4-D etc. are applied in lower doses for controlling the weeds before the emergence of the crop plants. These are applied before the sowing of the crop in the soil for effective weed control. The different examples of pre-emergent herbicides are shown below with the species of weed controlled along with their dosages:
- Application of the different primary & secondary tillage equipment properly & timely: The different primary & secondary tillage equipment such as harrows, tillers, planter, deep tillage equipment such as blade harrows etc. are to be a good mean of pre-emergence weed control in the field conditions. These tillage equipment would decrease the weed population by cutting & damaging them due to their blades or other metallic elements.
- Application of different physical or cultural methods for pre-emergence weed control such as:
- Fallowing the land: The weeds can also be controlled on large scales by keeping the land fallow for a season or two. This will bring the weed seeds in upper layers by allowing them complete dominance for growth & development, and it would be very easy to remove them after growth by the use of different techniques of weed control.
- Use of different mulches: The use of mulch is also a good means of pre-emergence weed control as it would not allow the weed seeds to grow by the covering of the open land in which weeds flourish.
- Use of the different beneficial cropping systems like double cropping or triple cropping which do not allow the weeds to grow & developed from the croplands.
- By the use of different conventional & conservational tillage practices like zero tillage or minimum tillage which recommend the cultivation of crops in the remaining stubbles of previous crops which do not allow the space for the growth & development of weeds before the crop emergence.