Field and soil management
Key learning outcomes
- Understand the role that soil management, including cultivation strategy, can have for determining weed abundance
- Understand the use of cultivations (outside of the cropping period) as a control method, and the factors that determine the success of these methods
Choices made around cultivations and establishment methods strongly influence the long and short-term weed abundance on far. This module will give you the tools to judge the merits of cultivation choices in isolation and as part of wider strategy to use cultivation as an effective tool for managing weed populations. This will include discussions on depth of cultivation and timing of the cultivation, and the interaction of both with different weed species.
The role of field and soil management in weed control
This is a presentation developed by Philippe Delval, ACTA, France. The video is about five minutes long. Additional notes, comments and links to additional content are given below the presentation.
Comments, notes and resources referenced in the video
Action on the cultivated plant
During intercropping period
Maintaining a good level of pH and organic matter in soils
It is recognized that a soil high in organic matter is less favorable for the development and the propagation of soil-borne pests.
During cropping period
Adapting irrigation to health risks
While optimising the growing conditions for the crop, the weed can be held back by limiting water resources in a certain growth stage, at locations in the field or at different soil layers (e.g. by using drip irrigation).
Reasoning fertilization by practicing fractional or localized contributions
Excess nutrients can be detrimental to the crop by promoting the spread of disease, increasing their susceptibility to pests may encourage the development of weeds. Managing fertilization makes the crop more competitive with weeds and more resistant to pest attacks.
IWMTOOL: one IWM factsheet describes field management
Liming = Same as for crops, each weed species prefers a certain range of pH level. Through liming, soil acidity can be regulated and growing conditions may become less favourable for weeds to germinate and grow. Simultaneously, crop growth may be promoted with increased pH as a result of liming
Nutrient placement = The strategic placement and timing of nutrients (fertilization) can be a strategy in managing weeds in combination with many tillage types. Plants compete for the resources that they share during different stages of their life cycle. In general, weeds have a high nutrient requirement and will absorb as much or even more than the crops.
management = Because the response to the soil water level varies between weeds and crop plants during different growth stages, strategic water management can be integrated in a weed management strategy. While optimising the growing conditions for
the crop, the weed can be held back by limiting water resources in a certain growth stage, at locations in the field or at different soil layers (e.g. by using drip irrigation).
Stubble management can help to prevent further weed growth, weed seed development and vegetative propagation in the soil after harvest. Direct nonchemical methods (e.g. mowing or shallow tillage operations) can be used freely unless a cover crop has been established. Early and shallow stubble management stimulates germination of freshly ripened crop and weed seeds, kills the resulting seedlings and reduces the input into the soil seedbank.
IWMGAME [arable crops]: one card gives measures that can be used during intercropping. However, it have only curative effects. You can play this card during the intercropping period and these methods may have side effect on soil fauna.
Performing deep tillage or intercropping ploughing
The main role of ploughing is to bury the seeds of annual plants which have a high annual rate of decay, that is, seed viability is short. Otherwise, systematic or frequent ploughing can bring some seeds with a longer lifespan back to optimal emergence conditions and therefore have an unwanted effect. Ploughing can also play a role in the burying of crop residues harboring the conservation forms of any pests. However, it can also help to bring to the surface forms of conservation of any diseases.
Carrying out shallow tillage in intercropping
The period between harvesting and sowing the next crop may be suitable for some surface work on the soil to eliminate some of the emerged weeds.
Practice no-till or simplified cultivation techniques (SCT) in intercropping
Simplified cultivation techniques (or no-till techniques) have beneficial effects on soil erosion, participate in carbon storage in the soil and improve soil quality. In fact, as the soil has little or no mechanical disturbance, the soil's biological activity increases as does its organic matter content.
IWMTOOL: Two factsheets have been produced on tillage type and cultivation depth
Primary tillage is traditionally performed at depths varying from 15 to 35cm. Inversion tillage (e.g. ploughing) is often considered to be a good start for integrated weed management tactics. Secondary tillage operations are shallower and are used to prepare the seed bed and incorporate amendments such as fertilizers. When these secondary operations are performed close to seeding, they will control any emerged weed seedling, but at the same time stimulate new weed seeds to germinate causing new flushes of weed seedlings during early crop growth.
Cultivation depth is an important factor to consider for all operations that involve soil disturbance, e.g. primary and secondary tillage, stubble management, seedbed preparation, sowing and mechanical weeding. In some cases deeper cultivation is required to bury weed seeds or to control perennial weeds, where in other cases cultivation must be very shallow to prevent germination of new weeds.
IWMGAME [arable crops]: One card represents measures that can be used during intercropping period. It has preventative and curative effects, but can also have negative effects on soil quality and soil fauna.
Preparing for sowing by creating a false seed bed
False seed bed consists of stimulating the emergence of weeds by suitable soil preparation. These are then destroyed after their germination by preferentially mechanical or thermal methods. This technique can also be managed using herbicides. False seed bed results in a clean seedbed and minimal soiling of the crop. In the long-term, the annual repetition of false seed bed contributes to the reduction of the seed stock for the following crops (“out-stocking” operations).
Seed bed preparation is a form of secondary tillage that can control emerged seedlings when performed close to seeding. Using shallow tillage operations, newly emerged weeds are controlled without the use of herbicides. However, seedbed preparation also stimulates new weeds to emerge, resulting in more weed seedlings during early crop growth.
Another important reason for a well-prepared seedbed, could be the advantages for crop emergence and mechanical weeding.
Especially fine-seeded crops will benefit from a fine and levelled seedbed as the crop emergence will be more homogenous. In case of mechanical weeding, a well-prepared seedbed makes weeding more effective.
IWMGAME [arable crops]: One card represents measures that can be used during intercropping period. It has preventative and curative effects but may also have negative effects on soil quality and soil fauna.
Covering the base of the plantations to control weeds
The placement of leaf mulch, geotextiles or mulch films on the surface of soils or growing substrates makes it possible to prevent or limit the development of weeds at the foot of cultivated plants. They can indeed constitute a physical barrier on weed emergence and also limit the light necessary for the growth of weeds.
Practicing weeding by occultation in pre- or post-sowing
This weeding method, the principle of which is to cover the soil with an opaque film before cultivation, allows the germination of weeds and their destruction by the absence of light without raising the temperature, which is different from solarization.
IWMTOOL: Two factsheets are dedicated to dead mulching
Cover crops can be killed and left on the soil surface as a dead mulch. Also other materials can be used as a dead mulch; as long as they provide a dense soil cover, mulches can have a significant effect on weed suppression.
IWMGAME [perennial crops]: Two cards cover these measures. They only have preventative effects on competing weeds. It concerns only intra-row in perennial crops to avoid competition on the row with the crop. You can play it during intercropping period and this method also has beneficial side effects. This method is not effective on perennial weeds.