Chapter 5: Interplant Interference and Competition
5.8 Summary
Weeds compete with crops usually for light, water and nutrients. A given field has limited amounts of these resources available and the plants that best compete for them will be able to build the most biomass (and for a crop, yield). In this chapter we looked at different types of competition, as well as different plant responses. We wrapped up the chapter learning about the Critical Period of Weed Control and how this principle helps guide farmers when addressing weed pressures in their cropping systems.
Key Takeaways
Key takeaways from this chapter include:
- Weeds and crops compete for resources including: water, light, nutrients, oxygen, CO2, and space. Most frequently weeds and crops compete for water, light, and nutrients.
- Law of Constant Yield means a certain cropping area can only produce a set amount of biomass, whether that is crops or weeds. Biomass production is limited by the least available input or resource.
- Different types of competition include: interspecific competition, and intraspecific competition.
- Plants are able to directly compete for resources and/or respond to competition through survival mechanisms in order to still reproduce the population.
- Plants respond to increased plant density with either plasticity or mortality.
- Weed control thresholds (should I spray?) can be determined by considering a variety of thresholds: competition threshold, economic threshold, no-seed threshold, cosmetic threshold, or in terms of time from planting and competition (Critical Period of Weed Control).
- The Critical Period of Weed Control occurs when crop plants are unable co-exist with weeds, or outcompete weeds without losing yield.