Assessing the Impact of Weeds on Rice Growth and Productivity: Experimental Designs and Quantitative Approaches.

Weeds represent one of the most critical biotic stress factors in rice-based cropping systems, often causing severe yield losses. Understanding crop-weed interactions under both current and projected climate change scenarios is essential for safeguarding rice productivity. Weed species, such as Echinochloa colona and Alternanthera paronychioides, exert profound competitive effects on rice, with early crop growth stages being particularly vulnerable. During this period, rice seedlings encounter simultaneous challenges of weed interference and abiotic stresses, such as water limitation, resulting in oxidative damage, impaired physiology, and significant yield reductions. These interactions highlight the urgent need for systematic and quantitative approaches to evaluate the impact of weeds on rice performance. This chapter presents detailed methodologies for assessing weed impacts on rice growth and productivity, including experimental designs, measurement protocols, and analytical frameworks. The outlined approaches enable accurate quantification of competition dynamics and yield losses, providing a foundation for developing effective and sustainable weed management strategies tailored to diverse rice production systems.