Revisiting the concept of the critical period of weed control

Abstract

Weeds are a major biotic constraint to the production of crops. Studies on the critical period of weed control (CPWC) consider the yield loss due to the presence of all weeds present in the crop cycle. The CPWC is the time interval between the critical timing of weed removal (CTWR) and the critical weed-free period (CWFP), and the weed presence before and after the extremes of CTWR and CWFP may not significantly reduce crop yield. The crop yield is taken into consideration and weed density or biomass of individual weeds (annual or perennial) is not so important while calculating the CPWC. Only weed density or biomass is considered for calculating weed control efficiency of a particular management practice for which the weed seed bank is also a criterion. However, weed biomass is the outcome after competition experienced by each weed species with the fellow crop and the weeds. Consequently, the weed pressure in the subsequent season will be the cumulative effect of the preceding season too, which is unaccounted for in CPWC. It is argued that in organic farming or low-input farming systems, where herbicides are not used, the concept of CPWC can be misleading and should be avoided. It is concluded that CTWR is more meaningful than the CPWC.

Critical Period for Weed Competition in Sesame under Iraqi Irrigated Areas

“…The number of capsules per plant was directly proportional to the increase in removal periods, Removing weeds for three, four, and five weeks came at the same level of significance with the weedy-free treatment. These results support previous studies, which confirmed that increasing the weed removal periods leads to improving yield components, including the number of capsules per plant [6,12,14]. As for sesame varieties, Had variety excelled with the highest average for this trait 178.3, which did not differ significantly from the Wadaa variety, which recorded the number of capsules per plant at 169.8.…”

“…There is a significant improvement in the weed removal periods, sesame varieties, and their interaction in terms of the effect of the number of capsules per plant according to t the data presented in Table (6). All weed removal periods differed significantly from the weedy check, which recorded the lowest average18 capsules per plant.…”

“…It is also defined as the period from the beginning of the germination or emergence of the crop to the period during which weed competition does not have any economic loss on the crop, even if weeds grow after this period [5]. CPWC varies depending on the crop species, weeds flora as well as on the environment in which the crop grows, and climate conditions [6]. There are several ways to determine this period.…”

Revolutionizing Rice Farming: Maximizing Yield with Minimal Water to Sustain the Hungry Planet

“…This can lead to reduced plant growth and yield, and again, reduce water use efficiency. Controlling weeds can reduce their competition for water, nutrient, space and light, thereby increasing water availability, water use efficiency and yield of rice plants [67]. Therefore, it is more advantageous to implement early weed control measures such as pre-emergence herbicides, manual weeding, and mechanical weed removal, as opposed to late season weed control, to maximize water use efficiency in rice cultivation [68].…”

Maximizing Water Use Efficiency in Rice Farming: A Comprehensive Review of Innovative Irrigation Management Technologies

“…The time of weed removal is more important in these methods. Early control of weeds helps with better crop establishment and turns crop weed competition in favor of rice plants [122]. The use of herbicides ensures that weeds are controlled at the time of germination.…”