Effect of water stress on weed germination,growth characteristics, and seed production:a global meta-analysis

Authors: SINGH, MANDEEP - University Of Nebraska; THAPA, RESHAM - North Carolina State University; KUKAL, MEETPAL - Pennsylvania State University; Mirsky, Steven; JHALA, AMIT - University Of Nebraska

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2022
Publication Date: 10/21/2022
Citation: Singh, M., Thapa, R., Kukal, M.S., Mirsky, S.B., Jhala, A.J. 2022. Effect of water stress on weed germination,growth characteristics, and seed production:a global meta-analysis. Weed Science. https://doi.org/10.1017/wsc.2022.59.
DOI: https://doi.org/10.1017/wsc.2022.59

Interpretive Summary: Weeds compete for water with crops among other resources and the competition increases under water-limited environments. We performed a quantitative review of the existing evidence base to understand how water stress effects germination, above- and below-ground growth characteristics, and seed production of weeds. Overall, our results indicate that: 1) water stress significantly reduced all indices related to weed germination/emergence, growth (seedling radical/root length, plant height, leaf area, leaves per plant, total biomass, root biomass, and shoot biomass), and seed production (inflorescences and seeds per plant) with the exception of root:shoot ratio, and 2) water stress effects intensified as moisture becomes more deficit or water stress intensity increased. Weeds will adjust their growth morphology to cope up with the water stress and will continue to germinate, survive, grow, flower, and produce seeds even under severe drought or water stressed conditions. This research will be useful for researchers and agricultural professionals to determine weeds' relative adaptability and its infestation in water-limited environments and hence formulate multi-tactic integrated weed management strategies for farmers.

Technical Abstract: Weeds compete for soil moisture with crops. This competition for soil moisture is exacerbated in water limited conditions and can manifest as multidimensional impacts on critical attributes such as weed germination, growth characteristics, and seed production. However, these impacts have not been systematically recorded and synthesized in a unified fashion across diverse studies. To address this knowledge gap, a global meta-analysis was conducted using 1,196 paired observations from 86 published studies assessing the effect of water stress on weed germination, growth characteristics, and seed production. These studies were conducted during the last five decades (1970-2020) across four continents (Asia, Australia, Europe, and North America). Imposed water stress was expressed using metrics such as solution osmotic potential ('solution), soil water potential ('soil), or soil moisture as percent field capacity, all of which are commonly used to represent water availability in production agriculture. Water stress inhibited weed germination, growth, and seed production, and the quantitative response intensified with increasing water stress intensity. A 'solution greater than -0.8 MPa completely inhibited germination of both grasses and broadleaves weeds. A 'solution between -0.09 to -0.32 MPa reduced weed seed germination by 50% to that of unstressed conditions. Moderate soil water stress intensity equivalent to 30-60% field capacity inhibited growth characteristics (branches or tillers per plant, leaf area, leaves per plant, plant height, root, and shoot biomass) by about 33% and weed seed production by 50%. Severe soil water stress intensity below 30% field capacity inhibited weed growth and seed production more intensely by about 51% and 88%, respectively. Although water stress inhibits growth in most weed species, it does not entirely suppress weeds’ ability to germinate, grow, and finally produce flowers and seeds, resulting in weed seedbank accumulation. This poses management challenges for producers because weed seeds can persist in soil for many years, depending on weed species and environmental conditions. Quantitative information on weeds’ response to water stress compiled via this meta-analysis is instrumental to predict and model the multi-dimensional responses of weeds to water stress intensity, so as to design multi-tactic integrated weed management strategies for reducing weed seedbank and improving crop water use efficiency in water-limited environments.