The role of light in the emergence of weeds: Using Camelina microcarpa as an example

Authors: ROYO-ESNAL, ARITZ - Universitat De Lleida; Gesch, Russell - Russ; Forcella, Frank; TORRA, JOEL - Universitat De Lleida; RECASENS, JORDI - Universitat De Lleida; NECAJEVA, JEVGENIJA - Latvijas Universitate

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2015
Publication Date: 12/30/2015
Publication URL: http://handle.nal.usda.gov/10113/61889
Citation: Royo-Esnal, A., Gesch, R.W., Forcella, F., Torra, J., Recasens, J., Necajeva, J. 2015. The role of light in the emergence of weeds: Using Camelina microcarpa as an example. PLoS One. 10(12):e0146079. doi:10.1371/journal.pone.0146079.

Interpretive Summary: Understanding the emergence pattern of weed and crop seedlings in the field greatly helps to develop ways to better manage them and to make timely management decisions. Several models have been developed to help describe and better understand the processes of seed germination and emergence for certain plant species and most of these use soil temperature and moisture as factors to help build these models. Hydrothermal time (HTT)-based models are those that incorporate both soil temperature and moisture conditions over time into modelling seedling emergence. HTT models often work well for the given species in the area or environment where they were developed but sometimes fail in their accuracy for describing emergence of the same plant species when it is grown in a different environment. Light is another important factor that can affect germination and emergence, especially for some weed species whose seed can sometimes be dormant for a period of time. For such species, light can often overcome seed dormancy and allow it to germinate. In this study a team of ARS scientists and researchers from the University of Lleida, Spain grew a common weed species Camelina microcarpa (camelina) in both Spain and Minnesota, USA and collected data to model its emergence under the two different environments. HTT models were developed that either included or did not include light as a factor in modelling camelina’s emergence. The results showed that a common HTT model worked well for describing the emergence of camelina in Spain but lost some of its accuracy when used to describe emergence in Minnesota. However, when light was included as a factor in the model, the accuracy was improved for describing emergence under both environments (Spain and USA). This study is one of the first to show that by combining light as a factor with HTT, emergence models may be developed that have world-wide application rather than just for a local area or environment. This information will benefit scientists, agricultural consultants, and extension specialists studying weed and crop emergence patterns and developing better management practices for weeds and crops. The results of this study directly pertain to ARS National Programs 305 (Crop Production) and 304 (Crop Protection).

Technical Abstract: When modelling the emergence of weeds, two main factors are considered that condition this process: temperature and soil moisture. Heat is needed to have enough metabolic movement to generate energy and grow, while the need for turgor pressure is evident for root and shoot elongation, which leads to emergence at the soil surface. In this process, light is usually a residual factor that most models do not consider. But it could have an important role, as it can alter directly or indirectly the dormancy and germination of seeds, which are critical to the emergence process. In this paper the best way of including light as a factor in emergence models is explored (i.e., photoperiod or radiation) and compared with the classical hydrothermal time (HTT) model. Camelina microcarpa is used as an example. The use of hourly estimated HTT is also compared with the daily based HTT. Results suggest that HTT based models are accurate enough for local applications and are improved if HTT is estimated hourly, while including light as a factor in the form of solar radiation appears to be the most promising for developing models with worldwide application.