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Title: Describing Polygonum aviculare emergence in different tillage systems

item ROYO-ESNAL, ARITZ - Universitat De Lleida
item GARCIA, ADDY - Universitat De Lleida
item TORRA, JOEL - Institute De Recerca I Tecnologia Agroalimentaries (IRTA)
item Forcella, Frank
item RECASSENS, JORDI - Universitat De Lleida

Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2015
Publication Date: 4/15/2015
Publication URL:
Citation: Royo-Esnal, A., Garcia, A.L., Torra, J., Forcella, F., Recassens, J. 2015. Describing Polygonum aviculare emergence in different tillage systems. Weed Research. 55(4):387-395. doi: 10.1111/wre.12154.

Interpretive Summary: Prostrate knotweed is a nuisance weed of winter-growing crops in Mediterranean type environments. It also is a summer annual weed of lawns and pathways in cold temperate regions. Over a three-year period, knotweed emergence in small grain crops was tracked on a weekly basis in northeastern Spain, and its densities were recorded before and after applications of broadleaf herbicides. Grain crops were grown in four tillage systems each year: direct drill (i.e., no-till), subsoiler, chisel plow, and moldboard plow. Emergence data from the chisel plow system were used to develop and validate a computer model that simulated the extent and timing of seedling emerging from the soil in response to soil temperature and soil moisture. Simulations from a previously developed germination model, which is based solely on temperature, were compared to emergence simulations and observations. Direct drilling substantially lowered populations of prostrate knotweed and resulted in the highest small grain yields. The emergence model simulated seedling recruitment well in all tillage systems except direct drill, presumably because too few weeds emerged in this system to provide reliable data sets. Time periods between 50% and 90% seedling emergence typically extended 30 days during mid winter, which represented the window of opportunity for effective control with postemergence herbicides. Comparisons of the germination model (temperature-based) and simulation model (based on temperature and moisture) showed logical agreement: close overlap on an abnormally wet year when temporal soil moisture differences were minor, and germination preceding emergence during drought years when soil moisture differences would be expected to be critical. In summary, direct-drilled small grain crops have high yields and minimize populations of prostrate knotweed. Farmers who cannot direct drill their crops may face greater problems with prostrate knotweed, but can use the emergence model to better time their postemergence herbicide applications to maximize control. This information is of value to small grain farmers, extension educators, crop advisors, and the agrichemical industry.

Technical Abstract: Effects of four tillage systems (direct drill, subsoiler, chisel plough and mouldboard plough) on the dynamics of Polygonum aviculare populations were studied over three growing seasons. Densities before and after herbicide application and cumulative emergence on a weekly basis were determined in each growing season in small grain crops in northeastern Spain. Cumulative emergence in chisel plough was used for the development of an emergence model for P. aviculare, based on hydrothermal time estimated with the STM2 program. The emergence model was compared to a thermal time based germination model from Argentina. Results showed that direct drilling, besides obtaining highest crop yields every season, was the unique tillage system that effectively reduced P. aviculare populations because of seed bank depletion. The model described accurately seedling emergence in different tillage systems, although it failed in direct drilling, probably due to low emergence. The comparison of the emergence model with the thermal time germination model showed that there is a delay in emergence in years with short or long drought periods, while emergence follows germination almost simultaneously in those years without droughts. The use of the germination model permitted the estimation of the minimum seed bank required for the observed emergence sequences and, consequently, an approximation to the population dynamics of P. aviculare in each tillage system could be performed. To better control this weed, direct drilling may be the best tillage option, but if this cannot be implemented, the hydrothermal time model is a practical tool that can describe the emergence and assist in the control of P. aviculare in different tillage systems.