A Simulation Model for predicting the emergence and growth behavior of parthenium hysterophorus in changing climate

Abstract

Parthenium hysterophorus is the most aggressive and invasive herbaceous weed posing a serious threat to the agricultural system because of rapid and competitive growth behavior in changing climate. Sustainable weed control strategies and development of weed emergence model could be included as profitable tools for crop planting date, herbicide application and tillage operation time. To predict the emergence and growth behavior of parthenium by using population based threshold models, a series of experiments was conducted under controlled and field conditions. In lab experiments, germination response of parthenium was studied at different constant temperature (5, 10, 15, 20, 25, 30, 35 and 40 °C) and fluctuating (day/night) temperature (15/5, 20/10, 25/15, 30/20 and 35/25 °C). Parthenium showed better response by assessing more germination and less germination time at temperature of 20 – 25 oC and fluctuating temperature of 25/15 oC. Use of germination modeling approach proposed the base temperature (7.2 oC), optimum temperature (20 oC) and ceiling temperature (42.8 oC) for this weed. Moreover, germination behavior was also studied at different water potentials (-0.25, -0.5, -0.75 and -1.0 MPa) under different temperature regimes (10, 20 and 30 °C). Hydrothermal time model predicted more germination (82.80 and 54.80 %) response of parthenium at water potential (from 0 to -0.25 MPa) with temperature of 20 oC respectively and also recorded base water potential (Ψb(50) of -0.54 MPa for germination. Regarding dormancy behavior of seed stored for 150 days in soil filled pots at different soil moisture conditions (dry, moist and fluctuating moisture) at 10, 20 and 30 oC, the highest germination percentage was recorded in fluctuating moist soil conditions after all storage intervals at each storage temperature, which is an ideal condition for breaking dormancy of parthenium seeds. In field experiments, parthenium was sown throughout the year (March 2018 – February 2019) for predicting the emergence and growth behavior of parthenium at different temperatures under prevailing climatic conditions. Germination modelling approach proposed more germination potential of parthenium in month of October and March as compared to other months, but biomass production was greater in growth period of high temperature (summer season). In case of field trial at three ecological conditions (Faisalabad, Layyah and Chakwal), higher emergence and growth was recorded in Faisalabad as compared to other climatic conditions indicating more invaded area by the parthenium weed. To be concluded that use of hydrothermal time modeling approach is helpful for assuming the emergence and growth behavior of parthenium in changing climate and ultimately supportive in time scheduling of parthenium weed management in cropping system.