Effect of seeding rate on pennycress agronomic performances across contrasting environments
Among emerging non-food oilseed species, pennycress (Thlaspi arvense L.) has attracted considerable attention in the scientific community since it possesses many traits that can easily support its integration in existing rotation systems. Pennycress is highly cold-tolerant and provides a living cover over winter, reducing soil erosion and nutrient leaching, furthermore the shortness of its cycle easily allow double cropping. Due to the presence of seed dormancy accompanied by a very slow growth during winter months, the definition of an effective seeding rate allowing an optimal stand establishment and guarantying good competition against weeds still remain an open question for pennycress. At this scope similar field experiments to identify the optimal seeding rate for pennycress were established under contrasting environmental conditions, at Bologna (Italy, 44°30’ N, 11°21’ E) and at Morris, Minnesota (USA, 45°35’ N, 95°54’ W). Despite similar latitudes the two locations are characterized by diverging climatic conditions: the mean annual temperature is 5.6 °C in Morris and more than double in Bologna (13.4 °C). Annual precipitation is similar (~ 650 mm year-1 ) but in Italy the majority of rainfall occurs during winter, while in Minnesota it occurs during the summer months. Five different seeding rates (250, 500, 750, 1000 and 1500 seeds m-2 ) were tested in Bologna during 2017-18 growing season. In Morris three increasing seeding rates corresponding to about 300, 600 and 900 seeds m-2 were tested during 2014-16. In Italy the pennycress line Elisabeth, supplied by ARS-USDA, were tested while in Minnesota the lines MN-106 and Beecher were compared under the different seeding rate. Sowing was performed in September in both locations. Winter survival was satisfactory in both environments, generally better stand establishment was associated to increased seeding rate. Plants in Bologna were much taller at harvest than those in Morris (91 vs. 57 cm), probably in relation to milder temperature allowing unhindered growth to pennycress during the whole winter. Pennycress seed yield in Morris was highly influenced by environmental conditions reaching on average of all treatments 0.6 Mg DM ha-1 in the 2014-15 and just 0.2 Mg DM ha-1 in 2015-16. In Bologna seed yield was on average of all treatments slightly higher (0.7 Mg DM ha-1 ), but differences among seeding rates became evident at densities >1000 seeds m-2 which had significantly higher seed yields. The full characterization of seeds in terms of oil content and fatty acid composition will also be performed with respect to the effect of seeding rate and environment on pennycress potential productivity.