Evaluation of Seed Persistence in Cow Cockle

Abstract

ABSTRACTCow cockle [Vaccaria hispanica (P. Mill.) Rauschert] is an introduced summer annual weed in North America and has been investigated as a potential crop for the Canadian prairies. Seed persistence contributes to volunteers in subsequent crops; therefore, it is undesirable in this prospective crop. To determine whether cow cockle is persistent and forms a seed bank, two comparative experiments (field and laboratory) were conducted from 2008 through 2011. In the field, seedling recruitment and residual seed bank were measured for a cultivated and a weedy cow cockle population under spring and zero‐tillage systems. In the lab, seeds of 15 populations were rapidly aged at elevated temperature and relative humidity (45°C and 60% RH). The time taken in aging days for viability to fall to 50% (p50) was used to determine relative seed longevity. In the field study, the weedy population had higher seedling emergence and a larger residual seed bank in most locations. Populations did not differ in the size of the seed bank under spring tillage, whereas a larger soil seed bank of weedy population was observed in no‐till treatments. In the lab, the populations showed considerable differences in seed longevity. Although the cultivated population showed less seed persistence compared to the weedy population, both field and laboratory studies suggested that a considerable amount of seed of the cultivated population persists in the soil even after 3 yr; and this may pose some concerns for the production of cow cockle as a crop in the Canada.