Characterizing Population Growth Rate ofConvolvulus arvensisin Wheat–Sunflower No‐Tillage Systems

Abstract

Convolvulus arvensisL. is an important perennial weed that infests wheat (Triticum aestivumL.) and sunflower (Helianthus annuusL.) in Spain. Many fields of this rotation have been converted to no‐tillage or reduced tillage, so perennial weeds such asC. arvensishave become more troublesome since they cannot be reduced in abundance by repeated tillage or cultivation. The population growth rate (PGR) is important in forecasting future population trends, and it can be used to develop weed control strategies in which applications of herbicides are spatially targeted to minimize possible damage. The objectives of this study were to assess and map PGR ofC. arvensisin a wheat–sunflower no tillage rotation and to determine the temporal stability of the distribution function ofC. arvensisPGR was calculated over the course of four growing seasons (1999–2002) in a wheat–sunflower crop rotation in no‐tillage systems. Spatial variability of PGR was analyzed by geostatistics. Temporal stability of the distribution function ofC. arvensisPGR over time was established by a generalization of the two‐sample Cramér‐von Mises test for a difference between two univariate probability distributions. Year and crop influenced PGR, being larger in the sunflower phase (PGR = 0.52) than in the wheat phase (PGR = 0.16) of a sunflower–wheat rotation system because the density ofC. arvensiswas greater when growing in competition with wheat than with sunflower. The PGR showed a moderate degree of aggregation in patches in both rotations, although the temporal stability of the PGR distribution function was not observed. Overall, PGR became stable over the four growing seasons. Knowledge of growth rate spatial dynamics could improveC. arvensismanagement if it were complemented with spatially herbicide targeted applications.