Search

Organic hydromulches can be an interesting alternative for weed control in perennial crops, but can also reduce soil water evaporation. To examine the effect of a hydromulch layer on soil water content in dry conditions laboratory experiments were conducted at constant 25°C, 40% air RH. Both for small soil containers with a short time course and for larger soil columns (with two sensors at depths of 6 cm and 11 cm) with a longer time course, the presence and also the thickness of hydromulch were significant factors for the temporal evolution of soil water content. Two distinct stages of the evaporation process, the first or initial stage and the last or final stage, were identified, analysed and compared for these experiments. General linear models performed on the soil water content temporal evolutions showed significant differences for the first and last stages at the top and bottom of the soil columns with and without hydromulch. Hydromulch application delayed the evaporation process in comparison with the control. Moreover, the hydromulch layer, which was tested for mechanical resistance to punching, offered enough resistance to prevent its perforation by the sprouts of weed rhizomes.

Digitaria sanguinalis can exhibit a smut caused by Ustilago syntherismae. In the present paper, we deal with the phenotypic expression of the grass that can be observed under field conditions. Plants can be apparently healthy, completely smutted or show both tendencies, inflorescences bearing spikelets and at the same time sori (single individuals). Plasticity in fitness-related traits such as tillering pattern and the proportion of inflorescences with spikelets or completely transformed into sori at individual level was examined in distinctive individuals. In the study period 2011–2014, we observed and collected 244 individual plants (3.2% of the plants reaching the reproductive stage) with between 1 and 12 tillers. The mean number of reproductive structures per plant was 24.2 (20.4 exhibiting sori and 3.7 bearing spikelets). The spatial and temporal dynamics of the single individuals at plot scale was also analysed. We discuss the importance of individual responses from the perspective of plant resistance in the broadest sense: any system that can prevent infection or reduce the impact of fungi. Furthermore, we consider the importance of this subpopulation in disease prevalence. [ABSTRACT FROM AUTHOR]

Effective weed management has been identified as a limiting factor in the adoption of conservation tillage systems. In view of this fact, weed communities were characterized in order to evaluate similarities and differences under three tillage systems: chisel (minimum tillage), moldboard plow (conventional tillage), and no-tillage. The study was carried out near Barcelona throughout a 4-year (1997–1998 to 2000–2001) rotation of winter crops (pea: Pisum sativum L., wheat: Triticum aestivum L., wheat–barley: Hordeum vulgare L.) on a deep silt loam Calcixerollic Xerochrept soil. Analyses of variance based on a randomized complete block design were performed on total aboveground weed biomass (g m−2), monocotyledon and dicotyledon biomass, and the biomass of each species. Three main effects were considered: tillage, block and year (crop). Data were combined in order to compute one Shannon–Wiener diversity index for each year and tillage system. The year (crop) effect was the most important factor, followed by the year (crop)×tillage interaction; winter pea had the lowest weed biomass. Tillage system had no effect on total weed biomass. The mean biomass of Avena sterilis L. was greatest under minimum tillage, while those of Diplotaxis erucoides (L.) DC and Sonchus tenerrimus L. were greatest under no-tillage. The highest Shannon–Wiener diversity index was obtained for the no-tilled weed community, and was related to the highest richness and highest evenness. As tillage system had no effect on weed biomass and although the no-tillage system had the richest and most diverse weed community, the weed flora would not constitute an obstacle to an increasing use of no-tillage system for cereal production in the study area. [Copyright &y& Elsevier]