Effect of Mulching and Irrigation on Container-Grown Plant Production

Water stress is one of the primary constraints to plant productivity worldwide. Water availability for irrigation in agriculture and nursery industry will be reduced in the forthcoming years. Since weeds are strong competitors for water, sustainable methods for weed control may reduce water use in the nurseries. Biodegradable mulches can be an alternative to standard weed management and it is also reported that mulching can reduce evaporation from containers. The aim of this work was to evaluate the effect of mulch on daily water use. Four hundred eighty plants of Thuja plicata 'Martin' were potted into 3 L containers. Four biodegradable mulching materials were tested and compared with both chemical control (oxadiazon) and unmulched control. Two types of overleaf irrigation were scheduled (normal water amount and 33% of normal water amount); moreover two weed managements were planned (hand weeding - 3 times during the growing season - and no weeding until the end of the trial). Ornamental growth (shoot dry weight) was measured at the end of the growing season. Both weed number and weed shoot dry weight per container were recorded. Water content per pot (as a percentage) was evaluated weighting containers every two hours during the day after the morning irrigation (5:30 AM - solar time). Substrate temperature was measured in the hottest day period. Mulch, normal irrigation regime and regular hand weeding affected positively plant growth. Weed dry weight was significantly higher only in unmulched control. Mulch didn't affect substrate water content; this result emphasizes that transpiration was the main component of water loss from the substrate. An inefficacy of mulch in order to limit root medium temperature was observed.