Managing water use and growth of a perennial ryegrass living mulch in Christmas trees

Graduation date: 1989A living mulch system consists of growing a regulated cover crop\ud with an economic crop. Living mulches are often interplanted with\ud horticultural crops, but competition for water can adversely affect\ud crop production. Various management practices may limit the negative\ud effects.\ud Studies were conducted for two purposes: (1) to determine if\ud water use of perennial ryegrass (Lolium perenne L.) could be reduced\ud by mechanical or chemical suppression, and (2) to examine water-use\ud patterns and effects of a living mulch grown in strips between rows of\ud Douglas fir (Pseudotsuga menziessi M.) and grand fir (Abies grandis\ud D.) Christmas trees.\ud Small bucket-lysimeters were used to measure water consumption of\ud four treatments: bareground, and mechanically suppressed, chemically\ud suppressed, and unsuppressed perennial ryegrass, cv. Manhattan II.\ud Sublethal rates of fluazifop-P (butyl (R)-2-[4-[[5-(trifluoromethyl)-\ud 2-pyridinyl]]oxy]phenoxy]propanoic acid) were applied to chemically\ud suppress the grass. Evapotranspiration (ET) calculated by the Food\ud and Agriculture Organization Blaney-Criddle method and actual ET data\ud were compared.\ud Unsuppressed ryegrass used 9% more water than ryegrass either\ud chemically or mechanically suppressed. Bareground used 61% less water\ud than the unsuppressed grass.\ud Results of the living mulch field trials indicated strips of\ud perennial ryegrass and indigenous vegetation grown between rows of\ud Christmas trees used more water than bareground, regardless of the\ud suppression treatment. Measurements taken during the study indicated\ud there were no significant differences in tree growth among treatments