Response of young apple trees to grass and irrigation.

摘要

Ground covers and irrigation are important components of orchard floor management systems that affect fruit tree vigor and productivity. Three experiments were conducted in a greenhouse to determine the relative water use of candidate ground covers (roughstalk bluegrass, RB, Poa trivialis), Chewing's fescue (CH, Festuca rubra subsp. commutata Gaudin), creeping red fescue (RF, Festuca rubra L. subsp. rubra), tall fescue (TF, Festuca arundinacea Schreber, Fawn), and perennial ryegrass (PR, Lolium perenne L., 'Saint') and the response of apple trees to those ground covers and to drip irrigation applied at two soilless substrate depths. Grass ground covers with large and deep root systems (TF and PR) used more water than a shallow-rooted grass (RB) and leaf water potential decreased more rapidly in apple trees grown with TF than RB when irrigation was withheld. Although apple tree shoot growth was greater with shallow- than deep-rooted grass, photosynthesis, transpiration, and root biomass distribution were not differentially affected by grass type. When grown with RB or TF, irrigation depth affected apple tree growth. During the first season in the greenhouse, deep irrigation at 37 cm depth increased apple root length density near emitters but shoot growth was less in apple grown with deep irrigation compared with apple grown with surface irrigation (0 cm) and with split irrigation at 0 and 37 cm. During the second season in the greenhouse, deep irrigation was beneficial to trees grown with grass that had large, deep root systems (TF) but it did not completely overcome interference effects of grass on apple trees, regardless of grass root system size or distribution. The results indicate that grasses with shallow root systems may be grown beneath apple trees and that split irrigation at two depths can provide flexibility that is necessary for water management of ground covers and apple trees.