Peter Parchomchuk

Drip-fertigation of apple trees affects root distribution and development of K deficiency.

The locations of root intersections were mapped relative to micro-emitters in spring, 1996 for Gala apple (Malus domestica Borkh) on M.26 rootstock, which were established and grown for 8 yr under micro-irrigation with fertigation. Root distribution was mapped for trees that had been irrigated daily between May and October using drip or microjet systems and fertigated each year during May. Drip-irrigated trees had nearly half of their total root intersections within 30 cm depth and lateral distance from the emitter. Roots of microjet-irrigated trees were more widely distributed over a soil volume extending to 60 cm depth and 90 cm lateral distance from the trees. Leaf K concentrations had decreased to near deficient concentrations for drip-irrigated trees after 5 yr.Root distribution mapping and soil sampling were undertaken in spring 1997 for N-fertigated Gala on M.9 apples, planted in 1992 on the same soil, with or without annual K applications during 1992–1996. Fertigation of 15 g K tree−1 each year in...

Soil and peach seedling responses to soluble phosphorus applied in single or multiple doses

Abstract Two methods of measuring phosphate (P) adsorption were assessed as a means of predicting soil and plant responses to P fertigation for four British Columbia (B.C.) orchard soils. In Method 1, soils at 0.1 bar moisture tension were incubated for 1, 7, 14, 28, 56, or 84 days with solutions of H3PO4 supplied as a single or eight weekly doses. In Method 2, soils were equilibrated with P solutions at 1:10 soil:solution ratio for one day. Langmuir adsorption maxima calculated from the latter data ranged from 99 to 372 mg/kg. Solution P concentrations after one day for single dose incubations and 1:10 soil:solution equilibrations were highly correlated. Solution P concentrations remained elevated for 12 weeks after both single and weekly doses in incubated soils. Four availability indices were derived from the adsorption studies:solution P after one day equilibration for both methods and the fraction of the P adsorbing surface covered by added P at either one or fifty‐six days. Peach seedlings (Prunus p...

Gewurztraminer Grapevines Respond to Length of Water Stress Duration

Abstract Gewurztraminer grapevines planted in 1989 were subjected to one of three durations of water stress (deficits imposed at postbloom, lag phase, veraison) in combination with three vineyard floor management strategies (clean cultivated, total herbicide, permanent sod). Data were gathered on vine performance, fruit composition, and water relations from 1991-96. Yield per vine, cluster weight, and berry weight were reduced linearly with duration of water deficit. Transpiration, stomatal conductance, and leaf water potential were likewise reduced with increased duration of water stress. Titratable acidity decreased and pH increased with duration of water stress, but °Brix was unaffected. Decreasing duration of water stress increased free volatile terpenes (FVT) at harvest, as well as increased potentially volatile terpenes (PVT) at both veraison and harvest. Maintaining a permanent sod tended to reduce all yield components, especially berry weight, but basic fruit composition was unaffected. FVT were highest at both veraison and harvest in berries from clean cultivated plots; however, PVT concentration was highest in berries from permanently sodded plots. Permanent sod treatments displayed lowest transpiration rate and stomatal conductance. Monitoring physiological response (particularly stomatal conductance) of the plant to reduced soil moisture provides a reliable indication of when to relieve irrigation deficits, as opposed to relying on soil moisture monitoring and/or visual assessment of water stress.