Soil Matric Potential, Plant Water Relations, and Growth in Asparagus

Abstract Soil moisture treatments were initiated in a greenhouse study using 14-weekold asparagus ( Asparagus officinalis L. cv. Jersey Giant) seedlings. Treatments consisted of drying pots to a minimum soil matric potential ranging from –0 .0 5 to –1 .5 MPa prior to rewatering. After 10 weeks, root and fern dry weights, fern height, and shoot number were reduced by reducing soil moisture, with the largest decreases occurring between soil matric potentials of –0 .0 5 and –0 .1 MPa. Root : shoot ratios increased with decreasing soil moisture. In a growth chamber study, 4-month-old seedlings were watered to pot capacity and allowed to dry to a soil matric potential of —1.5 MPa. Xylem potential, relative water content (RWC), and shoot growth were measured daily as soil dried from field capacity to —1.5 MPa. Xylem potential was correlated with growth or RWC. Shoot growth ceased at a fern xylem potential of —1.8 MPa. RWC was reduced from ≈95% at pot capacity to 80% at a soil matric potential of — 1.5 MPa. These data indicate that asparagus exhibits characteristics of drought-tolerance. However, despite its apparent drought-tolerance, maximum growth occurs in young asparagus plants when soil water potential is close to field capacity, indicating that consistent irrigation would be beneficial in newly established plantings.