Darlene Wilcox-Lee

Soil water deficits and asparagus : II. Bud size and subsequent spear growth

Abstract Soil moisture stress in one year may negatively affect spear growth in the following year. We tested this hypothesis by applying soil water potentials (SWP) of −0.05, −0.3, or −0.5 MPa to asparagus plants and evaluated the effects of prior SWP history on bud size and spear growth assessed under ideal growing conditions. Total and viable bud numbers decreased linearly as SWP decreased. Although bud diameter within a bud cluster was variable, in general, as SWP decreased bud diameter decreased. SWP history had no effect on harvested spear number though total spear weight was less in the −0.3 MPa SWP than in the −0.05 or −0.5 MPa. Spear elongation rates were similar for all SWP and averaged 0.029 mm/h. Spear diameter distributions were significantly affected by SWP history. Chi-square test for the −0.05, −0.3, and −0.5 MPa were 6.6, 12.0, and 23.4, respectively, with increasing values indicating a departure from the expected distribution of spear diameters. Results indicate that SWP near field capacity are needed for optimum asparagus spear size and yield.

Soil water deficits and asparagus: I. Shoot, root, and bud growth during two seasons

Abstract Although considered to be drought tolerant, asparagus has been shown to respond to supplemental irrigation. Asparagus plants were dried to soil water potentials (SWP) of −0.05, −0.3 or −0.5 MPa before irrigating during two seasons in a greenhouse. SWP were applied for four months and then crowns were stored to simulate dormancy. After storage, crown re-growth was assessed, followed by re-initiation of the SWP. In the second year, the −0.05, −0.3, and −0.5 MPa treatments were nested in the first years SWP (total nine SWP treatments) to test the response of asparagus growth to prior SWP history. In both years, during the SWP period, whole plant harvests were made monthly and growth evaluated. In the first year, as SWP decreased, fern number and dry weight, storage root number and dry weight and bud numbers decreased linearly regardless of the harvest date. Storage had no effect on storage root number, though total root dry weight decreased during storage in all SWP. In the second year, fern, storage root, and bud numbers and root dry weight corresponded to the 1988 SWP regardless of the 1989 SWP early in the year. However, as the second growing season progressed, storage root and bud numbers and plant dry weights decreased linearly as SWP decreased and reflected the influence of the 1989 SWP. When supplied with adequate irrigation in the year after low SWP, asparagus growth improves and does not appear to have a long term negative effect on plant performance.