Evaluation of a mini-container accelerated transplant system : the black spruce winter crop

Abstract

The effects of four factors on nine attributes of black spruce (Picea mariana (Mill) B. S. P.) seedlings were investigated. The seedlings were produced under an accelerated transplant system that used a 6 ml Castle and Cooke container. The experiment had two stages. The first stage investigated the effects of the duration of the greenhouse phase (DURATION), outplanting date (OUTPLANTING DATE) and acclimatization of seedlings to outdoor environmental conditions before transplanting (ACCLIMATIZATION) on seedling attributes at the end of the greenhouse phase. The seedling attributes were height and the number of roots outside the growing medium. The second stage investigated the effects of these same factors plus shade in the transplant beds (SHADE) on seedling attributes during, and at the end of, the first growing season. Seedling mortality in the transplant beds and bud-set were monitored during the growing season. Total height, top dry weight, root dry weight, bud diameter, and root collar diameter were measured at the end of the growing season. Analysis of variance was used to investigate the effects of the factors on the response variables. The major conclusions were these. The greenhouse cultural factors studied affected both the morphological state of the seedling and its physiological fitness at the time of transplanting. DURATION was especially influential in this regard. At 7 weeks the seedlings were small and experienced high mortality if transplanted. By 10 weeks the seedlings were larger and survived the transplanting operation well, but they were predisposed to set bud soon after transplanting. Thirteen-week-old seedlings were even larger, and were beginning to outgrow their containers. They survived transplanting well, but were even more predisposed to set bud. DURATION effects also influenced the morphological state of the transplants at the end of the first growing season. Seedlings that set bud early had short, stocky stems with large buds and a high root:top ratio. Seedlings that did not set bud early had tall slender stems with small buds and a low root:top ratio. OUTPLANTING DATE, SHADE and ACCLIMATIZATION also affected the crop and interacted with DURATION and one another. The results provide insight into the first year response of seedling grown under the Castle and Cooke accelerated transplant system to cultural factors over which nurserymen have control.