Edward F. Durner

Mode of action and use of plant growth retardants in reducing the effects of environmental stress on horticultural crops

Transient environmental stress can have a significant effect on the yield and quality of horticultural crops. In addition, the geographical range suitable for commercial crop production may be limited by an almost predictable seasonal occurrence of temperature or water stress at critical stages in crop development. For example, in fruit production in a temperate zone, flowering often begins prior to the average last frost date, and pollination and fruit set in grain crops often occurs during periods of consistently low rainfall. Moreover, vegetable transplants, targeted for the early market, frequently suffer from water stress as a result of root injury during planting, and chilling injury associated with an early planting date.

Conditioning alleviates reduced yield of smaller plugs of ‘Albion’ strawberry (Fragaria X ananassa Duch.) in off-season plasticulture production

ABSTRACT The influences of plug size, planting density, and mulch colour on responses to photoperiod and nitrogen conditioning of ‘Albion’ strawberry (Fragaria x ananassa Duch.) plants were evaluated in off-season field production in New Jersey, USA. Three different sized plug plants (7.6 cm square pots, 24-cell plug trays, or 50-cell plug trays) were conditioned with natural days (ND, natural daylength) or long days (LD, natural daylength supplemented with 24 h incandescent radiation) for one week followed by ND plus 100 ppm nitrogen (N) for 4 weeks or LD plus 800 ppm N for 4 weeks. Plants were then established in plasticulture on black, white, or silver mulch. In a second experiment, plug plants (439 cm3) were conditioned with LD and nitrogen then established in plasticulture on black, white, or silver mulch at 3 planting densities (0.46, 0.23, and 0.16 m2•plant−1 (2, 4, and 6 plants•m−2)). Fruit were harvested from August through October in both experiments. Conditioning enhanced off-season fall production. White plastic enhanced survival, productivity, and fruit size and larger plugs were more productive than smaller ones. If smaller plugs are desired, conditioning prevents the reduction in yield observed with non-conditioned smaller plugs.

Long-day and nitrogen conditioning of ‘Albion’ strawberry (Fragaria X ananassa Duch.) enhances off-season field production

ABSTRACT Experiments conducted over 2 years evaluated photoperiod and nitrogen conditioning of ‘Albion’ strawberry (Fragaria x ananassa Duch.) plants for off-season field production in New Jersey, USA. Plants were conditioned the first year with natural days (ND, natural daylength) or long days (LD, natural daylength supplemented with 24 h incandescent radiation) for one week followed by 100 or 800 ppm N for 4 weeks under ND or LD. The second year, plants were conditioned with ND or LD for 1 week followed by 1 to 6 weeks of 100 or 800 ppm nitrogen (N) under ND or LD. After conditioning, plants were established in plasticulture. Ripe fruit were harvested from August through October both years. LD conditioning enhanced precocity by approximately 9 days in both studies. Productivity was also enhanced by conditioning with LD or elevated N. Plants grown on silver or white mulch were more productive than those grown on black mulch in the first study, but not the second.

Conditioning is not needed for late summer and early fall production of June-planted ‘Albion’ strawberry (Fragaria X ananassa Duch.) in the plasticulture system

ABSTRACT Two plant types [direct planted, cold-stored dormant crowns (crowns) or dormant crowns grown in a greenhouse for 3 weeks prior to field planting (plugs)] of ‘Albion’ strawberry (Fragaria x ananassa Duch.) were evaluated in off-season field production under LD (long day: natural daylength supplemented with 24 h incandescent radiation) or ND (natural daylength) in New Jersey, USA. After 1 week under LD or ND plants received either 100 or 800 ppm N for 4 weeks. Inflorescence, runner, and branch crown production were monitored and fruit harvested from July through September. Field conditioning was ineffective for enhancing total yield of June-planted ‘Albion’ in off-season production. If early summer planting is anticipated, conditioning is not needed. Growing plugs in the greenhouse before transplanting to the production field is not beneficial and reduces productivity with the early summer plantings. Extending the daylength with continuous incandescent lighting to mimic LD during production is not recommended for early summer planting as productivity and fruit size are reduced under continuous low level lighting.