A pine tree substrate (PTS), produced by grinding loblolly pine trees (Pinus taeda), offers potential as a viable container substrate for greenhouse crops, but a better understanding of the fertilizer requirements for plant growth in PTS is needed. The purpose of this research was to determine the comparative fertilizer requirements for chrysanthemum (Chrysanthemum ×grandiflora ‘Baton Rouge’) grown in PTS or a commercial peat-lite (PL) substrate. The PTS was prepared by grinding coarse (1-inch × 1-inch × 0.5-inch) pine chips from debarked loblolly pine logs in a hammer mill fitted with 3/16-inch screen. The PL substrate composed of 45% peat, 15% perlite, 15% vermiculite, and 25% bark was used for comparative purposes. Rooted chrysanthemum cuttings were potted in each of the substrates on 15 Oct. 2005 and 12 Apr. 2006 and were glasshouse grown. Plants were fertilized with varying rates of a 20N–4.4P–16.6K-soluble fertilizer ranging from 50 to 400 mg·L−1 nitrogen (N) with each irrigation. Plant dry weights and extractable substrate nutrient levels were determined. In 2005 and 2006, it required about 100 mg·L−1 N more fertilizer for PTS compared to PL to obtain comparable growth. At any particular fertilizer level, substrate electrical conductivity and nutrient levels were higher for PL compared to PTS accounting for the higher fertilizer requirements for PTS. Possible reasons for the lower substrate nutrients levels with PTS are increased nutrient leaching in PTS due to PTS being more porous and having a lower cation exchange capacity than PL, and increased microbial immobilization of N in PTS compared to PL. This research demonstrates that PTS can be used to grow a traditional greenhouse crop if attention is given to fertilizer requirements.

Physical disturbance of plants or plant parts results in a mechanical stress response from the plant. Mechanical stress applied naturally or under controlled conditions inhibits growth in mass and dimensions of major plant parts. Wind and precipitation are important natural sources of mechanical stress. Under field conditions, cultivated plants experience these natural mechanical stresses plus those caused by irrigation and contact with farm machinery or workers during cultivation. Some horticultural practices, such as staking of trees or potted plants, pinching or pruning stems, deadheading flowers, bagging potted plants, or training branches, are mechanical stresses that affect plant growth. Handling practices in plant science research, such as cross-pollination or tagging of flowers (Frizzell et al., 1960) or repeated attachment of leaf chambers for measurement of water status or photosynthetic rates (Marler and Mickelbart, 1992), also can affect plant growth and physiology.

Tomatoes have been linked to outbreaks of salmonellosis, demonstrating the need to identify sources of contamination. Objectives of this study included determining the ability for Salmonella enterica serovar Montevideo to be internalized into tomatoes from contaminated irrigation water and seed stock, and establishing whether Salmonella Montevideo can survive in fertilizer solutions. Six treatment groups (five plants per group) were irrigated with 350 ml of 7 log CFU/ml of Salmonella Montevideo every 14 days for 70 days, each group receiving an increased number of contaminated water events progressively: group 1 received one contaminated watering at day 0, and group 6 received a total of six contaminated waterings. Group 7 was a control, and group 8 was grown from seeds soaked in 8 log CFU/ml of Salmonella Montevideo for 24 h. All plants were watered daily with uncontaminated water. Three replications were completed. Fruit from every plant, and roots, stems, and leaves of one plant per treatment were sampled. All tomatoes were negative for Salmonella Montevideo; five root samples tested positive. For fertilizer studies, a commercially available fertilizer, two custom mixed and 1.0% dilutions of each (total of six solutions), and sterile water were inoculated with 8 log CFU/ml of Salmonella Montevideo and stored at 25 degrees C. Solutions were sampled at 24, 48, and 72 h. There were no differences (P > or = 0.05) between survival of Salmonella Montevideo in diluted fertilizers and the control. Results indicate Salmonella Montevideo is unable to contaminate tomato fruit via irrigation water and seed stock but can survive in fertilizer solutions.

Mechanical conditioning is an excellent means of regulating the growth of vegetable transplants and some ornamental bedding plants. It improves the stature, appearance, handling characteristics, and overall quality of treated plants. The application procedures reported for transplants have included wind, shaking, brushing, and more recently impedance; all of which result in physical displacement of the growing points. Brushing has been most commonly studied for mechanical conditioning in high density transplant production. Brushing reduces plant height, increases stem and petiole strength, improves insect resistance in the greenhouse, tends to improve stress tolerance and enhance stand establishment in the field, and has no effect on crop yield. Although growers using the technique have been very pleased with the quality of brushed vegetable transplants, widespread commercial application of brushing is limited by a lack of automation.

Broccoli (Brassica oleracea L. Group Italica cv. Green Duke) seedlings were subjected to brushing with a piece of cardboard (40 strokes/min, 1 min twice daily), wind (7 m·s-1 for 5 min twice daily) or drought (visible wilt for 2 hours daily) treatments. Plant response to treatment was affected by seasonal or environmental conditions. All conditioning treatments reduced leaf dry weight and area, stem dry weight and length, and the total shoot and root dry weights in an experiment conducted in Sept. 1986 (Fall 1986). However, in experiments conducted the following year, broccoli transplants treated in March (Spring 1987) showed little response to the treatments, while transplants treated in August (Fall 1987) showed only a moderate response. In Fall 1986 and 1987, brushing improved field establishment as measured by the rate of shoot dry weight gain over the period of field establishment. Yield of the primary head of broccoli transplants treated in either Spring or Fall 1987 was not affected by the conditioning treatments. Brushing may provide an effective alternative to drought or plant growth retardants in conditioning broccoli transplants prior to field planting.