Development of a Double Crop Production System Using Retractable Roof Houses

摘要

Double cropping containerized tree liners in a retractable roof greenhouse (RRG) increases the incentive for their production in Midwest nurseries. The objectives of this study are to evaluate possible acceleration of tree production using double cropping in a RRG at The Ohio State University, Columbus, Ohio, with subsequent upshifting to a pot-in-pot (PIP) system. Two tree species were selected to be grown in the RRG, red maple (Acer rubrum 'October Glory') and greenspire littleleaf linden (Tilia cor data 'Greenspire'). All the trees were grown from tissue culture and they had a start height of 20-25 cm. All the plants were put into 11.3-L containers with a soilless mix in the RRG. The roof and sidewalls were programmed to close at 21 °C during the day and 10de gC during the night from October to December and plants were irrigated using aerial irrigation three times per day. From December to March half of the plants were with bottom heat (BH) using low watt propagation mats set at 5 °C and the other at ambient temperature (AT). Diu-ing winter, plants were watered as needed and protected from freezing temperatures using a propane heater. From March to June the irrigation was applied using cyclic-micro-irrigation two times per day, applying 500 ml per pot. From June to September, irrigation was applied one time per day, appljdng 250 ml of water per pot. Plants were fertilized two ways starting in April: control release (CR) fertilizer (40 g of 19-5-8) apphed at potting and a combination of 20 gof the CR applied at potting and supplemented with liquid fertilizer (LF) (21-7-7 at 400 ppm) delivered with an injection system every 2 weeks. The same total nitrogen was delivered in the CR and the CR + LF treatments. Plants were arranged in a split plot design (main plot: temperature, subplot: fertilizer) with 4 rephcations. Measures consisted of height, caliper, leaf area, and shoot and root dry weights, EC, pH, and NOg. No significance differences were found between AT and BH for all the measurements (Table 1.). No significance differences were found between the CR and CR+LF treatments for height, leaf area, dry shoot, and root weights (Table 2), EC, pH and NOg. The caliper was significantly bigger (8.48 mm) in the CR+LF in comparison with the CR(7.82 mm). After 1 year, heights and cahpers of hnden (107 cm and 8.61 mm, respectively) and maple [95.39 cm and 7.76 mm, respectively (Table 4)] liners were produced at Ohio State University, supporting our hypothesis that RRG liners can be produced inOhio. Tables of the results after 1 year of growth.