Abstract
We found that the most effective and economical method for establishing native shrubs on extensive areas of retired cropland in southern Arizona makes use of drip irrigation and 3.8-l (1-gal) transplants (outplants). In March 2001, we established a small (8 ha [20 ac]) field trial to test the effectiveness of different combinations of transplanting, seeding, drip irrigation, and furrow irrigation. Treatments utilizing transplants and drip irrigation had higher survival and lower densities of weed species than other treatments tested. Based on these results, we planted again in November 2001 using drip-irrigated transplants to examine the effectiveness of this method over a larger scale (85 ha [210 ac]). As a further refinement of this method, we tested various sizes of container stock and determined that transplants of 3.8-l (1-gal) size had superior growth and survival when compared to smaller-sized transplants. The total cost of this method is approximately US$ 4430/ha ($1790/ac), but it is more likely to succeed as compared with direct seedings, which is a commonly used approach to revegetation in southwestern ecosystems. Although a drastic effort, our technique holds promise for revegetating environments in the hottest and driest parts of the Sonoran Desert in southern Arizona.
