Active ground optical remote sensing (AGORS) devices mounted on overhead irrigation booms could help to improve seedling quality by autonomously monitoring seedling stress. In contrast to traditionally used passive optical sensors, AGORS devices operate independently of ambient light conditions and do not require spectral reference readings. Besides measuring red (590–670 nm) and near-infrared (>760 nm) reflectance AGORS devices have recently become available that also measure red-edge (730 nm) reflectance. We tested the hypothesis that the additional availability of red-edge reflectance information would improve AGORS of plant stress induced chlorophyll breakdown in Scots pine (Pinus sylvestris). Our results showed that the availability of red-edge reflectance information improved AGORS estimates of stress induced variation in chlorophyll concentration (r² > 0.73, RMSE < 1.69) when compared to those without (r² = 0.57, RMSE = 2.11).

Land management practices, invasive species expansion, and changes in the fire regime greatly impact the distribution of native plants in natural areas. Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), a keystone species in the Great Basin, has seen a 50% reduction in its distribution. For many dryland species, reestablishment efforts have focused on direct seeding but achieved only minor success due to irregular seed germination and poor survival. We investigated the effects of container volume and fertilization on the performance of nursery-grown Wyoming big sagebrush seedlings following outplanting. Additionally, to evaluate the impact of site preparation, one-year-old seedlings were outplanted into tilled and untilled field conditions. Initial seedling size increased with container volume; larger seedlings exhibited significantly higher root collar diameter (RCD) growth than smaller seedlings. As container volume increased from 108 to 251 and 336 cm3, seedling survival on the ...

With about half the amount of water, subirrigated Metrosideros polymorpha Gaud. (Myrtaceae) grown 9 mo in a greenhouse were similar to those irrigated with an existing fixed overhead irrigation system; moss growth was about 3X greater in the fixed overhead system after 3 mo. Moss growth was affected by the rate of preplant controlled release fertilizer added (more fertilizer, less moss) and moss maturity, quantified as presence or absence of sporangia, was slowed with subirrigation. About 5 g nitrogen (N) leached per m2 (0.02 oz/ft2 ) of greenhouse bench under the fixed irrigation system, whereas none was lost from subirrigation. Besides Metrosideros macropus, the USDA Forest Service and Purdue University are evaluating subirrigation for nursery production of other species. To date, the results indicate subirrigation may be a useful technique for growing native plants with large canopies where conventional irrigation systems are less effective, or where water use or other environmental concerns are paramount.