Irrigation in pine nurseries

Abstract

This review provides information and opinions about irrigation practices in pine nurseries. Even when nurseries receive more than 15 mm of rainfall week-1, managers irrigate seedbeds to increase germination, increase seed efficiency, and increase root growth. In the southern United States, a 7-month old pine seedling in an outdoor nursery typically receives 2 to 6 kg of water supplied from either sprinklers (39 nurseries) or center-pivot irrigation (12 nurseries). Most nursery managers do not intentionally subject the crop to moisture stress, since most reforestation sites receive adequate rainfall, and many studies show that reducing root mass does not increase seedling performance. In fact, nursery profits can be reduced by more than $13,000 ha-1 when deficit irrigation reduces average seedling diameter by 1 mm. Although some researchers believe that failure to properly drought stress pine seedlings might increase outplanting mortality by up to 75%, research over the past 40 years does not support that myth. When pine seedlings average 5 mm (at the root-collar), water stress is not a reliable method of increasing tolerance to an October freeze event. In several greenhouse trials, researchers grew and tested seedlings that nursery managers would classify as culls (i.e., dry root mass < 0.5 g). Unfortunately, it is common for researchers to make irrigation recommendations without first developing a water-production function curve.

Use of boron in conifer and hardwood nurseries

“…In coastal regions with more or less than 1 m of rainfall, aquafers may contain boron at <0.6 mg L -1 and >2.0 mg L -1 , respectively (Glenn and Lester 2010). At nurseries with historically low rainfall in the summer or fall (Hopmans and Clerehan 1991;South and Nadel 2020), irrigation will reduce the risk of seedlings exhibiting a boron deficiency (Landis 2001).…”

“…At one bareroot pine nursery (Stone et al 1982), no irrigation and less than 6 mm of rainfall in October (Madison County, FL -1979) contributed to a boron deficiency. The practice of ceasing all irrigation after the fall equinox (South et al 1989;South and Nadel 2020) is now an outdated practice, in part, because it increases the risk of a boron deficiency which can decrease outplanting performance. -Olson 1998).…”

Evaluation of the Control of Environmental Variables in a Pine Seedling Greenhouse

“…A greenhouse is a facility with special characteristics conditioned for the production of plants or seedlings, where environmental conditions are managed in such a way as to neutralize the effects of climatic phenomena, generating favorable environmental conditions for their development [10][11][12]. In greenhouses it is also possible to control the quality of the water, which can even be gray water recovered for irrigation [13].…”