Effect of Different Irrigation Regimes on the Early Development of Pot-Grown Black Locust Saplings

Abstract

Black locust currently is considered to be the most important tree species of short-rotation forests in Hungary with the purpose of either woody biomass or industrial wood. Despite the general supposition on the drought tolerance of the species, water availability seems to be a more limiting factor to exploit the growing potential of highly productive new varieties than nutrient amendments. Preliminary measurements of the current study were made on the connection between the depth of the water-retaining soil layer and the growth of saplings on black locust plantations. A significant negative correlation was found between the depth of the water-retaining layer, the stem diameter and the height of the saplings. To investigate the phenomenon, a model experiment was launched with loamy sand soil in the pots. During six weeks, pots were watered every morning up to the weight referring to the 30, 40, 60 and 80% of field capacity (FC). Our results showed that 30% FC was only sufficient for the survival of the saplings, growth was only noticeable at plants with 40% FC or more. During the first 4 weeks, differences in growth and cumulative evapotranspiration between the 60% and 80% FC treatment were not considerable. However, in the last two weeks, saplings with the highest FC produced substantially higher biomass, resulting in a one-third higher final weight than those of FC 60%. Even with the limited soil capacity of the pots, water use of these saplings of 1 m height and 1 cm stem diameter exceeded 1.5 L per day. Our results confirmed that black locust is a water-intensive species with a high water use potential, which emphasizes the importance of irrigation on nurseries and the first years of plantations.