Deep planting with shelters improves performance of different stocktype sizes under arid Mediterranean conditions

Oliet, Juan A. and Artero, Francisco and Cuadros, Simon and Puertolas Simon, Jaime and Luna, Lourdes and Grau, Jose M. (2012) Deep planting with shelters improves performance of different stocktype sizes under arid Mediterranean conditions. New Forests, 43 (5-6). pp. 925-939. ISSN 0169-4286

Abstract

Increasing plant size has been considered a way to improve survival and growth of planted containerized stock under dry conditions. Additionally, deep planting provides advantages to seedlings in dry areas because roots are placed deeper into the soil where there is likely more water available. In this study, we tested the effect of Zizyphus lotus stock size (300, 400 and 1,000 cm(3) container volume) and planting depth (0 cm and 15 cm below ground level, shallow and deep, respectively) with shelters in a factorial experiment in the arid coastal flats of Southeastern Spain. In the nursery, total biomass of Z. lotus produced in 1,000 cm(3) container volume averaged 219 % of those grown in 300 and 400 cm(3), although no significant differences were found in shoot-to-root ratio or nutrient status. Root growth potential (RGP) of plants produced in 1,000 cm(3) container (209 mg of new roots dry mass) was significantly higher than those of the two other volumes (63 mg in average), but the ratio shoot mass:RGP did not vary significantly between container volumes. After outplanting, and during the first year, volumetric water content (12-20 cm deep from ground level) averaged 3.9 % higher around the deep- versus shallow- planted treatments. Predawn water potential (psi (pd)) of seedlings measured in July of the first year differed significantly among planting depths, with lower values for shallow-planted (-3.3 MPa) than for deep-planted (-2.7 MPa) seedlings. However, predawn water potential did not differ among the three container sizes. Survival 40 months after planting was significantly higher for deep-planted seedlings (58.5 %) than for shallow ones (42.7 %), but no differences appeared for container size. PAR radiation at shoot height within the shelter was lower during winter for deep-planted seedlings than for shallow-planted seedlings, and relative differences among planting depths were reduced in summer. Based on survival results, we concluded that deep planting with seedlings of Z. lotus produced in 300 cm(3) container is a very effective way to improve planting success under the arid conditions of our experiment.