Microclimatic conditions affect lettuce growth in apple tree-lettuce intercropping

Garden-orchard systems, an innovative way to produce fruits and vegetables together, consist in intercropping various vegetables with fruit trees.
We studied the effects of 20-year old apple trees (Malus × domestica Borkh) on drip-irrigated lettuce crop (Lactuca sativa L., var.
Olana) without fertilization.
Lettuce growth dynamics, soil properties and microclimate were investigated in order to quantify the interactions between the two crops during one growing season.
Leaf area and biomass dynamics of lettuce as well as soil mineral nitrogen and soil water content were monitored on five lettuce beds located at a distance of 1.5 to 5 m from the trees.
Light interception by apple trees was characterized using 21 global radiation sensors, while air temperature and relative humidity were measured using 15 probes.
Furthermore, nitrate in soil solution was monitored at 30 and 90 cm depth using ceramic suction lysimeters.
Apple trees decreased air temperature on the hot summer.
During a heat spell on a sunny summer day, the measured temperature difference between the lettuce beds closest to the apple trees and those situated 5 m from the row was 2°C. Shading reduced lettuce transpiration by intercepting solar radiation and lowering air temperature, which increased the lettuce’s growth rate in summer.
Nitrate in soil solution was very low for all lettuce beds (under 5 mg NO₃-N L^‑1).

IV International Symposium on Horticulture in Europe – SHE2021

T. Ramananjatovo, E. Chantoiseau, G. Buck-Sorlin, P. Guillermin, R. Guénon, M. Delaire, P. Cannavo

garden-orchard system, nitrogen, light interception, air temperature, soil moisture

https://doi.org/10.17660/ActaHortic.2021.1327.31