Effect of Regulated Deficit Irrigation, Soil and Nitrogen Application Rate on Some Biological Properties of Young Sweet Cherry Trees on Clonal Rootstock Gm

摘要

The need for intensifying sweet cherry production in Bulgaria necessitates the use of dwarfing rootstocks, such as the recently developed clonal rootstock Grand Manil. Experiments were carried out with cv. Stella/GM_9 on three soil types - Fluvisol, Chromic-Luvisol and Vertisol, using drip irrigation. A RDI (Regulated Deficit Irrigation) regime, used in Southern France, was verified and rated under the climatic conditions in S. Bulgaria. The soil water potential (PSI_(soil)), stem water potential (PSI_(stem)), stomatal conductance, photosynthesis and transpiration rate, growth and yield were studied. In the pre-planting application of PK + N, an induced plant water stress, as a result of a PSI_(soil) and PSI_(stem) increase, was established. In Fluvisol, this negative effect of the N-application rate was not noted. Critical values of the PSI_(soil) and PSI_(stem) indicating a disturbance of the water balance of the plants, and a water stress were established as well as the optimum N-application rate on the three studied soils. The assessed RDI regime proves adequate for the Fluvisol and insufficient for the Chromic-Luvisol and Vertisol.