Changes produced by the application of biostimulants on almond rootstocks properties during the nursery process

During the last ten years we have assisted to the consolidation of the almond crop that has remarkably increased its cultivation area causing a high demand for both plants and products related to growth stimulation. Accordingly, in the present work we aim to study the changes produced by the contribution of two biostimulants (humic and fulvic acids or aminoacids) on the properties of almond tree rootstocks. This kind of studies are of interest to the nursery cultivation industry where rapid growth of trees and good adaptation to their cultivation environment are required. Plants' radicular and vegetative systems responded differently according to the rootstock selection. The fastest and vigorous vegetative development was observed in GN rootstock whereas GF 677 showed the greatest number of main roots and RP-R of secondary roots. Differences on antioxidant activity and phenol content have also been found between rootstocks. All the tested samples were found to have a high antioxidant power and a high phenol content but GN stood out in this regard over the other rootstocks under study. The efficiency of the biostimulants applied has been verified. Both biostimulants promoted the development of the aerial part of the trees but biostimulant 2 did it to a greater extent. Biostimulant 1 was able to duplicate the number of main roots in RP-R and during the first year of study, biostimulant 2 originated an increase of the weight of the root system by 26.44% for RP-R, 16.93% for GF 677 and 48.00% for GN. In view of these results, synthetic chemical fertilizers can be at least partially replaced by biostimulants.