Application of biofertilizers in ‘Gala’ apple orchards at planting: consequences in mineral content, agronomic and physiological performance

An orchard of Malus domestica Borkh 'Gala Redlum', grafted on M9 rootstock, with 3472 trees ha(-1) (3.20x0.90) was planted during 2018 with 2 doses of 3 different biofertilizers in order to analyse biometric changes, mineral uptake and physiological-based indicators. These trees were fertilized with 70% of the standard program (C100) and equal to C70, both used as controls without biofertilizers. At the same time, other trees were planted in 33-L pots with substrate for destructive tests. Mycoshell (R) (a combination of endomycorrhizae Glomus spp. with humic and fulvic acids - Myc), Kiplant All-Grip (R) (Bacillus megaterium 1x10(8) cfu mL(-1), Pseudomonas fluorescens 1x10(8) cfu mL(-1), Pseudomonas putida 1x10(8) cfu mL(-1) - Allg) and Kiplant iNmass (R) (Azospirillum brasilense 1x10(8) cfu mL(-1), Bacillus megaterium 1x10(8) cfu mL(-1), Saccharomyces cerevisiae 1x10(8) cfu mL(-1) - iNm) were tested using the lowest dose in destructive tests and 2 doses in field tests. Myc was applied only before the plantation (2 or 4 tabs plant(-1)) and Allg and iNm during each of the crop cycles (6 or 12 L ha(-1)). After the second year of trials all the treatments with biofertilizers seems to increase phosphorus, magnesium, sulfur and micronutrients content in leaves, more than in C70, and in some cases to similar values of C100. Myc2 and Allg12 promoted quicker increases in soil phosphorus and potassium content. Trunk growth was similar in field tests but annual vegetative growth was higher in the trees biofertilized with Myc4, Myc2, Allg12 and iNm12 than in the controls with the same among of fertilizers (C70). Fruit growth rate was also increased by the use of biofertilizers. Allg12, Myc2, Myc4 and iNm6 produced more than the controls (C70 and C100), with significant differences between Allg12 (7.69 +/- 0.45 kg tree(-1)) and Allg6 (4.91 +/- 0.37 kg tree(-1)) or iNm12 (5.19 +/- 0.33 kg tree(-1)). iNm6 and Allg12 had also higher photosynthetic rates. During 2018, leaves from biofertilized trees had lower specific leaf area than C70 and close to C100, differences that tended to approach in 2019. SPAD also showed differences for C70, mainly iNm in both doses and Allg12. Pot tests showed higher length of the main root in non-treated trees, but a higher number of secondary roots in biofertilized trees and a higher root weight and root density in Allg trees. However, there was a greater development of above-ground part in all biofertilized trees as can be seen by their total weight, higher in biofertilized trees with iNm, followed by Allg and Myc. iNm registered the higher trunk length and weight and number and weight of branches. Field trials are ongoing to make long-term assessments about biofertilizers potential.