Phenology-based application of weed-derived bio-formulations enhances growth, yield, fruit quality and leaf nutrient status of ‘Gala Schniga Schnico’ apple under high-density orchard systems

Growing demand for sustainable intensification of apple production, coupled with rising input costs and increasing environmental concerns, has intensified the search for eco-friendly alternatives that can enhance orchard productivity while reducing dependence on conventional agrochemical inputs. Weed-derived bio-formulations represent a promising class of plant biostimulants owing to their diverse composition of bioactive secondary metabolites capable of modulating plant growth, nutrient acquisition and stress responses. Therefore, the present study evaluated the effects of phenology-based foliar application of weed-derived bio-formulations on vegetative growth, yield, fruit quality and leaf nutrient status of ‘Gala Schniga Schnico’ apple under high-density orchard systems. Field experiments were conducted during 2024–2025 in two orchard systems located at Nauni (EMLA9 rootstock) and Kandaghat (MM111 rootstock) using a split-plot design with four replications. Five treatments comprising different combinations of stage-specific bio-formulations were evaluated. Among them, T 1 , consisting of sequential applications across nine phenological stages, produced the most pronounced responses. Compared with the control (water spray), T 1 significantly increased fruit set from 38.56% ± 1.99 to 44.67% ± 2.14 and yield from 2.81 ± 0.37 to 4.83 ± 0.63 kg tree⁻ 1 ( P ≤ 0.05). Fruit quality was also improved, with higher firmness (7.67 ± 0.07 vs. 6.58 ± 0.04 kg cm − 2 ), total soluble solids (12.44 ± 0.22 vs. 10.83 ± 0.25 °Brix) and total sugars (11.19 ± 0.23 vs. 9.91 ± 0.26%). Leaf nutrient status was enhanced, with nitrogen, phosphorus and potassium concentrations increasing by 29.2%, 50.0% and 18.6%, respectively, relative to the control. Pearson’s correlation analysis revealed significant positive associations among vegetative growth, nutrient status, yield and fruit quality traits. Principal component analysis showed that the first two components explained 97.57% of the total variation, with PC1 and PC2 accounting for 68.96% and 28.60%, respectively. These findings demonstrate that phenology-based application of weed-derived bio-formulations can serve as an effective and sustainable biostimulant strategy for improving productivity, fruit quality and nutrient status in high-density apple orchards.