Investigation of organic and biofertilizer sources and harvesting time on quantitative and qualitative characteristics of Salvia officinalis L.

In the conventional agricultural systems, the excessive use of chemical inputs, such as chemical fertilizers, increased the agricultural productivity. Detrimental implications from intensive agricultural practices and long-term use of chemical fertilizers have been well evidenced on the environment and human health. Intercropping system and application of organic fertilizers and biofertilizers including vermicompost and arbuscular mycorrhizal fungi (AMF) are recommended in the development of sustainable agricultural systems. The objectives were evaluating the effect of different fertilizer sources on the quantity and quality characteristics of Salvia officinalis L.

The experiment consisted of two successive phases at the Miandoab, Iran in 2019-2020. The first was cultivation of spring green manure until the soft dough stage of barley and flowering stage of hairy vetch then returned to the soil, and the second phase was cultivation of medicinal plant of sage. Two species, barley (Hordeum vulgare L.) and hairy vetch (Vicia villosa), were used as green manure. In second phase, a field experiment study was carried out as split plot in time based on a randomized complete block design (RCBD) with 16 treatments and three replications. The main plot factor was eight different fertilizer sources including control (C), barley monoculture (B), hairy vetch monoculture (V), 75% V + 25% B, 50% V + 50% B and 25% V + 75% B, AMF: arbuscular mycorrhizal fungus (Rhizophagus intraradices) and vermicompost. Also the sub plot factor was harvesting time (first and second harvest). In AM fungi treatments, 80 g of the soil containing mycorrhizal fungi hyphae and the remains of the root and spores was added to soil in planting times. Also, vermicompost (2 t ha-1) was applied to the soil before planting. Analysis of variance of the data and mean comparison based on least significant difference (LSD) test and interaction effect slicing of different fertilizer sources × harvesting time were carried out by using of SAS 9.3 statistical software.

The plant height, number of lateral branches, number of leaves, chlorophyll index, leaf dry weight, stem dry weight, essential oil percentage and yield was significantly affected by interaction of diffirent fertilizer sources×harvesting time. The highest of dry matter yield was achieved under AMF followed by 50% V+ 50% B. Also the highest of chlorophyll index and essential oil percentage of sage was obtained in 50% V + 50% B and first harvest. Also, the first harvesting time increased by 33.9, 10.7 and 40.7% this trait in comparison with second harvest. In addition, the maximum of essential oil yield was observed in AMF followed by 50% V+ 50% B in first harvest. Chemical analysis of the essential oil of sage demonstrated that in all treatements, cis-Thujone, 1, 8-cineole and camphor were the main dominant components. The maximum of cis-Thujone, 1, 8-cineole content was achieved in 50% V+ 50% B and second harvest. Also, the highest of camphor observed in 25% V+ 75% B treatment and first harvest. The roots of green manure plants can uptake nutrients from the lower layers of soil and transfer them to the aerial parts of plant. By incorporating green manure, the sage growth characteristics improved as a result of increasing soil microbiological processes and releasing of nutrients. Also, mycorrhizal fungus inoculation enhanced plant performance by increasing root surface area, turgor pressure adjustment, gradual availability to nutrients and water. Since essential oils are terpenoid components so that for the biosynthesis of precursor compounds (isoprenoids) such as isopentenyl pyrophosphate and dimethylallyl pyrophosphate necessary Acetyl-CoA, NADPH and ATP and mineral nutrients like N and P. Treating plots with 50% V + 50% B and AMF increase the essential oil percentage and compounds through releasing of nitrogen and phosphorus into the soil. Also, the higher morphological traits, essential oil percentage and yield in the first harvest than the second harvest can be attributed to longer growing period and optimal growth conditions (day length, sunlight, ambient temperature).Treating plots with green manure and AMF improve the morphological traits, quantity and quality of sage essential oil through adjustment the soil chemical properties. According to the quantity and quality indicators, application of 50% V+ 50% B as green manure and AMF can be suggested as an efficient and eco-friendly agricultural strategy in sage cultivation.