Response of potted herbs to different solid organic fertilizations

In organic cultivation systems, the fertilization management and the soil or growing media are the main determinants of the crop performance and product quality.
However, the synchronization of N mineralization from diverse sources of organic fertilizers with the plant demand is challenging.
For organic potted plants such as herbs or ornamentals, liquid organic fertilizers are often used by growers as the total required amount of solid organic fertilizers mixed to the growing media may result in soil salinity and growth reduction.
Nevertheless, liquid organic fertilizers are generally more expensive compared with solid organic fertilizers and lead to clogging problems of the irrigation system.
On the other hand, the mineralization rate of organic fertilizers varied with their origin, C/N ratio and the physicochemical and biological properties of the growing media.
Thus, we have compared, by using a randomized complete block experimental design with 10 replicates, nine combinations of solid organic fertilizers to a commercial liquid fertilizer: 1 – poultry pellets (PP), 2 – PP + alfalfa meal (AM), 3 – soybean hydrolysate (SH), 4 – SH + AM, 5 – PP + SH, 6 – blood and feather meals + PP, 7 – frass, 8 – PP + frass, 9 – PP + shrimp meal, and 10 – conventional liquid fertilizer (CLF) in order to evaluate their impact on the growth and quality of six potted herbs (basil, coriander, mint, parsley, rosemary and thyme). The growing medium used was a mix of peat and wood fiber with a peat control treatment (11 – CLF control). Total nutrient composition was similar for all treatments.
After 42 days of cultivation, measurements showed the effect of fertilization treatments on plant height, photosynthetic performance (Chl, Fv/Fm, PIndex), fresh and dry biomass, biological activity (FDA), pH, EC, and substrate N levels.
For the studied herb species, the highest fresh and dry plant biomass were observed under the liquid fertilization followed by the 100% animal-based solid fertilizer treatments (PPFBM and PP), while the lowest values were obtained under the fertilization treatments containing soybean hydrolysate 9-1.5-7 (SH, PPSH and SHAM). Plant productivity was not related to the biological activity of the growing medium neither its N concentration.
The control peat growing media performed better than the peat-based growing media with the wood fiber.
The SH treatment reduced the SPAD index and Fv/Fm ratio of mint, while for basil the liquid fertilizer reduced the PI, Fv/Fm (except for PPAM and SH) and SPAD index (except for SH and PPSH) compared with solid fertilizer treatments.
Replacing 50% of the PP by SH reduced the PI and SPAD index of basil.
For the 6 studied herb species, our results invalidated our hypothesis that the requested plant nutrients can be provided to the growing media by a mix of solid animal- and plant-based fertilizers.
Further studies are then needed to investigate the possibility of combining solid organic fertilizers with a minimum of liquid fertilization to better meet the nutrient needs of herbs during their short growth cycle.

XXXI International Horticultural Congress (IHC2022): International Symposium on Agroecology and System Approach for Sustainable and Resilient Horticultural Production

A. Brégard, T.T.A. Nguyen, N. Zyromski, M. Dorais

growing media, organic amendments, organic greenhouse horticulture, basil, coriander, mint, parsley, rosemary, thyme, nitrogen, nutrients, protein hydrolysate

https://doi.org/10.17660/ActaHortic.2022.1355.47