Influence of zoocompost and harvesting time on honeysuckle leaves quality

Abstract

Honeysuckle (Lonicera caerulea L.) is characterized by a large composition of biologically active compounds: rich in anthocyanins and phenolic compounds. Although much research has been done on berries, there is still a lack of information on honeysuckle cultivation, fertilization, and other parts of the plant, such as leaves. Therefore, the the aim of this study was to evaluate the effects of zoocompost and harvesting time on honeysuckle leaves quality. The field experiment with the honeysuckle cultivar 'Indigo Yum' was carried out in 2024 in Alytus district (Lithuania) on the farm of edible honeysuckle. The bushes were planted in 2014. The experimental plots were arranged in a randomised design with four replicates for each treatment. The honeysuckle bushes were fertilized with black soldier fly (Hermetia illucens L.) larvae zoocompost at the beginning of the growing season at an application rate of 0 (unfertilised – control treatment), 1000, 1500, and 2000 kg ha-1 (four variants), respectively. The leaves of 'Indigo Yum' were harvested at different time: 1st harvest (27 April), 2nd harvest (40 days after 1st harvest), 3rd harvest (80 days after 1st harvest). During the study, the freeze-dried leafe samples were analyzed for chlorophyll, total carotenoids, total phenolic and total flavonoid compounds, and antioxidant activity. The results showed that the highest content of total chlorophyll was found in the 1st harvest leaves of 'Indigo Yum' with application of 1000 kg ha-1 zoocompost. The maximum contents of total carotenoids were reached in the 1st harvest leaves with application of 1500 kg ha-1. The highest total phenolic content was found in the 2nd harvest leaves with application of 2000 kg ha-1. The maximum content of total flavanoid were research in the 2nd harvest leaves with application of 1500 kg ha-1. The highest level of antioxidant activity was found in 3rd harvest leaves with application of 1500 kg ha-1 zoocompost. Overall, an application of zoocompost can be suggested to farmers as an alternative and environmentally friendly strategy to improve the quality of honeysuckle leaves. Furthermore, it was found that leaf harvesting time had a significant impact on their quality parameters.