Effect of living mulch on physiological and biochemical parameters of cherry leaves and fruits with organic growing technology

Abstract

In organic sweet cherry (Prunus avium L./Prunus mahaleb) orchard standard mechanical cultivation was compared with living mulch – spontaneous vegetation cover. Since 2013 the experimental orchard has been maintained with two different orchard floor management systems: standard mechanical cultivation (MC) – one discing at a 15 cm depth + manual weeding during the growing season was compared with living mulch (LM) – spontaneous vegetation cover. The natural vegetation of grasses was mowed 4 times during the growing season and the clippings were left on the ground for decomposition. Any other management was identical in each treatment. Synthetic fertilizers and chemical plant protection products were not used. It was established that total moisture content of the leaves was significantly reduced under LM (over 2 years) or did not differ significantly from MC (1 year). The water-retaining ability of the leaves did not differ significantly between LM and MC (2 years) or was higher in the conditions of LM (1 year). The total leaf area at the beginning of the study (1 year) was larger in MC conditions. In the following year, the difference between LM and MC was insignificant. In 2019, the total leaf area was significantly larger in the conditions of LM. An increase in the total leaf area under LM conditions led to a significant decrease in the specific surface density of the leaves, the accumulation of chlorophylls in them, and a decrease in the ratio of chlorophylls (a/b) due to an increase in the content of chlorophyll b (compared to the MC conditions). The difference in fruit size parameters, average weight of the fruits, total soluble solids, total sugars, titratable acidity, sugar-acid index were insignificant between LM and MC. Ascorbic acid and total anthocyanins content of sweet cherry fruit was significantly increased under LM conditions compared to MC. The results show that cherry trees gradually adapt to coexistence with natural herbs and, during stress, accumulate more physiologically active substances in the fruit. Key words: sweet cherry, organic orchard, living mulch, total leaf area, specific leaf density, chlorophylls, fruit size, ascorbic acid, anthocyanins.