Effects of long-term tea (Camellia sinensis) cultivation on the earthworm populations in northern Iran

Abstract

The earthworms’ abundance is usually one of the main indicators of healthy and productive soils. However, agricultural management practices affect the earthworm population and activities. Although there is a lot of information that shows the relation between land use/land cover change and earthworms activity, very little is known about these effects under tea cultivation. Thus the current study was done to determine the effects of long-term tea cultivation on the earthworm’s population and abundance in the tea plantations of Iran to distinguish effects of these practices on soil properties concerning earthworms. Hence, 58 locations of tea cultivations were randomly selected in Guilan and Mazandaran province. Earthworm were sampled by manually excavating and sorting four 30×30 cm pits by 30 cm deep in each location. Earthworms were enumerated in the field and taken to the lab for identification. Once identified, the earthworms will dry in the oven at 60oC for 48h and the dry weight registers. Some physicochemical properties of the mineral soils were determined in the laboratory. The finding indicated that the earthworms were only observed in the two from 58 locations: Bazkiagorab (Lahijan) and Shekarposhteh (Tonekabon). Three species as Perelia kaznakovi, Aporrectodea trapezoides, and Dendrobaena veneta were recorded from Bazkiagorab but only P. kaznakovi was identified in Shekarposhteh. The total population of all identified earthworms was 22 and 3 m-2 in the Bazkiagorab and Shekarposhteh, respectively. Results of the physicochemical analysis showed that 35% and 51% of the soils had a pH less than4.5 and organic carbon less than2%, respectively. Available phosphorus and potassium in 80% and 65% of the soils were less than 25 and 150 mg/kg, respectively. It can be concluded that monoculture and long-term tea cultivations had a negative effect on the earthworm population, in addition, it has strongly acidified the soil. It is recommended that native nitrogen-fixing trees mixed planted with tea, and more attention should be paid to nutrient Best Management Practices in tea plantations.