Intercropping improves soil nutrient availability, soil enzyme activity and tea quantity and quality

Intercropping has long been an important agroforestry technique that has been applied worldwide. While intercropping increases soil carbon and nitrogen, an elucidation of its effects on the activities of soil enzymes and product quantity and quality remains elusive. Here we examined the effects of the intercropping of chestnut trees (Castanea mollissima Blume) in tea (Camellia sinensis L.) plantations on the seasonal dynamics of soil nutrients, soil enzyme activities, and tea quantity and quality in a temperate region in China. We collected soil samples from 0 to 20 cm (topsoil) and 20-40 cm (subsoil) depths in May, July, September, and November 2011, and examined the tea quantity and quality from bud samples collected in late April to early May 2011. We found that the effects of intercropping on soil nutrients and enzyme activities were strongly dependent on the sampling date. Soil pH and organic matter, nitrogen, phosphorus, and potassium content, as well as soil enzyme activities (catalase, urease, dehydrogenase, invertase, and polyphenol oxidase) increased on average with intercropping; however, the effects were more pronounced in the spring and early summer than late summer and fall for most nutrient and enzyme activities. Intercropping also increased the tea length and weight and tea quality by reducing the amino acid and catechin content, while increasing theanine and caffeine. Our analysis suggests that chestnut tree shading, enhanced soil nutrient availability, and the augmented activity of soil enzymes, facilitated the increase of tea quantity and the improvement of tea quality. Our results indicate that intercropping chestnut trees in tea plantations as a diversity treatment improves resource availability, ecosystem function, and product quantity and quality in the agroforestry ecosystems.