Effects of artificial grass on improving soil quality and agronomic traits of chestnuts in a Castanea henryi orchard

This research evaluated the benefits of green manure for soil quality recovery, compared with those of traditional clear tillage and chemical herbicide application methods, in a Castanea henryi orchard in the typical red soil hill region of Fujian. A randomized block design was adopted, with each block having an area of 0.3 ~ 0.5 ha. The experimental site was cleared of natural weeds, trialed with two grass species (Vulpia myuros, VM; Lolium perenne, LP) and three legume species (Vicia villosa, VV; Astragalus simicus, AS; Chamaecrista rotundifolia, CR) as green manure crops, and treated with glyphosate spraying (GS) and clearing tillage treatments (CT), with three replicates of each. The physical and chemical properties, microbial biomass carbon and nitrogen of soils, and agronomic traits of chestnut in the five green mature and the two control treatments in the C. henryi orchard were analyzed. It was found that: 1) Compared with the CT and GS treatments, the soil quality of all grass cultivation treatments was significantly (P < 0.05) improved. In 0 − 10 cm and 10 − 20 cm soil layers, the contents of alkali-hydrolyzable nitrogen and microbial biomass carbon (MBC) of the VM treatment were the highest. The contents of alkali-hydrolyzable nitrogen were 74.14 and 54.87 mg·kg⁻¹; the contents of microbial biomass carbon (MBC) were 1.42 and 1.15 g·kg⁻¹. The contents of exchangeable calcium and magnesium of the LP treatment were the highest. The contents of exchangeable calcium were 128 and 93.39 mg·kg⁻¹; the contents of magnesium were 114.95 and 66.28 mg·kg⁻¹, respectively. The VV treatment had the highest microbial biomass nitrogen (MBN) content, which were 47.68 and 30.89 mg·kg⁻¹, respectively. 2) Compared with that of the CT and GS treatments, the contents of starch, soluble sugar, protein, fat, phosphorus, potassium, calcium, and magnesium in the fruits of green manure crops were all increased. The transverse and longitudinal diameters of chestnut in the VM treatment were 26.6 mm and 33.1 mm, the weight of a single fruit was 13.54 g, which was significantly higher than that of CT and GS treatments, and the per unit yield of chestnut was higher than that of CT and GS treatments, which were 59.44% and 111.25%, respectively. 3) Mantel test and random forest analysis showed that MBN, soil hydrolyzed nitrogen, and exchangeable magnesium were not only the key factors affecting the agronomic traits of chestnut fruit, but also the most important factors affecting the yield of chestnut. In conclusion, grass cultivation can improve the soil quality of C. henryi garden, improve the agronomic characteristics of C. henryi fruit, and increase income for chestnut farmers. In this research, the VM treatment had the best performance and could be the best choice for ground management of C. henryi orchards in southern China.