Effect of fertilizer managements on soil quality and productivity in tea farms

Maintenance of soil quality through optimal fertility managements is important for agricultural productivity. A field experiment was conducted in the period of 2006–2011 in a subtropical tea (Camellia sinensis cv. Huangguanyin), to provide more accurate assessment of soil organic carbon (SOC) fractions, physico-chemical characteristics, microbial properties, enzyme activities and tea yields. The experiment included six treatments: non-fertilizers (CK), mineral fertilizers (NPK), half-mineral fertilizers plus half-poultry manures (1/2 NPKOM), poultry manures (OM), half-mineral fertilizers plus half-poultry manures plus legume residue (1/2 NPKOM + L), mineral fertilizers plus legume residue (NPKL). Results indicated that the heavy fraction of organic carbon (HFOC) was highest in the all treatments, followed by the light fraction of organic C (LFOC), whilst lowest in permanganate oxidizable organic C (KMnO₄-C). In addition, OM and 1/2 NPKOM + L treatments had higher contents of HFOC, LFOC, microbial biomass C (MBC), KMnO₄-C, particulate organic C (POC) and dissolved organic C (DOC), larger amounts of bacterial, Gram-positive bacterial, actinobacterial and fungal PLFAs, stronger activities of phosphatase, protease and urease, higher levels of soil nutrients, including SOC and total N (TN), and higher contents of silt and clay particles. In contrast, NPK treatment resulted in lower levels of these SOC fractions and smaller amounts of Gram-positive bacterial PLFAs. Additionally, OM, 1/2 NPKOM + L, NPKL, 1/2 NPKOM and NPK treatments significantly (P < 0.05) increased tea yields by 105.31%, 101.74%, 91.17%, 82.43%, and 60.25%, respectively, compared to CK. Moreover, tea yields also showed a close correlation with these soil quality indices. The results demonstrated that OM and 1/2 NPKOM + L treatments could be recommended as the better fertilization practices for tea soils in southeast China.