Soil Microbiological and Biochemical Properties as Affected by Different Long-Term Banana-Based Rotations in the Tropics

Abstract

Soil microbiological and biochemical properties under various field crop rotations such as grains, pastures and vegetables have been studied intensively under short–term period. However, there is limited information about the influence of banana–based rotations on soil organic C, total N (TN), microbial biomasses and enzyme activities under long–term crop rotations. A field experiment arranged in a randomized complete block design with three replicates was carried out at the Wanzhong Farm in Ledong (18° 37′–18°38′ N, 108°46′–108°48′ E), Hainan Province, China, to compare the responses of these soil parameters to long–term (10–year) banana (Musa paradisiaca)–pineapple (Ananas) rotation (AB), banana–papaya (Carica) rotation (BB) and banana monoculture (CK) in a conventional tillage system in the Hainan Island. Soil pH, total organic C (TOC), dissolved organic C (DOC), TN, total P (TP) and available P (AP) were found to be significantly higher (P < 0.01) in AB and BB than CK at 0–30 cm soil depth. Microbial biomass C (MBC) and N (MBN) were observed 18.0%–35.2% higher in AB and 8.6%–40.5% higher in BB than CK at 0–30 cm. The activities of urease (UA), invertase (IA), dehydrogenase (DA) and acid phosphatase (APA) showed a mean of 21.5%–59.6% increase in AB and 26.7%–66.1% increase in BB compared with CK at 0–30 cm. Higher pH, TOC and DOC at 0–10 and 10–20 cm than at 20–30 cm were obtained despite of the rotations. Soil MBC and MBN and activities of UA, IA and DA decreased markedly (P < 0.01) with increasing soil depth in the different rotation soils as well as the monoculture soil. In general, soil microbial biomass and enzymatic activities were more sensitive to changes in banana–based rotations than soil chemical properties, and consequently they were well–established as early indicators of changes due to crop rotations in the tropics.