Photosynthesis and Leaf Traits of Tree Species Influenced by Green Manure Associated with Soil Treatments

The use of green manure (GM) associated with soil decompaction treatments has shown to be an alternative to improve soil attributes. This study associated the use of GM with tree species nitrogen-fixing and non-nitrogen-fixing (N-fixing and non-N-fixing, respectively), hypothesizing that non-N-fixing species are more beneficial by GM. The experiment was carried out in a disabled clay extraction deposit. Previously, chemical analysis and mechanical resistance to soil penetration was registered in order to characterize the initial soil properties of the experimental site. The soil treatments were scarification (SCA), scarification + harrowing (SCAH), and subsoiling + harrowing (SUBH) with presence/absence of GM (+GM and -GM, respectively) and four native tree species, N-fixing (Dalbergia ecastophyllum (L.) Taub., Inga laurina (Sw.) Willd., and non-N-fixing (Psidium cattleianum Sabine and Schinus terebinthifolius Raddi), were planted. Growth and leaf traits were measured after 6 and 12 months. The response patterns of leaf attributes were well defined in the non-N-fixing species. Over time, GM increases the level of chlorophyll (Chl) in N-fixing species and, consequently, improves the maximum quantum yield for photosystem II (PSII) primary photochemistry (phi P-o), quantum yield for PSII electron transport (phi E-o), the number of active reaction centers (RC/CSo), and the performance index (PI/abs). GM increased these same photochemical parameters in non-N-fixing species after 12 months. The samples cultivated in the SCA and SUBH treatments showed a better performance. The species responded in different ways to GM, which improved the leaf traits in non-N-fixing species. GM improved the leaf traits of N-fixing species. The positive effect of GM over time give us a good alternative for fertilization in revegetation areas. Furthermore, our findings shown that the subsoiling promotes the highest soil decompaction, which associated with GM, can be efficiently used in projects of revegetation of degraded areas.