4.3 Strategy for agro-ecological reclamation of post-tin mining
areas
Evaluation of soil characteristics showed the current post-tin mining
areas have many severe constraints for crop growth and environmental
reclamation. Major constraints included sandy soil texture, the absence
or limited weatherable minerals (potential native nutrient sources), the
dominance of quartz mineral in tailings, the low water holding capacity,
the extreme low in soil organic matter and all nutrients, and nutrient
susceptible to leaching. Reclamation of soil capability to retain
nutrients and water was prerequisite. We proposed the strategic approach
in the view of long-term investment in agroecological reclamation as
follows: (i) levelling measures of on-site mounds resulted from
refused material dumping; (ii) building up soil organic matter
content (SOM) of sand tailing using green manure or compost to increase
soil organic C, supply various nutrients, promote microbial activities
and aggregate formation, reduce soil temperature, and increase soil
ability to hold water and nutrients; (iii) establishing a
special cultivation technique. Direct planting on soil tailings with
sandy texture dominated by quartz minerals is unlikely to allow crop
growth as shown in Fig.3a. Hence, the “pot planting point” technique
could be introduced to overcome the unfavourable conditions for crop
development. The technique is experimentally being tested in the field
and is still collecting more data (Fig.3c). Crop performance using pot
planting point technique showed rigorous growth of Paspalum grass
(Paspalum atratum ) (Fig. 3d) and various legumes, namely
Gliricidia (Gliricidia sepium , Jacq.) (Fig.3b, background),
Sesbania (Sesbania grandifora (L) (Fig.3b, front), Indigofera
(Indigofera zollingeriana ) (Fig. 3e), Stylosanthes
(Stylosanthes quianensis ) (Fig. 3f) and Lab lab (Lab lab
purpureus ) (Fig.3g). This technique is highly promising to restore soil
productivity and ecological recovery in post tin mining areas; and(iv) complete fertilizer application and selection of crops
with an ability to fix nutrient from the atmosphere. The suggested
adaptive legumes with nodules on roots to fix atmospheric N are
Indigofera (Figure S3a) and Lab lab (Figure S3b).