The reclamation of acidic colliery spoil. IV. The effects of limestone particle size and depth of incorporation

Published source details Costigan P.A., Bradshaw A.D. & Gemmell R.P. (1984) The reclamation of acidic colliery spoil. IV. The effects of limestone particle size and depth of incorporation. Journal of Applied Ecology, 21, 377-385.
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Summary

Acidic colliery spoil may require application of large amounts of limestone for long-term control of acidity to enable vegetation to establish and grow successfully. However, addition of very fine agricultural powdered limestone that is normally used may have disadvantages because of rapid dissolution. Therefore, one solution may be to apply limestone as coarser particles. The effects of three different grades of limestone (up to 3 mm diameter) on perennial rye-grass Lolium perenne, white clover Trifolium repens and bird’s-foot trefoil Lotus corniculatus growth was investigated in a glasshouse experiment.

Spoil collection and treatments: Spoil (<2 cm diameter, pH 3.2) was collected from Higher Folds colliery (National Grid ref. SD 684005), Greater Manchester, northwest England. This was enriched with 1% w/w ground industrial pyrite (<0.5 mm) to ensure a high rate of pyrite oxidation (thus acidification). The spoil was fertilized (125 kg/ha N as ammonium nitrate, 150 kg/ha P as superphosphate and 50 kg/ha K as potassium sulphate) and a factorial randomized block design of two limestone rates (20 and 100 t/ha), three limestone particle sizes: fine (an agricultural powdered limestone: 60% < 0.3 mm), medium (0.5-2 mm diameter) and coarse (2-3 mm diameter); and four types of vegetation (no plants, L.perenne, T.repens and L.corniculatus (four replicates) was implemented. Seed wa sown at 200 kg/ha with appropriate Rhizobium innoculation for the two legumes.

Plant growth and harvesting: Spoil and seeds were placed in polypropylene plant pots (14 cm diameter). The pots were kept in a glasshouse and watered with deionized water daily as required. Shoots were harvested after 13 weeks and regrowth was harvested at 19, 33 and 59 weeks after sowing. At every harvest apart from the first, 40 kg/ha N was applied as ammonium nitrate. Surface pH was measured after 42 weeks.

Plant growth: Shoot dry weights at the first harvest showed that Lolium and Lotus behaved similarly with little effect of limestone grade at 100 t/ha, but growth was much less with coarse than with fine or medium limestone at 20 t/ha. Trifolium growth was also reduced at 20 t/ha with coarse limestone but growth was much greater at 100 t/ha with coarser limestone than with the fine grade. At later harvests, the coarse limestone slowly became more effective and by 59 weeks limestone grade had no significant effect on growth.

Spoil pH: The surface spoil pH at 42 weeks showed a large and significant effect of limestone application rate and grade. Average pH values at 20 t/ha and 100 t/ha limestone application rates were - no plants: 5.7, 6.7; L.perenne: 4.8, 6.7; T.repens: 4.8 6.5; L.corniculatus: 3.8, 6.6.

Conclusions: In this experiment, later harvests indicated that the coarse limestone slowly became more effective, presumably as soil pH became more amenable (less acidic) to plant growth. Spoil pH was affected a little by plant species, this being attributed to differences in transpiration rates affecting spoil aeration.

Note: The compilation and addition of this summary was funded by the Journal of Applied Ecology (BES). If using or referring to this published study, please read and quote the original paper, this can be viewed at:http://links.jstor.org/sici?sici=0021-8901%28198404%2921%3A1%3C377%3ATROACS%3E2.0.CO%3B2-1