Add lime or similar chemicals before/after planting non-woody plants: brackish/saline wetlands
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 3
Background information and definitions
This action involves adding chemicals – such as lime (CaO or Ca(OH)2), limestone (CaCO3), magnesium oxide (MgO), fly ash (residue from burning coal) and biochar (a type of charcoal) – to areas planted with marsh or swamp vegetation. These calcium and/or magnesium-rich chemicals may reduce acidity and modify nutrient availability (Weil & Brady 2016), potentially increasing plant survival or growth.
Related actions: Add lime or similar chemicals to wetlands, other than to complement planting.
Weil R.R. & Brady N.C. (2016) The Nature and Properties of Soils, Fifteenth Edition. Pearson, USA.
Supporting evidence from individual studies
A controlled study in 1980–1981 on reprofiled borrow pits in North Carolina, USA (Broome et al. 1982) found that liming had no significant effect on the biomass of planted smooth cordgrass Spartina alterniflora. Limed and unlimed plots supported statistically similar above-ground cordgrass biomass in seven of seven comparisons after one growing season (limed: 7–172 g/m2; unlimed: 6–100 g/m2) and in one of one comparisons after two growing seasons (limed: 2,380 g/m2; unlimed: 1,804 g/m2). The result was the same when lime was applied to fertilized or unfertilized plots, and at two different lime doses (see original paper). Methods: In June 1980, wild-harvested smooth cordgrass plants were planted into coastal land that had been reprofiled (to 6–43 cm above mean sea level; salinity <20 ppt) after excavation of sediment for construction. The site was dry during planting but rewetted after. Some plants were limed after planting (dolomitic limestone; 2,240–4,500 kg/ha) whilst others were not limed. The study does not clearly report the experimental design (including number of plants and plots). In October 1980 and 1981, living cordgrass was cut from 0.25-m2 quadrats then dried and weighed.Study and other actions tested
A replicated, paired, controlled, before-and-after study in 2011–2012 in two salt-contaminated bogs in New Brunswick, Canada (Emond et al. 2016) found that liming reduced the biomass of planted salt marsh vegetation. After one year, limed plots supported a lower above-ground biomass of planted vegetation (26 g/m2) than unlimed plots (42 g/m2). This result is not based on an assessment of statistical significance. Methods: In summer 2011, eighty 9-m2 plots were established (in four blocks of 20) on bare, salt-contaminated peat (0.5–1.4 ppt). Sixty-four of the plots were planted with vegetation (chaffy sedge, prairie cordgrass, or mixed salt marsh plant fragments). Half of the plots were limed (18 g in planting holes; increasing soil pH to 3.8). The other half were not (soil pH 3.5). Some limed and unlimed plots were also fertilized. In July 2012, vegetation was cut from a 250-cm2 quadrat in each plot, then dried and weighed.Study and other actions tested
A replicated, randomized, paired, controlled study in 2011–2012 in a greenhouse in New Brunswick, Canada (Emond et al. 2016) found that liming had no significant effect on seed germination rate of two salt marsh herbs, but reduced the height of transplants of one species and reduced the above-ground biomass of both. For both species, a statistically similar number of seeds germinated over two months in limed and unlimed pots (data not reported). After four months, chaffy sedge Carex paleacea transplants were shorter in limed than unlimed pots, whilst prairie cordgrass Spartina pectinata height did not significantly differ between limed and unlimed plots (data not reported). However, above-ground biomass of transplants was significantly lower for limed than unlimed chaffy sedge (high lime: 30; low lime: 50; no lime: 87 g/m2) and significantly lower for heavily limed than unlimed prairie cordgrass (high lime: 31; low lime: 54; no lime: 69 g/m2). Methods: In October 2011, five pots of salt-contaminated peat were planted per treatment: sedge or cordgrass, with no lime (pH 3.8), low lime (2.5 kg/m3; pH 4.7) or high lime (7.5 kg/m3; pH 6.2). Pots were kept in five groups, each containing one pot of each treatment. Seeds and transplants were kept in the dark at 4°C for three months before planting. Seeds were also kept in brackish water for two weeks before sowing. Seed germination was recorded after two months. After four months, all transplants were measured, cut, dried and weighed.Study and other actions tested