Glacially abraded rock flour from Greenland: Potential for macronutrient supply to plants

Abstract

Rock flour (RF) is a fine‐grained material produced naturally by glacial movement and resulting bedrock abrasion. In Greenland fluvial transported RF from the inland ice sheet sediments in riverbeds and marine outflows. This fine‐sized RF (50% < 9.8 µm) has a high reactivity and may therefore potentially be used to rejuvenate nutrient poor soils and provide nutrients to plants. The aim of this study was to evaluate the ability of a RF from Greenland to supply P, K, Mg, and S to plants. A double‐pot system was used, in which ryegrass (Lolium perenne L.) could take up nutrients from both a hydroponic solution and a soil‐compartment with or without RF amendment; a soil mixture or pure sand was used in the soil‐compartment to estimate RF‐soil interaction effects. Omission of single nutrients from the hydroponic solution allowed assessment of which nutrients the RF in the soil‐compartment was able to supply. Ryegrass biomass was harvested four times during 62 days. We found that RF could supply K continuously to plants grown in soil or sand, but insufficient to fully circumvent K deficiency. During 62 days 5.8% and 4.3% of the applied K from RF was accumulated in the aboveground plant tissue in soil and sand, respectively. Mg was supplied from RF to plants in sand, but no significant effects were observed in soil, possibly due to background soil Mg availability. The amounts of P and S supplied to plants were insignificant. These results indicate the potential of Greenland RF to act as a slow release K and Mg fertilizer.

Glacial Rock Flour as Soil Amendment in Subarctic Farming in South Greenland

“…The experiment showed that GRF-application had no significant impact on the biomass production. This is consistent with pot trial experiments with ryegrass [15]. Little effect was found on above and below ground biomass using glacial rock flour from Greenland, even though the applied amount of GRF was 5% of the soil weight (corresponding to an application rate of 30 t GRF ha −1 ).…”

“…The δ 15 N values in the AGB reflected the proportion of 15 N vs. 14 N in the plant tissue (Figure 6c). As seen, T3 and T4 tended to have a lower 15 N abundance than T1 and T2, though with only T3 being significantly different from both T1 and T2. The δ 13 C values (Figure 6d) represented the ratio of 13 C/ 12 C in the AGB.…”

“…For the analysis, 2-3 mg of highly homogenized plant material and approximately 20 mg of milled soil and GRF were weighed into tin cups and combusted at 1700 • C. The produced gasses were then measured in an elemental analyzer (Flash 2000, Thermo Scientific, Waltham, MA, USA). An isotope mass spectrometer (Thermo Delta V, Thermo Scientific) simultaneously measured the ratio of 15 N/ 14 N and 13 C/ 12 C, respectively. Prior to sample analysis, the elemental analyzer was calibrated with standards of known C and N composition (peach leaves for plant material and soil standards from Elemental Microanalysis, Okehampton, UK, for soil samples).…”

“…Consequently, contrasting findings have been reported. Several studies have observed a substantial supply of K, Ca, and Mg to plants from rock powder, while some have also exhibited a liming effect [12][13][14][15][16]. Most studies, however, have only shown negligible effects from experiments with rock powder or even negative effects on yields [17][18][19].…”

“…Most studies, however, have only shown negligible effects from experiments with rock powder or even negative effects on yields [17][18][19]. Not surprisingly, glacial rock flour (GRF) cannot replace the need for applying regular NPK fertilizers and lime to keep agricultural yields high [15,[20][21][22]. One form of rock powder that has not received much attention is so-called glacial rock flour produced by glaciers eroding the underlying bedrock as they move over terrain.…”