Lime movement through highly weathered soil profiles

Abstract

Applying lime is a fundamental practice for abating acidity in highly weathered soil, but better management strategies for no-till systems are needed to prevent surface pH elevation with little to no subsurface effects. This study was conducted to quantify chemical changes within the soil profile in response to lime and straw applications under both greenhouse and field conditions. Four controlled environment experiments (soil columns) and one field study were conducted on soils classified as Rhodic Hapludox and Rhodic Eutrodox. The soil column experiments evaluated four lime rates (0, 3.9, 7.8, or 15.6 Mg ha −1 ) and four straw rates (0, 4, 12 and 16 Mg ha −1 ) either individually or in combination. Lime treatments were surface applied or incorporated in the top 5-cm, while straw treatments were incorporated in the top 5-cm. In the field, lime rates of 0, 8.3 and 33.2 Mg ha −1 were incorporated into the 0 to 10-cm depth in both a soybean [Glycine max] monoculture and diversified cropping system with white oat (Avena sativa), soybean, black oats (Avena strigosa), corn (Zea mays) and wheat (Triticum aestivum). Both field and soil columns studies showed minimal lime movement into the soil profile with chemical changes being limited to 2.5-cm below where it was applied or incorporated regardless of cropping system. Surface application of high lime rates promoted chemical stratification resulting in dramatic increases in topsoil pH and exchangeable Ca and Mg levels with minimal mitigation of subsurface soil acidity. Other studies also suggest that lime movement into the soil profile can vary depending on the experimental condition. Therefore, additional investigations across a wider geographic area, greater range of weather and climatic conditions, methods and rates of lime application need to be conducted to improve lime recommendation for high weathered soil managed using no-till practices.

Ameliorating soil acidity–reduced growth of rigid ryegrass (Lolium rigidum) in wheat

“…As a result, aluminum concentration was only high in the B1 horizon of the non-incorporated pots, where pH remained consistently low (Table 1). These results supports the findings of Nunes et al (2019) that incorporation is required to change soil pH at depth. Australian soils can be highly acidic to depths of 40 to 100 cm, naturally or due to agronomic practices (Isbell 2016).…”

“…An international review of liming experiments indicated that the application method of lime (surface, plow, subsoiling) did not affect the change in soil pH achieved through liming, although the review did not specifically consider varying soil depths (Li et al 2019). Rainfall can be low in Australian agricultural areas, and both field and pot studies indicate that in weathered soils, lime will not move farther than 2.5 cm through the soil profile without incorporation (Nunes et al 2019). Lime incorporation through cultivation will bury weed seed, changing the emergence patterns of the weed in subsequent seasons (Chauhan et al 2006a).…”

Slow movement of alkali from surface-applied lime warrants the introduction of strategic tillage for rapid amelioration of subsurface acidity in south-western Australia

“…With more-precise sampling from the soil pit face, the increase in soil pH in our study was restricted to the top 0.15 m depth ( Fig. 2e and f), similar to that measured by Nunes et al (2019). Unlimed control plots were acidified at all sampling depths at 0.010 pH units per year.…”

“…There was no evidence of increasing soil solution pH below 0.20 m depth, contrary to the evidence reported by Whitten (2002) in which a much higher watering regime was applied compared with our experiment. Our experiment suggests that the potential to treat subsurface soil acidity by surface incorporation of high rates (3-6 Mg ha -1 ) of lime is limited and likely only to be effective in less-acidic topsoil (pH > 5) in higher rainfall regions, but the rate of improvement in pH is slow as measured by Nunes et al (2019), and slower than that measured by Whitten (2002). This prompted us to test whether strategic deep tillage is a better solution for deep incorporation of lime for rapid amelioration of subsurface soil acidity.…”

“…More recent literature suggests that, under both field and controlled environment conditions, the significant increase in soil pH is restricted to the few centimetres below the liming depth (Li et al 2019;Nunes et al 2019). Some reports indicate that the rate of the vertical movement of alkalinity from lime is affected by soil characteristics (for example, initial soil pH, soil organic carbon (OC) and soil texture), climate, time, application rate and lime quality parameters (Conyers and Scott 1989;Whitten 2002;Caires et al 2005).…”