Recementation of crushed ortstein by leaf extracts, selected organic acids, and a soil amendment

Ortstein (a soil layer cemented by organic carbon, aluminum, and iron; commonly referred to as hardpan) inhibits blueberry (Vaccinum corymbosum) growth. Growers have used deep tillage to break up ortstein, however, the benefits appear to have only been temporary. This study was conducted to determine if 1) crushed ortstein will recement, 2) depodzolizing species will reduce recementation, and 3) a commercially available soil amendment, Super Symbex 4X, will reduce recementation of crushed ortstein. Ortstein from Saugatuck sand (sandy, mixed, mesic Typic Durorthod) was crushed and passed through a 2-mm (0.079-inch) sieve and used in column experiments to assess recementation. Pieces of uncrushed ortstein were added to some columns to evaluate changes in cementation. Aqueous blueberry leaf extracts were added daily to columns for 1.5, 3, 6, and 12 weeks. Duplicate columns were treated with Super Symbex 4X and distilled water. Aqueous leaf extracts from bent grass (Agrostis perennans) and fescue (Festuca rubra) were added for 12 weeks. Solutions of protocatechuic acid (PCA), rho-hydroxybenzoic acid (rhoHBA), catechol and vanillic acid (VA) were added to crushed ortstein and allowed to stand for 5 weeks. Super Symbex 4X was added to the crushed ortstein and mixed with the organic acids at the recommended rate. Extensive recementation (96% aggregation) of crushed ortstein occurred after only 1.5 weeks of treatment with green blueberry leaf extract in the column experiments. Bent grass and fescue leaf extracts caused less and weaker recementation than blueberry. Addition of Super Symbex 4X to ortstein pieces did not produce an increase in size as did blueberry, bent grass and fescue leaf extracts. PCA, rhoHBA and VA had high levels of recementation. The water control and catechol did not show high levels of recementation. Addition of Super Symbex 4X to the organic acid and crushed ortstein decreased recementation with the strongly recementing organic acids, PCA, rhoHBA and VA. Super Symbex 4X appears to have potential to retard recementing of crushed or broken ortstein. Bent grass and fescue cover crops may not retard recementation of crushed ortstein.