Recementation of Crushed Ortstein by Blueberry Leaf Extract

ferred to as hardpan, varies in occurrence and thickness within fields. Blueberry growers in southwest Michigan Cementing of sand grains by organo-Al and organo-Fe complexes have experienced diminished growth in some blueberry is thought to be a gradual process and takes at least a few thousand years. The resulting ortstein inhibits root penetration. Blueberries plantings. This occurs in isolated regions of fields in (Vaccinium corymbosum L.) in isolated regions of blueberry fields which the remainder of the plants have reached full size in Michigan experience reduced growth that has been attributed to and production. Ortstein has been reported to reduce the presence of ortstein. Growers have used deep tillage to break up blueberry growth (Lilly et al., 1975) by acting as a barrier ortstein in these regions with only temporary benefits. This study was to water percolation and root penetration. Growers conducted to determine (i) if crushed ortstein would recement upon have attempted to break up the ortstein with deep tillage exposure to aqueous blueberry leaf extract, (ii) rate of recementation, before replanting blueberries. This was thought to be a (iii) the degree of recementation, (iv) the strength of recemented permanent solution, but some growers now believe that materials, and (v) the nature of the cementing agents. Crushed ortstein the broken ortstein has recemented. from Saugatuck sand (sandy, mixed, mesic, shallow, ortstein Typic The objectives of this study were to determine (i) if Durorthod) was passed through a 2-mm sieve and used in column experiments to assess recementation. Aqueous blueberry leaf extracts crushed ortstein would recement, (ii) the rate of recewere added daily to crushed ortstein columns for 1.5-, 3-, 6-, and mentation, (iii) the degree of recementation, (iv) the 12-wk periods. Green and brown blueberry leaves were used to pre- strength of recemented materials, and (v) the nature of pare extracts and compare the effect of leaf age on recementation. the cementing agents. The degree and strength of aggregation were assessed by determining the amount of treated ortstein remaining on a 2-mm sieve, and by MATERIALS AND METHODS tensile strength analysis of aggregated material. Extensive recementation (96% aggregation) of crushed ortstein occurred after 1.5 wks. Ortstein was collected from a blueberry field near West Cementation was highest in the upper layers and decreased with depth Olive, MI (8608 W, 4254 N). A trench was dug by hand in in the column. Degree and strength of cementation tended to increase Saugatuck sand that has a Bhsm (ortstein) horizon that begins with duration of the experiment. Green leaf extract caused more at about 20 to 50 cm and generally exceeds 25 cm in thickness. recementation of crushed ortstein than brown leaf extract. Recemen- Cemented Bhsm horizon material was extracted from the sidetation is thought to result from relocation of Al by organic compounds, walls. The material was then air-dried, crushed, passed through originating from leaf extracts, to contact points between sand grains. a 2-mm sieve, and mixed thoroughly. This crushing process was more intensive than the breaking of the ortstein by growers during the deep tillage process. The original ortstein had