STRUCTURAL STABILITY STATUS AS AFFECTED BY LONG-TERM CONTINUOUS MAIZEAND BLUEGRASS SOD TREATMENTS

The effect of long-term continuous fertilized and unfertilized corn an d bluegrass crops on the structural stability status of a clay loam so il was studied. Water-stable aggregates were measured with and without an ethanol pretreatment and before and after the extraction of unboun d lipids and after hydrophobic lipids were extracted with chloroform. Compared to corn, sod and wooded plots had three to four times more st able aggregates associated with the dispersive and dissolution action of water and two to three times more stable aggregates associated with slaking forces. The data also indicate that the stability of aggregat es associated with bound organic materials was affected by cropping hi story rather than fertilization. Although the unbound lipids varied si gnificantly between treatments, the unbound lipids were responsible fo r a similar amount of stable aggregates when compared against dispersi ve and dissolution action of water and slaking forces. The results ind icate that the mono- and diesters compounds had disappeared in the Apl layer of fertilized corn, whereas these compounds were still present under unfertilized corn, sod and wooded areas. From a practical viewpo int, the results suggest that under natural conditions, soil aggregate s (dry or wet) may be more affected by the dispersive and dissolution action of water than by slaking forces caused by air entrapment follow ing sudden rewetting.