Knezek, B.D., L.W. Jacobs, and B.A. Bricker
Presented at the Campus Symposium (2001-04-19 )
This study was located at the MSU W. K. Kellogg Biological Station at the LTER site (established by the U. S. National Science Foundation). The project goal of maintaining soil pH and soil extractable P, K, Ca, Mg, and micronutrient levels within parameters acceptable for normal production under various cropping strategies was generally achieved. The mean soil pH value (5.6) for the unmanaged, untilled site (TMT 8) is significantly lower than the mean soil pH value (6.2) observed in treatments 1 through 7. The lower pH on the midsuccessional never tilled site (TMT 8) appears to be due to Ca and Mg depletion in the soil surface after years of weathering. The soil extractable levels of phosphorus, potassium, calcium, and magnesium are significantly lower in treatment 8 when compared to treatments 1-3 that had received fertilizer during the eight years of the experiment. These results indicate that differential soil extractable P, K, Ca, and Mg were not significantly different in treatments maintained according to best conventional fertilizer practices. The area under continuous alfalfa (TMT 6) did tend to have lower available nutrient levels than other agronomic treatments. The fast growing Populus clone (TMT 5) had the least impact on soil surface pH, P, and K over the eight years of the experiment, presumably due to the deeper rooted nature of the crop. Significantly greater amounts of 0.1 N HCl and 0.005 N DTPA soil extractable Fe and Mn were present in treatment 8 as compared to treatments 1 through 7 possibly due to the lower soil pH present in treatment 8. Soil test data confirm that establishing differential soil fertility levels when the beginning soil nutrient levels are high is a long term process regardless of cropping sequence.
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