Lumbricus terrestris and no-till: Infiltration processes and soil physiochemical properties affecting their survival
Abstract
With the growing popularity of conservation tillage, there is interest in physical, chemical, and biological changes soils undergo during their conversion from conventional to conservation tillage systems. One area which has only recently been investigated is the ecology and effects of L. terrestris ("night crawlers") in these systems. Fields with and without L. terrestris were examined by analyzing soil physiochemical properties, farming practices, and drainage indexes in an effort to explain why some fields have not been recolonized after conventional farming processes had ceased. Results indicate the lack of populations of L. terrestris could be due to a variety of factors. One is the lack of sufficient source perimeter to the area of the field. Another is nutrient deficiencies. Magnesium, potassium, pH, % calcium and % magnesium saturation of the CEC were significantly lower in fields devoid of L. terrestris than in fields with them. A series of fields which were devoid of L. terrestris were then seeded in the fall and spring of 1994. First, the effects of L. terrestris on infiltration rates was measured. Sprinkler infiltration tests were performed on 1.2 $\rm m\sp2$ quadrats where L. terrestris has been seeded and adjacent unseeded quadrats. Results showed significant increases in infiltration rates, provided that the population was sufficiently high. Next, a comparison of methods (ponded vs. sprinkler) for determining infiltration rates was made. Data indicated that at the end of 55 minutes, there were no significant differences between methods or between worm treatments for final infiltration rates and cumulative infiltrated volume. Probably the populations were not high enough for a difference in worm treatments to be seen under this short infiltration period. However, at the end of two hours of ponding, there were significant increases in infiltration rates in seeded quadrats. Water retention curves were shifted slightly in the seeded quadrats, with the van Genuchten alpha parameter being significantly different. As populations increase over time differences in infiltration methods may become apparent.
Degree
Ph.D.
Advisors
Kladivko, Purdue University.
Subject Area
Agronomy|Ecology|Soil sciences
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