Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Agricultural and Biosystems Engineering

First Advisor

Ramesh Kanwar

Second Advisor

Stewart Melvin


Data were collected from subsurface drains on 36, 0.4-ha plots at Iowa State University's Northeast Research Farm near Nashua, IA to determine crop and tillage management effects on water flow and nitrate-N loss through subsurface drains. From 1990 to 1992, four tillage systems (chisel plow, moldboard plow, ridge till and no-till) were used with two crop rotations (continuous corn (Zea mays L.) and corn-soybean (Glycine max L. (Herr.)) rotation) and a single-spring fertilizer application. From 1993 to 1995, tillage systems were reduced to chisel plow and no-till, while fertilizer management changed to include single-spring fertilizer, spring-summer split fertilizer and fall manure application;The amount of nitrate-N lost in subsurface drainage was influenced more by subsurface drainage volume than nitrate-N concentration in drain effluent. Tillage had minimal effects on drainage volume, although no-till plots showed greater preferential flow than chisel plow plots. Significant differences in drain flow only occurred under continuous corn between 1990 and 1992, when the no-till system had higher drain flow than moldboard plow;Tillage affected nitrate-N concentrations in drain effluent during 1990 to 1992. Moldboard plow plots had higher concentrations than no-till plots possibly because of differences in bypass flow, denitrification and mineralization. Nitrate-N concentrations were not influenced by tillage after management systems were changed. However, plots where continuous corn had been grown for 15 yr had higher drain flows and nitrate-N losses in 1993 than where corn was planted into plots that had been rotated with soybean;Nitrate-N concentrations and losses were always higher with continuous corn than with corn-soybean rotation. Corn yields with split fertilizer applications were as high or higher than yields from single application treatments, but nitrate-N losses were essentially the same. Swine manure was difficult to apply at desired rates, resulting in wide variations in yield, nitrate-N concentrations and nitrate-N losses among years. This suggests that manure should be used to supply only a portion of crop nitrogen needs with additional fertilizer added based on late-spring soil nitrate tests.



Digital Repository @ Iowa State University,

Copyright Owner

David L. Bjorneberg



Proquest ID


File Format


File Size

122 pages