Effects of tillage, nitrogen source and nitrogen rate on corn response and selective soil properties in a corn-soybean rotation
Corn producers in Iowa adopt no-tillage (NT), strip-tillage (ST) or chisel plow (CP) and either commercial fertilizer or liquid swine manure produce corn. The rising cost of commercial N fertilizers raises concerns about using alternative and viable sources of N and P for corn production. The objectives of this study were to evaluate 1) the responses of corn to three tillage treatments (NT, ST and CP) and four N rates (0, 84, 168 and 252 kg N ha−1) of liquid either liquid swine manure or commercial fertilizer N and 2) the effects of tillage on soil temperature, compaction, moisture storage and water extraction by corn root system. The study was conducted at the Northeast Research and Demonstration Farm of Iowa State University near Nashua. The soil at the study site is Kenyon (fine loamy, mixed mesic Typic Hapludolls) soil. The experimental design was a randomized complete block with split-plot arrangement in three replications. The tillage treatments were randomly assigned to each replication as main plots and the N rates of either N source as the subplot. Results of the study showed no significant impact of tillage treatments on plant biomass and corn yield. Increasing soil N application increased corn yield and corn stalk NO3-N concentrations for both N sources. At N rates higher than 100 kg N ha−1, corn showed a luxury consumption of N for both N sources. Soil temperature in the ST treatment compared favorably with CP, but showed an overall advantage over NT, which consistently recorded lower soil temperatures and ERI. Soil moisture storage for all tillage treatments at the top 30 cm and 0 to 120 cm were not significantly different for both N sources. Soil water extraction by corn roots did not show significant differences for all tillage treatments and both N sources. Soil penetration resistance measurements for tillage treatments did not show significant differences but increased with soil depth especially in the top 20-cm soil depth and late in the growing season for both N sources.