Title: Management Practices Effect Soil Quality and Plant Productivity Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 15, 2008
Publication Date: January 14, 2009
Citation: Mikha, M.M. 2009. Management Practices Effect Soil Quality and Plant Productivity. Meeting Abstract. Presented as a keynote speaker at the 2009 Farmers Agriculture, Conservation and Technology Conference. Liberal, KS. Jan. 14, 2009. Technical Abstract: The predominant cropping system in the Central Great Plains, winter Wheat-Fallow (W-F) rotation, is not sustainable. Decreases SOM content are associated with tillage and W-F primarily because of tillage during the fallow period. The tillage frequency could have an effect on soil quality, SOM conservation, and greenhouse emission (especially carbon dioxide, CO2). Selected soil quality parameters were evaluated in (i) a continuous maize study initiated in 1990, this included tillage (no-tillage (NT) and chisel-disk (CT)) and N sources (none, beef manure (M), and fertilizer (NH4NO3)) on a Kennebec silt loam (Manhattan, KS); (ii) alternative crop rotations plots (with reduced fallow frequency) established in 1990 on a Weld silt loam (Akron, CO); and (iii) the effect of tillage on CO2 flux and soil water content was evaluated on a farmer’s field that has been under no-tillage management for 12 years (Akron, CO). We investigated the effects of manure addition (Kansas site) and cropping intensity (Colorado site) on soil C, soil aggregate-size distribution, particulate organic matter (POM), soil microbial communities, and enzymatic activities of C cycling. Soil samples (0-2 inches depth) were fractionated into two groups of aggregate size: macroaggregates (>250 'm) and microaggregates (<250 'm) by wet sieving. Carbon dioxide flux was measured using in situ infrared analyzer (Li-COR machine). At the Kansas site, a greater amount of soil C was associated with NT-M than NT-fertilizer. Aggregate-size distribution was affected by tillage and M addition. Significant amounts of macroaggregates were present in NT compared with CT, with corresponding shifts in the proportion of microaggregates in CT. Tillage, aggregate size, and their interactions (p<0.05) significantly affected aggregate-associated C and N. Relative yield was significantly affected by N source (manure vs. fertilizer). The combination of NT and M sustained corn yield (more than 60%) even after 7 years of terminating M application. Continuous cropping increased soil total C compared with W-F rotation at the Colorado site. Aggregate-size distribution was affected by tillage, but not by cropping intensity. Enzyme activity of '-glucosaminidase, '-glucosidase, and '-galactosidase were affected by rotation phase and fallow frequency. Principal Component Analyses (PCA) of Fatty Acids Methyl Ester (FAME) profiles demonstrated shifts in the microbial community structure between the alternative systems compared with W-F rotation. In 2005, the CO2 flux was 70% grater with the 1st time tillage than with no-tillage (NT) especially during the first 2 seconds after running a v-blade sweep in the surface 10 cm of soil. While the CO2 flux was only 40% greater than NT with the treatment that was tilled for the two years (2004 & 2005). At the 24 hour to 4 week period, the CO2 flux was positively affected by soil water content (SWC). Greater SWC after 2 weeks of tillage increase CO2 flux by more than 37% with tillage treatments compared with NT. This increase could be due to SOM decomposition which was promoted by tillage practice. In general, no-till enhanced the storage of soil organic C by increased physical protection of C in macroaggregates. Fourteen years of no-tillage and continuous cropping with reduced fallow frequency have a positive effect on soil aggregation and soil biochemical functioning. No-tillage showed 80% less CO2 flux and 11% greater SWC compared with both tillage treatments even after 4 weeks of measurement.