Gentry, L.E. and S.S. Snapp
Presented at the All Scientist and GLBRC Sustainability Meeting (2009-05-05 to 2009-05-07 )
Corn stover as a bioenergy feedstock will put greater demand on the soil resource and challenge farm managers to engage agricultural practices that avoid C depletion and soil degradation. Here at KBS, we have introduced corn stover removal (vs. corn stover retention) into a long-term crop rotation study (the Living Field Laboratory established in1993 by Dr. Richard Harwood) that uses cover crops and composted dairy manure as carbon supplements to offset residue removal in two corn cropping sequences (continuous corn vs. corn-soybean-wheat). This trial is a randomized complete block design with the two crop sequences represented within a main plot of management system (compost or no compost), and a split plot of cover crop or winter fallow. In 2008, we imposed a split-split plot to investigate the impact of stover removal. Corn stover removal was conducted by cutting standing corn at the base and raking biomass from half of each plot. Using a backpack blower, we removed approximately 90% of the above-ground portion of the corn crop to impart greater stress on the system. This will enhance the magnitude of differences between stover removal and stover retention and better test the efficacy of cover crops and/or composted dairy manure as C supplements. We have been managing this long-term experiment since 2006 and during this time we have grown the same corn hybrid each year, providing an excellent baseline of crop response and soil characterization information. After a good growing season at KBS in 2006, both 2007 and 2008 experienced a drought. The drought in 2007 occurred during vegetative development, while in 2008 it became very dry during grain fill. Our preliminary data show the profound influence that “year” (i.e. weather pattern) has on overall plant growth and harvest index (HI is the amount of grain divided by the whole plant biomass).
Year |
Corn Grain Yield |
HI |
Stover Biomass |
Mg ha-1 |
% |
Mg ha-1 |
|
2006 |
8.7 |
58 |
6.3 |
2007 |
7.4 |
59 |
4.9 |
2008 |
5.1 |
45 |
6.9 |
Agricultural models generally use 50% for corn HI, which would overestimate stover biomass by 39% and 50% in 2006 and 2007; however, this would underestimate stover biomass by 27% in 2008. It is interesting to note that the year with the lowest grain yield produced the greatest amount of stover biomass. Understanding the relationship among corn grain yield, harvest index, and weather pattern will improve estimates of corn stover production. Ultimately, we hope results from this study can be used to quantify the amount of stover that can be sustainably harvested from a variety of soil types and cropping systems, using cover crops and/or compost to maintain soil organic matter.
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