Intercropping Maize and Kura Clover (Trifolium): A sustainable System for Feed and Biofuel Production

Invited by Pedro Gerstberger -----

Maize silage is a major source of energy for dairy cattle in the northern USA, and crop residues remaining after maize grain harvest is viewed as a promising, low-cost raw material for cellulosic ethanol production. However, removal of essentially all plant residue for either of these purposes results in excessive erosive soil and humus loss (Gallagher et al., 1996), prompting the need for alternative soil conserving production systems. Furthermore, the ever-increasing cost of nitrogen fertilizer encourages the search for cropping systems that rely on biologically fixed nitrogen. Legume living mulches have been tested in the northern USA as a means to meet nitrogen requirements of maize (Eberlein et al., 1992; Hartwig & Ammon, 2002), but perennial legumes evaluated reduced maize yields or failed to recover after maize harvest. Kura clover (Trifolium ambiguum) seems to be ideally suited to serve as living mulch in northern latitudes. It is extremely persistent through frigid winters and produces rhizomes that allow it to fill in gaps that may otherwise be invaded by weeds (Albrecht & Kim, 1998).

Our research (Zemenchik et al., 2000; Affeldt et al., 2004) has demonstrated that with adequate suppression, kura clover can be managed to provide minimal competition to maize and that this system results in reduced soil erosion (Schwab and Albrecht, research in progress) and nitrate leaching (Ochsner et al., 2010) compared to conventional maize production systems. Furthermore, all of the nitrogen required for maize silage or grain plus straw production appears to be available through the suppressed clover (Berkevich, 2009), and kura clover recovers to full production by June the following season (Sabalzagaray & Albrecht, 2006). This permanent living mulch could offer farmers a way to keep soil and nutrients on their fields (and out of our surface and ground water), while nearly eliminating the need for commercial nitrogen fertilizer for maize production.

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