Extension Update by Jenny Rees

What a beautiful week weather-wise! The winds this weekend have allowed leaves to drop from deciduous trees/shrubs. With the temperature fluxes this fall, many trees and shrubs still maintained leaves in spite of hard frosts. They hadn’t completely formed an abscission layer (cells at the attachment point where the leaf petiole meets the stem). Now that leaves are falling, it’s important to keep them mulched into lawns or raked up to avoid conditions like snow mold in lawns. Leaves are also great materials to add to vegetable and flower gardens as they can improve organic matter and act as a mulch. If added to perennial flower beds, make sure to remove the leaf material when hostas begin to leaf out in the spring. This is because slugs decomposing leaf litter also like to feed on plants such as hostas.

Residue Management: My goal in writing about residue management is to share recent research to aid in answering questions received. There’s a lot of ways that corn residue is managed: processing with the combine, various types of tillage, grazing, baling, spraying products, and cover crops (with thought of lowering Carbon:Nitrogen ratio and increase microbial populations). On a year to year basis, depending on the soil moisture and temperature, combinations of these practices may work well for individual field situations. Unintended consequences of practices include wind and water removing loose residue and/or soil from fields.

A few recent questions have included impacts of spraying various products and also about spraying nitrogen. While I know farmers have tried various products, sugar, and applied UAN to corn stalks, we didn’t have any on-farm research studies with those products for the purpose of residue decomposition, so don’t have data to share. Data is also very limited in scientific journals. If any of you considering products would be willing to test them via on-farm research, please let me know and I’d be happy to help you set that up and help with data collection.

There is a recent study from Illinois where residue management included using Calmer Bt chopper stalk rollers that sized residue into smaller pieces vs. standard stalk rollers. In addition to each mechanical control treatment for residue management, AMS or a biocatylist product were also added. The researchers found a 7% enhanced reduction of corn residue with the chopped residue vs. the standard stalk rollers (46% compared to 39% reduction) but there were no differences with the addition of AMS or the biocatylist product.  

Iowa State conducted a three year study evaluating the effects of conventional tillage, no-till, and strip-till on residue breakdown on Bt and non-Bt corn residues. They did this by placing bags of residue of Bt and non-Bt hybrids in the three different tillage systems and evaluated decomposition after 3, 6, 9, and 12 months in a corn/soy rotation. The results showed no significant difference between tillage systems or Bt and non-Bt hybrid decomposition (34-49% of residue remained in all treatments).

These researchers also studied the impact of nitrogen applications on corn residue breakdown over two years in no-till. Immediately after harvest, three N rates (UAN 32 percent) of 0, 30 and 60 lb N/acre were applied to corn residue. A specific amount of residue was placed in nylon mesh bags and left in the field for 3, 6, 9, and 12 months, after which residue decomposition was evaluated. The different rates of N resulted in no differences in rate of decomposition. In general, the longer the residue remained in the field, the more it decomposed over time, regardless of N rate. Thus the authors shared that applying N after harvest for residue decomposition was not effective nor economical as soil and air temperatures decreased over time after harvest. They shared that in general, decomposition of crop residue is primarily influenced by soil moisture (near field capacity) and temperature (above 50F) as these factors influence microbial activity.