Brief Summary of Minutes of Annual Meeting

Over a 5-year period, no-till showed the highest SOC levels while conventional tillage had the lowest SOC on severely eroded soils in Guam. Soil OC was generally higher at depths below 10 cm for all tillage Treatments. Inclusion of sunnhemp (Crotalaria juncea L.) as a cover crop on conventionally tilled soils increased SOC in the upper 10 cm of the soil but not as high as no-till. Regardless of tillage/residue treatment, all soils have SOC contents of <1.5% under cropped/cultivated conditions. (GU) After 3 years of corn residue removal, no significant reduction in grain yield was observed due to the residue removal. However, only with adoption of no-till and N rates > 150 lbs N/A with little residue removal were potential SOC increases observed. On a poorly drained site, 2.5-3.5 T/A residue needs to be retained to maintain SOC, while, 3.0-3.5 T/A is needed on a well drained site. Removal of 100% of the residue regardless of tillage or increased N fertilization resulted in higher soil bulk density and reduced soil aggregation. (IA) Studies on long-term (25 year) tillage plots showed that cover crops did not affect corn or soybean plant populations over a 6 year period. Effects of combining cover crops with residue removal over 3 cropping years on corn and soybean yields were mixed and appear to be more related to tillage practice. (IL) Severe drought affected residue removal studies in that significant plant death occurred at both sites studied. Yields were > 75 % lower than normal, resulting in very low residue levels at both sites affecting the ability to remove residue in a meaningful manner. (KS) Collection of crop residue from seven long-term (>10 years) diverse no-till cropping systems shows a potential need for increased N fertilizer applications to compensate for heavy residue accumulation in some systems. (ND) No difference in crop yields among different residue removal treatments on two 4-year trials on irrigated corn were observed. Greenhouse gas (GHG) emissions were lower where corn stover was removed than where it was not removed. A winter rye cover crop to mitigate C losses due to stover removal did not affect CO2 emissions. Residue removal effects on soil erodibility may be greater than that on corn yields and soil C pools in the short term under irrigated conditions. (NE) Residue retention had significant impact on water runoff and sediment transport in simulated rainfall studies. Residue management treatments had clear effects on corn grain and stover yield in 2012 on both 8 year old and 1 year old study sites. Complete residue removal reduced grain yields 40-45% while 50% removal reduced grain yields 12-23%. (OH)

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