Hope you had a blessed Easter weekend! Reminder that soil temperatures can be viewed at: https://cropwatch.unl.edu/soiltemperature.
Hay and Forage Resources: Resources for buying/selling hay, corn residue, and other forages can be found at the following:
- Nebraska Hay & Forage Hotline: https://nda.nebraska.gov/promotion/hay/index.html
- Nebraska Hay Exchange: http://www.hayexchange.com/ne.php
- Crop Residue Exchange: https://cropresidueexchange.unl.edu/
Fire Damage to Crop Residue: With the dry conditions and various fires that have occurred, have received questions regarding the nutrient value in the residue and/or soil impacts. When residue is burned, most nitrogen and sulfur in the residue are lost; however, the phosphorus and potassium are retained in the ash (as long as they don’t blow away).
In spite of this, short-term nutrient loss from the residue is none to minimal. Research from the University of Wisconsin looked at the need to replace nitrogen to the succeeding corn crop when soybean residue was either removed or not removed. They found no difference in nitrogen impacts to the corn crop regardless if the residue was removed; this suggests there is no need to replace the nitrogen in burnt soybean residue. Research from USDA-ARS in Nebraska, when looking at corn residue removal prior to corn planting, also suggested no need to replace the nitrogen lost from the residue. They found increased mineralization due to the change in C:N ratio when residue was removed. Previous research compiled in this resource from South Dakota State shared the same sentiments: https://openprairie.sdstate.edu/cgi/viewcontent.cgi?article=1365&context=extension_extra. The SDSU resource is also helpful when walking through a dollar value of other loss considerations.
Regarding longer-term nutrient loss, a UNL NebGuide shares for every 40 bu/ac of corn or sorghum, approximately one ton of residue is produced. Each ton of corn and sorghum residue contains approximately 17 lb N, 4 lb P2O5, 37 lb K, and 3 lb S. For every 30 bu/ac of soybean residue, approximately one ton of residue is produced with 17 lb N, 3 lb P2O5, 13 lb K, and 2 lb S for each ton of residue produced.
Perhaps the greatest losses to consider are organic matter, soil loss, and soil moisture. Regarding organic matter, the soil holds the greatest portion of this. One year of residue is minimal, attributed with the potential of increasing organic matter 0.03-0.06%, depending on tillage type, crop, etc. Soil erosion due to wind/water can result in organic matter loss and loss of more productive soil. This is hard to quantify. Perhaps the more important factor is the soil moisture losses in no-till, non-irrigated fields, particularly in a dry year such as this. Paul Hay, Extension Educator emeritus, years ago shared with me several documented situations where yield losses due to moisture loss were estimated. Corn planted into burned no-till, non-irrigated soybean stubble ranged from 15-28 bu/ac yield loss in two situations. There was 0-3 bu/ac yield loss associated with soybean planted into burned, no-till, non-irrigated corn residue in two situations. Use of soil moisture probes can give an indication of soil moisture differences between burned and non-burned areas of fields or between fields. Direct yield comparisons between fields are difficult to make due to planting dates, hybrids/varieties, agronomic practices, etc., but important to still collect and assess.
Crabgrass Preventer timing: Crabgrass germinates when soil temperatures are maintained at 55F for 5-7 consecutive days. You can watch the CropWatch soil temperature maps at the link listed above. Or, use a meat thermometer (that you dedicate to only taking soil temperature!) for your own lawn situation at a 2-4” depth. Typically, towards the end of April/beginning of May is a good time for the first application, but it will vary by year. So far, this timing is holding true for 2022. When crabgrass preventer is applied too early, it can move out of the zone where the crabgrass seed is germinating. Would also recommend that you consider splitting your crabgrass herbicide application. Apply half of the highest labeled rate when soil temps warm and the other half 6-8 weeks later. Often there’s a flush of crabgrass later in the season and splitting the application can help with that It’s helpful for the products to be watered in within 24 hours for best results.