Soil Temperatures and Nitrogen
Considering the price of nitrogen fertilizer, maximizing nitrogen applications is very important this fall. This is true for both anhydrous ammonia and liquid swine manure. Because anhydrous ammonia rapidly converts to ammonium in the presence of soil moisture and liquid manure is about 80% in the ammonium form of N, we want to keep N in that form in our soil. Ammonium is positively charged and is attracted to the negatively charged soil exchange. This form is not subject to leaching or denitrification. Warmer soil temperatures allow microbial conversion of ammonium to nitrate, which is negatively charged, not held in soil and subject to leaching. This article provides good insight to value of manure, application timing and the soil processes that take place.  Get the most bang for your buck: time your manure and anhydrous applications well.   Applications of these N sources should be delayed until soil temperature is 50 degrees F and falling. You can track soil temperature trends for the previous three days at this Iowa Mesonet link. 

Soil Fertility and Rising Fertilizer Prices 
Many of the phone calls I have received in the past 10 days are about concerns with rising fertilizer prices and what, if any, fertilizer should be applied this fall or next spring.  Antonio Mallarino's article, Soil-test interpretations for fall fertilization and liming decisions with high fertilizer prices and after highly variable rainfall and crop yields, provides insight for making fertility decisions.  

Hold off on fertilizing soils that are in the "High" or "Very High" testing categories due to lack of expected yield response on these soils. The average percentage of P and K applications expected to produce a yield response is only 5% for "High" testing soils and <1% for "Very High" testing soils. 

If possible, continue to fertilize soils in the "low" or "very low" testing categories even with high fertilizer prices as they have a high probability of paying back yield that exceeds the cost of fertilizer. The average percentage of P and K applications expected to produce a yield response is 80% in "Very Low" testing soils and 65% for "Low" testing soils. 

Soils that are currently in the "Optimum" category benefit less from fertilization than the "Low/Very Low" testing soils, but still generally produce  above break-even results.  

Start with good soil tests. 
Know which analytical methods and sample handling procedures were used. 
Use PM 1688, A General Guide for Crop Nutrient and Limestone Recommendations in Iowa to make future fertilizer application decisions. This is available as a free download.  

If you are looking to invest dollars in your fertility program and don't need additional P and K, review your soil pH results and consider liming fields as needed. This step is often neglected as part of the fertility planning process. Need help? Reach out to any of the ISU Extension and Outreach Field Agronomists. 


Herbicide Planning for Next Year with Anticipated Supply Chain Shortages
Some things to consider among the rumors about pesticides being in short supply and if you choose to take early possession of pesticides: 1)  store pesticides in a locked place; 2) keep all pesticides in their original containers; 3) account for temperature of storage to prevent pesticide from freezing; 4) check containers frequently for leaks; 5) clean up spilled chemicals quickly and appropriately; 6) FOLLOW ALL LABEL INSTRUCTIONS FOR STORGE REQUIREMENTS. This Penn State Extension article provides a list of best practices, Safe Storage of Pesticides.