With harvest finishing early and the potential for some nice fall weather ahead, farmers may be tempted to get a jump on spring field work by doing tillage and fertilization this fall. There also may be financial incentives such as product discounts or moving expenses from one year to another.
The following agronomic concerns should also be considered:
1. Soil nitrates may be higher than normal this fall, especially in rain-fed fields. Take soil samples and determine residual soil nitrate levels before deciding on fertilizer nitrogen (N) application rates.
2. Dry soils are difficult to sample and may affect results. Soil organic matter and soil nitrate results should be fine, but some soil pH and potassium may be affected by the dry conditions.
3. Dry soil conditions may make tillage difficult.
4. Knife applications, including sealing of anhydrous ammonia injection tracks, also may be more difficult in dry soil conditions.
5. Wait to apply N until soil temperatures drop below 50° F since the conversion of anhydrous to nitrate is much slower below 50° F. Leaching is more likely on sandy ground.
Wait Until Soil Temps are 50° and Falling Before Applying Anhydrous
6. Fall application of other forms of N is discouraged due to potential N loss between application and when the crop needs the N.
7. If soil conditions are not conducive to soil sampling, use historical trends and make adjustments based on recent fertilizer application and yield history. Corn removes about 70 lbs. N, 35 lbs. P2O5, and 30 lbs. K2O for every 100 bu. Soybeans remove about 37 lbs. P2O5and 60 lbs. K2O for every 50 bu.
8. Monitor rain and snow infiltration between now and the next growing season and make fertilizer adjustments next spring if excessive rain may have caused leaching.