JenREES 10/30/22

Grateful to hear the corn moisture is dropping and to see more replant corn being harvested! As November 1st is around the corner, some may be thinking about fall fertilizer. It’s important to consider soil temperatures regardless of the date one can apply fall fertilizer in area NRDs. Soil microbial activity and the conversion rate of ammonium to nitrate is very low when the soil temperature is less than 50oF. Thus, apply anhydrous ammonia (and manure) when the soil temperature at the 4” soil depth is below 50°F and trending cooler. We’re currently hovering above that mark and probably will be above it with the warmer air temperatures this week. You can view soil temps at:

With the dry conditions, make sure there’s a good seal. One may also wish to consider if the anhydrous is deep enough and consider how it may impact your seed zone next spring if we remain in dry conditions. Be aware that soil nitrates are typically higher than normal after a dry growing season, especially in non-irrigated fields and even more so in non-irrigated fields that had wildfire damage.

As one looks at soil test results this fall, also be aware that soil pH and potassium (K) results are often lower than expected due to dry conditions, particularly in non-irrigated situations. It is true that below-normal yields result in lower phosphorus and potassium removal from the soil. However, as Dr. Antonio Mallerino from ISU shares, “a couple of processes may counteract this possible increase and most likely will result in lower soil-test P and K results than expected.

  • Below normal rainfall from the time of physiological plant maturity until the time of soil sampling results in much less K recycling to the soil than normal, and consequently lower soil-test K levels than with normal fall rainfall.
  • While a small soil-test P reduction is possible, it is also less likely.  
  • Scarce or no rainfall since early September slows down the normal reactions between soil nutrient pools, which often results in lower soil-test K levels. Plants are like pumps taking up P and K from the soil, but the uptake decreases sharply a couple of weeks before the crop reaches physiological maturity. Normal rainfall allows for the replenishment of the available nutrient pools from the less available pools.
  • Soil pH values likely will be less than normal (more acidic) with drought, with differences ranging from 0.1 to 0.4 pH units being common. This is because small concentrations of soluble salts normally present in the soil solution are not leached to deeper layers by rainfall, which results in higher hydrogen ion concentration and greater acidity in the topsoil. On the other hand, drought has little effect on the soil buffer pH, which is used to estimate the lime requirement.”

He suggests, if possible, to wait on soil sampling until at least a week after a ‘meaningful’ rain event occurs; he suggests that would be one that wets the profile at least 6”. Since that’s not looking likely, if obtaining soil samples this fall, it’s important to obtain a full soil core when sampling and be aware that the K results will be low, P should be fairly on track, and pH will also be low.

Returning to the Farm Workshop Dec. 9-10 at Holthus Convention Center in York: This is a workshop series for families who are in the transition process of bringing members back to the farm or ranch. The series assists families and agricultural operations with developing financial plans and successful working arrangements to meet their unique needs. It will guide families in developing estate and transition plans, setting personal and professional goals and improving the communication process between family members. The workshop fee is $70 per person. It also includes two follow-up virtual workshops in the evenings on Jan. 12 and Feb. 2. Registration & more info:

About jenreesources

I'm the Crops and Water Extension Educator for York and Seward counties in Nebraska with a focus in irrigated crop production and plant pathology.

Posted on October 30, 2022, in JenREES Columns and tagged , . Bookmark the permalink. Leave a comment.

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