Nitrogen and Corn Production

With the surging cost of fuel and fertilizer, already narrow profit margins are getting tighter. We have tools that will help you make an informed decision on your corn’s nitrogen needs. Over-application of nitrogen on corn fields not only impacts the environment, but also can negatively impact profit your bottom line. We offer free nitrogen testing for corn with two types of tests. 

Pre-Sidedress Soil Nitrate Test 
The basis for Pre-sidedress Soil Nitrate Test (PSNT) is taking soil samples just before sidedressing after the spring wet period, but before the period of major N demand by corn, and determining the nitrate-N available in the soil at that time. The results are then used to make sidedress N recommendations. Research has shown that when the soil nitrate-N level is above 21 ppm, there is little chance of an economic response to adding additional N to the field. At soil nitrate- N levels below 21 ppm, sidedress N will be required to achieve optimum economic yield. The table below can be used to estimate an appropriate N recommendation in this situation.  Agronomy Factsheet: Nitrogen can be added to the soil by manure and legume crops. Field and crop histories are needed to account for any N contributions from manure and previous legume crops. To assist the Conservation District to more accurately determine sidedress recommendations, please fill out the PNST Soil Report and Information Form and submit it with your soil sample.

Chlorophyll Meter Test
The chlorophyll meter test can be used to estimate the nitrogen status of the growing corn crop based on the color of the corn leaves. This test is also a presidedress test, run at the critical time just before the major demand by the crop. The color of the leaves is read directly on the plant in the field with a handheld meter. No samples need to be collected and analyzed and the results are available immediately. A high N fertilized reference plot is recommended to properly calibrate the meter, but is not necessary. However, there are many factors that can contribute to leaf color. Chlorophyll meter testing is valid only on fields that have received less than 15 lbs. of N per acre, applied at or before planting.Agronomy Factsheet on Chlorophyll Meter Testing. Both of these tests are recommended for use primarily on fields where there are significant organic N contributions, such as a history of manure applications or a use of forage legumes in the crop rotation cycle. These tests have limited value on most fields without organic N contributions. Both tests will need to be done when the corn plant is at the sixth leaf stage or 10 to 20 inches tall. Pre-Sidedress Nitrogen Test (PSNT) requires soil samples to be taken, and tested in our office. We have 3 soil augers available for loan. Keep an eye on the corn height and give us a call at least one week prior to needing the results so we can fit you into our schedule. 

Corn Stalk Test
There is limited funding available to provide free corn stalk tests on a first-come, first-serve basis. The corn stalk test can be used to identify fields/situations where soil nitrogen uptake, thus nitrogen application, was excessive. Corn stalk testing combined with your records of manure application, fertilization and crop rotation can be useful for making future management decisions. Late Season Corn Stalk Sampling Procedures. Stalk sampling can be done anytime between about the 1/4 milkline stage of the grain and up to 3 weeks after the grain forms a blacklayer. Depending on planting date, location, etc., this sampling window usually is from about the later part of August until the later part of October. If any of your fields will be taken for silage, you will need to sample before the silage harvest (often about 1/2 milkline stage). To more accurately determine whether availability of N was adequate for crop production, please fill out the Corn Stalk Test Information Form and submit it with your corn stalk sample. Call the Adams County Conservation District to arrange for drop off of the corn stalks. We will arrange for delivery of the samples to the lab. Please contact Vy Trinh at 334.0636 ext 3045 or email Vy Trinh with any questions.