5/22/2008 11:22:00 PM
The weather has certainly put a “damper” on planting progress. All of Ohio has been impacted one way or another with the Southwestern Ohio area getting most of the rain. Just in the last week or ten days, the Nye farm got 2.6 inches of rain. I know there are several producers close to being done planting but we need a couple of really good days of suitable planting conditions and weather to finish. Let’s hope this weekend dries us out, warms us up and allows our grain producers to finish planting.
The one thing that concerns me is the prolonged cold and wet conditions will or have created replant scenarios in certain fields. Producers need to continue scouting their fields for emergence issues, insects, disease and weed competition.
Weather forecasts keep predicting warmer, drier weather with more continual improvement. The fact of the matter is it has not come soon enough. Reports are that the 2008 May has become one of the five coldest Mays in reported history.
Thoughts of our future weather outlook (thirty to ninety days) are uncertain. Weather experts say that LaNina effects and current model trends point toward a drier June and then a near normal July/August rainfall. If you want to look at more details on the future weather forecasts I suggest you visit the following website http://www.cpc.noaa.gov/index.php.
Depending on planting progress, it won’t be long before producers start considering sidedressing nitrogen on corn. Fertility specialists at Ohio State University, Robert Mullen and Ed Lentz, suggests the presidedress soil nitrate test (PSNT) or late spring nitrate test (LSNT) as a soil testing tool that can be used to aid in nitrogen management decisions. Soil samples are generally collected between mid-May to mid-June whenever sidedress applications of nitrogen are being made. The question is when should I use the PSNT and what does the PSNT tell me as a crop manager?
Mullens and Lentz note the goal is to provide better nitrogen recommendations for crop producers. Nitrogen transformations that occur in the soil are dynamic and strongly influenced by environmental conditions because it is the result of soil biological activity. The transformation we are primarily concerned with in agriculture is the mineralization of organic nitrogen to inorganic forms (initially ammonium and eventually nitrate). If mineralization rates for soils could be predicted for a given growing season nitrogen recommendation strategies could be improved. Because accurate models do not exist to quantify this phenomenon we must rely on a snapshot in time of what has occurred in the soil (i.e. the PSNT/LSNT) or some other alternative method (reference/nitrogen rich strips). The PSNT/LSNT conducted on soils that do not have a manure history or previous forage legume crop rarely return levels high enough to prompt a decision. The PSNT/LSNT is almost exclusively promoted for fields that have received recent manure applications or where corn is following a forage legume crop. Presidedress soil nitrate tests should not be taken when preplant commercial fertilizer nitrogen was applied. This can result in an elevated PSNT level indicating a low probability of nitrogen response.
Depending upon the PSNT/LSNT level Mullens and Lentz suggest we get an estimate of the likelihood of seeing a response to additional nitrogen fertilizer, but we do not get an actual nitrogen recommendation. PSNT/LSNT values near 25-30 ppm are unlikely to benefit from additional nitrogen fertilizer, and the higher the value the less likely the need for supplemental nitrogen. The problem arises when PSNT/LSNT values are less than 25 ppm. PSNT/LSNT values below this level may or may not respond to additional nitrogen fertilizer, but the stock recommendation would be that they do require more nitrogen. There can be sites that have a low PSNT/LSNT value but show no response to nitrogen fertilization. This is a major limitation of the PSNT/LSNT. Bottomline: if the PSNT values are above 25 ppm, adequate nitrogen should be available for this year’s corn crop. If it is less than 15 ppm, the normal nitrogen rate should be applied. Between 15 and 25 ppm, other factors should be considered before reduction of the normal nitrogen rate.
Producers might also consider utilizing the economic based 2008 Nitrogen Rate Calculator. The calculator can be found at http://agcrops.osu.edu/fertility and a user’s guide for the calculator can be found at http://agcrops.osu.edu/fertility/documents/users_guide_03_06.pdf. This is a helpful management tool for determining economical nitrogen applications for your operation.
Nitrogen management is also important for pastures. Cliff Little, Extension Educator in Guernsey County recently addressed the importance of nitrogen in a pasture management system.
In general nitrogen has the greatest potential to influence pasture production, or dry matter (DM) production. When is it economical to utilize nitrogen on a pasture? According to Little, the answer is, when you need more forage and when the legume content of the pasture is less than 35 percent.
When is the best time to apply nitrogen to a pasture? Plants will utilize available nitrogen when they begin actively growing. We know that cool season grass pastures will produce 60-70 percent of their total annual production in the spring with fall being the next major bump in growth. Therefore, consider these time periods when making an application of nitrogen to grass pastures.
How much nitrogen do I apply? Consider the value of the forage you are producing.
For example:
Let’s break the growing season and timing of nitrogen applications into three periods, May, June and August. Applying nitrogen at each of these time periods will result in a different yield potential and therefore a different level of economic efficiency. If we expect a fescue/orchardgrass pasture with ten percent legume to yield in response to N the following:
20 lbs. of DM per lb. of N applied in May
10 lbs. of DM per lb. of N applied in June
14 lbs. of DM per lb. of N applied in August
(These yield estimates will vary)
If urea is $500/ton and value comparable hay at $100/ton, how do the economics work out? Example calculation:
$500 ÷ 920 lbs. of N in a ton of urea = 54 cents/lb. of N
We will utilize 50 units of actual nitrogen. 50 lbs. x .54 = $27 per acre to apply fifty units of nitrogen, not including spreading.
Based on the example:
The May application could result in 20 lb. DM x 50 units N = 1,000 lbs. DM.
The June application could result in 10 lbs. DM x 50 units N = 500 lbs. DM
The August application could result in 14 lbs. DM x 50 units N = 700 lbs. DM
Remember, comparable hay was worth $100/ton and is 87 percent DM. Therefore the value of this forage is $100/.87 = $114.94/ton of DM or 5.7 cents/lb. of DM.
How do the economics compare on these three different applications?
The May fertilization resulted in:
1000 lbs. DM x $.057/lb. = $57 increase in value less $27 cost of N = $30 benefit/acre
The June fertilization resulted in:
500 lbs. DM x .057/lb. = $28.50 increase in value less $27 cost of N = $1.50 benefit/acre
The August fertilization resulted in:
700 lbs. DM x .057/lb. = $39.90 increase less $27 cost of N = $12.90 benefit/acre
If you need more pasture growth and can utilize nitrogen, consider utilizing it in 50 unit increments of actual nitrogen and during periods of when you need forage growth. For more information on pasture fertility management ask your local Extension Office for a copy of “Fertility Management of Meadows,” ANR-5-99.
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EDITOR’S NOTE — Tony Nye is an Extension agent for The Ohio State University Extension office for Clinton County in natural resources and agriculture.
