Crops

Nitrogen and no-till

If soils under tillage have lost as much as 50 percent of their original stable organic matter and a farmer initiates a practice of continuous no-till, it is my understanding that stable soil organic matter will move upward to approach pre-plow levels. Let's say no-till practice raises organic matter by 1 percent and the top six inches of an acre of soil weigh 2,178,000 pounds at 100 pounds per square foot this would then result in an increase of 21,780 pounds of stable or near-stable organic matter. If organic matter is 5 percent nitrogen, this would then sequester 1,089 pounds of nitrogen in the soil of each acre.

How is it then, that in Publication G9176, Fertilizer Management for No-Till Corn and Grain Sorghum in Missouri, it can say that no extra nitrogen is required when initiating no-tillage practice? It would seem that no soil organic buildup matter would be building up or that the buildup would be so slow as to be insignificant.

Organic matter will increase with many no-till systems. I question that it would reach 5 percent. Values from 2.5 to 3.5 percent are likely more typical. No-till is not the only way to increase soil organic matter in row crop systems. Highly productive continuous corn grain management has led to increases in soil organic matter because of the large amount of root and stover biomass generated each year. Conversely, organic matter buildup will be slower with low residual crops such as soybean in no-till systems.

If I understand your question correctly, you suggest that we should add additional nitrogen fertilizer to promote and account for the sequestering of nitrogen in the formation of soil organic matter. I suggest looking at the problem this way. The source of the biomass that builds soil organic matter is residual plant materials after growing a crop. A crop fertilized at the optimum rate to maximize yield will maximize the biomass produced by that crop. Any additional fertilizer will not increase yield but will increase losses from the field. Underfertilization will reduce yield, potentially reducing biomass production. To maximize organic matter production with a specific crop requires optimizing the fertilization rate for high yield.

In tilled systems, tillage following growth of the crop speeds the break down of the residual biomass. Nitrogen in that biomass will be released to the soil more quickly and potentially be prone to more rapid losses. In no-till the immediate release of nitrogen from residuals will be slower but the higher soil organic matter levels will support a higher rate of nitrogen release compared to the tilled system over the growing season. Research has not shown dramatic differences in nitrogen requirements of no-till versus tilled corn. I expect the source of the nitrogen in the soil organic matter represents reduced nitrogen losses from the no-till system. It is nitrogen incorporated into a growing crop but not released to the soil.

The process of organic matter accumulation is a slow process. The annual increase in nitrogen in the soil organic matter will be slow. Adding one ton of soil organic matter represents an increase of approximately 75 pounds of soil nitrogen. Under the best of circumstances this would be a rapid buildup in soil organic matter. There is typically enough excess nitrogen in most corn systems to support this level of annual increase.

John A. Lory
Associate Professor of Extension
Division of Plant Science

Fertilizer for hay crop

My dad passed away and left me the farm. I was wondering when fertilizer should be applied to a hay crop used for feeding cattle. Should it be done in the fall or early spring? How do you know what it needs?

You need to test your soil to find out how much fertilizer is required for your hay crop. The guidelines on how to take a representative sample, testing fees and the sample information forms can be obtained from the MU Soil and Plant Testing Laboratory. There you can learn how to take and submit a representative soil sample. Send the sample with the sample information form and a check made out to MU Soil Testing to:

Soil and Plant Testing Laboratory
23 Mumford Hall
Columbia, MO 65211

The cost for a regular fertility test is $10 per sample. The test includes salt pH (pHs), neutralizable acidity (NA), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and organic matter and cation exchange capacity (CEC). The soil test report will provide recommendations on how much lime and fertilizer is required and the application time for hay crop.

Manjula Nathan
Director
Soil Testing and Plant Diagnostic Services

Storing turkey litter

I am interested in buying turkey litter. However, I must wait until the current crop is harvested to spread and incorporate the litter on the field. How much of the nutrient level would I lose if I simply store it outside in a pile for one to two months?

Stockpiling poultry litter will not affect its nutrient content too much. While the stack stands it will go through a composting process. This will reduce its volume and some nitrogen will be lost, but not much. The nutrient concentration of phosphorus and potassium will actually increase and the nitrogen concentration will stay about the same after composting. Nitrogen losses are not high because most of the nitrogen is tied up in organic matter and will only be released as the litter breaks down in the soil.

My biggest concern with this plan is the water quality laws for storing poultry litter. Long-term stacking of poultry litter in uncovered infield stacks is not allowed. Infield piles are only allowed for temporary storage of up to two weeks and must be at least 300 feet from any water feature (stream, lake). After that additional steps are needed to insure the piles do not wash into local streams. Stacking manure for more than 14 days requires covering the stacks with tarps, using stack houses or stacking in an approved composting facility.

John A. Lory
Associate Professor of Extension
Division of Plant Science

Orchardgrass persistence

I was hoping to find some information on orchardgrass. What are the seeding rates, persistence and planting dates?

Regarding seeding rates for orchardgrass, check G4652 Seeding Rates, Dates and Depths for Common Missouri Forages. It has all the vital data for establishment of common Missouri forages. Regarding its persistence, it is not really persistent in pure pastures. It is susceptible to rust and probably winterkill. We normally see it persist in hay fields, especially alfalfa and orchard grass hay fields.

Craig Roberts
State Forage Specialist

Nitrogen and corn yield

Is there a publication that compares the cost of fertilizer to corn yield obtained? For example, if a certain amount of fertilizer yields of 140 bushels, how much more is needed to get to 150 bushels? Is the cost justified?

I will assume that you are talking about nitrogen fertilizer, since corn almost always gives large yield responses to nitrogen, and much less so for other fertilizer nutrients.

The problem is that every field is different. I've done 40 or 50 experiments with nitrogen rates in farmer fields--some fields didn't need any and some fields needed 300 pounds nitrogen per acre (that is, they made more money at that rate than at any lower rate).

Averaged over 30 experiments that were just in a grain rotation (no manure or alfalfa), the nitrogen rate that maximized profit with corn at $2 and nitrogen at $.20 per pound was 140 pound per acre.

Nitrogen prices are getting higher, at $.30 per pound it took only 120 pounds per acre to maximize profit. But that's certainly not true for all fields, just for the average of this set of good production fields.

Our research has shown that there are usually areas in a field that don't need much fertilizer and areas that need a lot. Unfortunately we haven't come up with any good way to tell which areas fall into which category, except waiting and watching the color of the corn and responding to that.

A direct answer to your example: If it's actually possible to go from 140 bushels to 150 bushels using fertilizer, it is almost always cost-effective. On average it would probably take an extra 20 to 30 pounds of nitrogen, certainly no more than 50. Even with high prices, the fertilizer more than pays for itself. The problem is knowing whether adding more fertilizer will give you the yield bump. And as I've said, that is very different from field to field, and very hard to predict.

Peter Scharf
Associate Professor
Plant Sciences