Section 6 – Land Base Requirement

This section will help you estimate the amount of crop land necessary to recycle the manure nutrients your animals produce. This section will not result in calculating manure application rates for specific crops and fields. That will be done in Section 13. It will calculate the amount of land necessary to utilize the manure nutrients from the animal feeding operation so that a strategic plan can be developed that is environmentally sound and meets regulatory requirements.

To complete Section 6, you will need the following information:
• The manure nutrient production estimates from Section 4.
• What crop will be grown to utilize the manure nutrients?
• What is the expected yield of that crop?
• What is the nutrient uptake per unit of production for that crop (from Table A)?
• What is the method of manure application (from Table B)?
• What is the timing of manure incorporation into the soil (from Table B)?

The ratio of nitrogen to phosphorus in most crops in greater than the ratio of nitrogen to phosphorus in most manure. Therefore, more tons of manure is needed to provide the nitrogen requirements of a crop than is needed to provide the phosphorus requirements. Conversely, more acres are needed to utilize the manure phosphorus than to utilize the manure nitrogen. The land base requirement thus involves two calculations: one for the acres needed to utilize nitrogen and one for the acres needed to utilize phosphorus.

You can copy this section and fill in your own information and calculations in the space below the examples.

Crop Production Data:

Step 1: What crop will utilize the manure nutrients?

Example: Corn

Step 2: What is the yield goal of the crop?

Example: The yield average for the past five years is 100 bushels per acre. Adding 5 percent gives a yield goal of 105 bushels per acre.

Step 3: What is the uptake of nutrients for the crop?

Example: Using Table A, corn takes up and removes from the field 0.90 pounds of nitrogen per bushel of yield.
105 bu/ac x 0.90 lb N/bu = 95 lb N per acre

Again, using Table A, corn takes up and removes from the field 0.36 pounds of P2O5 per bushel of yield.
105 bu/ac x 0.36 lb P2O5/bu = 38 lb P2O5 per acre

Manure Application Data:

Step 4: Calculate the amount of manure nitrogen (N) that is available to the crop. Note that some manure N is in the ammonium form which is volatile and can be lost to the atmosphere. The remainder of the N is in organic form which will be slowly mineralized and most of it will be available for the crop. Table B estimates the percentage of N that the crop will be able to use depending on the method of manure application and when it is incorporated into the soil.

Example: All the manure from the open feedlot in Section 4 is broadcast with a box spreader and tilled into the soil within four days.
18,315 lb. N x 0.6 = 11,000 lb. N available to the crop over several years time.

Step 5: Calculate the amount of manure phosphorus (P2O5) available to the crop. Note that it will be 80 percent available to the crop if manure is incorporated.

Example: All the manure from the open feedlot in Section 4 is broadcast with a box spreader and tilled into the soil within four days.
25,640 lb. P2O5 x 0.8 = 20,500 lb. P2O5 available to the crop.

Land Requirement for Manure Utilization

Step 6: How many acres are needed for nitrogen utilization?

Example: 11,000 lb N ÷ 95 lb N/ acre = 115 acres

Step 7: How many acres are needed for phosphorus utilization?

Example: 20,500 lb P2O5 ÷ 38 lb P2O5 / acre = 540 acres

Manure Utilization Strategy

As one can see, the annual manure production in the example will provide enough nitrogen for 115 acres but enough phosphorus for nearly 5 times that or 540 acres. Fortunately, most North Dakota soils are low in phosphorus. Since phosphorus at moderate concentrations can be held by the soil, manure phosphorus can be applied at rates greater than the current crop needs and banked for use in future years. Therefore, the most cost effective strategy is to apply enough manure to provide the nitrogen needs of the corn crop, but only apply it once every four or five years. That will allow the corn crop to utilize the phosphorus so it does not accumulate to a level where it becomes a water quality hazard. With any manure application strategy, soil tests for phosphorus should be done regularly. If soil P2O5 exceeds 150 ppm, no manure should be applied to that field.