This week, I found some time to sort through a pile of paperwork on my desk marked as story ideas. In the pile was the Fertilizer Institute's 4R Pocket Guide, one of the handouts given to attendees at the Conservation Technology Information Center's 2024 Conservation in Action Tour in June.
The 4Rs of nutrient management are a set of guidelines for keeping nutrients on the field. Applying the right source of fertilizer at the right rate, at the right time and in the right place improves farmer profits and decreases environmental impact. The 4R Pocket Guide gives a short explanation of each R, and the table below, listed under the right rate section in the booklet, caught my attention. It lists how much nitrogen, phosphorus, potassium and sulfur each crop removes.
"The selection of a meaningful yield target attainable with optimal crop and nutrient management and its variability within fields and season to season thus provides important guidance on the estimation of total crop nutrient demand," the guide says. "For nutrients unlikely to be retained in the soil, the most economic rate of application is where the last unit of nutrient applied is equal in value to the increase in crop yield it generates (law of diminishing returns)."
|
CROP**
|
UNIT
|
N
|
P2O5
|
K2O
|
S
|
| Alfalfa (DM) |
ton
|
51
|
12
|
49
|
5.4
|
| Barley grain |
bu
|
0.99
|
0.4
|
0.32
|
0.09
|
| Beans (dry) |
bu
|
3
|
0.79
|
0.92
|
0.52
|
| Bromegrass (DM) |
ton
|
32
|
10
|
46
|
5
|
| Canola grain |
bu
|
1.9
|
1.2
|
2
|
0.34
|
| Corn grain |
bu
|
0.67
|
0.35
|
0.25
|
—
|
| Cotton (lint) |
bale
|
32
|
14
|
19
|
—
|
| Flax grain |
bu
|
2.5
|
0.7
|
0.6
|
0.19
|
| Millet grain |
bu
|
1.4
|
0.4
|
0.4
|
0.08
|
| Oat grain |
bu
|
0.77
|
0.28
|
0.19
|
0.07
|
| Peanut nuts |
ton
|
70
|
11
|
17
|
—
|
| Potato tuber |
cwt
|
0.32
|
0.12
|
0.55
|
0.03
|
| Red clover (DM) |
ton
|
45
|
12
|
42
|
3
|
| Rice grain |
bu
|
0.57
|
0.3
|
0.16
|
—
|
| Rye grain |
bu
|
1.4
|
0.46
|
0.31
|
0.1
|
| Sorghum grain |
bu
|
0.66
|
0.39
|
0.27
|
0.06
|
| Soybean grain |
bu
|
3.25
|
0.73
|
1.18
|
—
|
| Sugarbeet root |
ton
|
3.7
|
2.2
|
7.3
|
0.45
|
| Sugarcane |
ton
|
2
|
1.25
|
3.5
|
—
|
| Tomatoes |
bu
|
2.5
|
0.92
|
5.7
|
—
|
| Wheat straw |
bu
|
0.7
|
0.16
|
1.2
|
0.14
|
| Wheat (spring) grain |
bu
|
1.49
|
0.57
|
0.33
|
—
|
| Wheat (winter) grain |
bu
|
1.16
|
0.48
|
0.29
|
—
|
*Reported nutrient removal coefficients may vary regionally depending on growing conditions. Use locally available data whenever possible.
**DM = dry matter basis; otherwise moisture content is standard marketing convention or at the stated moisture content.
The Fertilizer Institute provides this example of how to use the table above for nutrient balancing and determining how much fertilizer each crop needs: A 200 bushel per acre corn crop removes 70 pounds of P2O5 from the soil (200 x 0.35 = 70). So, the maintenance P2O5 application would be 70 pounds per acre.
More information about right rate and basics about other 3Rs are available in the Fertilizer Institute's 4R Pocket Guide.
