Nutrient Management · Economics · Crop Staging · Pest & Weed · Soil Health · State Stats
Agricultural Fast Facts
The complete on-farm reference — corn N rates, a manure nutrient value calculator, P&K by soil test, crop staging, GDU, pest thresholds, herbicide MOA, a breakeven calculator, and state production data, integrated with live commodity and fertilizer prices. Free for every US farmer.
Agronomic recommendations are calibrated to Upper-Midwest guidelines (UW Extension A2809). Growers in other regions should confirm rates, lime, and calendar dates with their state land-grant extension — values shift by region.
Maintained by Sigurd Lindquist · last reviewed June 8, 2026 · sig@farmers1st.com
Enter your soil test values — get your P₂O₅ / K₂O recommendation. Uses the Bray P1 method (common across the Corn Belt). High-pH or Western soils tested by Olsen P: multiply × 1.6.
Soil Test → Recommendation Calculator
P Category
—
K Category
—
Apply P₂O₅ (lb/ac)
—
Apply K₂O (lb/ac)
—
P₂O₅ Cost
—
K₂O Cost
—
Total P+K $/ac
—
Based on live DAP/MOP prices
Soil Test Category Breakpoints (ppm)
Category
Bray P1 (ppm)
K (ppm)
Interpretation
Very Low
<11
<61
Deficient — yield loss likely
Low
11–15
61–90
Below optimum — good response likely
Optimum
16–25
91–130
Sufficient — maintenance rate
High
26–50
131–200
No response expected — reduce or eliminate
Very High
51–75
201–300
No response — draw down levels
Extremely High
>75
>300
Do not apply
Corn P₂O₅ & K₂O Recommendation Tables
Corn Yield Goal (bu/ac)
Soil Test Level
V.Low
Low
Opt
High
V.High
Ex.High
Phosphate (P₂O₅) lb/ac
131–150
95
85
55
30
—
0
151–170
100
90
60
30
—
0
171–190
110
100
70
35
—
0
191–210
115
105
75
40
—
0
211–230
125
115
85
45
—
0
231–250
130
120
90
45
—
0
251–270
140
130
100
50
—
0
Potash (K₂O) lb/ac
131–150
85
70
40
20
10
0
151–170
90
75
45
25
10
0
171–190
95
80
50
25
15
0
191–210
105
90
60
30
15
0
211–230
110
95
65
35
15
0
231–250
115
100
70
35
20
0
251–270
120
105
75
40
20
0
Soybean P₂O₅ & K₂O Recommendations
Yield Goal (bu/ac)
Soil Test Level
V.Low
Low
Opt
High
V.High
Ex.High
Phosphate (P₂O₅) lb/ac
46–55
80
70
40
20
—
0
56–65
90
80
50
25
—
0
66–75
95
85
55
30
—
0
76–85
105
95
65
35
—
0
86–95
110
100
70
35
—
0
Potash (K₂O) lb/ac
46–55
115
100
70
35
20
0
56–65
130
115
85
45
20
0
66–75
145
130
100
50
25
0
76–85
155
140
110
55
30
0
86–95
170
155
125
65
30
0
Olsen P users: Multiply Olsen P × 1.6 to approximate Bray P1.
Nutrients Removed at Harvest
Crop & Component
Yield Unit
lb P₂O₅
lb K₂O
Corn
Corn, Grain
per bu (56 lb @ 15.5%)
0.38
0.29
Corn, Silage
per ton (65% moisture)
3.6
8.3
Corn Stover
per ton DM
4.6
32
Soybean
Soybean, Grain
per bu (60 lb @ 13%)
0.80
1.4
Soybean Straw
per ton DM
5.4
19
Alfalfa & Forage
Alfalfa / Red Clover
per ton DM
13
60
Small Grain Silage
per ton DM
11
44
Small Grains
Wheat, Grain
per bu (60 lb @ 13.5%)
0.50
0.35
Barley, Grain
per bu (48 lb @ 14.5%)
0.40
0.35
Oats, Grain
per bu (32 lb @ 14%)
0.29
0.19
Nutrient Removal Calculator
Field Nutrient Export Estimator
P₂O₅ /ac
—
K₂O /ac
—
Total P₂O₅
—
Total K₂O
—
Plant Population by Row Width
Row Width
20"
28"
30"
32"
36"
38"
40"
Row length for 1/1000 ac
26'1"
18'8"
17'5"
16'4"
14'6"
13'9"
13'1"
Formula: Count plants in that row length × 1,000 = plants/acre. Count at least 3 rows.
Bu/Acre Calculator — Shelled Corn
Corn Yield Calculator
Bu @ 15.5%
—
Bu / Acre
—
Available Nutrient Content by Manure Type
1st year [2nd year] N available. Solid = lb/ton; Liquid = lb/1,000 gal. Manure analysis strongly recommended — content varies considerably between farms.
Incorporate promptly. Each hour of surface exposure costs significant N through volatilization, especially in warm, windy conditions.
Manure Type
N — 1st yr [2nd yr]
P₂O₅
K₂O
>3 Days
1 hr–3 days
<1 Hour
Dairy
Solid >20% DM (lb/ton)
2 [1]
3 [1]
3 [1]
3
6
Solid 11–20% DM (lb/ton)
2 [1]
2 [1]
3 [1]
3
5
Liquid 4–11% DM (lb/1000 gal)
7 [2]
10 [2]
12 [2]
6
17
Liquid <4% DM (lb/1000 gal)
4 [1]
6 [1]
7 [1]
3
11
Beef
Solid (lb/ton)
3 [1]
4 [1]
5 [1]
6
10
Liquid (lb/1000 gal)
5 [2]
6 [2]
8 [2]
6
12
Swine
Solid (lb/ton)
7 [2]
9 [2]
12 [2]
10
8
Liquid finish indoor (lb/1000 gal)
17 [4]
22 [4]
28 [4]
14
22
Liquid finish outdoor (lb/1000 gal)
7 [2]
9 [2]
12 [2]
6
8
Poultry
Chicken solid (lb/ton)
24 [5]
27 [5]
29 [5]
35
26
Turkey solid (lb/ton)
26 [5]
28 [5]
31 [5]
35
25
Horse
Solid (lb/ton)
2 [1]
3 [1]
4 [1]
5
6
Manure Nutrient Value Calculator Live prices
What is your manure worth at today’s fertilizer prices? Enter type, incorporation timing, and application rate — get dollar value per acre and total field savings.
Based on UW Extension A2809 SMP-buffer calibration (Upper Midwest). Other regions vary — consult your state land-grant extension for locally calibrated lime recommendations.
Micronutrient Reference — Upper Midwest
Nutrient
Responsive Crops
Deficient
Method
Typical Rate
Key Notes
S
Soybeans, alfalfa, small grains
<10 ppm
KCl
10–20 lb S/ac
Sandy soils, low OM, high rainfall. AMS (24% S) common source. Note: soil S tests have poor predictive reliability — apply S on sandy/low-OM soils as insurance regardless of test result.
Zn
Corn, beans, soybeans
<0.5 ppm DTPA
DTPA
1–2 lb Zn/ac
High pH (>7.0), high P, cold wet spring. Corn “white bud.”
B
Alfalfa, clover, sunflower
<0.5 ppm
Hot water
0.5–1 lb B/ac
Sandy soils, low OM. Toxic range narrow — do not over-apply.
Mn
Soybeans, oats, wheat
<5 ppm DTPA
DTPA
0.5–1 lb Mn foliar
High pH (>6.5), organic soils. Foliar preferred.
Fe (IDC)
Soybeans
pH >7.3 + CaCO₃
SPAD
IDC-tolerant varieties
Most common on calcareous (high-pH) soils.
Tissue Test Critical Levels
Corn — Ear Leaf at R1 (Silking)
Nutrient
Deficient
Sufficient
Excess
N %
<2.7
2.7–3.5
>4.0
P %
<0.25
0.25–0.50
>0.60
K %
<1.7
1.7–2.5
>3.0
S %
<0.15
0.15–0.50
—
Zn ppm
<15
15–60
>200
Soybean — Uppermost Trifoliate at R3
Nutrient
Deficient
Sufficient
Excess
N %
<4.0
4.5–5.5
>6.0
P %
<0.22
0.26–0.50
>0.70
K %
<1.4
1.7–2.5
>3.0
Zn ppm
<15
21–55
>100
Fe ppm
<50
51–350
—
Corn Growth Stages — Interactive GDU Timeline
Click any stage to see GDU accumulation, crop description, and key management windows. Based on base 50°F GDUs.
Select a stage above to view details
Soybean Growth Stages — Interactive Timeline
Vegetative (V) and reproductive (R) stages with GDU accumulation from emergence. Click any stage.
Excellent waterhemp activity. Rotate with Group 2 avoided fields.
Waterhemp management priority across the Corn Belt: Confirmed resistance to Groups 2, 5, 9, 14 (and in some populations, 27) makes waterhemp the highest resistance-management priority in most corn and soybean regions. Use 3+ MOA programs with effective soil residual, and do not rely on post-only programs.
A central Corn Belt timeline. Planting and maturity windows shift roughly one to two weeks per ~150 miles of latitude — check your state Extension or USDA NASS Crop Progress for local dates.
Date / Window
Corn
Soybean
Notes
Apr 20 – May 15
Optimal planting window
—
Soil temp ≥50°F at 2" depth for 3 consecutive days
May 1 – May 20
—
Optimal planting window
Soil temp ≥50°F; avoid Sudden Death Syndrome risk from cold early planting
June 1
Significant yield drag begins
Moderate yield drag
~1% yield loss per day after June 1 for corn; beans more flexible to June 10
Late June – July
Critical pollination window
Bloom & pod set
Drought or heat stress during this window has largest yield impact
Late Aug – early Sep
Black layer / physiological maturity
R7 (begin maturity)
Monitor for early frost risk — especially in northern areas
Sep 15
Average first frost (northern areas)
Harvest window opens
Frost before black layer can cause quality issues
State-Level Production Data
U.S. crop production at a glance, with per-state detail from USDA NASS — the national source for acreage, yield, and production across all 50 states.
U.S. Corn — 2025
Production17.0 B bu
Avg yield186.5 bu/ac
Harvested91.3 M ac
U.S. Soybeans — 2025
Production4.26 B bu
Avg yield53.0 bu/ac
Harvested80.4 M ac
National totals: USDA NASS Crop Production 2025 Summary (final). Select any state for its full USDA NASS profile.