Bushel Weight Guide

Standard Bushel Weights by Grain

Each grain has a standard bushel weight established by USDA:

Why Test Weight Matters

Test weight is important for several reasons:

Grain marketing: Elevators discount grain below standard test weight. Discounts start at 1-2 lb below standard and increase with severity. At 54 lb/bu corn (2 lb below standard), discount is typically $0.05-0.10/bu.

Storage capacity: Lower test weight grain takes more bin space. 100,000 bushels of 52 lb corn takes the same space as 107,700 bushels of 56 lb corn.

Feed value: Higher test weight grain generally has higher feed value per pound. Livestock feeders prefer high test weight grain for consistent feed conversion.

Milling quality: Higher test weight grain produces more flour, starch, or ethanol per bushel. Processors pay premiums for high test weight.

Transportation: Grain is sold by bushels but transported by weight. Low test weight grain costs more to transport per bushel.

Factors Affecting Corn Test Weight

Corn test weight is affected by many factors:

Genetics: Some hybrids consistently produce higher test weight than others. Check hybrid characteristics when selecting seed.

Weather during grain fill: Cool, sunny weather during R3-R6 produces higher test weight. Heat and drought reduce test weight.

Frost before maturity: Frost stops starch accumulation, resulting in lower test weight. Frost at R5 can reduce test weight 3-5 lb/bu.

Disease: Leaf diseases reduce photosynthesis, reducing starch accumulation and test weight. Stalk and ear rots directly damage kernels.

Harvest moisture: Corn harvested at higher moisture (25-30%) and dried gently typically has higher test weight than corn left to field-dry.

Drying temperature: High drying temperatures (>140°F) cause stress cracks that reduce test weight. Low-temperature drying preserves test weight.

Hybrid maturity: Full-season hybrids generally have higher test weight than short-season, but only if they reach maturity.

How to Measure Test Weight

Test weight is measured using standardized equipment:

Official test weight apparatus: Cox funnel and 1-quart cup. Fill cup from a specific height, level off, weigh, multiply by 32 to get lb/bu.

Portable moisture tester: Most portable moisture testers also measure test weight. Less accurate than official method but convenient.

Elevator testing: Elevators measure test weight on every load. Results printed on scale ticket.

Combine yield monitor: Modern yield monitors estimate test weight, but should be verified with official measurement.

Standard test weight measurements are at the grain's standard moisture content. Test weight increases as grain dries (less water = denser grain).

Improving Corn Test Weight

Several management practices can improve corn test weight:

1. Hybrid selection: Choose hybrids with consistently high test weight
2. Plant appropriate maturity: Don't push full-season hybrids in short-season areas
3. Plant early: Earlier planting allows more grain fill time
4. Manage leaf diseases: Apply fungicide to protect photosynthesis during grain fill
5. Maintain balanced fertility: Potassium particularly important for grain fill
6. Control insects: Ear-feeding insects reduce kernel fill
7. Harvest at proper moisture: 22-25% moisture preserves test weight
8. Dry gently: Use low-temperature drying (<140°F) to avoid stress cracks
9. Avoid frost damage: Plant early enough to mature before frost

Low Test Weight Grain: Causes and Uses

Low test weight corn (below 54 lb/bu) has several causes and uses:

Common causes:

• Frost before maturity
• Drought during grain fill
• Leaf disease (gray leaf spot, NCLB, tar spot)
• Ear rot (Fusarium, Gibberella)
• Insect damage (corn earworm, western bean cutworm)
• Poor hybrid choice or wrong maturity
• High drying temperature stress cracks

Uses for low test weight corn:

• Livestock feed (reduced value but still usable)
• Ethanol production (lower yield but acceptable)
• Industrial processing (depends on end use)

Low test weight corn should be tested for mycotoxins before feeding. Frost-damaged corn is more prone to mold development in storage.

Test Weight and Grain Yield

There's often confusion about test weight vs. yield:

Test weight measures grain density (lb per bushel).

Yield measures total grain production (bushels per acre).

These are independent — you can have high yield with low test weight, or low yield with high test weight. However, conditions that produce high yield (good weather, healthy crop, adequate fertility) also tend to produce high test weight.

Test weight and yield relationship: In a typical year, test weight above standard (56 lb/bu corn) doesn't increase yield, but discounts apply below standard. Some high-test-weight hybrids yield slightly less than average-test-weight hybrids — don't chase test weight at the expense of yield.

Storing Grain to Preserve Test Weight

Proper storage maintains test weight:

• Dry to proper moisture: 15% for short-term storage, 13-14% for long-term
• Cool grain quickly: 40°F by November, 30°F by December
• Aerate regularly: 1-2 hours per week to maintain uniform temperature
• Inspect weekly: Look for crusting, musty smell, temperature increases
• Protect from insects: Treat with diatomaceous earth or fumigate if needed
• Avoid mixing: Don't mix low-test-weight grain with high — discounts apply to entire lot

Test weight doesn't change in storage if grain is properly dried, cooled, and aerated. Wet grain or warm grain can develop molds that reduce test weight.