Plants per acre = 43,560 ÷ (in-row spacing in feet × between-row spacing in feet). For tomatoes at 18 in × 48 in: 43,560 ÷ (1.5 × 4) = 7,260 plants/acre. For corn at 8 in × 30 in: 43,560 ÷ (0.67 × 2.5) = 26,136 plants/acre. Use our calculators to get exact numbers for your spacing and field size.
Plant population is the foundation of yield. Too dense: plants compete for light, water, and nutrients; increased disease pressure; smaller ears/fruit; lodging (falling over). Too sparse: wasted sunlight and land; lower total yield; more weeds. The optimal population balances individual plant performance with total area utilization. Modern corn hybrids achieve maximum yield at 30,000-36,000 plants/acre — 50% higher than 1970s hybrids, because modern varieties tolerate higher density without barrenness.
| Crop | In-Row | Between-Row | Plants/Acre |
|---|---|---|---|
| Tomato (staked) | 18-24 in | 48-60 in | 5,800-7,260 |
| Pepper | 12-18 in | 36-48 in | 7,260-14,520 |
| Lettuce (head) | 10-12 in | 12-18 in | 29,040-43,560 |
| Broccoli | 18-24 in | 36-48 in | 5,808-9,680 |
| Carrot | 2-3 in | 12-18 in | 116,160-261,360 |
| Onion (dry) | 3-4 in | 12-18 in | 87,120-174,240 |
| Cucumber (trellis) | 12-18 in | 48-72 in | 4,840-10,890 |
| Squash (bush) | 24-36 in | 48-72 in | 2,420-5,445 |
| Crop | In-Row | Between-Row | Plants/Acre |
|---|---|---|---|
| Corn (grain) | 6-8 in | 30 in | 26,136-34,848 |
| Soybean | 2-3 in | 15-30 in | 104,544-174,240 |
| Wheat (drilled) | 1-2 in | 7-10 in | 1,254,000-2,988,000 (seeds) |
| Cotton | 4-6 in | 38-40 in | 26,136-41,454 |
| Sunflower | 12-18 in | 30 in | 11,616-17,424 |
| Alfalfa (drilled) | broadcast | 6-8 in rows | ~1,500,000 seeds/acre |
A stand count tells you your actual plant population vs. target. Method: 1) Measure 1/1000 acre length based on row width. For 30-inch rows: 17 ft 5 in (1/1000 acre). For 15-inch rows: 34 ft 10 in. 2) Count plants in that length in 5-10 representative locations. 3) Average the counts and multiply by 1000 = plants/acre. 4) Compare to target. If below 90% of target, consider replanting (for corn) or accepting lower yield (for soybeans, which can compensate with branching). Stand counts are most accurate at V2-V4 (2-4 leaf stage) for corn and after full emergence for all crops.
High fertility + irrigation = can push higher populations (more plants can be supported). Low fertility + dryland = reduce population by 10-20% (fewer plants share limited resources). In dry years, over-populated fields suffer more because each plant has access to less water. In irrigated, high-fertility fields, the yield-limiting factor is usually light interception, so higher populations are beneficial.
Early-maturing varieties = smaller plants = can plant denser. Late-maturing varieties = larger plants = need wider spacing. Short growing season (northern latitudes, high elevation) = use earlier varieties and higher populations to maximize light interception in limited time. Long growing season = later varieties with wider spacing, allowing individual plants to reach full potential.
Row spacing is often determined by equipment (30-inch rows for corn headers, 15-inch for soybean drills). Narrower rows (15-20 inch corn) can increase yield by 3-8% through faster canopy closure and less weed pressure, but require specialized equipment. Bed planting (vegetables) allows precise spacing and drip irrigation. Transplanting vs direct seeding: transplants allow more precise spacing and earlier maturity, but cost more per plant.
Calculate your planting: Use our Seed Rate Calculator for exact seed amounts, Area Converter for acres-to-hectares, and Germination Calculator to adjust for emergence rate.