Ag Assistant™ & Coefficient of Variation (CV) in Corn

You may occasionally see Ag Assistant™ flag a field for high CV (Coefficient of Variation). CV measures how uniform stand counts are across a field. Higher CV values indicate greater variability, which can impact yield potential and management decisions.

Why should a grower care about a high CV?

A high CV is not just a statistical flag – it signals real crop stress that can translate into bushels lost at harvest.

In agronomic terms, CV quantifies how consistently plants emerged, established, and developed. High variability leads to uneven canopy closure, intensified plant-to-plant competition, and reduced light interception efficiency – all of which directly suppress grain fill and final yield.

CV measures the distances between consecutive plants in a row (e.g., 6", 7.5", 5", 8", 6.5"...), then calculates the standard deviation of those distances and divides by their mean. The result tells you how erratic the planter or the seed germination quality was. A low CV could mean seeds landed at very consistent intervals, a high CV could mean you have a mix of doubles, skips, and irregular gaps.

How is CV Calculated?

CV (%) = (Standard Deviation ÷ Mean) × 100

Example:

10 stand counts — Mean = 32.6 plants, SD = 3.0

CV = (3.0 ÷ 32.6) × 100 = 9.2% (Excellent)

CV Value Ranges

CV Range (%)	Variability Level (Uniformity)	What It Means	Recommended Action
< 10%	Excellent	Highly uniform stand; minimal variability	No intervention needed
10% – 15%	Good	Acceptable uniformity for most production systems	Monitor; minor adjustments may help
15% – 20%	Moderate	Noticeable variability; yield drag likely	Investigate root cause; review inputs
20% – 30%	High	Significant variability; meaningful yield loss probable	Priority review of planting & soil management
> 30%	Very High	Severe variability; major agronomic problem	Immediate investigation and corrective action

Note: CV interpretation thresholds can vary depending on the agronomic source and the metric being evaluated, such as emergence timing, plant spacing, stand uniformity, or yield. The ranges shown here are intended as general guidelines to help assess field variability and identify potential areas for further investigation.

Implications of High CV

Yield Impact

Uneven canopy causes taller plants to shade smaller neighbors, reducing yield potential of weaker plants and increasing ear barrenness.

Agronomic Efficiency Loss

Fertilizer applied to gaps or weak-stand zones goes underutilized, raising cost per bushel and risking nutrient loss to leaching.

Management Timing Challenges

Growth-stage spread across the field makes herbicide, fungicide, and insecticide timing suboptimal for a portion of the crop.

Water Use Inefficiency

Patchy stands create uneven water demand, reducing irrigation efficiency and increasing drought-stress risk in thinner areas of the field.