Corn: Plant Analysis

Excerpt from Agronomy Guide for Field Crops (Chapter 3)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
   • Interpretation of Plant Analysis for Corn - Table 3-22
2. Foliar Fertilization
3. Updates on Corn: Plant Analysis
4. Related Links...

Introduction

The most appropriate growth stage for sampling corn for plant analysis changes for different nutrients. For most nutrients, sampling the mid-third of the ear leaf at silking is most appropriate. Refer to Table 3-22. Interpretation of Plant Analysis for Corn. For phosphorus and zinc, however, sampling the whole plant when 5-6 leaves are visible is more appropriate.

¹Yield loss due to nutrients deficiency is expected with nutrient concentrations at or below the "critical" concentration.
²Maximum normal concentrations are more than adequate but do not necessarily cause toxicities.

Plants suspected of having nutrient deficiency should be sampled as soon as the problem appears. For plants with six leaves or less, sample the total above-ground plant. From seven leaves to silking, sample the youngest fully developed leaf. Take separate samples from areas with and without symptoms for comparison. For sampling at times other than silking, samples should be taken from both deficient and healthy areas of the field for comparative purposes.

A soil sample should be taken from the same area and at the same time as a plant sample.
For more information, see the section Plant Analysis.

Foliar Fertilization

The foliar application of nutrients to corn has not proven effective in most instances. The rates of nutrients required cannot be applied as a foliar spray without causing damage to the leaf, unless numerous small applications are made. The exception is correction of some of the micronutrient deficiencies, but even in this case it is often more economical to apply the nutrient to the soil.

Plate 8. Fertilizer injury burns the primary root, delaying growth until secondary roots develop. Plant emergence will be uneven.

Updates on Corn: Plant Analysis

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