Fact Sheets And Publications

Estimating Yield Goal for Crops

Introduction

Many crop management decisions require farmers or their agronomist, crop consultant, or nutrient consultant to make an estimation of the expected yield from a given field. Farmers recognize that yields for the same crop are variable from field-to-field and that a given crop cannot be expected to produce a consistent yield across the entire state. Climate, crop genetics, crop management (intensity as well as management skill level), and the physical and chemical properties of soils have significant effects on crop yield. Soil conditions, especially, vary considerably from farm to farm and field to field, and conditions can vary even within an individual field. In addition, advances in crop genetics (e.g., increased drought and pest/disease resistance) can increase yield potential for field crops from 0.5 to 2 bu/A annually, depending on the crop. For these reasons, it is important for the grower to establish a realistic yield goal for each field each year to project production cost, promote farm profitability, and protect environmental health. The purpose of this publication is to outline the proper methods for estimating yield goal.

Why Use a Realistic Yield Goal

The primary reason for using realistic yield goals is economics. Yield goals are necessary if growers are to control their unit cost of production to improve farm profitability. Several production decisions, including crop species selection, seeding rate, and fertilizer recommendations, are directly impacted by the yield goal. For example, crop species selection is strongly influenced by yield goal. On fields that cannot be irrigated, the choice between growing dryland corn and grain sorghum frequently rests with the expected yield from the field. If the farmer has determined that a given field has a realistic yield goal of 70 to 90 bu/A for dryland corn, corn should be the crop selected. If, however, the farmer has determined that a given yield level is not realistic for that field, the crop of choice is grain sorghum in rotation with soybeans. For fields with realistic soybean yield goals of less than 15 to 20 bu/A (perhaps due to soybean cyst nematode infestation or frequent drought conditions), farmers should again consider a crop rotation with a non-host, drought-tolerant crop, such as grain sorghum.

Another production decision affected by yield goal is plant population. On droughty soils, reduced seeding rates are used to improve crop drought tolerance. This directly affects production costs both through seed costs and through final yield levels attained.

Yield goals also directly influence the amount of nitrogen (N), phosphorus (P), and potassium (K) applied to the crop. With the exception of N, fertilizer recommendations for macro- and micronutrients are based on the results of a soil sample analysis and expected yield goals (P and K). If yield goals are too high, the grower may spend money on fertilizer that is not needed. Fertilizer use can be a large part of the projected cost of production. If yield goals are set too low for the crop, the recommended nutrient rates will not be sufficient to produce the maximum economic yield and again farm profitability will be reduced.

A second important reason for using yield goals is the environment. If yield goals are too high, growers could mistakenly apply too much N and/or P as commercial fertilizer or manure. The use of N and P in excess of crop needs not only wastes money, but also increases the potential for N and/or P to move off site during erosion, runoff, or leaching events. Nutrients that move from the root zone of the plant can pollute local waterbodies and groundwater.

A third reason for using realistic yield goals is successful marketing. Since yield goals strongly influence production practices, they have a direct impact on a grower's projected cost of production. Decisions that involve forward contracting, futures options, and other marketing tools depend on accurate anticipated costs of production. Farm profitability is directly influenced by marketing decisions.

Available Methods for Estimating Yield Goal

While there are a number of methods available for setting realistic yield goals, Delaware growers are required by law to choose one of two approved methods for determining yield goal. These approved methods are 1) taking an optimal rolling average or 2) using soil productivity charts (in the absence of actual yield data). These methods are used to guide nutrient management decisions in the nutrient management plan, which is required for an operation applying nutrients to 10 or more acres.

The preferred method for estimating yield goal is the optimal rolling average: With this method, the farmer uses the field yield averages for the past seven years and then drops the lowest three yields. The remaining highest four yields are averaged to provide the estimated yield goal (Table 1). It is important to note that due to crop rotations, the last seven years of data for a specific crop may not be from contiguous years.