From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Fall 2001, No. 3


Ever expect to fill a 50-gallon water barrel to the very top when a portion of one of the vertical staves is broken off? Of course not. The barrel fills to the top of the broken stave and any additional water pours out….wasted. And it doesn’t matter how strong the other staves are or how well they fit together, making a water-tight seal. The broken stave determines the capacity of the barrel.

Crop production works much the same way. Each management decision and each input is a stave in the barrel. The ultimate yield and quality of a crop are determined by how well the staves fit together, creating a complete barrel. If one input falls short, i.e., a short stave, then crop potential is limited by that one inadequate input.

Not all factors affecting production are controllable. Some things we just live with, such as the vagaries of weather, field topography, depth to bedrock, length of growing season…and others. These factors determine the ultimate capacity of the barrel.

Many factors, however, are controllable. These are the staves on which to focus. For example, nutrient balance, insect and weed control, variety selection, and planting date are all inputs…staves in the barrel…that can separate a high yielding, profitable crop from a crop disappointment.

High yields are associated with low inputs per unit of production…more efficient production. This is because the skillful grower balances inputs to achieve a specific yield goal and manages for that goal. The grower does not apply nitrogen to produce 250 bushels per acre of corn, but only supplies phosphorus and potassium for 200 bushels. Nutrient imbalance in this case is the short stave and prevents all other inputs from being utilized to their maximum.

Knowledge of the actual amounts of nutrients being removed by each crop combined with soil and tissue testing will prevent a nutrient deficiency or nutrient imbalance from becoming a short stave. For many years we have relied on the native fertility of our soils to provide a significant portion of the required nutrition. However, yields…and, therefore, nutrient removal… are much higher today, and most fields have been cropped for many years.

The trend towards less fertile fields is continuing. For example, nationally the ratio of fertilizer nitrogen to K2O applied is 2.5 to 1. So even though crops require approximately equal amounts of nitrogen and potassium, growers are relying heavily on native soil potassium fertility to balance the nitrogen requirement. In the western states, the discrepancy in the nitrogen to potassium ratio is even greater….on the order of 5 to 1. It is important to monitor the rates of nutrient depletion. Utilizing native fertility is not an issue…until it creates a short stave. Without careful monitoring, yield potential may be lost for several years before the deficiency is identified.

Applying inputs to fill a 50 gallon barrel when a short stave limits capacity to 40 gallons is wasteful…and costly. Don’t pour away potential profits. Pay attention to all production inputs and manage each one for a specific yield goal. Remember…the short stave can be costly.

— AEL—

For more information, contact Dr. Albert E. Ludwick, Western Director, PPI, P.O. Box 970, Bodega Bay, CA 94923. Phone: (707) 875-2163. E-mail:
Copyright 1996-2018 by Potash & Phosphate Institute. All rights reserved.