A solid fertility program and timely early-season management decisions are necessary to optimize wheat yield and grain quality. When determining the crop nutrient needs, producers must realistically assess their yield potential. With this knowledge, a successful fertility plan should be created using results from a recent soil test to accurately meet the specific needs of a field. Ideally, soil testing is completed in the late summer or early fall before planting so that accurate rates are applied. While basic soil tests for nitrogen (N), phosphorus (P), and potassium (K) are common, a more comprehensive test that includes micronutrients can provide deeper insight into your field’s needs and explain past crop performance issues. Micronutrients are required in small quantities. It is important that micronutrients are not applied without a soil test as high quantities can be toxic.
Table 1. Nutrient requirement per bushel grain yield for the growth and development of winter wheat harvested for grain. The total levels of nutrients removed from the field will vary based on the wheat system. Silage and baled hay will remove larger qualities of nutrients than if you just harvest the grain.
| Nutrient | Uptake in lbs. per Bushel grain yield | Key Function | |
| Nitrogen | N | 1.5 to 2.2 lbs | Yield, Protein Content, Overall Growth |
| Phosphorus | P?O? | 0.6 to 0.7 lbs | Root Development, Tillering, Energy Transfer, Cell Development |
| Potassium | K?O | 1.2 to 1.5 lbs | Water Regulation, Disease Suppression |
| Sulfur | S | 0.2 to 0.25 lbs | Nitrogen Utilization, Protein Synthesis |
| Chloride | Cl | ~ 1.1 oz | Water Regulation, Disease Suppression |
| Zinc | Zn | ~ 0.03 oz | Photosynthesis and Chlorophyll Production, Enzyme Activation, Metabolic Processes |
| Manganese | Mn | ~ 0.08 oz | Photosynthesis, Enzyme Activation |
| Iron | Fe | ~ 0.09 oz | Photosynthesis and Chlorophyll Production, Enzyme Activation, Metabolic Processes |
| Copper | Cu | ~ 0.01 oz | Photosynthesis, Lignin Production (Straw Strength) |
| Boron | B | ~ 0.007 oz | Pollination, Cell Wall Development |
A soil test is the only way to know with certainty how much fertilizer you actually need to apply. When soil testing, deeper samples (greater than 6 inches) will always provide a more accurate recommendation of the crop’s nutrient requirement. Nutrient availability and uptake are heavily influenced by soil texture (CEC), soil moisture, soil pH, and temperature. Under drought conditions, nutrient uptake is often reduced even if the nutrients are present in the soil. Fall soil sampling also allows you to match the soil fertility levels with the specific crop use (i.e. grain, grazing, or both). Nitrogen is generally the most limiting nutrient in crop production. Young wheat needs a small amount of nitrogen for fall growth and tiller development. Applying too much N in the fall can lead to excessive growth which may promote winter-kill or foliar diseases and increases the risk of N loss through leaching.
In dryland systems, excess fall growth can use soil moisture which is more valuable later in the season. If there is little winter and spring precipitation, excess fall growth can curtail spring development. For these reasons, splitting N applications between fall and late winter/early spring as recommended ensure N is “in the right place at the right time” to optimize N efficiency and yield. While N is generally the most limiting, P is very important for fall applications. Phosphorus is essential for early root development and tiller formation. Because P is immobile in the soil, it should be applied with the starter fertilizer and incorporated.
Although many Texas wheat producers are already planting, it is not too late to submit soil samples to make accurate in-season fertility decisions. Soil samples can be submitted to the Texas A&M Soil Testing Laboratory (https://soiltesting.tamu.edu/ using Microsoft Word – soil submittal form2025) or to your regional private lab. Recommendations may vary between labs because of the soil test and varying recommendations based on common production systems.
References:
Stichler and McFarland. 2001. Crop Nutrient Needs in South and Southwest Texas. Texas A&M University. Texas Agricultural Extension Service. B-6053. https://ccag.tamu.edu/wp-content/uploads/sites/10/2020/12/PUB_soil_Crop-Nutrient-Needs.pdf
Wheat Production Handbook. 1997. Kansas State University Research and Extension. C-529 https://bookstore.ksre.ksu.edu/pubs/wheat-production-handbook_C529.pdf
This Extension Education Tip is provided by Dr. Jourdan Bell, Texas A&M AgriLife Extension Agronomist, Amarillo, (806)-341-8925, Jourdan.bell@ag.tamu.edu
