As I was tearing down our display after another successful Crop Production Show, I reflected on the many questions and comments that producers from around the province had throughout the week. The most common questions asked revolved around producers re-evaluating their fertility program after a very dry growing season. How much residual N do I have remaining in the soil from the previous year? Can I cut out potash and sulfur from my fertility program to reduce costs? How much nitrogen can I seed place? All are valid questions.
Despite volatile markets and low commodity prices, producers still need to maximize crop yields and crop quality to achieve the highest net return per acre. In order to do this we need to manage our nutrients accordingly, making sure we supply the soil with what it needs using correct blends and correct rates. A soil test can provide this information, and the cost may be the wisest dollars spent by producers this spring.
Soil testing is an essential part of nutrient management planning, and is the most practical method of assessing nutrient value in the soil. Although testing is not 100% accurate, it does provide a reasonable estimate of the soil's nutrient availability. Soil testing also manages the risk by identifying yield-limiting factors and estimates the probability of crop response to added nutrients.
Once the soil test is complete, the next step is to create a balanced fertilization program. As an ag retailer for the past decade, I spent a considerable amount of time reviewing soil tests and creating balanced fertilization programs for producers. To maximize yield and crop quality, we must provide the plant with adequate amounts of all essential nutrients. By providing the plant what it needs - at the correct time, at the proper placement and in the proper blend - you will ensure the production of a healthier plant with a well developed root system. Healthier plants will improve the crop's ability to cope with disease and pest problems. The crop's tolerance to dreaded environmental conditions such as heat and drought will also be significantly improved due to increased efficiency in the plant's water use. Most important, a healthy plant limits the impact of the above stresses on yield and profit potential.
When designing a balanced fertilization program, one has to always keep in mind Leibig's theory of the law of the minimum. This law states that crop yield is proportional to the amount of the most limiting nutrient. When this nutrient is added, crop production is raised until it is controlled by the next most limiting nutrient. Although nitrogen will always be the most important nutrient, it can only be effective if all other nutrients are in sufficient quantity to meet crop requirements. There are 16 elements known to be essential for plant growth. To maximize yields, all elements must be present in the correct amounts and the correct proportions to each other. Excess amounts of certain nutrients can affect the availability of other nutrients and cause deficiency symptoms.
The amount of fertilizer that can be seed placed is dependent on many variables. Cereals can tolerate more fertilizer in the seed row than the smaller seeded crops such as canola and flax. Ultimately too much fertilizer in the seed row will cause ammonium toxicity and lead to germination damage. Soil conditions such as organic matter content, texture, and soil moisture will ultimately affect the amount of fertilizer that can be placed with the seed this spring. Generally, a crop seeded on heavier textured soil with higher organic matter levels will tolerate greater amounts of seed placed fertilizer than coarser textured soil with lower organic matter levels. In addition, producers should also take into consideration seedbed utilization. The method of seeding (e.g. use of a disc, knife, hoe opener, or spread tip) and the amount of row spacing will also affect the amount of fertilizer that can be seed applied. The general rule of thumb is the higher the seedbed utilization, the greater amount of fertilizer that can be safely applied with the seed.
Everybody knows about the attributes of nitrogen and phosphorous to crop production. One must not, however, downplay the benefits provided by potash and sulfur. Unfortunately these products tend to be dropped from fertilizer programs when producers are looking to cut costs. Be aware that both elements are macronutrients and, as such, the plant does require them in large amounts. The incorporation of potash and sulfur into a fertilization program will ultimately result in improved crop yield and quality.
Have you ever noticed increased lodging in your crops? Are you seeing a higher incidence of disease or crops that cannot withstand drought? If so, your crop may be lacking in potash. With the exception of nitrogen, there is no other fertilizer nutrient required in higher amounts by plants than potassium. Generally our soils do contain high potassium reserves, however only a small fraction is plant available. It has been documented that cereals and oilseeds require 70 to 90 lbs/acre of potassium. Some high use crops such as barley require approximately 95 lbs/acre. Field peas require an astounding 135 lbs/acre of potassium. Potassium plays an important role in regulating the opening and closing of the stomata on plant leaf surfaces. This is particularly important, especially in drier years. When potassium is deficient, plant water losses increase and plants are more susceptible to water stress. Potassium serves a number of other functions in the plant, including disease suppression, straw strength maintenance, protein synthesis, and enzyme activation.
Sulfur is the third most limiting nutrient in prairie soils. The black, dark gray, and gray soil zones of the prairies, along with coarser textured soils, usually have lower reserves. Sulfur is required for protein production and in the formation of chlorophyll.
Sulfur deficiencies will be evident by the yellowing of the newest leaves. Other symptoms include short spindly stems and an upward cupping of younger leaves. Sulfur requirements vary from one crop to the next. For example, broadleaf crops such as alfalfa and canola need larger amounts than cereal crops. Make no mistake - the inclusion of this nutrient in your fertilization program will positively impact crop yield and quality.