Wheat fields turning green early

As yards are turning green, so are the wheat fields. Farmers call this phenomenon greenup. Greenup is a descriptive term referring to fields that have started spring growth of new leaves. A field should be completely green in color before a farmer says they are at the greenup growth stage. It is unusual to see this much green before St. Patrick's Day. This early occurrence is most likely from the strong El Nino pattern occurring in the eastern Pacific Ocean. The last time we saw this pattern was in 2016, 1998, and 1982. This greening of yards and wheat fields is about two weeks earlier than normal. Farmers will become actively engaged in many field activities after greenup. One of these activities is fertilizer application. Because wheat is a grass crop, it requires large amounts of nitrogen for optimal yields. Nitrogen is expensive, so farmers will follow best management practices to only apply what is needed by crop, which will also benefit water quality by reducing the potential for nitrogen to enter ditches and streams. These practices involve the time of application type of fertilizer selected, and the amount applied. Farmers do not inject nitrogen fertilizer to avoid injuring plant crowns since wheat is planted in narrow rows and vegetation is already above ground. Several decades ago, farmers would have applied fertilizer when the ground was frozen. This practice was for the convenience of application but since the plants were dormant at this time, there was a considerable chance that the nutrients would run off the field with rain events or thawing soil. The wheat plants were not able to use this nitrogen until new spring growth occurred, so when does wheat need nitrogen? Large demand for nitrogen does not occur until jointing. Jointing is when the plants switch from a vegetative growth stage to reproductive. At jointing, plants will be upright and the growing point that will produce grain has moved above the soil surface and will continue to move up the elongating stem until the emergence of the spike. Jointing usually occurs the last week of April. However, it may be sooner because of warmer temperatures occurring now. The term jointing comes from the visible nodes along the stem that has a leaf attached. The nodes feel or look like bumps (joints) along the fully elongated stem. Wheat stems will have four leaves along the fully elongated stem (four nodes). However, university research has shown that significant yield losses are likely to occur if nitrogen application occurs after jointing. Unfortunately, extended rain events may occur around jointing to prevent a timely nitrogen application. Early applications also have a greater potential for loss since the crop is only taking up small amount at that time. However, since the wheat is growing, the potential for loss is manageable. Thus, a compromise, and practical solution, is for a farmer is to apply nitrogen as soon as the soils are fit for equipment after greenup. Thus, farmers apply nitrogen as soon as the field is fit for equipment and before the crop reaches jointing. However, a farmer may choose to add with early applications a compound making it less prone to field losses. These are often called stabilizers. Nitrification and urease inhibitors are examples of stabilizers. This would be an additional input cost, so the farmer has to consider whether the risk is great enough to justify the extra expense. Nitrogen fertilizers for wheat will be in a dry or liquid form. Urea is the most common dry form and urea-ammonium nitrate, aka 28%, the liquid form. An advantage of liquids is that other chemicals such as herbicides can be added to the mix. It is also easier to apply a liquid more uniformly than a dry form. These products require different types of equipment for application. Thus, the farmer may decide on which form to use based on the equipment available. However, the cost of the fertilizer type heavily ways on their final decision. Besides application time and nitrogen form, farmers will carefully determine the amount of fertilizer needed for a given field – based on university recommendations. A farmer will have to provide an expected yield for these recommendations, often called yield goals. There are many ways to estimate yield potential. A common method used by farmers is to review yields from the past five years. They throw out the highest and lowest year, and then average the remaining three years to determine their yield goal. They then take this yield goal and match it to a nitrogen rate curve to determine the amount of nitrogen needed. Nitrogen rate curves have been completed by Ohio State University research to determine the amount of nitrogen needed to obtain a certain yield. These rates can be found in "Extension Bulletin 974, Tri-State Fertilizer Recommendations for Corn, Soybean, Wheat, and Alfalfa." Recommendations do not allow nitrogen credits for the previous soybean or cover crop. However, it does recommend subtracting any nitrogen applied prior to planting. Most farmers will apply around 20 pounds of nitrogen per acre at or prior to planting. Thus, the recommendation for a 100-bushel wheat crop is 120 pounds of total nitrogen per acre minus the 20 pounds from the fall giving a spring nitrogen rate of 100 pounds. Wheat fields have come out of their winter hibernation early this year because of the abnormally warm March temperatures. Over the next several weeks, people may see fertilizer being applied to wheat fields. Fertilizer is not a pesticide, so nearby homeowners do not need to be concern about a harmful product being applied near their abode. Farmers protect the environment (water quality) and reduce their costs by following the best management practices for nitrogen by using the right source, the right rate, and the right application time. Lentz is agriculture and natural resources educator with Ohio State University Extension Office — Hancock County.