Research Progress Report, No. 4

The fertilizer application method used for producing small grains in interior Alaska is not always a matter of choice but of necessity. Farmers must fertilize, till, and seed a large acreage in a short time to complete the seeding operation no later than the last week in May. In most years, this allows time for the crop to mature before being damaged by autumn frosts. A typical fertilizer application for barley is 380 pounds per acre dry, blended material consisting of 100 pounds urea as the primary nitrogen (N) source, 100 pounds monoammonium phosphate, 100 pounds ammonium sulfate, and 80 pounds potassium chloride. This combination provides an application ratio of 77-51-48-24 pounds per acre N, P20 5, K20 , and sulfur (S). This means a farmer planting 1000 acres of barley must handle 190 tons of fertilizer material. The most expedient method is to use a 10- to 20-ton capacity, trailer-type, broadcast spreader which minimizes refilling time. If fields are tilled after fertilization, the material is mixed into the soil; otherwise the fertilizer remains on the soil surface. There are several reasons to investigate other methods of fertilizer application even though this system has worked reasonably well. Most barley produced in interior Alaska is seeded on lands which have been cleared of native vegetation in the last ten years (Lewis and Thomas 1982). Soils are naturally infertile and are cool throughout the growing season (Siddoway et al. 1984), and most have been cropped for only three or four years. Delucchi (1983) reported higher yield response when phosphorus (P) was banded with the seed than when equal applications were broadcast. This is not atypical for P-deficient soils (Cooke 1982). Some farmers in Alaska’s interior have begun to band a starter or “ pop-up” fertilizer in the row with the seed at the time of planting. Monoammonium phosphate (11 pounds N and 51 pounds P20 5 per acre) is typically used. Starter fertilizers banded with the seed render nutrients readily available to the seedlings and may boost plant growth early in the season helping seedlings overcome stress due to cold soil temperatures at planting and during early growth (Veseth 1986, Paul 1987). Yields could potentially be increased and/or fertilizer requirements reduced. A general rule has been to band no more than 140 pounds per acre total fertilizer containing no more than 15 to 20 pounds N per acre with the seed (Loynachan et al. 1979). Particular caution is urged when urea is used as an N source (Cooke 1982, Robertson 1982). There is a possibility of seedling injury from excessive salts or the release of toxic quantities of ammonia near the seed. Several farmers in the interior of Alaska have banded the total nutrient requirement for barley with the seed using urea as the major N source. Good yield results have been reported for several years with no evidence of crop injury at rates of up to 450 pounds of total material per acre. Delucchi (1983) speculated that in wetter soils, typical of newly cleared lands, salts may tend to dissolve and diffuse away from the seed thereby lessening the potential for seedling damage. Banding the full nutrient requirement for barley with the seed may increase yields over those found when the equal amount is broadcast, thus increasing returns. Elimination of the broadcast operation will reduce costs slightly. Urea is available locally at a lesser cost than other N sources which must be shipped into the state and may be more cost effective than other formulations