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Effects of N, P, and K Fertilization on Barley Grown in a Newly Cleared Subarctic Soil¹

Alaska has vast areas of undeveloped land with the potential for agricultural expansion. To develop renewable resources from oil royalty monies, the state has initiated a 24,000 ha agricultural demonstration project near Delta Junction, Alaska. Little is currently known, however, concerning the natural fertility of these virgin soils. A 4³ factorial experiment was established, with barley (Hordeum vulgare L. var. ‘Otra’) as the test crop, to determine responses to fertilization the first 2 years after clearing on a Typic Cryopsamment soil. Fertilizer was applied before seeding each year at 0, 45, 90, and 135 kg Nha; 0, 34, 68, and 102 kg P/ha; and 0, 34, 68, and 102 kg K/ha. Grain yields, protein contents, and subsequent soil-test levels were measured.

Nitrogen increased grain yields from 2 quintalha with no applied N in 1979 to 25 quintallha with 135 kg Nha and from 4 quintaVha with no applied N in 1980 to 31 quintalha with 135 kg Nha. The yield response to N was linear throughout the 0 to 135 kg Nha range in 1979, and both the linear and quadratic regression terms were significant in 1980. Cooler initial soil temperatures, lack of native residual nutrients, or N immobilization may have contributed to lower overall yields in 1979. Grain protein increased linearly with added N both years. Phosphorus increased yield up to 34 kg Pha, with little response beyond that in either year. In 1979, both P and K were significant in increasing the yield response to N. In 1980, only K increased the yield response to N. Neither P nor K fertilization significantly increased grain protein contents.

Multiple-regression equations were developed to predict grain yields and protein contents with rates of fertilizer applied. When considering only N, P, and K fertilizer additions, equations with relatively high coefficients of determination were obtained for the first 2 years of production (Yield: R² = 0.929,0.937 for 1979 and 1980; and protein: R² = 0.684, 0.842 for 1979 and 1980, respectively). Thus, the application of fertilizer accounted for much of the variation in yield and protein contents.

Key Words: Growth responses • Protein contents • Virgin soil • Multiple regression • Fertilizer interactions

² Graduate research assistant and associate professor, Dep. of Agronomy, Iowa State Univ., Ames, IA 50011, and associate professor and assistant professor, Agric. Exp. Stn., Univ. of Alaska, Fairbanks, AK 99701 and Palmer, AK 99645, respectively.

Received for publication September 25, 1981.