Effect of Sulfur Deficiency on Yield and Nitrogen Content in Bitterbrush (Purshia tridentata) Seedlings on Granitic Soils

Abstract

AbstractPrevious studies by the authors have shown that addition of N (in the presence of P, K, and S) to an infertile soil derived from a granitic parent material may depress the yield of bitterbrush [Purshia tridentata (Pursh) DC.] seedlings and increase the concentration of plant N. The study presented here was conducted to determine the separate effects that added K or S would have on yield and N content of bitterbrush when applied together with N and P to the soils in question. Bioassay using both bitterbrush and barley (Hordeum vulgare L.) revealed an S deficiency in the soils that ranged from slight to strong. Bitterbrush seedlings growing on the S deficient (NPK‐treated) soils weighed significantly less than those growing on NPS‐ and NPKS‐treated soils and averaged 2.07% total N compared to only 1.15% total N for plants from all other treatments. Yield and N content of barley on the NPK‐treated soils were strongly affected only on the soil that was most deficient in available S. The results for bitterbrush were confirmed in subsequent experiments where bitterbrush was fertilized with three rates of N with and without S. In this test, the bitterbrush seedlings that received 224 kg/ha of N without S accumulated significantly more inorganic N than the seedlings that received S. Ammonium‐N accumulation was about 4.5 times higher than that of (nitrate + nitrite)‐N and was highest in roots and lowest in leaves. Reduced yield of affected seedlings may result from inhibitory effects of accumulated inorganic N or inhibition of S‐amino acid formation caused by S deficiency.