NUTRIENT BALANCE AND P, K, CA, MG, S AND B ACCUMULATION IN A NORWAY SPRUCE STAND FOLLOWING AMMONIUM-SULFATE APPLICATION, FERTIGATION, IRRIGATION, DROUGHT AND N-FREE-FERTILIZATION

The nutrient balance and above ground accumulation of macro nutrients, except for N, resulting from improved or deteriorated availability of water and nutrients in a 25 year old Norway spruce stand in SW Sweden is presented. The site and the productivity of the stand is typical for the area. Treatment include irrigation (I); artificial drought (D1); ammonium sulphate addition (NS); N-free-fertilisation (V) acid irrigation with liquid fertilisers including a complete set of nutrients according to the Ingestad principle (IF). At start of the experiment the stand contained 86.5 t dry mass, 342 kg N, 33 kg P, 142 kg K, 172 kg Ca, 36 kg Mg and 34 kg S ha(-1). Enhanced accumulation vs control of S was seen in the NS and IF treatments. In the V and IF treatments P accumulation was 7-9 times higher and Ca and Mg, 2-4 times higher compared to the control. K accumulation was increased for the IF treatment. B that accumulated in the needles was decreased in the NS and D1 treatments and increased in the IF and V treatments, as compared to the control. The gross accumulation of nutrients relative to the amounts added was in the IF and V treatments 56 and 47% for P, 40 and 64% for K, 40 and 24% for ME and, 22 and 8% for S, respectively. We conclude that application with N-free fertilizer, Skogvital (V), including macro nutrients and essential micro nutrients, results in a fast and efficient accumulation above ground of P, K, Ca, Mg and B. The treatment is efficient when aiming at restoring nutrient imbalances in Norway spruce. Application with ammonium sulphate at a rate of 5-6 times higher than the current deposition of N and S did not lead to decreased accumulation above ground of any of the macro nutrients P, K, Ca or Mg. The accumulation of B, however, was significantly reduced. Results from this and other studies indicate that today, N alone, generally is a growth limiting nutrient for Norway spruce in Southern Sweden.