Early field performance of sand-coated (Conniflex®) and insecticide-treated Norway spruce seedlings planted on spot mounds and undisturbed soil with and without the addition of arginine phosphate (ArGrow®Granulat) nutrition

In Nordic countries, mechanical site preparation is used to enhance seedling growth and protect them against pine weevil (Hylobius abietis (L.)) damage. However, there is growing demand to reduce forest regeneration costs and harmful environmental impacts of site preparation. This has increased interest to explore alternative methods. Arginine phosphate nutrition may provide an alternative to intensive site preparation to improve growth. Still, in undisturbed soil, some protection against pine weevil is needed. In this study, we evaluated the early field performance of sand-coated (Conniflex®) and insecticide-treated (lambda-cyhalothrin, KarateZeon) Norway spruce (Picea abies (L.) Karst.) container seedlings planted on spot mounds and in undisturbed soil with and without the addition of arginine phosphate (ArGrow®Granulat) nutrition. Over two growing seasons, spot mounding improved the height and diameter growth of the seedlings and reduced the pine weevil damage compared to undisturbed soil. Arginine phosphate increased the first-year height and diameter growth in KarateZeon-treated seedlings and second year height growth of the Conniflex-treated seedlings, but otherwise had no significant effects on damage or survival. Both protection methods offered similar level of protection. Based on our findings, the use of mechanical site preparation is still recommended, particularly in areas with high pine weevil feeding pressure.