Effects Of Phosphorus Topdressing Fertigation On Growth And P-uptake Of Larix Olgensis Seedlings

With the aim of improving the phosphorus efficiency and finding the best phosphorus applying method, Larix olgensis transplanted big seedlings, small seedlings and sowed seedlings were used as the experiment materials. The applied fertilizer was divided into two parts, one part phosphorus was applied into the soil as basal fertilizer before transplanting, other part was applied by fertigation as topdressing three times during the growing season. The experiment was arranged according to split-plot design with different amounts of P (163,326,489 kg·ha-1) as main treatments and fertigation ratios (0,25%,33%,50%,100%) as side treatments. The results showed that different seedlings had different best amounts of phosphorus, but reach the same on the best fertigation ratio. 1)The seedling growth of the transplanted big seedlings was affected by different amounts of phosphorus significantly, seedlings height, diameter, first-order lateral root in diameter at junction≥1mm and biomass were best under the amount of 489 kg·ha-1, so the best amount of phosphorus for the transplanted big seedlings was 489 kg·ha-1; 2) For the transplanted small seedlings and sowed seedlings, seedlings growth was not affected by differrent amounts of phosphorus significantly, however, seedlings height, diameter, first-order lateral root in diameter at junction≥1mm and biomass were increased with the increasing of phosphorus. Because seedlings height and diameter reached the national seedlings standard with the amount of 163 kg·ha-1P, so it was the most economic fertilization quantity for the transplanted small seedlings and sowed seedlings.3)For the three types of seedlings, P concentration, P content, phosphorus use efficiency were greatly effected by fertigation ratios on the whole, and most of these indicators reached the maximum values under 33% fertigation ratio. Therefore, taking 33% of phosphorus to be applied by topdressing fertigation during the growing season was the best phosphorus applying method for Larix olgensis transplanted and sowed seedlings, but for the appropriate amount of phosphorus,163 kg·ha-1 was the best choice for transplanted small seedlings and sowed seedlings, and 489 kg·ha-1 was optimal for the transplanted big seedlings.