Studies on optimum models for cultivating Dahurian Larch seedlings on frigid regions

Abstract

The optimum models for cultivating the seedlings of Dahurian Larch (Larix gmelini Rupr.) were studied in the central nursery of Tahe Forestry Bureau from 1989 to 1993. The results were as follows: The optimum models of the main morphological standards of the seedlings were 30000 kg/hm² of decomposed ash for improving soil, 70,000 kg/hm² of excrement and 1,500 kg/hm² of calcium superphosphate as basal fertilizer, and 500 kg/hm² of (NH₄)₂ HPO₄ and 220 kg/hm² of urea as top dressing. During growth period of the seedlings, the growth was greatly checked when the soil water suction (SWS) was within 50∼73.3 kPa or below 10 kPa but greatest when SWS was within 30 ∼ 40 kPa in initial growth stage and within 10–20 kPa in last growth stage. The method for determining the optimum sowing time is to measure the depth of soil thawing, accumulated temperature above 5°C both at 5 cm of the depth of of soil and in atmosphere. In Tahe region, the optimum sowing time for Dahurian larch is about on May 10 when the depth of soil thawing, the accumulated temperature above 5 °C at 5 cm of the depth and the accumulated temperature above 5°C in atmosphere reaches 40 cm, above 46°C and above 56 °C respectively. The optimum seedlings density for this region is 600–800 individuals/m².