In the cultivation of poplar forests, the phenomenon of high density is relatively common, and most farmers want to receive close planting. According to our investigation, we believe that the excessive planting density not only increases the cost, but also has a smaller size, lower price, and lower profitability for the production of wood, while the benefits of cultivating large diameter materials are higher. Therefore, in the production, no matter what cultivation mode is adopted, in the case of technology, capital, land contracting period and other conditions permitting, large-diameter materials should be cultivated to obtain higher returns. In the process of poplar cultivation, we must not only achieve "rapid growth, yield," but also to achieve "high quality" in order to create higher economic benefits. The following points are highlighted in the following investigations: (1) Planting density should be integrated in all aspects of production and a reasonable density should be designed. The row spacing of 2m83m is the limit density of poplar planting, and it can only produce small diameter timber with lower price. The rotation period is 4 to 5 years; the reasonable density of middle diameter wood production is 3m5m or 3m6m, and the rotation period is 8 to 0 years. The diameter of timber is 22-25cm. The reasonable density of large-diameter materials is 5m6m or 6m6m. The rotation period is 12-13 years and the diameter of timber is 33-35cm. (2) Soil and Fertilizer Management Loose soil weeding can improve the physical and chemical properties of the soil. In the early stage, thinning can be used in combination with thinning, and weeding and weeding should be performed once a year after weed closure, which is very effective in promoting forest growth. Poplar is very demanding on the water, generally should be watered 3 to 4 times a year. In early March, germinate and return to Qingshui before germination; from May to June, irrigation promotes raw water and promotes the expansion of branches and leaves; in November, irrigation and freezing water are encouraged to promote root growth. After the fertilization, it should be irrigated with drought. Fertilize sub-basal fertilizer and top dressing. The basal fertilizer is applied in a hole in the planting of trees. Generally, 5 to 10 kg of organic fertilizer or 250 g of superphosphate is used to mix the fertilized material and the mature soil and backfilled in a root activity layer of 30 to 60 cm. Fertilizers were applied to fertilize the ditch at the edge of the canopy. The length of the ditch was 80cm, width 20cm, depth 20 to 30cm, and urea 250g. For better mixing of nitrogen and phosphorus, the ratio is n:5 phosphorus oxide = 3:1. Watering, cultivating and weeding should be conducted promptly after fertilization. (3) Plastic pruning and pruning should be carried out during autumn and winter when the trees in the early spring stop growing. It should be emphasized that the shaping should begin after the end of the first year of growth or in the spring of the second year, until a straight trunk has been formed in 3-5 years of tree height. The method of shaping is to cut out the competing side branches that affect the growth of the top of the top of the tree. As the trees grow taller, they also need to repair the thick competition branches in the lower part of the canopy and in the middle, until they are less than 8 meters in size. If the diameter of the upper branch of the tree trunk below 8 m is 10 cm in diameter, the side branches shall be trimmed and the branch shall be trimmed from the bottom up to a height of 8 m so as to ensure that the stem core is no more than 10 cm apart. The pruning height is approximately 1 to 3 years with a small amount of pruning, 4 to 5 years of pruning to 1/3 of the tree height, and 6 years later pruning to 1/2 to 2/3 of the tree height. The scent issued on the trunk should be promptly removed. (4) Thinning can obtain small diameter materials in advance, and large diameter materials are used during the main cutting. The income from the sale of small diameter timber can be used for the management and protection of medium-term trees, and it is difficult to buffer the funds. What needs to be explained here is that thinning does not increase timber production, but it is to obtain small diameter materials in advance. After the thinning of a dense forest (2m 3 m or 2m 5 m), the effect of increasing tree thickness is not obvious, and it is not suitable for thinning. The medium-density forest with the initial planting density of 3m5m or 3m6m can be harvested in the 6th year; in the 11th to 14th years, large-diameter timber of 30cm or more is harvested. According to our survey, the medium-density forest thinning and finally harvesting the large-diameter timber cultivation model has an annual average benefit higher than no thinning, but it is less profitable than the direct cultivation of the large-diameter timber cultivation model. In the case of insufficient funds, it is also worth cultivating a mode of cultivation.
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