Research Results on the Effects of Tillage Practices

1.2.3. Research results on the impact of tillage measures

In recent years, the application of mechanization in afforestation, especially industrial afforestation, has been of interest to foresters. A typical example is the research work of Do Dinh Sam and colleagues (2001), through the underground plowing experiment to plant Eucalyptus uro on degraded land in Phu Ninh (Phu Tho), the author showed that the productivity of Eucalyptus forests planted on underground plowed land is much higher than that of places where the land is prepared manually. After 8 years, in places where the land is prepared by underground plowing, the standing tree reserve of Eucalyptus uro can reach 16m 3 /ha /year, but in places where the land is prepared manually, it only reaches 5m 3 /ha /year. On the contrary, on sloping land that has not been degraded in the Southeast, Pham The Dung and colleagues (2005) tested two methods of manual and mechanical land preparation to plant Acacia hybrid forests. The results showed that the growth ability of Acacia hybrid in the manual land preparation method was better than the mechanical land preparation method. After 3 years, the mechanical land preparation formula only reached 8.74 - 8.87cm in diameter and 9.82 - 9.92m in height, but in the manual land preparation formula, it reached the corresponding values of 9.40-10.38cm and 11.33-11.71m. The author commented that on sloping land that is still loose, using machinery to process vegetation, level tree stumps and plowing thoroughly will cause soil erosion, leaching and accelerate the degradation process. Therefore, it is necessary to depend on soil and terrain conditions to determine the appropriate land preparation method.

Research by Le Dinh Kha and Ho Quang Vinh (1998) shows that improved varieties and other intensive techniques play an important role in increasing the productivity of planted forests. To increase the productivity of planted forests to the highest level, it is necessary to apply a combination of improved varieties and other intensive techniques. Combining improved varieties with intensive afforestation techniques can create high productivity in forestry production. In Cam Quy (Ba Vi - Ha Tay), when planted under intensive conditions (with plowing and appropriate fertilization), at the 2-year-old stage, hybrid Acacia has a trunk volume of 19.6 dm 3 / tree, in the extensive formula, the trunk volume is 4.7 dm 3 / tree. While the parent Acacia species planted in the same intensive conditions can

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The volume of the tree trunk only reaches 2.7 - 6.1 dm 3 / tree, while in the extensive formula, the volume of the tree trunk only reaches 0.6 - 1.2 dm 3 / tree.

1.2.4. Research results on the effects of fertilization on the growth and productivity of planted forests

Fertilizing forest trees is also one of the intensive farming methods in our country that has been applied in the past 10-15 years. Fertilizing aims to supplement nutrients to the soil and support rapid plant growth in the early stages. In particular, fertilizing with manure not only improves the chemical properties but also improves the physical properties of the soil. The most prominent is the project of fertilizing Acacia hybrid in Cam Quy (Ba Vi - old Ha Tay) by Le Dinh Kha and colleagues (1999). Nowadays, due to limited sources of organic fertilizers, the common fertilizers for planted forests are synthetic mineral fertilizers such as NPK, superphosphate or organic microbial fertilizers... and are often used as basal and top dressing for planted forests in the first 1-2 years. Some of the most prominent recent works include the research of Do Dinh Sam (2001), the author arranged 14 different fertilizer formulas for Acacia hybrid planted on ancient alluvial soil in the Southeast. After 2 years of age, the results showed that Acacia hybrid grew best in formulas of 150-200g NPK combined with 100g microbial fertilizer, the standing tree reserve could reach 26m 3 /ha / year. Next is the research work of Nguyen Dinh Hai (2003) who arranged 8 different basal fertilization experimental formulas for 3 varieties of Caribbean Pine ( P. caribaea var bahamensis -1167; P.caribaea var hondurensis -1160 and P. caribaea var hondurensis - Dai Lai variety) on poor soil in Cam Quy (Ba Vi - old Ha Tay), the experimental results showed that after 14-36 months of age, all 3 varieties of Pine above grew well in the fertilization formula of 200g P 2 O 5 / tree. On acid sulfate soil in Thanh Hoa (Long An), Pham The Dung (2003) also tested different basal fertilization formulas for Eucalyptus species E. camaldulensis and E. tereticornis . The results showed that fertilizer had a clear effect on the growth of both Eucalyptus species mentioned above, especially in the fertilization formula of 50-100g NPK combined with 50-100g P/root, which increased the height growth by 31-36% compared to the control at the stage.

3.5 years old. In another experiment with Acacia hybrid planted on yellow-gray feralit soil in Tan Lap (Binh Phuoc), Pham The Dung (2004) also showed that Acacia hybrid grew well in the basal fertilizer formula of 100g NPK combined with 500g Song Gianh microorganisms/tree. Surveying 14 standard plots of Eucalyptus uro plantations from 1.5-5 years old in 6 different locations, Nguyen Duc Minh and colleagues (2004) showed that the effectiveness of NPK fertilizer is always higher than that of organic microorganisms or superphosphate applied separately, fertilizing 300g NPK/tree is more effective than fertilizing 200g NPK/tree and 100g NPK/tree. Similarly, surveying 14 standard plots of Acacia hybrid plantations from 1.5 to 5.5 years old in 5 different provinces, the author showed that Acacia hybrid plantations fertilized with 100g NPK/tree as base fertilizer and 100g NPK/tree as top dressing in the second year had higher growth than forests with only basal fertilizer.

Ngo Dinh Que and colleagues (2004) have established technical regulations for fertilizing four main tree species: Acacia hybrid, Eucalyptus uro, Pinus resina and Dipterocarpus sylvatica based on a collection of previous research works and additional research. In addition, Le Quoc Huy (2002) has also researched and perfected the technology of processing Rhizobium preparations for Acacia hybrid, Acacia mangium in nurseries and young forests to improve the quality of seedlings and productivity of planted forests.

Recently, the work "Research on scientific and technological solutions to develop raw wood for export" by Nguyen Huy Son (2006) has built an experiment on intensive planting of Acacia hybrid in Dong Hy - Thai Nguyen, including the experiment on basal fertilization and top dressing in the second year including: 100g NPK (5:10:3) + 400g VS + 50g lime powder/root, it is predicted that after 7-8 years it can reach 25-30m 3 /ha/year. Also in Dong Hy - Thai Nguyen with some Eucalyptus species, fertilization: 200g NPK (5:10:3) + 100VS + 50g lime powder/hole, it is predicted that after 7-8 years it can reach 25-30m 3 /ha/year.

Thus, fertilizing planted forests is one of the intensive technical measures that has been focused on research. Most authors agree that fertilizer has a quite clear effect on the growth ability of plant species, especially forest plant species for industrial raw materials.

However, each plant species on each site type has different fertilizer needs.

1.2.5. Research results on the effect of density on the productivity of planted forests

Density is one of the factors that determine the productivity of planted forests. Too high a density will affect the growth of plants, but low density will waste land, requiring labor to care for and kill weeds. Moreover, low density with strong branch growth will affect the quality of raw wood. What is the most effective initial planting density? This issue must be based on the purpose of planting forests, and also depends on the location where the planting is done. According to the experience of some raw material planting companies today, they often plant from 1660-2500 trees/ha for fast and medium growing species. Is this density optimal? This question still has no scientific answer. When evaluating hybrid Acacia plantations in the Southeast region, Pham The Dung and colleagues (2004) surveyed 4 models with different initial planting densities: 952; 1111; 1142 and 1666 trees/ha, the analysis results show that after 3 years of planting, the highest yield is in forests with a density of 1666 trees/ha (21m 3 /ha/year), the lowest yield is in forests with a density of 952 trees/ha (9.7m 3 /ha/year). The author believes that for hybrid Acacia in the Southeast region, the most suitable planting density is from 1111-1666 trees/ha.

The technical process of intensive forest planting to supply paper materials in the northern mountainous provinces has prescribed a planting density of 1200-1500 trees/ha for some species of Pine, Acacia and Bodhi, 1000 trees/ha for Eucalyptus, the process of intensive forest planting of Eucalyptus E. urophylla also prescribes a planting density of 1110-1660 trees/ha. The technical standard for teak forest planting stipulates a pure planting of 200-2500 trees/ha, intercropping can be from 1000-1250 trees/ha (Department of Science, Technology and Product Quality) (2001). Although the above standard processes have prescribed specific densities for some types of intensive forest planting, they are only temporary, it also depends a lot on each type of soil and each new variety that has been improved and supplemented,...

To determine the appropriate planting density on the Feralit soil developed on shale in the North Central region, the project "Research on scientific and technological solutions to develop raw wood for export" by Nguyen Huy Son (2006) arranged experiments with 3 types of density: 1330 trees/ha (3x2.5m); 1660 trees/ha (3x2m) and 2500 trees/ha (2x2m), mixed varieties of Acacia hybrids BV5; BV10 and BV33, propagated by cuttings. According to statistics, after 1 year of planting, the survival rate was quite high, reaching 98% - 100%, after 2 years the survival rate in the experimental formulas decreased but still reached 91.67% - 93.52%. Growth data and variance analysis results showed that after 1 year, planting density began to have a negative effect on the growth ability of Acacia hybrid in terms of diameter, height and canopy diameter (Ftt>F05). After 2 years of age, this effect became more negative (Ftt>F05). The best density was 1330 trees/ha, followed by 1660 trees/ha and the worst was 2500 trees/ha. Also studying the density of forest planting with the goal of paper chip materials, Nguyen Huy Son (2006) arranged a density experiment on ancient alluvial soil in Dong No (Binh Phuoc) including 3 formulas: 1100 trees/ha (3x3m), 1660 trees/ha (3x2m), 2220 trees/ha (3x1.5m), seedlings were propagated by mixed cuttings of TB03 and TB12 lines with a ratio of 1:1:1:1. Treating the ground cover and preparing the soil by mechanical method, plowing the whole area 25cm deep, plowing the rows 40cm deep, uniform basal fertilization 200g NPK + 100g microorganisms. After 24 months of age, the survival rate between the density formulas varied from 86.46-97.90%. The highest density was 1100 trees/ha and gradually decreased with increasing density, the lowest was 2220 trees/ha. The growth capacity of diameter and height between density formulas after 24 months of age was significantly different (Ft>F05), the highest was at the density of 1100 trees/ha with a diameter of 7.72cm and a height of 8.79m, followed by the density of 1660 trees/ha with corresponding values of 6.46cm and 7.40m, the lowest was at the density of 2220 trees/ha with corresponding values of 5.58cm and 7.12m. Thus, density has a significant influence on the growth capacity and productivity of planted forests.

1.2.6. Research results on policy, economics and market

Along with the innovation of forestry development strategy, the Government has issued a series of policies on forest and forestry land management such as: Land Law 2003, Law on Forest Protection and Development 2004; on land allocation and leasing of forestry land; investment and credit policies such as Law on Domestic Investment Encouragement, Decree 43/1999/ND-CP, Decree 50/1999/ND-CP, preferential credit, commercial credit, tax policy, benefit policy... The above policies have had a strong impact on the development of forestry production, especially production forest planting.

In general, studies on economics and policies for developing production forests in Vietnam have recently received more attention, but have only focused on a few issues such as: analysis and evaluation of economic efficiency of crops, use of forestry land and some small studies on the market. The following authors' studies can be mentioned:

Vo Nguyen Huan (1997) evaluated the effectiveness of land and forest allocation in Thanh Hoa; from the study of types of production forest owners, he proposed key solutions to promote the internal strength of forest owners in sustainable management and use. The research results also pointed out the difficulties and limitations of the forest land allocation policy and proposed recommendations to improve the effectiveness of forestry land allocation and forest protection contracting.

Do Doan Trieu (1997) with research on building some scientific and practical arguments contributing to perfecting policies to encourage foreign investment in industrial raw material forest plantation.

Le Quang Trung and colleagues (2000) studied and analyzed policies to encourage the planting of Pinus latifolia forests and made 10 recommendations for the development of this type of forest.

Vu Long (2000) evaluated the efficiency of land use after the allocation and contracting of forestry land in the northern mountainous provinces; Do Dinh Sam and Le Quang Trung (2003) evaluated the efficiency of industrial forest planting in Vietnam.

Pham Xuan Phuong (2003) reviewed forest-related policies such as land policies and credit investment. The author also pointed out that the policies are very timely and meaningful, but there are still many shortcomings in the implementation process. The author also oriented to perfect the policies to have a master plan for the raw material forest planting area, forest owners can borrow capital to plant forests to ensure profits, ensuring that forests are planted with good seed groups.

Nguyen Xuan Quat and colleagues (2003) assessed the current status of planting raw material forests for the wood and forest products processing industry in recent times; Vo Dai Hai and Nguyen Xuan Quat (2005) assessed the actual implementation of the policy on benefit rights (Decision 178).

Research on forest product market is also of interest to many authors because this is an issue closely related to afforestation. Some research works can be summarized as follows:

Nguyen Van Tuan (2004) studied the current status and development trends of the paper raw wood market in the North Central region;

Ngo Van Hai (2004), in the study on input and output factors in the production of agricultural and forestry products in the Northern mountainous region, analyzed the advantages, disadvantages and efficiency of agricultural production in the mountainous region.

Vo Dai Hai (2005) conducted a study on the market for planted forest products in the Northern mountainous region and summarized the consumption channels for planted forest wood as well as non-timber forest products. The author also pointed out that to develop the market for planted forest products, it is necessary to develop forest product processing technology as well as form a joint venture method between people and forestry enterprises.

In 2004, Peter Core, director of the Australian Centre for International Agricultural Research (ACIAR), and his colleagues studied hybrid Acacia in Vietnam. The results showed that hybrid Acacia grew faster than the two parent species. The propagation of hybrid Acacia and the program

The selection process is meaningful for commercial acacia plantations. The report shows that the productivity of normal acacia is 12m 3 /year, while Acacia hybrid is 22m 3 /year under the same conditions, in the South it can reach 30m 3 /year and the exploitation cycle is shorter by 2-3 years, meaning that Acacia hybrid can be planted for 5 years and exploited, while other Acacia species is 7 years.

Do Dinh Sam and colleagues (2001) calculated the economic efficiency of Acacia hybrid plantations. The results showed that in the Central region, the NPV and IRR indicators both showed profitable business, IRR = 9%, in the Southeast provinces, the internal rate of interest IRR was quite high, about 17% - 19%. The author concluded that, with the cost of planting forests as at the time of the study, if the average productivity of planted forests did not reach over 15m 3 /ha / year, the internal rate of investment capital would not reach the calculated levels.

Dang Van Dung (2008) conducted a study on "Evaluation of growth and economic and social efficiency of planting Acacia hybrid for paper raw materials in Dak Lak and Dak Nong", giving the following results: Regarding economic efficiency, net profit (NPV) and IRR after a 6-year business cycle in Cu K'Roa was 17.76 million, IRR was 27.87%; Dak Ro was 21.77 million, IRR was 32.58%; Quang Khe was 8.8 million, IRR was 17.5%. Regarding social efficiency, the author concluded that a 6-year Acacia hybrid planting cycle in Cu K'Roa created 303 hectares/ha, Dak Ro was 275 hectares/ha and Quang Khe was 356 hectares/ha.

Ngo Que and colleagues (2009) conducted a study on land classification and economic efficiency of Acacia hybrid plantations in some ecological regions of our country. The study gave the following results: average revenue of 25,050,000 VND/ha, average net profit of 3,350,000 VND/ha/year, return rate of 27.16% and investment efficiency of 2.82 times at land level 1. The North Central region gave an average revenue of 26,700,000 VND/ha, average net profit of 3,550,000 VND/ha/year, return rate of 32.67% and investment efficiency of 2.99 times. The Central Highlands region gives an average revenue of 80,200,000 VND/ha, an average net profit of 5,200,000 VND/ha/year, a return on investment of 39.40% and an investment efficiency of 3.34 times for a 7-year business cycle, the Southeast region

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