There are many reasons for the land in the Central Highlands to be degraded, but in all, it is mainly due to the main human impact.
Degraded coffee land – Re-cultivation, coffee trees grow poorly. Photo: Truong Hong
Degraded land is understood as a land that is changed its original inherent properties and properties (in the negative direction) due to the impact of natural and human factors. Scientists have researched and ranked degraded soil in the Central Highlands according to four levels: None and mild degradation has an area of 1.84 million ha (accounting for 33.7%); degeneration averages 2.5 million hectares (accounting for 45.8%); 1,123 million ha of heavy degradation (accounting for 20.5%).
Consequence of soil degradation is the reduction of soil fertility, which is reflected in the criteria such as tight soil, strong acidity, ability to keep moisture, and poor nutrition; low fertilizer use efficiency; soil microbiota is mainly harmful microorganisms; Pests and diseases from the land develop rapidly and strongly affecting the efficiency of agricultural production due to low productivity, quality of products, high production costs, leading to the risk of going against the goal of sustainable agricultural development in the future of the region.
There are many reasons for the land in the Central Highlands to be degraded, but in all, the main cause is mainly due to the impact from people.
Monoculture
The Central Highlands is a region specializing in coffee and pepper cultivation in Vietnam, accounting for 88% and 63%, respectively. This also shows a clear situation of monoculture in current cultivation. The area of coffee and pepper increased uncontrollably during periods of high prices, people massively develop the area even on inappropriate land types and terrain, disrupting the balance of the ecosystem. Thai. Even though newly reclaimed land for initial cultivation has fertile fertility, after a period of monoculture cultivation, the soil will degenerate along the way of degradation (acid soil, loss of organic matter, loss of soil. soil structure, nutrient depletion), impaired soil health; production is poor, crop yields are low and uncertain.
Over 1.1 million hectares of agricultural land in the Central Highlands are severely degraded. Photo: Truong Hong
Researches of the Central Highlands Agro-Forestry Science Institute show that, within 30 years, the cultivated land of coffee monoculture was rapidly acidified; Average soil pH has decreased from 0.5 to 1.2 units; content of alkaline earth cations decreased by 40-70%; absorption of soil (CEC) reduced by 30-40%; appeared clay layer at a depth of 30-40 cm; organic content decreased by 20-40%; tight, poorly drained soil leads to increased soil erosion on the surface after rains on sloping land. The acidification process, reducing the organic content, the alkaline earth cations occur at a faster speed, more clearly on coffee cultivated soils with a slope of 7-15%; bare planting (no shade trees). In cassava growing areas with steep terrain (usually above 8%), cultivation does not go hand in hand with measures to prevent soil erosion and leaching of the vast majority of ethnic minorities and poor farming households. land is degraded quickly, losing productivity. On these areas, after 2-3 years of cultivating cassava, the organic content has decreased by 40-60%; tight, rock-inert, rock-inert soil, the yield decreases by 50-70% compared to the newly explored land.
Excessive use of fertilizers or chemical pesticides
This is a common cause of land degradation in the Central Highlands today. Due to the effect of quick and effective chemical fertilizers, agricultural farmers pay first attention to using chemical fertilizers in order to achieve high productivity and high income. Up to 60% of coffee farmers and 45% of pepper farmers used fertilizers in an unreasonable, unbalanced manner, and 70% of farmers applied chemical fertilizers at much higher doses than recommended and compared with energy. productivity is achieved. The amount of nitrogen fertilizer applied by farmers to plants is usually very high, sometimes 300% higher than recommended; followed by a higher phosphorus amount from 50 – 200%; Most of the potassium fertilizers are lower than recommended; Especially when the price of coffee and pepper agricultural products is high, up to 90-100% of farmers apply higher chemical fertilizers with the desire to achieve maximum productivity and income. The percentage of farmers interested in organic fertilizers is still low, only about 40%. Studies have also demonstrated that continuous use of high amounts of fertilizers results in a faster rate of soil acidification; organic matter degrades more quickly; CEC decreased faster; Harmful microorganisms in the soil develop faster and therefore soil quality degrades more quickly. Evidence shows that on the areas planted with coffee and pepper, chemical fertilizers applied at high doses for many years and then replanted, the growth, development of the plant slower and the rate of stunted and dead plants. is higher than the area using a reasonable and balanced chemical fertilizer.
According to the natural law, when cultivation is specialized and intensive with the impact of climate change, more and more pests appear in fields. To protect the results of labor, farmers have used chemical pesticides with increasing numbers and types; spray at higher concentrations and doses than recommended; especially at times of high agricultural prices. This leads to biodiversity poverty; imbalance in natural enemies; the balance of microbiota in the soil is broken; forming populations harmful to soil and plants; Since then, the land has been polluted, degraded and lost production capacity.
In addition, in terms of ecology, applying chemical fertilizers at high doses for many consecutive years, the abuse of chemical plant protection drugs leads to the risk of polluting the ecological environment and affecting safety and hygiene. food.
Deforest
The forest was cut down for cultivated land
The state of deforestation for cultivation land is easily seen in remote areas, ethnic minorities, sometimes along the main roads; especially when the prices of certain crops were at high level, typically coffee in the 1990s; pepper in the years 2014 – 2016. The forest was cut down, causing the land to no longer have any protective vegetation cover or with poor coverage, so the soil quickly lost its fertility, burned organic matter. soil was eroded, fading gradually. The rate of soil degradation is proportional to the extent of land cover, precipitation, and slope of the soil. Every year, the Central Highlands loses an amount of about 167 million tons of land, an average of one hectare of natural land loses nearly 29.7 tons / year. The loss of soil leads to a significant amount of loss of nutrients; Along with the amount of soil lost due to erosion, it will deposit rivers, streams, irrigation works, and hydropower dams, affecting the safety of dams in the rainy season. Because forest land is mainly sloping land, during cultivation does not pay attention to measures to prevent erosion, wash away soil in the rainy season, keep moisture in the dry season or even do not pay attention to fertilizing the soil. This leads to the situation that after a few years of cultivation, the soil is depleted in terms of nutrients, texture loss, alkaline cations, and soil alkalinity are lost with annual soil drift; soil quality decreased; Thin farming layer leads to loss of production capacity and some of the abandoned areas become deserted.
In addition, deforestation has contributed to increasing the harmful speed of climate change, extreme weather phenomena occurring with a thicker frequency (droughts, rain, floods …) also contributes to acceleration. agricultural land degradation in the Central Highlands.
All the above information is warning that land degradation in the Central Highlands has been happening more and more in size and severity.
Thus, the issue that needs to be concerned now is that the area of agricultural land that is degraded is increasing due to the serious changes of the soil properties in terms of physics, chemistry and biology, and it is difficult to recover during the period. short-term or impossible to recover without building and drastically implementing an overall strategy to restore degraded land in the Central Highlands.
