Farming 06: Managing Coffee Land – Whole Farming is a special column from Helena Coffee Vietnam that provides an overview of what you can and/or can’t control, as well as how to exercise what controls you can to create a sustainable crop and a good cup of coffee.
Erosion and soil leaching during coffee cultivation is the cause of the deterioration of coffee soil fertility.
Coffee can be grown on soils with different slopes, but it is necessary to pay attention to erosion management solutions, typically in the Central Highlands, Vietnam with heavy and concentrated rain conditions.
The higher the slope, the longer the slope length, the greater the rainfall, the greater the frequency of rain, and the greater the amount of soil loss due to erosion.
Erosion will cause the soil to quickly become discolored, and lose its productive power due to the nutrient content being washed away by the water flow (acidic soil, alkaline cations, alkaline soil is washed away, the soil’s ability to exchange cations is mainly H, Al+3+), the composition of the grain level changes in a bad direction (the soil structure is broken) leading to limited growth and development of coffee plants, low yield, and not high fertilizer use coefficient, leading to increased investment costs.
The amount of soil erosion on coffee land has a relationship with slope, soil cover. With a slope of 7-8 degrees, annual rainfall in the range of 1520, the total amount of soil erosion can reach 50.2 tons / ha / year; With the same rain, when the slope increases to 10-12 degrees, the amount of soil erosion can reach 113.1 tons / ha / year – Ho Cong Truc, Luong Duc Loan, 1997
Under normal conditions, the basic coffee stage is from 1 to 2 years old, the amount of soil loss due to erosion is from 50 to 60 tons, and the most lost nutrients are organic matter, calcium, total protein, easily digestible potassium, and magnesium.
The loss of these nutrients contributes to the acceleration of soil degradation; especially increasing the rate of soil acidification, reducing the efficiency of fertilizer use, and affecting productivity and production costs.
Mechanized techniques designed to maintain moisture in the soil can be quite expensive and laborious such as placing drip irrigation devices. In contrast, mulching straw is much cheaper and more effective as a means of retaining moisture in the soil.
The effect of mulch is simple: it creates a physical barrier that reduces the likelihood of evaporation of water in the soil caused by wind and heat from the sun. Mulching has the added benefit of preventing precipitation from compacting the soil.
It is estimated that a raindrop can exert a downward force equivalent to 349 times its own weight, and can create a hole 1cm deep into the weak ground. So, where the ground is not sufficiently covered with foliage, (especially when the plant is very young), a ground cover such as mulch or palm leaves can both prevent the soil from compacting and prevent it from drying out its surface. – BaristaHustle
A study comparing the effects of mulching and drip irrigation found that “both have a significant impact on coffee plant growth and photosynthesis, but the surface coating method is more practical than the drip irrigation method” (K. de Alcantara Notaro et al., 2014).
This is quite true because coatings can be produced at a very low cost from organic matter. The increase in the rate of photosynthesis directly affects the yield of coffee plants.
Plants grown with mulch, irrigation or nitrogen fertilizers produce a higher number of fruit-bearing nodes (MGR Cannell, 1973).
In a coffee farming course for the Food and Agriculture Organization of the United Nations, they advise the following approach to land management (from Covering the bare soil):
If you leave the soil bare, the rain will damage the soil and destroy its structure. Water washes away mineral salts, and the sun decomposes humus very quickly. The soil becomes poorer and does not provide enough nutrition for coffee plants. So the coffee tree will not give much fruit. The surface cover will protect the soil from erosion – you can take advantage of cut vegetation (weeds) or other organic mulch. In this way, the soil is protected from the sun and rain while providing additional organic matter to the soil from the rotting plant part. You can also use cover crops to protect the ground typically such as legumes. Between rows of coffee trees, legumes not only protect the soil, but also provide nitrogen to the soil.
Hanna Neuschwander, the author of several studies and communications director for World Coffee Research (WCR), mentioned that an important area WCR is exploring is intercropping coffee which covers crops.
By planting crops such as beans and peas interspersed with coffee crops, farmers can obtain a secondary source of income/food source, as well as the benefits of these plants returning nitrogen to the soil (nitrogen fixation).
This farming practice is particularly helpful in controlling how weeds take away nutrients from the soil. On steep grounds, cover crops are an effective solution for weed control and erosion prevention.
The drawback of cover crops is the need for additional investment (you have to buy seeds), and the economic value is not as high as a commodity. Instead, it is used as a means to regulate the nitrogen balance in the soil and prevent weed growth.
The HRN Stiftung case study in Uganda shows that this method is effective in increasing moisture in drought-affected soils.
However, their research suggests that this approach is unlikely to be widely implemented until the cost benefits to farmers can be more convincing. The barrier to this problem is the cost of seeds.
In the conditions of the Central Highlands, especially the rainy season, the rainfall is concentrated mainly in 6 months from May to November, the amount of land on the basic eroded coffee gardens is quite large, on average about over 5 tons/ha / year.
Therefore, to limit the risk of soil degradation, it is necessary to have solutions to control soil erosion; contribute to helping coffee plants grow and develop well, and quickly cover the soil surface, thereby having a good effect on limiting soil erosion during cultivation.
Intercropping corn, peanuts, and yellow flowers in coffee gardens is basically a biological solution that contributes to limiting soil erosion compared to non-intercropping control from 11-60%; in which the solution of intercropping yellow flowers has the best effect of reducing soil erosion.
Biological solutions combined with mechanics
In Vietnam, for coffee gardens, in addition to biological solutions to manage soil erosion, the application of mechanical or mechanical solutions combined with biology has a very good effect on controlling soil erosion.
Applying a mechanical solution such as creating a basin reduced soil erosion by up to 70% compared to the control. Mechanical solutions combined with biology (ditching combined corn and peanuts) also reduced soil erosion by about 62%.
However, deciding what kind of barrier is best for coffee land is based on some general principles:
- Conservation or development of existing flora. If the soil is very steep, the trees that have already grown there or the plants you plant new will protect the soil from landslides. Grasses and plants with strong roots will help hold the soil and water, so always take advantage of the available flora.
- Slows down the flow, but allows good drainage. It is important to keep the water moving, whether downhill or into the soil. Poorly designed barriers can lead to water stagnation, allowing mosquitoes to breed and spread malaria and other diseases.
- Fix problems as soon as they occur. Heavy storms can cause ditches to clog ditches, or barricades to become avalanches. In these cases, it should be corrected soon to avoid further erosion.
- Start from the top down. The water flowed downhill. By starting from the top, it is, therefore, advisable to protect the crop system (coffee) below by using many smaller barriers (higher barrier density towards the end of the slope).
Some models of biological barriers incorporate mechanics