Improving fertility of rice intensive land - Prospective solutions

Mekong Delta is one of the largest rice production regions of the country. However, in recent years, rice productivity in areas of intensive triple rice cropping or flood protection dikes tends to decline. The most recent research by scientists shows that the main reason is due to soil degradation and degradation. Therefore, in the process of cultivation, technical measures are needed to improve soil fertility, improve crop productivity and quality.

The model of 3-crop rice cultivation is put into production in the Mekong Delta since the early 80s of the twentieth century and the area of ​​3-crop rice is growing rapidly, concentrating in alluvial lands along Tien and Hau rivers. Some areas in the past have been flooded by farmers and localities to increase the crop. Therefore, rice productivity in some intensive areas tends to decrease. The reason is that unreasonable land use leads to degraded land. Since 1999, the Department of Soil Science and Land Management, Department of Agriculture and Applied Biology, Can Tho University has collaborated with KU Leuven University, Ghent of Belgium, to carry out the research project. 'Minimize the unfavorable properties of land for sustainable rice production in the Mekong Delta'. Currently, the project is implementing phase 2 (from 2002 to 2008, to comprehensively survey and manage land appropriately for the Mekong Delta to ensure sustainable development.

Through research and surveys of rice intensive areas in Vinh Ngon, Vinh My, Chau Phu, Tinh Bien (An Giang) districts, Cau Ke district (Tra Vinh), Cai Lay district (Tien Giang) and Moc Hoa district (Long An), scientists said: land in these areas is being degraded, discolouration leads to a decrease in rice productivity. The reason is due to the continuous cultivation of 3 crops a year, the land is flooded with 8-10 months, leading to the reduction of organic decomposition, reducing the ability to supply nutrients from the soil, reducing the activity of microorganisms. beneficial things . The areas of rice cultivation with dykes to prevent floods are no longer alluvial so the fertility and fertility of the soil are significantly reduced.

The rice crop rotation model with upland crops improves rice yields in areas of intensive cultivation.(Photo: Documentation of Can Tho University)

Scientists have focused on investigating the chemical, physical and biological properties of soil in these areas as a scientific basis to recommend agriculture and farmers to manage and use land appropriately, effective. Through research on the physical color of soil on some rice intensive areas, Ms. Nguyen Minh Phuong, an officer of the Department of Soil Science and Land Management, said: 'There are two main types of physical colors. The areas of rice intensive farming are the compacting and structural degradation of the soil. Continuous cultivation of rice for a long time, increasing mechanization in the preparation of soil together with the process of leaching and accumulation of clay particles down to the lower layers creates compactness. The decline in organic matter and wet plowing will cause the soil structure to be degraded '.

Another study of soil organic matter shows that irrational cultivation leads to a decline in the quality of organic matter in the soil, affecting the productivity and quality of crops. Even with chemical fertilizer, plants still take about 50% to 80% of the nitrogen from the soil. Therefore, it is necessary to enhance the ability to supply nitrogen from the soil by measures: rotation of rice with upland crops, organic fertilization of the soil, time needed to dry the soil between the two crops by drying the soil. From 2 to 4 weeks . Dr. Nguyen My Hoa, Deputy Head of the Department of Soil Science and Land Management, said: 'The rotation of rice with upland crops, soil drying between two crops will make Organic soil changes from one form to another in a way that benefits plants for use, increasing the amount of nitrogen in the soil '.

The results of a field experiment by farmers in Cai Lay district, Tien Giang province in the autumn-winter crop in 2005, showed that: the model of 3-crop rice cultivation yielded about 3.3 tons / ha, while rice yield In the model of rice - corn - rice rotation, nearly 4.1 tons / ha, rice - green bean - rice model reaches over 4.5 tons / ha. The experiment in the 2006 winter-spring crop in Cau Ke district, Tra Vinh province also gave similar results: the rice intensive farming model only achieved a yield of 2.9 tons / ha, while the rice yield in the rice rotation model - corn - rice reached 4.3 tons / ha, rice - soy - rice model reached 3.2 tons / ha.

Depending on the ecological region, the rice yield in the rotation models increased compared to the rice monoculture of 7-20% is one of the highlights of the rice crop rotation model compared to rice monoculture both inside and outside. flood dike area. On the other hand, rice crop rotation also improves the durability of soil structure as well as the physicochemical and biological properties of soil. Master Trinh Thi Thu Trang, an officer of the Department of Soil Science and Land Management, said: 'The experiments were carried out in areas of intensive rice cultivation, sometimes up to 7 crops / 2 years. , leading to depleted nutrient resources in the soil. Rotation of colored rice shows a marked improvement in rice yield. Therefore, farmers need to change the monoculture of rice before the soil is depleted. '

In addition to crop rotation, scientists propose a number of other technical measures to improve and restore soil fertility. It is to improve the organic matter in the soil by applying organic fertilizer or straw fertilizer that has been incubated . Use fungi and bacteria to decompose straw to restore nutrients to the soil. Carry out appropriate soil preparation measures: for vegetable cultivation, it is recommended to apply at appropriate humidity; For rice cultivation, small plows should be used in the preparation of soil to limit the compressive effect in wet soil conditions. These measures have also been carried out in the experimental model and give positive results.

Currently, scientists continue to study the economic efficiency of rotation models to propose appropriate solutions to convert rice monoculture to color rice rotation in the above-mentioned intensive rice areas. . Other technical measures are also being investigated to make conclusive and accurate conclusions. Since then, transfer and dissemination to the agricultural and farmers sector has been widely used.

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