Paddy field has its own characteristics, such as strong water and fertilizer conservation ability and high organic matter content. The main disadvantages are heavy soil texture, high reducing substance content and high groundwater level.
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China Shuitian
Paddy fields are named for their abundant water resources. In China, it is mainly distributed in the eastern monsoon region. The real big paddy fields are concentrated in the southern region. This is an area where rice is planted and mainly produced.
Soil: The soil in paddy fields in southern China is called paddy soil. Paddy soil is formed under the influence of certain natural environment and various farming measures after human beings grow rice. Because of long-term irrigation and dry-wet alternation, soil properties different from dry land have been formed.
When paddy soil is irrigated, the topsoil is saturated with water and in a reduced state; In autumn and winter, in the seasons of drainage, air drying and dry field, the plough layer is in an oxidation state. This periodic dry-wet alternating process forms the unique physical, chemical and biological properties of paddy soil.
Under the condition of flooding and anoxia, the decomposition of organic matter is slow, the humification degree is high, the fertilizer efficiency is stable and long, and the nutrient loss is less.
However, if the soil is highly reductive and the organic matter is decomposed anaerobically, a variety of organic acids will be produced, which will hinder the oxygen secretion ability of rice roots. When the reducibility is strong, it will also produce toxic substances such as methane and hydrogen sulfide to poison the rice roots, and in severe cases, the rice roots will turn black, rot and die.
According to the research, a certain reducing environment in paddy field is beneficial to the growth of rice. In the reduced state, almost all inorganic nitrogen exists in the form of ammonia nitrogen, which is suitable for rice absorption and utilization. At the same time, ammonia nitrogen is a cation, which is easily adsorbed by soil colloid and is not easy to lose.
Another characteristic of paddy soil is that after the paddy field is flooded, the pH value often increases and the redox potential decreases, thus promoting the hydrolysis of iron phosphate, reducing iron phosphate to iron phosphate, and reducing iron-silicon complex.
Therefore, the content of available phosphorus and silicon dioxide in soil is increased, which is beneficial to rice absorption. However, in sandy paddy fields with strong leakage and paddy fields with high active iron and aluminum content and mainly calcium phosphate (except for a large amount of residual organic matter in soil), available phosphorus decreased. For this kind of paddy field, it is necessary to increase the application of organic fertilizer and phosphorus fertilizer at the same time to meet the demand of rice growth for phosphorus.
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