Basic knowledge of soil

First, the soil texture

1 , sand

These soils contain more sand and contain less clay. The intergranular pores are large, the small pores are small, the total pore size is small, the water is easy to infiltrate, the internal drainage is fast, and the capillary action is weak. If the groundwater level is low, the groundwater can not be relied on the rise of the capillary tube to return to the topsoil, so the drought resistance is weak. Because of the good permeability of the intergranular macropores, the water vapor rapidly diffuses in the soil and escapes to the atmosphere, so the evaporation is strong and the water retention performance is poor. Therefore, in the utilization management of sand, it is necessary to pay attention to the selection of drought-tolerant varieties, ensure timely irrigation of water sources, and prevent excessive water supply and leakage.

The sand minerals are mainly composed of quartz, and the nutrient content is small. Because of the good aeration, the aerobic microbial activity is strong, and the organic matter decomposes quickly and is not easy to accumulate, which can promote the early development of crops. However, due to its small cohesiveness, poor fertilizer retention and easy to lose nutrients, the fertilizer is short. The application of quick-acting fertilizer on sand is often fierce and unstable, and the strength of the front is large and the stamina is insufficient. Therefore, the principle of following the basic fertilizer, topdressing and heavy, and thinning the application is followed.

The sandy soil has less water content and less heat capacity. It receives solar radiation during the day and increases its temperature quickly. The heat dissipation at night is also fast, so the temperature difference between day and night is large, which is beneficial to the growth of roots and tuber crops. In early spring, the temperature of sandy soil rises rapidly, so it is also called “warm soil”. In the late autumn, when it encounters the cold wave, it cools down quickly and is vulnerable to freezing damage.

The sandy soil is long and easy to cultivate. However, due to the high content of silt and fine sand, it is easy to precipitate and close after soaking in water ("closed sand" phenomenon). This is because the flaky mica has more sand, or contains more sand and coarse particles, and has a lower organic matter content. It lacks agglomerate structure. In the water flow, the soil particles are deposited quickly and tightly, or the water particles are filled with water. The large pores between the sand grains. If the soil is used as a paddy field, the transplanting will be carried out while ploughing.

2 , clay soil

In clay soil, the content of fine particles is high and there are few sand grains, and the pores between the grains are narrow, but the total porosity is much larger than that of sandy soil, and the water storage capacity is large, and the vertical infiltration and drainage of rainwater or irrigation water is extremely difficult (sticky) The water swells and swells to block the pores, and the permeability is poor.

Viscous soil is rich in mineral nutrients and has a strong adsorption capacity for positively charged ionic nutrients, so that it will not be lost by rain or irrigation water. Since the fine pores of the clay soil are often occupied by water, the ventilation is not smooth, the activity of the aerobic micro-organisms is suppressed, the organic matter is slowly decomposed, and thus it is easy to accumulate, so the fertility is strong.

The clay soil has a large amount of water storage, a large heat capacity, and a small temperature difference between day and night. In early spring, the soil temperature rises slowly, so it is called "cold soil" or "cool soil." In the case of short-term cold wave infiltration, the clay soil is also slower to cool down, and the crop is less damaged by freezing.

Clay with low organic matter content tends to bond into large clods, which is particularly poor in ploughing. It is hard to dry when dry, muddy when wet, short for ploughing, high resistance to tillage, and cracked after sticky soil, which easily damages plant roots. For such soils, organic fertilizer should be added, attention should be paid to drainage, and intensive cultivation should be carried out under suitable water content conditions to improve its structural and ploughing properties.

3 , loamy soil

It is a type of soil texture between sandy soil and clay soil. It also contains the right amount of sand, powder and cosmid. It has the advantages of both sandy soil and clay soil in nature, and is an ideal soil for general agricultural production.

Second, the soil type

(a), red soil

1. When the soil is acidic, the soil is too acidic or plants that are not suitable for acidic soils can be used to improve the soil with lime.

2. There are many free iron and aluminum oxides, and the effect of phosphorus fixation is strong. The application of phosphate fertilizer increases the yield significantly, and it is better to apply alkaline calcium magnesium phosphate fertilizer.

3, soil is sticky, nitrogen, phosphorus, potassium nutrients and organic matter are very low, it is necessary to increase the application of organic fertilizer to improve the soil, and increase the application of compound fertilizer to improve soil fertility.

4. The soil is generally deficient in zinc and boron trace elements, and it is necessary to supplement zinc fertilizer and boron fertilizer for sensitive crops.

(two), yellow soil

The yellow soil is higher than the red soil, and is generally distributed at an altitude of 700-1200 meters. The characteristics of yellow soil are similar to those of red soil, but the organic matter content is higher and the texture is lighter than that of red soil.

(3) Paddy soil

Sulfide toxicity of rice in flooded environment: H ₂ S is toxic to rice (H ₂ S is an inhibitor of cytochrome and catalase, affecting the physiological metabolism of rice), mainly characterized by physiological black The roots, when severely pulled up, can smell some odor. Fe ² formed by H ₂ S and Fe ^{2+ in} soil is deposited on the surface of rice roots, and (chemical) black roots are also formed. Among the controlling factors of the amount of H ₂ S, pH plays a decisive role, and the higher the pH, the lower the H ₂ S content. Acidic paddy soil can increase soil pH by applying lime (ie, reduce soil acidity) to avoid sulfide poisoning.

(four), purple soil

1. The purple soil is strongly weathered and the chemical weathering is weak. The soil texture is light and the organic matter content is low. It is necessary to increase the application of organic fertilizer to improve the soil and promote soil ripening.

2, mineral nutrient rich, total phosphorus and total potassium content are high, generally potassium can meet the needs of crops, but because the soil's available phosphorus is not high, so still need to apply phosphate fertilizer.

3, soil nitrogen is insufficient, need to apply nitrogen fertilizer.

4, the soil is generally lack of zinc, boron and molybdenum trace elements, the need to supplement the corresponding micro-fertilizer for sensitive crops.

(5), lime soil

1, generally neutral to alkaline reaction, phosphate fertilizer should use superphosphate. For the acid red lime soil with strong leaching, it is better to use alkaline calcium magnesium phosphate fertilizer.

2. The soil organic matter content is high, humic acid and calcium condense into humic acid calcium, the soil texture is more viscous, the upper layer is mostly clay loam to loam, the lower layer is clay, and the soil structure is better.

3, soil available phosphorus, potassium level is medium, rich in calcium and magnesium. Low effectiveness of boron, zinc and copper on alkaline soils

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