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Soil texture and soil moisture are necessary conditions for the survival of crops, and there is a very close relationship between them. Soil texture and characteristics influence the choice of crop species and varieties, as well as the formulation and implementation of integrated irrigation and water and fertilizer schemes.
The general soil consists of three parts: sand, silt and clay. The relative content of these ingredients will affect the soil texture and soil water holding capacity. In most soil types, small particles form larger particles, called multigrain. The multiple grains are bonded to each other to form soil blocks. There are many pores between soil particles, multigrains and soil blocks.
The distribution of pores in the soil is very important. Porosity is defined as two types: small pores and large pores. Small pores are commonly referred to as "capillary pores." In sandy soils, the porosity is persistent and stable. In cohesive soils, the porosity changes with changes in soil moisture.
Soil water holding capacity is affected by soil texture and soil type. If in the sandy soil, 15% of the soil water content can meet the needs of normal crop growth, while the same water content in the neutral soil is only at the critical point of crop water demand, and the sticky soil cannot meet the needs of crop survival. Water is fixed in the soil pores and forms a water film with the surrounding soil particle surface. When the soil dries out due to infiltration, evaporation, and root absorption, water in the large pores is absorbed first, while water in the small pores is also absorbed. When the crop needs water, it first absorbs water from the large pores.
The water retention mechanism of soil particles is mainly based on the water retention of the particle surface. Sand grains, powder grains and clay particles are bonded and aggregated with each other to form a soil structure. A good soil structure has more soil voids and better water retention than a compact structure. The loam has better water holding capacity (it consists of many small particles and has a larger surface area). The sandy soil has weak water holding capacity (it is mainly composed of large particles and has a small surface area).
Soil structure affects irrigation schemes in two ways:
1. It determines how fast the soil absorbs water. Because it affects the selection of the dripper flow rate and the determination of the dripper distance, it must be understood before the drip irrigation system is designed.
2. It determines how much water is stored in the root zone and how much water is available for crops to absorb.
Soil water content is expressed in four forms: saturated water capacity, field water capacity, wilting point and available water. Saturated water holding capacity means that all pores in the soil are filled with water. The water holding capacity in the field reaches the maximum, and the soil reaches an equilibrium point where water is no longer lost with the leakage of the field. The root system can easily absorb water from the soil. At the same time, the soil is well ventilated and airy, which is conducive to the breathing of the root system. Grow. The wilting point is the lower limit at which the root system cannot absorb water from the soil. Beyond the wilting point, the crop cannot survive and the crop wilting is irreversible. Effective water is the soil water content between the field water holding capacity and the wilting point. The field water holding capacity refers to the maximum water holding capacity in the field, and the wilting point refers to the minimum water holding capacity in the field to maintain the water required for crop survival.
Soil pH is used to determine soil pH. pH is the negative logarithm (base 10) of the concentration of hydrogen ions (H + or more accurately H3O +) in the solution.
In water, the pH is generally between 1-14, and 7 is neutral.
The pH value is below 7 and it is acidic, and above 7 it is alkaline.
Soil pH is considered a major variable in the soil because it controls many chemical reactions. It affects the effectiveness of crop nutrients by controlling the chemical form of nutrients. Most crops have a pH range of 5.5 to 7, but many plants can adapt and thrive outside this range.
Ideal soil conditions:
The drainage is good, the soil layer is deep, the loam layer contains sufficient air (10-12%), the groundwater level is 1.5-2 meters from the surface, the soil bulk density is 1.4 g / cm3, and the effective water content is 15% (per meter of soil layer It contains 15 cm of water) or more and is considered good soil conditions.
• The soil's chemical properties, such as pH and low fertility, can be easily adjusted or controlled by using drip irrigation systems for precise fertilization or acid injection.
• Although poor soil texture is difficult to improve and is often considered a limiting factor for crop growth, drip irrigation systems can overcome this difficulty through precision irrigation, controlled irrigation frequency, and irrigation schemes.
November 4, 2016
Chengdu Xinxin Electronic Technology Co., Ltd. Editorial Department
Editor: Little Devil in Gourd