On "soil compaction", this article says the most comprehensive!
Soil compaction refers to the lack of organic structure on the surface of soil due to the lack of organic matter. Under the influence of external factors such as irrigation or rainfall, the soil structure is destroyed and the soil is dispersed. After drying, the soil surface is consolidated by cohesive force.
First, how is soil compaction formed?
(1) the content of organic matter is an important index of soil fertility and aggregate structure, and the reduction of organic matter leads to soil compaction. Soil organic matter content is low, which affects microbial activity, thus causing the formation of soil aggregate structure, resulting in soil compaction.
(2) to the soil in excess fertilizer potassium, potassium replacement of potassium in the particularly strong, can form a replacement out of soil aggregate structure of multivalent cations, and potassium ion is not monovalent key bridge, the bridge of soil aggregate structure was destroyed, also destroyed the aggregate structure, resulting in soil compaction.
(3) the aggregate structure of soil is an important indicator of soil fertility, and the destruction of soil aggregate structure leads to the decrease of soil water holding capacity, fertility retention and permeability, resulting in soil compaction.
(4) the aggregate structure of soil is negatively charged soil; clay particles and organic matter are linked by positively charged multivalent cations.
(5) soil acidity or alkalinity is too large or too small, as follows acid rain.
Two, cause soil compaction factors
1, farming methods
In the farming process, many people choose rotary tillage farming, which can reach the surface smooth, fine soil, saving benefits, and high popularity, but the rotary depth is too shallow, the soil texture is too sticky, more clay content in the clay, and the plough layer average of less than 20 cm in soil the capillary pores are less. After the ventilation, water, temperature and less rain, easy to plug the pores, causing soil surface crust.
2, excessive use of chemical fertilizer
(1) in fertilizer use, people often ignore the harmful effects of chemical fertilizers. Excessive and the use of chemical fertilizers in frequency, reduce the amount of straw returning, the soil organic matter supplement, low organic matter content of soil structure variation, soil nutrient imbalance, especially potassium and ammonium nitrogen fertilizer use, a damage caused by soil aggregate structure, influence the microbial activity, causing acid-base the soil is too large or too small, leading to soil compaction.
(2) the application of organic fertilizer was seriously insufficient, and the soil organic matter decreased with heavy nitrogen, light phosphorus and potassium fertilizer. Humus could not be supplemented in time, resulting in soil compaction and cracking.
1) nitrogen fertilizer application: microbial nitrogen supply increased 1, the corresponding consumption of carbon increased 25, the consumption of carbon sources on soil organic matter, organic matter content is low, influence microbial activity, thus affecting the formation of soil aggregate structure, soil compaction.
2) the excessive application of phosphate fertilizer: the phosphate ion in phosphate fertilizer combines with cations such as calcium and magnesium in soil to form insoluble phosphates, that is to say, they waste phosphate fertilizer and destroy soil aggregate structure, resulting in soil compaction.
3) applying potassium overdose: potassium ion replacement of potassium in the particularly strong, can form a replacement out of soil aggregate structure of multivalent cations, and potassium ion is not monovalent key bridge, the bridge of soil aggregate structure was destroyed, also destroyed the aggregate structure, resulting in soil compaction.
3, the use of plastic products
In greenhouse facilities, because plastic film and plastic bags is not clean, in the soil can not be completely decomposed, the formation of massive harmful substances. In China, the waste plastic which enters the landfill every year with the domestic waste accounts for 3%-5% of the landfill waste, most of which are plastic bag garbage, which are not easy to degrade in the soil and cause soil compaction.
4, mechanical repression, tillage
Because of the deep influence of mechanical tillage, soil aggregate structure was destroyed. The annual application of fertilizer in the soil is only partially absorbed by crops in the season, while the others are fixed by the soil, forming a large amount of acid salt deposits, which lead to soil compaction.
5, unreasonable irrigation
Because of the unreasonable use of flood irrigation, drought, coupled with dry climate and other factors, makes the most of the water in a short period of time by evaporation, caused by soil compaction, may also be caused by the flood water precipitation phenomenon, cause serious destruction of soil aggregate structure, soil forming plate.
6, accumulation of harmful substances in soil
In some areas, groundwater and industrial waste water and toxic substances are high, and long-term use of irrigation and accumulation of toxic substances cause excessive surface soil compaction.
7, rainstorm water and soil erosion
After the rainstorm, small soil particles are taken away from the soil surface, resulting in destruction of the soil structure.
Three, the harm of soil compaction
1, plant root respiration was blocked
In the case of soil compaction or long-term flooding, the cell respiration in the roots of the plant decreased, while the nitrogen and other nutrients existed in the ionic state. The active transport was carried out when absorbed, and the energy produced by cell metabolism was consumed. Respiratory depression, so the energy supply is insufficient, affecting absorption.
2, the plant root system can not develop normally
Soil aggregate structure is an important index of soil fertility, soil aggregate structure damage resulting in soil moisture and fertilizer retention capacity and lower permeability, caused by soil compaction, the plant root in this state will lead to decreased activity due to hypoxia.
3, causing plant deficiencies
Plant nutrient deficiency symptoms, not necessarily is the lack of the elements in the soil, but because of soil compaction, soil pH is not suitable, or is caused by soil water supply imbalance in a series of problems such as the root absorption capacity decreased by