with the rapid arrival of industrial civilization in the past 200 years, china's 40 years of reform and opening up have achieved the achievements of western developed countries in the past 100 years. facts have proved that it pays the environmental costs such as high consumption, high pollution and high emissions brought by extensive development model.
among them, cultivated land pollution is a big problem in china.
if we trace the origin of food, we will find that almost all food, whether it is vegetables, fruits, grains, or meat and dairy products, comes from the soil (research shows that 95% of the food we eat comes from the soil). whether it is carnivores, herbivores, or omnivores, soil can provide them with a variety of food choices. no matter where you live, the soil silently provides us with the raw materials of animals and plants that we need every day.
why don't the fruits and vegetables we eat have the same taste?
why do more and more fertilizer use, but the output is lower and lower?
why soil borne diseases have become the most difficult problem in recent years
the root cause is that the soil is bad!
soil is the source of everything and the foundation of agriculture. it plays an important role in food security and basic ecosystem functions. without healthy soil, there is no future for human beings?
the land governance in developed countries in the world has been basically alleviated, and the united states has established a "super fund" to control soil pollution; the establishment of japan's soil remediation market is closely related to legislation; the european soil remediation market varies greatly from country to country, the united kingdom mainly adopts layered management for soil remediation, germany mainly adopts the "divide and rule" strategy, and canada mainly takes ten steps manage processes.
at present, the overall situation of soil environment in china is worrying, and pollution in some areas is relatively serious, which has become one of the outstanding shortcomings of building a moderately prosperous society in an all-round way.
from april 2005 to december 2013, china carried out the first national soil pollution survey, with an actual survey area of 6.3 million square kilometers. the total over standard rate of soil in china is 16.1%, among which the proportion of slight, mild, moderate and severe pollution points is 11.2%, 2.3%, 1.5% and 1.1% respectively.
according to the distribution of pollution, soil pollution in south china is more serious than that in north china; heavy metals in southwest and central south china exceed the standard in a large range; the content distribution of four inorganic pollutants, cadmium, mercury, arsenic and lead, is gradually increasing from northwest to southeast, from northeast to southwest.
the ph value of normal and neutral soil is about 7. the ph value of soil in different areas is different. take hebei soil for example, it should be neutral and alkaline, with a ph value of about 7-7.5. most of the chemical fertilizers we use now are acidic, especially the quality of the chemical fertilizers produced by some small factories is not up to standard, and the degree of acidity is more serious.
with the increase of planting years, root diseases will be particularly severe, and the yield and quality of crops will decline. at last, even if how to apply fertilizer, the yield will not go up. vegetable farmers often only pay attention to the application of chemical fertilizer, but not to an activation of soil biological properties. the deterioration of soil biological properties is one of the main reasons for crop yield reduction.
soil hardening the so-called "hardening" of soil is simply that the soil has hardened and the root system can't be rooted down
first, root necrosis
crop roots need to breathe and oxygen in the soil. the soil hardening will affect the permeability. if the water is poured, the oxygen in the soil will be compressed by the water. if the roots cannot breathe, the roots will retouch and the roots will start to necrosis.
second, the roots are getting shallower
at the middle stage of crop growth, the rate of root necrosis will exceed that of root growth, and the root system will appear premature senescence, that is, the root system will become shallower and shallower. (for example, the roots of greenhouse vegetables, tomatoes and cucumbers can only be cut down about 10 cm, but more often they become lateral roots and grow along the plastic film to both sides. if the root system is dug out, it looks very long. in fact, it is mainly lateral root.)
finally, it affects the ability of crops to absorb water and fertilizer
too shallow root system will affect the ability of crops to absorb water and fertilizer. when we apply fertilizer with water, no matter in furrow irrigation or flood irrigation, if 15 cm water is poured on the upper part of the ground, the normal loam soil will have water penetration of about 50 cm. (that is to say, one-time watering and fertilization, within 50 cm from the soil, has both water and fertilizer). however, if the root system of soil hardening is limited, the crops may only absorb about 10 cm of nutrients and water. this leads to crop water shortage and lack of fertilizer. in fact, we apply a lot of fertilizer and water! it's just not absorbed.
soil physical properties, chemical properties, biological properties and soil hardening affect each other. when the soil is hardened and fertilized, the soil salinization and acidification will be more serious, and the biological properties will also deteriorate. if the crops don't grow well, it's not that you use less fertilizer, but that the soil is sick. so what we should consider to do first is to improve the soil!
here are some ways of soil improvement for your reference:
1、 reasonable use of chemical fertilizer to improve the chemical shape of soil:
the chemical properties of soil are closely related to the utilization rate of chemical fertilizer. at present, the utilization rate of compound fertilizer is very low in many plots of china. (if compound fertilizer is used alone in some areas, the utilization rate can not reach 25%, that is to say, only about 25 jin can be absorbed by crops when 100 jin compound fertilizer is applied to the land, and the rest 75 jin will be wasted in vain, which will aggravate soil salinization or acidification.)
in fact, there is no lack of fertilizer in the soil for the fields that have been applied with a large amount of compound fertilizer all the year round. there are only a lot of nitrogen, phosphorus and potassium in the soil. the main problem is: how to activate the remaining nitrogen, phosphorus and potassium in the soil, or the nitrogen, phosphorus and potassium fixed by the soil, little by little, so that the crops can absorb and use them, rather than pursuing more chemical fertilizers. so we have been advocating organic fertilizer with chemical fertilizer to promote absorption. in this way, if the absorption and utilization rate of fertilizer can be increased to 80%, the damage to the soil will be less and less, and the soil itself has a buffer capacity, so the soil will grow better and better.
2、 supplement beneficial bacteria (biological bacteria fertilizer) to improve soil biological shape:
at present, the problems of hardening, acidification, salinization, barren soil, and soil fertility failure are mainly caused by the long-term accumulation, residue, and ineffective decomposition and transformation of chemical fertilizer in the soil. therefore, to solve the problem of soil ecological quality and crop yield is to increase the beneficial microorganisms in the soil. at present, the domestic bacterial fertilizer market is uneven. when we choose, whether large or small manufacturers, whether high or low bacterial content, we should do a good experiment and demonstration in advance.
3、 rational use of soil conditioner!
the role of soil conditioner is to stick the broken soil particles into small particles, that is, to restore the structure of soil particles. the soil conditioner will become particularly sticky under the action of water, and small particles will form soil colloid, which forms the structure of soil particles, ensuring the permeability and fertilizer conservation of the soil, and the root system is easier to penetrate. although soil conditioner can improve and regulate the soil, it is necessary to know what kind of soil it is for, some for alkaline soil, some for acid soil, and the dosage should be reasonably controlled. excessive use will cause other side effects.
4、 straw returning to the field
especially for the greenhouse soil, the effect of straw is very good, better than the effect of organic fertilizer alone. at present, many farmers still use immature manure as organic fertilizer, which is very harmful. whether it is chicken manure or cow manure, it can be fermented by adding straw.
take cow dung as an example. it is rich in organic matter, nitrogen, phosphorus and potassium. one layer of cow dung and one layer of straw are chopped together for fermentation. in this way, more organic matter can be decomposed. at the same time, high-temperature fermentation can eliminate most of the pathogenic bacteria. straw can be widely used in the land with serious soil salinization. straw can absorb part of salt and reduce soil salinization in the process of straw ripening.
in short, the consequences of soil degradation are quite serious!
soil improvement is both urgent and a complex and long project, we can not only be limited to one point, we should start from many aspects, clear purpose, targeted soil improvement.