Risks and problems of organic fertilizer and its countermeasures

Foreword

Plagued by food safety, with the rise of organic agriculture and ecological agriculture, organic farms and ecological farms have sprung up all over the country, and many people have chosen to grow their own vegetables and food. many investment institutions have also begun to enter eco-organic agriculture on a large scale, but the risks involved are not only capital and market, but more technology.

At present, organic farms or ecological farms in China, no matter what school they are, basically follow the bottom line of not using pesticides, chemical fertilizers, hormones and antibiotics. Since chemical products are not used, there must be alternative products. So organic fertilizers (including farm manure) replace chemical fertilizers, biological and plant pesticides instead of chemical pesticides, allowing crops to grow naturally instead of hormones. Using Chinese herbal medicine and plant extracts instead of antibiotics, people show their talents in finding a safe mode of production, and are making useful explorations and attempts for the development of safe agriculture.

This paper only talks about the risks, problems and solutions of organic fertilizer instead of chemical fertilizer.

What is organic fertilizer? Organic fertilizer refers to a variety of animal wastes (including animal manure, animal processing wastes) and plant residues (cake fertilizer, crop straw, deciduous leaves, dead branches, peat, etc.), the use of physical, chemical, biological or a combination of the three treatment technologies, after certain processing processes (including but not limited to composting, high temperature, anaerobic, etc.) Elimination of harmful substances (pathogens, diseases and pests, weed seeds, etc.) formed by innocuous standards, in line with the relevant national standards (NY 525-2011) and laws and regulations of the fertilizer.

Since the relevant national standards have been reached through harmless treatment, how can there be risks? Please note that there is no stipulation on antibiotic residues in this organic fertilizer standard. Secondly, there are only five heavy metal residue limits for heavy metal residues, and there are no restrictions on the residues of copper and zinc preparations which are widely used in farms.

At present, the raw materials for the production of organic fertilizer in China are basically derived from livestock and poultry manure in large-scale farms. The author has said on many occasions that the land of "ecological" farms that use livestock and poultry manure from conventional farms as a source of organic fertilizer for a long time, it is likely to be an ecological disaster area. This is not alarmist talk, but let us analyze it from the source, the process and the result.

Present condition

The discharge of livestock and poultry manure reached 3.18 billion tons in 2003, and it is estimated that by 2010, the discharge of livestock and poultry manure will reach 4.5 billion tons.

According to the statistics of the Chemical Industry Society and the Pharmaceutical Industry Association in 2005, the annual production of antibiotic raw materials in China is about 210000 tons, of which 97000 tons (accounting for 46.1% of the total annual output) are used in animal husbandry. Studies have shown that only 15% of antibiotic drugs can be absorbed and used by animals, and 85% are released into the environment through feces without being metabolized. According to the above data, the annual discharge of antibiotics into the environment through livestock and poultry manure is as high as 82000 tons.

The average contents of oxytetracycline, tetracycline and chlortetracycline in 32 pig manure samples from a farm were 9.09,5.22,3.57 mg/kg;23 respectively. The average contents of oxytetracycline, tetracycline and chlortetracycline were 5.97,2.63,1.39 mg/kg, respectively. According to the research of Food Safety Inspection Institute of Chinese Academy of Agricultural Sciences, the content of residual antibiotics such as chlortetracycline in some pig manure samples reached 200 mg/Kg. The investigation of livestock and poultry manure samples and farmland soil with livestock and poultry manure in the northern part of a province also showed that the detection rates of oxytetracycline, tetracycline and chlortetracycline in the topsoil were 93%, 88% and 93%, respectively.

According to statistics, the national livestock and poultry breeding industry uses 15-180000 tons of trace element additives every year, of which about 100000 tons are not used by animals and excreted with faeces. Among all kinds of trace element additives, copper, zinc and arsenic preparations are the most commonly used, so the heavy metal pollution caused by emissions is also the most serious.

The results of investigation on 61 livestock manure samples from an intensive farm in a province showed that the average contents of copper, zinc and arsenic in chicken manure were 107.5, 366.6 and 21.6mg/kg respectively, and those in pig manure were 765.1, 1128.0 and 89.3 mg/kg, respectively. According to the limits of heavy metals in different fertilizers, the main heavy metals in chicken manure and pig manure were copper, zinc and arsenic, among which zinc was the most common.

Wind insurance

Let's take a look at the possible risks of antibiotics and heavy metal pollution in livestock and poultry faeces from conventional farms.

Antibiotics are designed to inhibit and kill some bacteria, so they are bound to destroy the balance structure of soil microflora and the diversity of functional communities after entering the soil, so that soil microorganisms show a trend of "directional enrichment". And it has obvious inhibitory effect on the growth and development of microorganisms, animals and plants in the soil environment.

The introduction of antibiotics into the soil causes some pathogenic bacteria to produce drug resistance genes and enter the food chain through plants, animals, water sources and other ways.

Heavy metals artificially added to livestock and poultry feed accumulate after entering the soil. Some studies have shown that the content of heavy metals in the vegetable field which has been applied with pig manure for 10 years can exceed the national secondary soil standard and become heavily polluted farmland. Eventually these excessive heavy metals are either enriched (plants or herbivores) or migrated into the human food chain through groundwater.

Eventually, the antibiotics and heavy metals carried in these livestock and poultry faeces will enter our food chain through various ways, thus bringing potential harm to human health.

Can they decompose naturally in the soil?

Many studies at home and abroad have shown that the decomposition of antibiotics after entering the soil is extremely slow. For example, Danish scientists have studied the degradation of chloramphenicol and tylosin in Danish sandy soil. It was found that the time required to degrade 50% was 25: 34 days and 49: 67 days, respectively. Another study showed that it took about 44 days for oxytetracycline, 105 days for tetracycline and 160 days for chlortetracycline to degrade half of the soil containing antibiotics.

In the environment, the metabolites of some antibiotics can even be converted back to the original active drugs. It has been reported that chloramphenicol glycosylate can be converted to chloramphenicol and N4-acetyl sulfamethazine to sulfamethazine in liquid fertilizer.

In 83 samples of vegetables sold in a large city, 96% of the samples detected quinolone antibiotics to varying degrees, with an average of 146.6 micrograms / kg (fresh weight), while the safe daily intake value (ADI) for children was 60 micrograms. In addition, among the detected antibiotic residues, the contents of pollution-free, green and organic vegetables were generally higher than those of conventional vegetables.

On the other hand, the heavy metals discharged with livestock and poultry manure remain in the soil for a long time.

The results of long-term application of pig manure soil and non-pig manure soil showed that the contents of copper zinc and arsenic in pig manure soil and vegetables (leek green vegetables celery radish) were significantly higher than those in the control group. The highest content of copper, zinc and arsenic in the soil was 11 times, 5 times and 2 times that of the control group, respectively, and the highest content of copper and zinc in vegetables was 4 times that of the control group, and that of arsenic was 3 times that of the control group. The highest content of copper in the soil with pig manure was 133.98%. Zinc is 52.05%, arsenic is 12.04%; zinc in vegetables with pig manure is up to 117%.