Why is the land still hungry no matter how much chemical fertilizer is used?
Starting with this issue, the Ecology Weekly launches the "Ecological Restoration, Beautiful Golden Autumn" column, focusing on ecological restoration of soil, mines, wetlands, forests, rivers and other aspects, with interviews and reports on typical cases in various fields. We look forward to your attention.
On September 13, 30 agricultural experts from 8 provinces gathered in Xihua County, Zhoukou City, Henan Province, including the heads of the soil and fertilizer stations of 8 provinces. In the heart of this grain-producing region, they were to conduct on-site observation, on-site yield measurement, and complete results evaluation of a multi-year chemical fertilizer reduction experiment. Li Rong, director of the Cultivated Land Quality Monitoring Division of the National Agricultural Technology Extension Center of the Ministry of Agriculture, pulled out two soybean plants, one growing in the experimental plot and one in an ordinary plot. One had roots growing straight down, with more than 50 effective rhizobia that could be counted. The other had roots growing sideways, with more than 20 rhizobia, and when dug open they were still rotten.
Rhizobia can help soybeans fix nitrogen from the air and promote growth. Therefore, the survival rate of rhizobia is an indicator for measuring the growth health of leguminous plants.
Li Rong simply had the plot dug open to take a look. The improved land appeared soft and loose, known as "sponge soil," while soil that had long been treated with chemical fertilizer was hard and dense, which local people called "thousand-layer cake." Only then did everyone understand: "The roots cannot go down, no wonder they grow sideways." The experimental plot had been treated with "carbon-adsorbed polyglutamic acid organic water-soluble fertilizer," which has shown clear results in reducing chemical fertilizer and improving soil, and has already passed application testing in 64 regions across 12 provinces on more than 10 million mu.
Soil compaction prevents plant roots from going deep or spreading out
At the end of September, Xihua in Zhoukou was in the autumn harvest season for corn and soybeans, but major grain grower Cao Zitang was not in a hurry. Among those organized by the National Agricultural Technology Extension Center of the Ministry of Agriculture to observe on September 13 was his improved land. He is a major national grain grower and has equipped himself with "high-end" equipment such as spraying drones and self-propelled sprayers. In other people's fields, machines were busy harvesting, but Cao Zitang would wait another week.
Unlike the surrounding plots, the plants on Cao Zitang's restored plot had not dried up, but remained green and were maturing with living stalks. "The soil has sufficient nutrients and strong vitality. If it is not harvested, it is still filling grain and can still increase yield," Cao Zitang said. "In previous years, the crops were especially prone to drought, and we had to water repeatedly. Only later did we learn that the soil was compacted, so plant roots could not go deep or spread out."
Pulling out Cao Zitang's corn for comparison, the roots were clearly thicker and spread out in a large mass, firmly grasping the soil. Soil compaction is not easy to see with the naked eye, but plants feel it clearly. Last year, Xihua County asked him to run a pilot, spraying a water-soluble organic fertilizer called "carbon-adsorbed polyglutamic acid" while greatly reducing chemical fertilizer, but he was unwilling to take the risk. In the end, only after the deputy county head in charge of agriculture promised to compensate for losses did he try a few plots. This year, without saying a word, he applied all the polyglutamic acid he could get to his land, and he was not even willing to leave a comparison field.
Combined with methods such as dense planting and improved seeds, while others harvested 400 jin of soybeans per mu, his improved land produced 700 jin; while others harvested 700 jin of corn per mu, he harvested 1400 jin. For corn, more than 100 jin of chemical fertilizer was originally used per mu, and this year it was reduced to 60 jin. Major growers from Shanxi and Hubei all came to learn from him.
"This year the pollination period suffered heat damage, and the weather was extreme, so the yield contrast after land restoration was even stronger. In a normal year, my field's harvest exceeds that of compacted land by 30%, and I am confident of producing more than 200 jin more, with better quality too," Cao Zitang said.
In Laiwa Village, Xihuaaying Town, many plots have already been continuously restored for 5 years. This year, Cui Jinli's soybeans attracted villagers from far and near to visit. Such good beans had never grown in sandy soil. Harvest began on September 22, and the yield per mu exceeded 400 jin. But Cui Jinli was no longer surprised. Four years ago, when wheat was planted for the first time on the restored land, experts from the Provincial Academy of Agricultural Sciences estimated a yield of 1200 jin per mu, and he did not believe it. Because wheat here had never been measured in jin, only in bags: generally four to five bags per mu, about 500 jin. The result left a deep impression on him: a total of 10 mu and 4 fen of land produced 12880 jin.
As they were talking, a soybean worm crawled onto Old Cui. With heavy use of chemical fertilizers and pesticides, insects were no longer commonly seen in the fields. After the land was restored, the insects came back. Old Cui said that in those years, wheat came up in patches of green and yellow, and when the cause could not be found, more chemical fertilizer was spread. Only later did they learn that herbicide had run with rainwater into low-lying areas and "burned" the wheat yellow. Farmers did not know and would not "detoxify" the soil; they only thought there was not enough fertilizer, and in the end a vicious cycle emerged.
The organic water-soluble fertilizer farmers now use to restore soil is called "Nai'an," and its inventor is a genuine farmer: Dang Yongfu. He is 50 this year and has spent 26 years of hard work protecting the land. He has won honors including the National May 1 Labor Medal and the "Star of Science" medal from the United Nations International Academy of Ecological and Life Sciences and the International Ecological Security Cooperation Organization.
In Dang Yongfu's view, long-term use of chemical fertilizer on land is like a person eating only rich meat and fish; over time they naturally become ill, with thick blood lipids, high blood pressure, and all the complications arriving. No matter how much chemical fertilizer is used, the land is still hungry and needs a balanced diet; organic matter and minerals are indispensable.
Polyglutamic acid is non-toxic, hydrophilic, and biodegradable. As a soil conditioner, it balances acidity and alkalinity, solidifies heavy metals, and its effects in improving fertilizer efficiency and increasing plant yield have been widely recognized. Dang Yongfu's scientific research results significantly reduced the production cost of polyglutamic acid, and good results have appeared in long-term, large-scale field verification.
Overcoming difficulties and tackling the side effects of herbicides and chemical fertilizers
Dang Yongfu has gone hungry, and he has a different kind of feeling for grain.
In 1989, while farming at home, he used the herbicide Saturn for the first time. The effect was astonishing, but after application the crops went through a 10 to 15 day inhibition period, did not grow and turned yellow, with yield reduced by 10% to 30%. From the time that crop was harvested, he began thinking about overcoming the side effects of herbicides.
In the following years, he often looked for things to spread on the land, trying to neutralize the harm of herbicides. In 1995, Dang Yongfu went to the Shenyang Research Institute of Chemical Industry and asked Professor Chen Chang to help him treat the side effects of herbicides. Professor Chen Chang suggested that he might as well go with the trend and open his own herbicide factory. In 1996, the factory was completed, but Dang Yongfu resolutely shut it down, and not a single drop of herbicide was produced. This was because the more he investigated, the more frightened he became, worrying that the factory would cause serious pollution locally.
Out of helplessness and being moved, Chen Chang decided to help Dang Yongfu build a pesticide plant. The raw materials were beginning to take shape, but Chen Chang passed away in 1997. Yet it was precisely this pile of raw materials and the purification ideas Chen Chang left behind that became the starting point of Dang Yongfu's scientific research. Dang Yongfu began the "Long March" in the field of degrading residues.
By 2003, Dang Yongfu had completed the precise quantification of the main degrading agents. After that, the harm of herbicides was exposed in some places in Northeast China. Because farmers had applied excessive herbicides for many years, many plots became "dead land," where crops found it difficult to survive, which local people called "cancer fields." Dang Yongfu brought his product to Suihua, Heilongjiang, and the local plant protection station did not trust him: "Even German companies could not cure it, and the cost was too high. What makes you think you can?"
What Old Dang relied on was the effect: corn and soybeans grew again in the "cancer fields." In this way, he took "Nai'an" northward all the way, traveling throughout Heilongjiang, and in rural areas it became almost a household name.
In this process, Old Dang discovered problems in the application of chemical fertilizers. People complained that chemical fertilizer had "lost its strength"; fertilizer use increased, but grain did not. It takes 1.55 tons of coal to produce 1 ton of nitrogen fertilizer. Over more than 20 years, our chemical fertilizer use per mu increased 12 to 15 times, while yield per mu increased only about 40%.
In Old Dang's view, Henan has an accumulated temperature period of 8 months and the best soil quality, so in theory it should be able to grow the best wheat in the world. But dependence on chemical fertilizer has caused soil compaction and acidification, and the organic matter content in the soil has declined severely, so the plants grown are naturally not strong enough.
By chance, they cultivated microorganisms to secrete polyglutamic acid, purifying it in batches and reducing costs. Starting from this, Old Dang explored a feasible path for soil restoration, fertility activation, heavy metal passivation, pesticide residue degradation, and three-dimensional treatment of pest, disease, and weed pollution.
The road ahead is long, and it takes time for farmers to accept new soil restoration products
The improved and restored land proved that these degrading enzymes and polyglutamic acid used for land restoration are indeed good things. Li Rong said, "This is exactly the technology our country needs. It can adjust both acidity and alkalinity and can solidify heavy metals. On more than 10 crops it has shown significant effects in reducing fertilizer, increasing yield, improving quality, and raising efficiency, and the technology is at the leading level among similar international products."
However, good things are not necessarily accepted. Dealers were the first to resist, and Dang Yongfu was once chased and beaten by dealers. Dealers welcome new fertilizer applications such as soil testing and formula fertilization, but not technologies that reduce chemical fertilizer. Even though polyglutamic acid can reduce costs, increase yields, and restore soil, it still encounters rejection from time to time.
Under the action of polyglutamic acid, chemical fertilizer use per mu can be reduced from more than 100 jin to below 70 jin, and replacing it with carbon-adsorbed polyglutamic acid organic water-soluble fertilizer costs about 30 yuan, while still ensuring increased yield. According to the relatively conservative assessment of experts from the Ministry of Agriculture, this technology can increase grain yield by 8% while reducing chemical fertilizer by 30%. But farmers' notion of "more fertilizer, more grain" is deeply rooted; they want high yields and even higher yields, and are unwilling to reduce the amount.
On the large tracts of land in Northeast China and **, farmers have a high degree of acceptance of carbon-adsorbed polyglutamic acid organic water-soluble fertilizer, and major grain growers in the interior accept it quickly. But if this new fertilizer is not used well, a season's harvest may be ruined. Trading high risk for increased yield on two or three mu is not cost-effective. Therefore, small farmers, who misuse chemical fertilizer most seriously, are slow to accept it.
For farmers, heavy metal passivation and pesticide residue degradation are not closely related to immediate interests. An extra degradation step means higher costs, while its results are hard to show intuitively, and the market may not recognize them. Therefore, even with such good technology, they are not enthusiastic.
China has already set the goal of zero growth in chemical fertilizer and pesticide use by 2020, but achieving the goal is not easy. As experts have said, if good technology is to move toward large-scale application, it still faces many practical constraints, and the road ahead is long.