The "Cadmium Rice" storm is like a heavy punch, which wakes people up and focuses our attention on the farmland that we have neglected for a long time but depend on for survival. In the face of the table crisis, we urgently need to reflect on the rash advance of "forcing" local grain production with chemical fertilizers and pesticides in those years, and we need to come up with a plan to repair the land cautiously and efficiently at this stage.
"phytoremediation" means that by planting some plants that can enrich heavy metals, the heavy metals in the soil are transferred and adsorbed to the plants, and the plants are decomposed, and these plants are buried to increase the fertility of the soil and reduce the dependence of cultivated land on chemical fertilizers and pesticides. However, this method has a long cycle, which is often ignored in the flood of land development for quick success and instant benefit. Only where you dare to "be lonely" can you have the courage to use plants to repair the soil.
Since this year, a green campaign has been quietly launched in Chongming, a northern suburb of Shanghai. According to the plan, by the end of 215, Chongming will have planted a total of 66, mu of "green manure" to replace chemical fertilizers, which is equivalent to 3% of the entire Chongming Island. Can we win this battle between plants and fertilizers?
cultivate land at the same time
June 5th is the "awn seed" of the 24th solar term of the lunar calendar, and the arrival of this solar term means that "the wheat with awn can be harvested quickly, and the rice with awn can be planted", and the annual
"Three Summer Wars" (Summer Harvest, summer sowing and Xiaguan) has officially arrived. Farmers have ushered in the "busiest" season of the year by harvesting wheat and planting rice.
However, for most farmers, "Mangzhong" is not so pleasant. Influenced by weather and human factors, in the past "three summers", it was often the case that "when this kind of rice arrived, the wheat in the field was not completely confiscated". The reason was that there were too many wheat people and it was too late to harvest it, which affected the sowing and planting of the following rice and might affect the rice harvest. Luo Dingsheng, head of the Agricultural Service Section of Chongming County Supply and Marketing Cooperative, told reporters that if rice is planted one day late, the corresponding income of farmers will be reduced by 1%.
However, this year, rice farmers are very
"calm". The "awn seed" has just arrived, and many fields have entered the summer sowing stage. With the help of the transplanter, green rice seedlings have taken root in the field at the right time. This is due to Chongming's "reducing wheat and increasing green" from last year, that is, reducing the area of late-cropping wheat and increasing green manure planting.
what is green manure? That is, the green plant used as fertilizer is one of the traditional important organic fertilizers in China, which can effectively improve the soil structure, improve the quality of crops, improve the quality of crops, and reduce the pollution of fertilizers to soil and water sources. Since 26, green manure has been planted in Chongming County. From 29 to 212, the planting area of green manure was stable at about 1, mu. This year, the planting area of green manure in the county reached 231,6 mu, an increase of 135, mu over the previous year.
At present, broad bean, Chinese milk vetch and grass head are mainly used as green manure in Chongming. Take Vicia faba and Astragalus sinicus, which are planted in large quantities, as an example. Last year, the amount of Vicia faba seeds per mu was about 9 kg, which was mainly sown by shallow tillage and stubble removal. After the previous rice harvest, the Vicia faba seeds and rice straws were turned over and planted together, and the best sowing time was before November 1; The seed consumption of Chinese milk vetch is about 2.5 kg per mu, and it is mainly sown by interplanting in rice fields. The sowing will be finished before October 15th, and the growth period with rice will be kept at about 25 days.
It is reported that turning green manure into the field is generally between its full flowering period and pod setting period, "turning it into the soil in the middle and late April is the best, and it will decompose in about one month.
"Agricultural technicians told reporters that the contents of available nitrogen, available phosphorus, available potassium, organic matter and humus in the soil have been greatly improved after the green manure is turned into the soil, which can effectively improve the soil fertility. Long-term planting of green manure will continuously improve soil fertility, which will also effectively increase rice planting yield in the later period and achieve an effective combination of land use and land cultivation.
If you earn less, you should plant
Changqing Agricultural Planting Cooperative, which has 828 mu of grain fields, is a big grain grower in Sanxing Town. During the autumn sowing last year, all the 828 mu of grain fields were planted with green manure. Zhang Shengchang, the person in charge, admitted that he was crossing the river by feeling the stones. "At the beginning, I just heard that there were many benefits, but I didn't plant them, and I don't know if it was true.
After planting, Zhang Shengchang, who is sensitive to income, smelled the smell of "not earning much": according to the minimum purchase price of 2.24 yuan/kg, the output value of planting an acre of wheat is about 627.2 yuan, and the net cost income is 375.52 yuan; Planting an acre of green manure has no output value, only 33 yuan, which is subsidized by the government, has a net income of 25 yuan after deducting the cost.
In this way, the net income of green manure is less than 7% of that of wheat in the same planting area. However, Zhang Shengchang has no regrets at all: "For a big planter like me, the savings in labor, pesticides and fertilizers can not be underestimated, and the risk of continuing to plant wheat is greater than that of green manure." He calculated an account for the reporter. In the process of planting wheat, the cooperative had to invite people to do short-term work, weeding at least twice a season and applying fertilizer twice or three times. Now the labor cost is almost 8 yuan a day, and chemical fertilizers and pesticides are also an expense. In addition, the collected wheat should be transported to the grain drying field by car, and the transportation cost is another sum of money. If it rains continuously in the harvest stage, the wheat will be moldy if it cannot be dried in time, and the hard work of one season will be in vain.
In contrast, Zhang Shengchang has a preference for green manure nowadays. First, it doesn't take too much time to manage, as long as a round of herbicide is used before planting, and the labor cost is reduced a lot; Second, there is no planting risk; Third, the green manure is harvested early, which does not affect the subsequent rice planting. Zhang Shengchang revealed to reporters that some small changes have indeed taken place in the soil quality after planting green manure: "Generally, before planting rice, water should be pumped into the field first. In previous years, water was pumped into the field, and the color of the water was gray. This year, it was a little black, indicating that the fertility of the land has been enhanced. It should be that the organic matter and phosphorus and nitrogen fertilizer produced after the decomposition of green manure have played a role.
Compared with Zhang Shengchang, those farmers who have planted green manure for many years have benefited more from it. Chengqiao town Juxun Village currently has 2,2 mu of grain fields. After years of promotion, green manure was basically planted in the autumn sowing period. Gu Daying, a villager, planted 4 mu of land and planted green manure for more than 3 years. Gu Daying told reporters that the family had made a comparison, and the rice grown in the field with green manure was better in quality. After being made into rice, it was better in flavor, glutinous and taste.
"This land is no longer as solid as it used to be, but it has become looser. Last year, the master who drove a tractor joked with me and said that this land is much easier to turn up now."
palliative measures can also cure the problem
As a large agricultural county, more than half of the pollutants in Chongming come from agricultural non-point source pollution such as chemical fertilizers and pesticides, livestock manure and straw, and planting green manure has become a good way to reduce agricultural non-point source pollution.
Since 25, Chongming has carried out the recycling of pesticide packaging in 272 administrative villages in 18 townships in the county, effectively avoiding the harm to the atmosphere, water quality and soil caused by the natural decomposition of pesticide packaging. According to a statistical data, from December 211 to the end of May 212, Chongming County recovered 38, pesticide bottles and 1,767,5 pesticide bags, while from December 212 to the end of May this year, the county only recovered 192, pesticide bottles and 1,479, pesticide bags. This shows that due to the promotion of green manure, chemical fertilizers and pesticides are used less.
"In the past, problems were always found and then remedied, and the remediation cost of soil pollution was too high." Zou Jinzhong, deputy director of Chongming County Agriculture Committee, said that only by using green manure to reduce the use of chemical fertilizers and pesticides from the source is the "trick" to protect the soil. According to the investigation from the county agricultural department, chemical fertilizers and pesticides are basically not applied to green manure in this season. The planting mode of "green manure before rice" is 25 kg less urea, 2 kg calcium superphosphate and .1 kg less pesticide per mu than that of "wheat before rice". Based on the current planting of 23, mu of green manure in the county, it is equivalent to 5,75 tons less urea, 4,6 tons of phosphate fertilizer and 23 tons of pesticides in the county.
Another advantage of planting green manure is to remove
the "tail" for the summer harvest. During the wheat harvest season in previous years, burning straw became another "fixed operation" for some farmers' summer harvest. Even in recent years, the government introduced relevant subsidy policies to recycle straw and reduce burning, but it was still repeatedly prohibited. According to reports, crop straw contains nitrogen, phosphorus, potassium, hydrocarbon and organic sulfur, etc., especially the straw that has just been harvested has not been completely dried. After incomplete combustion, a large number of nitrogen oxides, sulfur dioxide, hydrocarbons and soot will be produced, and secondary pollutants such as ozone may also be produced under the action of sunlight, which will cause great pollution to the air environment.
In addition, burning straw will also make the ground temperature rise sharply, which can directly burn and scald beneficial microorganisms in the soil, destroy the soil structure, affect the full absorption of soil nutrients by subsequent crops, cause the decline of cultivated land quality and affect agricultural income.
turning green manure directly into the land can not only "fertilize" the field, but also effectively prevent straw burning and pests, which can be described as killing three birds with one stone. Although the pace of soil remediation is a little slow, this ecological road is full of dawn.
Chen Xihan, Zhu Jinghua