Soil root profile under conservation tillage mode.

In order to strengthen the protection and utilization of black land and protect the black land, the "giant panda in the arable land", various areas in the northeast have adopted protective measures such as returning straw to the field to "purge" the black land. However, there are different opinions on the pros and cons of returning straw to the field. In the end, is straw a "protective umbrella" for black soil or a "hotbed" for breeding diseases, insects and weeds? Returning straw to the field has become one of the focus of discussion in the implementation and promotion of conservation tillage.

During the drought season, in a cornfield in the Tieyou Agricultural Machinery Cooperative in Sunjiatun Village, Kai'an Town, Nong'an County, Changchun City, Jilin Province, thick straws cover the ground, like a quilt.

“Now that we are planting land here to implement conservation tillage has become the norm, farmers also fully realize the importance of protecting the straw, often saying,'Straw is a treasure, can not do without farming.' The villagers no longer burn straw, but are vying to use straw mulch no-tillage sowing technology for their own land. Not only does the straw need to be managed, the cost is low, but the seedlings emerge well later, saving money, effort, and worry." Chairman Ni Yong said as he picked up a shovel to pry up a small pile of soil, "Look, this is a protective tillage field covered by straws, and the soil is soft and moist."

As soon as he turned around, Ni Yong walked tens of meters to another cornfield, and pushed the shovel into the ground hard, only a few pieces of debris were scattered. "Look, this is the soil of an ordinary plot. It is hard and dry and can't be shoveled. We have proved through many years of comparative experiments that the plots that use all straw to return to the field perform better than traditional farmland in all aspects."

According to Ni Yong, the best effect in his cooperative’s experimental field is the corn field with full straw mulch and high stubble. Not only does the straw drift disappear, the soil compaction phenomenon is greatly alleviated, but also due to the water retention effect of the straw. , There will be no water accumulation in the rainy season, and corn will not suffer from drought during drought, which is very suitable for local promotion.

Also as a practitioner of conservation farming, Gong Xue, head of the Qiangsheng Agricultural Machinery Farmers Cooperative in Siping City, Jilin Province, was skeptical and shy away from the beginning of contact with conservation farming. However, the results achieved through conservation farming in the past few years can be seen in the field. With all the green corn seedlings, listening to the praise and approval from the surrounding farmers, these demonstration leaders are full of confidence.

"On the surface under the straw mulch, the plough layer soil cannot be blown away by wind or washed away by water. In the past, farmers burned straw and caused smoke everywhere. When the wind was blowing, the dust was flying. After using straw mulch, these problems disappeared. Remember we used to There are some sandy hills in the local area. When traditional ridge farming is used, continuous windy weather is encountered during the seedling period, the ridges are flattened by the wind, and the corn seedlings are uprooted. Now, after the cooperative adopts protective farming, the straw mulch is effective The role of windbreak and sand fixation is no longer afraid of wind." Gong Xue said that now the cooperative is more firm in the conservation farming model, more confident in farmers' acceptance, and more expecting the application effect.

Although the protection of black soil in my country has achieved certain results, and farmers’ enthusiasm for adopting conservation tillage has also increased, if there is no financial support from the state subsidies and the farmers pay completely, the effect of promotion is not satisfactory; in some areas, despite years of implementation However, the most suitable local conservation tillage model has not yet been summarized, and the unified technical route and standards are still being further explored and clarified; in some places, the comprehensive utilization of straw and straw returning to the field are still open for discussion.

In terms of retaining straw, many co-op directors and large grain growers have expressed a little helplessness.

“The first thing that needs to be reversed is the deep-rooted traditional concepts of farmers. In the past, farmers burned the stalks after harvesting corn, which saved time and effort, and the cooperatives had great resistance. In 2018, the cooperatives just started to promote straw mulching on a large scale. At that time, the surrounding farmers were very difficult to accept. At that time, some farmers raised doubts, saying that the straws are piled in the field, and the crops can grow well. Their attitude was very resisting.” Gong Xue said at the time he was holding a huge Through continuous comparison and experimentation, farmers’ thinking has been gradually changed, and they have shown them the many benefits of returning straw to the field. “At this point, farmers have a preliminary understanding of conservation tillage, and at the same time, farmers themselves have also calculated their own accounts. On average, each household earns at least 2500 yuan more. From then on, farmers will no longer burn straw casually."

Gong Xue said frankly that the pressure is really not small to watch the straw not being burned, but also to resist the gossip of the neighbors. However, when I see that the farmland is covered with thick layers of straw year after year, the "Maididi" has become a high-yield field, and I feel comfortable.

Regarding the prohibition of straw burning, although farmers' concepts have changed a lot, the comprehensive utilization of baling and leaving the field has become a major "resistance" on the way to the field.

"The full return of straw to the field does not mean that all the stalks after harvesting the corn cobs are laid back into the field, but it means that the stubble is left in the soil. The height of the stubble varies from 10 to 30 cm." Xu Daguang, a farmer of the Daguang family in Xuma Sanjia Village, Nong'an County, said, “This does not include the part consumed by the comprehensive utilization of straw off the field. In fact, the straw that can be left in the field can achieve at most three achievements.”

It is understood that straw feed and energy utilization account for a large proportion. In recent years, various parts of the Northeast have increased the promotion of new straw feed technology, gradually expanded the planting area of silage corn, and popularized the straw feed puffing technology. At the same time, with the development of herbivorous animal husbandry such as cattle and sheep, the demand for the use of straw for feed is gradually expanding. In addition, the promotion of the co-processing of straw and animal manure into bio-natural gas, and the use of straw as a raw material for fuel processing and power generation have also become one of the important projects to promote the comprehensive utilization of straw in various regions.

"To be honest, even if we want to expand the area covered by the full amount of straw returned to the field, we cannot find enough straw for a while. Now, returning the straw to the field is not a problem, but how much and what kind of straw is left in the field. Ni Yong said frankly that now the cooperative intends to continuously upgrade to full straw mulch no-tillage, and gradually improve the problems of the full straw mulch technology model and the planting conditions that farmers do not recognize by introducing straw return machines and strip tillage combined operation machines. Thus, it can break through the difficulties and create conditions for the large-scale promotion of high-standard conservation tillage, that is, the technical model of corn stalk full coverage.

While the country is promoting conservation tillage, a voice believes that returning straw to the field is just a "fairy tale", and that a large amount of straw returning to the field will aggravate the harm of diseases, insects and weeds, and become their "hotbed". Is it true?

Gong Xue has implemented conservation tillage for several years and reached the opposite conclusion-returning straw to the field can inhibit the growth of weeds and prevent soil compaction. "If the amount of straw is large enough and the coverage is uniform, the covered area will not grow grass. Moreover, the decay of straw can improve the physical properties of the soil, increase the aggregate structure, increase the porosity, and reduce the bulk density of the soil, which can effectively increase the soil activity. "

Everything has two sides. “Conservation farming may increase the density of insect populations due to the differences in the environment, climate, and specific operation methods in various regions. However, we have proved through a lot of data that these pests and diseases are within the normal range. No extreme abnormalities occurred. Moreover, after the seeds are processed, the pests can still be effectively controlled. At the same time, in the conservation tillage, the straw mulch will increase the neutrality or corrosivity such as earthworms and white star flower chafers. Insects, they can convert these straws into organic fertilizer through feeding and digestion, thereby increasing soil fertility.” Wang Zhenying, director of the National Corn Industry Technical System Pest Control Research Office, believes that although straw mulching may increase the density of insect populations per unit area , But overall the advantages outweigh the disadvantages.

"In the past two years, we have investigated more than a dozen counties and cities in Jilin Province and found that in the soil covered by straw, animal species have indeed become more abundant. They are mainly divided into three categories-the first category increases soil fertility and decomposes straw. The formation of humus soil, such as saprophytic grubs, earwigs, horseshoes, etc.; the second type is conducive to breaking the bottom of the soil plow, such as earthworms, etc.; the third type is the natural enemies of some pests, which feed on other pests, such as the larvae of step beetles. Therefore, it cannot be said arbitrarily that conservation tillage will lead to an increase in diseases, pests and weeds.” Conservation tillage experts in Jilin Province believe that we should find ways to reduce chemical substances in the soil and protect beneficial soil animals.

Some co-operative directors stated that conservation tillage is not a single technology, but close cooperation with links such as less tillage, no tillage, precision seeding, variable spraying, precision fertilization, and deep loosening of soil preparation, and formulate 3-5 Year-round farming mode.

Conservation farming is a systematic model. It is not only the process of returning straw to the field. Variety selection, straw return, no-tillage sowing, and production management should be refined, and the agricultural resources, farming methods, and field management should be refined as much as possible. Unification, in order to achieve the scale, standardization, and refinement of protective farming, can truly protect the black soil, realize the modernization of agriculture, and make the people's jobs more stable.