Editor's note: China has seen tremendous changes nationwide, from economic growth to environmental protection, from social improvement to cultural progress. In this series, China Daily maps the changes and tells the stories of the people who lived through them.

After growing his crops in the rich, black soil of Jilin province for decades, Zhang Wendi started to worry when he saw its fertility begin to wane day after day as yields declined.

The farmer from Quanyangou village in Lishu county didn't know how to solve the problem. Experience had taught him to use more chemical fertilizers, but the results were the opposite of what he expected.

Zhang is one of many farmers to have faced similar problems in Jilin. In recent decades, the long-term overuse of the province's black soil, its thinning and decline in organic matter have become a serious problem.

Thankfully, through the application of conservation farming methods, these problems are now being resolved.

Jilin is an important national producer of grain and one of the main locations of black soil, which is rich in organic matter and so ideally suited to growing crops.

According to data from the National Plan for Soil and Water Conservation (2015-30), there are 109 million hectares of the soil, including around 29 million hectares of farmland, in northeast China, spanning the provinces of Heilongjiang, Jilin and Liaoning and the eastern part of the Inner Mongolia autonomous region.

According to the Guideline on Protecting Black Soil in Northeast China (2017-30), excessive exploitation in recent decades has resulted in the erosion of black soil and threatens biological diversity and sustainable food production.

In addition, long-term farming and the overuse of fertilizers and pesticides have destroyed the soil's micro-ecosystem, and underground water reserves have been depleted by expanded rice-growing.

During his inspection trip to Jilin province in July 2020, President Xi Jinping stressed the need to prioritize food security, secure grain production, speed up the transformation of the agricultural development pattern and boost the experience gained.

Xi also visited Lishu, a major grain-growing area, with a cultivated area of about 260,000 hectares. He noted that black soil fields are capable of producing high agricultural yields, but face the problem of declining fertility, and measures need to be taken to protect it.

In 2009, China Agricultural University professor Li Baoguo and his students established a black soil protection workstation in Lishu. After years of research and cooperation with the Chinese Academy of Sciences and the county agricultural technology station, they devised their own model of conservation farming.

Wang Guiman, who works at the county agricultural technology station, said that one key to conservation farming is to plow less frequently by adopting no-tillage and stalk mulching practices.

"In the past, farmers usually plowed the land three or four times when they planted maize, which helped destroy the structure of black soil layers. Now, with mechanized planting, the processes of making straw, ditches, fertilizing, sowing and covering can be completed simultaneously," he said.

Wang said the reduction of rolling compaction as the result of using agricultural machines can help improve the soil's water percolating capacity, and maize straw returns potassium and nitrogen to the earth.

The Jilin government began to promote the Lishu model across the province in 2012.

Zhang Wendi was among the first group of farmers to implement the model. At first, he was hesitant, doubting it would ensure the production of the grain, but said that he later discovered that this model of planting not only helped with drought-resistance and increased the soil's fertility, but also increased the seeding rate and yield.

"With the traditional planting model, it can cost around 2,200 yuan ($339) per hectare from planting to harvesting, while the new model can save at least 800 yuan," he said. "Furthermore, the new model helps increase production by over 500 kilograms per hectare."

Since 2020, Zhang has contracted 420 hectares in Quanyangou village and now produces an average yield of 13,000 kg of grain per hectare.

"Black soil is fundamental to grain producers. Thanks to the Lishu model, the land is becoming more fertile, and we can grow more grain," he said.

According to the provincial government, the total area of conservation farmland in the province will reach 2.03 million hectares this year, and it is expected to increase to about 2.6 million hectares by 2025.

With the help of conservation farming and technology, grain production in Jilin has been increasing in recent years. In 2021, Jilin produced about 40.4 billion kg, an increase of 2.36 billion kg year-on-year.

Wang Xuejun, head of the Provincial Department of Agriculture and Rural Affairs, said that as a major agricultural province, grain production in Jilin is of widespread concern. He added that the province aims to produce about 50 billion kg of grain a year by 2030.

He also said that for the foreseeable future, the department will mainly focus on protecting the province's black soil land and developing high-standard farmland, cultivating high-quality crop seeds, enhancing mechanization and increasing the application of digital technology to agriculture.