Grassland agriculture development can draw on new models from abroad

As early as the Middle Ages, European agricultural production generally practiced the “two-field system”, that is, a simple system of rotating farmland between cultivation and fallow to regulate soil productivity. However, with the increase in Europe's population and the gradual depletion of land fertility, the “two-field system” could no longer meet the needs of social development, and the “three-field system” emerged. The “three-field system”, also known as the “three-zone rotation system”, divided cultivated land into three roughly equal farming zones: fallow land, spring-sown land, and autumn (winter)-sown land. Crops were rotated among the zones, with spring-sown cereals or legumes, and wheat or rye sown in autumn and winter, rotating year by year in a three-year cycle. The fallow land and the cultivated land after harvest were both used as common pasture, shared in common.

Compared with the two-field system, the three-field system could harvest twice a year, and the proportion of fallow land was reduced from 1/2 to 1/3. This helped reduce the risk of agricultural disasters or poor harvests, and also helped improve the utilization rates of cultivated land and labor, so the level of agricultural production was higher than that of the “two-field system”.

By the 19th century and later, in the face of population expansion and declining land productivity caused by the Industrial Revolution, Europeans found that the “three-field system”, which was based mainly on grain production, could no longer meet ever-growing economic needs. When grain yields began to decline, they realized that without forage grass and animal husbandry, agriculture was incomplete agriculture, so they began vigorously promoting grain-forage rotation.

The former Soviet soil scientist Williams proposed that grass-field rotation was a rational farming system. Based on research into the process of natural fertility restoration and the fertilizing effect of perennial mixed-sown forage grasses, he put forward the suggestion of restoring fertility through grass-field rotation, thus opening the path of shortening the process of restoring soil fertility under human intervention.

The United States also went through a similar process. During its period of rapid industrial development, the United States once relied excessively on chemical fertilizers and pesticides, using its developed agricultural machinery to grow corn continuously for many years in the central region, while the traditional rotation system was neglected. As a result, the soil suffered severe erosion, soil fertility declined markedly, pests, diseases and weeds ran rampant, corn yields fell, and economic benefits were severely damaged. In order to ensure the sustainable development of agriculture, the United States mandated a two-year rotation system. Of the 303 million hectares (equivalent to 4.545 billion mu) of cultivated land in the United States, rotated grassland reached 27%. In the U.S. state of Montana, after rotating spring wheat with leguminous forage, wheat yields increased by 40% compared with continuous cropping.

In Australia in the 1830s, a “wheat-fallow” farming system was once widely promoted in semi-arid areas, which damaged soil structure, reduced fertility, lowered crop yields year after year, and caused insufficient forage supply. Later, Australia used leguminous forage and grain rotation, and as a result, after “alfalfa-barley” rotation, barley grain yields increased by 17.4%-40.4% compared with continuous cropping; after “alfalfa-wheat” rotation, wheat grain yields increased by 18.2%-33.6% compared with continuous cropping. The successful application of crop and leguminous forage rotation enabled Australia to create the world-famous “wheat-sheep” farming system, which in turn made the country a major wheat exporter.

At present, after years of development, “grain-forage rotation” has become a basic farming system in developed countries. In the “grass-field rotation” of most developed countries, forage grass accounts for a relatively high proportion of agricultural land: 40% in the United States, 30%-40% in France, 58.8% in the Netherlands, 60% in Australia, and as high as 70% in Denmark and Ireland. The grain-forage rotation system ensures the yields of forage grass and crops while continuously restoring and improving soil fertility, making these countries relatively high in both per-unit and total grain output.

During China's primitive agricultural period, a fallow system similar to the “two-field system” was also practiced, but after the introduction of iron plows and cattle plowing into the traditional agricultural stage, the fallow system basically ended; instead, the focus was on increasing per-unit yields and making full use of land through intensive cultivation, taking the path of continuous land cropping. Therefore, in the current adjustment of agricultural production methods, summarizing foreign experience and promoting “grain-forage rotation” and vigorously developing grassland agriculture are of great significance.

(The author Wang Chengzhang is a professor at Henan Agricultural University, Zhu Xiaoyan is a lecturer at Hebei Agricultural University, and Lu Xinshi is president of the Grassland Industry Branch of the China Animal Agriculture Association)