Where in China are chestnut soils distributed, and what are they suitable for growing?
Chestnut soil, as the name suggests, is a chestnut-colored soil formed under a temperate semi-arid climate and the natural vegetation of dry steppe. It has a soft surface horizon and a calcic horizon somewhere within 1 m. The typical profile configuration is Ah-Bk-C. The entire profile is base-saturated, with a pH of 7.5~9.0. So, where in China are chestnut soils distributed? And what are they suitable for growing? First, let us understand the characteristics of chestnut soil.
The main feature of chestnut soil is that the upper part of the profile is chestnut-colored, while the lower part has a calcic horizon in the form of fungal threads, patches, or reticulate patterns. In the Soil Taxonomy of the United States, most chestnut soils have been classified as Mollisols. Such soils are called brown soils in France, and brown and dark brown soils in Canada. In the classification of the Food and Agriculture Organization and UNESCO, however, the name chestnut soil is still used.
Chestnut soil can be divided into ordinary chestnut soil, dark chestnut soil, light chestnut soil, meadow chestnut soil, salinized chestnut soil, alkalized chestnut soil, and chestnut soil-like soil. These soils all have relatively obvious processes of humus accumulation and leaching-deposition of lime, and most have weak processes of gypsification and salinization. The surface layer is chestnut or dark chestnut humus, with a thickness of 25~45 cm, and the organic matter content is mostly 1.5~4.0%; below the humus layer is a calcic horizon containing large amounts of grayish-white patchy or powdery lime, with a lime content of 10~30%.
Chestnut soil is extremely widely distributed in northern China, mainly in the northwest region and the Inner Mongolia Autonomous Region.
The soil properties of chestnut soils in China show obvious regional differences. The chestnut soils of the eastern Inner Mongolia Plateau have the characteristics of low humus, low salinization, low alkalization, and no gypsum or deep gypsum and weak argillization, while in the western Xinjiang region there is varying amounts of gypsum and salt accumulation in the subsoil, and the humus content is also relatively higher, but the soil shows no alkalization or argillization.
The humus content of chestnut soil is lower than that of black soil. It is a relatively fertile soil, serving both as a major pastoral base and supporting considerable dryland farming. Although chestnut soil is a soil type suitable for both farming and animal husbandry, rainfed dryland farming is limited by precipitation, so the overall direction of use should be mainly pastoral, as natural grazing and hay meadows, with appropriate development of dryland farming and irrigation.
Taking into account history and current conditions, dark chestnut soil should be mainly agricultural, combining farming, animal husbandry, and forestry; chestnut soil should be mainly pastoral, combining animal husbandry, farming, and forestry, and severely eroded sloping farmland should be returned to pasture; meadow chestnut soil should combine farming and animal husbandry; all other subtypes should be mainly pastoral.
Crops suitable for planting in chestnut soil are mainly cold-tolerant crops, chiefly wheat, oats, beans, potatoes, and flax; in areas with a longer frost-free period, millet, foxtail millet, corn, and sorghum are also planted.