Abstract
The cultivated land area per capita in China is relatively small compared to the world average. However, most of the coal output is coming from underground mining, resulting in land subsidence and the destruction of existing cultivated land. The Yellow River is known as a ground-suspended river due to its large sediment concentration. Using unpolluted Yellow River sediment to reclaim the coal mine subsidence not only solves the problem of sediment deposition, but also solves the problem of shortage of filling material. Some experimental studies revealed low soil productivity as a result of thin soil cover. To ensure crop growth and production in land reconstructed with Yellow River sediments, determining the optimal thickness of soil cover over the sediment is extremely important. There were four experimental treatments and one control treatment. Each treatment was repeated three times. The control treatment was an original soil profile with 30 cm topsoil plus 110 cm subsoil. The four experimental treatments with different thickness of soil covers had the same thickness of topsoil (30 cm) and Yellow River sediments (60 cm), and different thickness of subsoil, which were 10, 30, 40, and 50 cm, respectively. Thus, the total thicknesses of soil cover (topsoil plus subsoil) were 40 cm, 60 cm, 70 cm, and 80 cm, respectively. The topsoil, subsoil, and Yellow River sediments were collected from Liangshan County. The soil type is fluvo-aquic. Maize (Zea mays L.) is the main crop in Liangshan County. A greenhouse experiment was conducted to investigate the growth of maize. The results showed that (1) the peroxidase (POD) activity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content of maize leaf decreased with an increasing thickness of soil, while soluble protein (SP) and leaf relative water content (RWC) increased. (2) The dry biomasses of the shoot and root system in T70 and T80 were not significantly different from those in the control (3) Increased soil thickness is conducive to the storage of more water and available nutrients. Considering the time and cost of reconstruction, 70 cm is the optimal thickness of soil cover on Yellow River sediment to ensure maize growth.
Highlights
Leaf Antioxidant Activities, MDA Content, soluble protein (SP) Content, and Leaf relative water content (RWC). Both leaf POD and superoxide dismutase (SOD) activity decreased with increasing thickness of covering soil, respectively (Table 2)
The results revealed that 40 cm of covering soil was not a suitable thickness, and its water holding capacity was not enough to support maize growth
Under the same irrigation conditions, different thicknesses of soil spread over sediment had different water storage capacities, leading to varying degrees of water stress that affected maize growth, which would have resulted in differences in maize growth and oxidative stress [34]
Summary
Researchers have recognized the growing gap between population growth and the rapid shrinkage of land resources [3,4]. Underground coal mining leads to mining subsidence, resulting in large areas of land damage. In eastern China, deep subsidence results in waterlogging because of a high underground water level, which has meant that a considerable amount of farmland has lost the capacity for cultivation [6]. The farmland cannot be cultivated, which means that farmers lose their livelihood. These changes have resulted in social instability and have seriously hindered the sustainable development of local communities and economies [7]. It is imperative to reclaim farmland damaged due to coal mining subsidence
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