Erosion hazard evaluation for soil conservation planning that sustains life expectancy of A-horizon: the Black Soil Region of China

Authors: ZHANG, TIANYU - Northeast Normal University; Wilson, Glenn; HAO, YANFANG - Heilongjiang University; HAN, XIAO - Jilin Agricultural University

Submitted to: Land Degradation and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2021
Publication Date: 3/13/2021
Citation: Zhang, T., Wilson, G.V., Hao, Y., Han, X. 2021. Erosion hazard evaluation for soil conservation planning that sustains life expectancy of A-horizon: the Black Soil Region of China. Land Degradation and Development. 2021:1-13. https://doi.org/10.1002/ldr.3931.
DOI: https://doi.org/10.1002/ldr.3931

Interpretive Summary: The Black Soil Region (BSR) of northeast China is one of the most productive regions of the world. The depth of the topsoil (A horizon) is rapidly decreasing due to excessive erosion. The depth of the topsoil directly controls the crop yield and is seriously limited when the depth goes below 20 cm. A strategy to evaluate the erosion hazard by calculating the life expectancy of the soil (time until the topsoil is eroded to 20 cm) is proposed in order to plan soil conservation practices. The methods tested for the BSR (206,000 km2) of China were based upon the current thickness of the topsoil and the predicted soil erosion rate. Characteristics of the region such as climate, soil properties, topography and crop yields were collected to predict the soil erosion rate, topsoil thickness and corn yield under five conservation scenarios for 180 years in 10 year segments for BSR. The five scenarios include: (1) present conditions which involve numerous tillage operations with rows and furrows up and down long slopes, (2) rows aligned with the contour, (3) contour farming and terracing, (4) no-till farming and (5) partially includes (3) and (4). Degrees of soil erosion hazard for each scenario were determined based on soil life expectancy of the A horizon (SLEA), which is the time until 20 cm of soil horizon thickness needed for sustaining crop production is reached. Croplands with a soil life expectancy of <0 years, 0 to 20 years, 20 to 100 years, 100 to 1000 years and =1000 years were classified as “Damaged”, “High Hazard”, “Moderate Hazard”, “Low Hazard” and “No Hazard”, respectively. Currently, 8%, 5%, and 22% of the BSR is Damaged, High Hazard and Moderate Hazard, respectively. If nothing changes, 180 km2 of cropland will become “Damaged” and 0.8% of the crop yield will be lost every decade. A spatial resolution of 100 km2, which is approximately the size of townships, was used for planning and scheduling optimum conservation practices. The plan was designed to maintain all soils to have an A horizon above 20 cm by selecting and scheduling the implementation of conservation practices according to their degree of hazard. The optimum conservation practice was found to be No-till for all areas classified as Damaged, a combination of no-till, contour, and terraces for “High hazard”, “Moderate hazard” and “Low hazard” and continue the present practices for “No hazard” areas. A scheme for designing the optimum conservation schedule for each township was also suggested. Scheduling the implementation of conservation practices according to the township’s maximum erosion hazard will optimize the distribution of labor and serve as a training tool for later-acting townships.

Technical Abstract: The Black Soil Region (BSR) of northeast China is one of the most productive regions of the world and critical to China production. The depth of the A horizon is rapidly decreasing due to excessive erosion which is directly related to the productivity. A strategy for erosion hazard evaluation and soil conservation planning has been proposed and tested on the BSR (206,000 km2) of China. Climate, geomorphology, DEM, soil, landuse, runoff plot and corn yield data were compiled. Soil erosion rate, A horizon thickness and corn yield under five conservation scenarios during 2020~2200 was predicted with a spatial resolution of 30 m and a temporal resolution of 10 a. The five scenarios include Present (continue present practices), Contour (contour farming), Combo 1 (contour farming and terracing etc.), No-till (no-till farming) and Combo 2 (partially Combo 1 and partially No-till). Current soil life expectancy of A horizon (SLEA), which is the time until a critical horizon thickness needed for sustaining crop production (20 cm in this study) is reached, was calculated for each scenario. Erosion hazard degrees were determined with SLEA. Croplands with SLEA of <0 a, 0 a~20 a, 20 a~100 a, 100 a~1000 a and =1000 a, were classified as “Damaged”, “High hazard”, “Moderate hazard”, “Low hazard” and “No hazard”, respectively. Current area ratio of “Damaged” and “High hazard” and “Moderate hazard” was found to be 8%, 5%, and 22%, respectively. A spatial resolution of 100 km2, which is approximately the size of townships, was used for planning and scheduling optimum conservation practices. The plan is designed to maintain all soils to have an A horizon above 20 cm by selecting and scheduling the implementation of conservation practices according to their degree of hazard. If nothing changes, 180 km2 croplands will become “Damaged” and 0.8% of corn yield will be lost every decade. The optimum conservation practice was found to be No-till for “Damaged”, “Combo 2” for “High hazard”, “Moderate hazard” and “Low hazard” and Present for “No hazard”. An optimum conservation schedule was also suggested for each township. Scheduling the implementation of conservation practices according to the township’s maximum erosion hazard will optimize the distribution of labor and serve as a training tool for later-acting townships.