| Summary: | In Mexico, corn (Zea mays L.) is the most important crop (59% of its agriculture land) and the primary source of sediment yield. This study looks for alternatives to maintain corn productivity by means of sustainable soil and water conservation practices at central Mexico. In order to understand broad tendencies between soil erosion and crop productivity in the region, the EPIC (Erosion Productivity Impact Calculator) model was applied in the Texcoco's district as follows:1) Calibrate the model using 352 experimental corn plots established between 1972 and 1992 in 36 rural communities.2) Validate the model on a spatial basis, using GIS tools, by means of historic corn yields.3) Identify the most vulnerable areas where corn productivity is being affected by soil erosion.4) Analyze the relationship between soil erosion and crop productivity, over a 100 years of simulation, comparing the Current Management (CM) and the Recommended Management (RM) by governmental institutions.5) Evaluate the most feasible soil and water conservation practices for the region.From the calibration process, it was concluded that the EPIC model, under a wide range of environmental conditions, simulates very good corn yield (r2 between 0.88 and 0.90), annual runoff (r2=0.98), and annual sediment production (r2=0.96).Base on the official environmental inputs available in the region, the EPIC model can assess only a moderately strong relationship (r2=0.58) between the official historical crop records and the simulated ones.Comparison between CM and RM shows that the average crop yield in the region can be increased by 32.6% if RM were followed. Under the CM, the loss of soil fertility in the district reduces corn productivity by 3% over a hundred years. At least 50.0% of the region's agricultural area needs soil conservation practices, mainly on areas with slopes over 5%. If it is decided to grow corn under conventional till in such areas it is recommended to construct bench terraces in order to maintain soil erosion below 20 t/ha/yr. Corn under no till, besides control erosion, can also increase grain productivity by at least 40% (0.6 t/ha) by combining contouring, mulching, and manures.
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