Abstract
Increase in farm size (IFS) can reduce fertilizer use but it may accelerate soil erosion, particularly stream channel (SC) erosion and associated nutrient losses, due to reduced farmland heterogeneity. But these positive and negative environmental impacts of IFS have never been compared. The objectives of this study were to determine the SC erosion and associated nutrient losses following IFS, and clarify their influencing factors. The study was conducted in Nala watershed in southern subtropics of China. Six SCs were surveyed in just completed period (April 2018) and after one year of IFS (April 2019). The SC erosion significantly (P < 0.05) increased in entire watershed from 12.0 Mg ha−1 to 43.9 Mg ha −1, with a 301 % increase after IFS than before IFS. Accelerated SC erosion by IFS resulted in significant increase of total N loss from 9.91 kg ha−1 to 36.6 kg ha−1, with a 269.3 % increase. Similarly, total P loss significantly increased from 3.84 kg ha−1 to 14.2 kg ha−1, with a 269.8 % increase. Total N and P losses due to accelerated SC erosion amounted to 119 % N and 40 % P of fertilizer reduction following IFS. Field density, grass root density and ridges with perpendicular direction to SCs significantly correlated (P < 0.05) with SC erosion. Our study highlights the significant nutrient losses by accelerated SC erosion that should not be overlooked in IFS scheme in intensive agricultural regions.
Published Version
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