Long-term non-sustainable soil erosion rates and soil compaction in drip-irrigated citrus plantation in Eastern Iberian Peninsula

Agriculture is known to commonly cause soil degradation. In the Mediterranean, soil erosion is widespread due to themillennia-old farming, and newdrip-irrigated plantations on slopes, such as the citrus ones, accelerate the process of soil degradation. Until now, the published data about soil erosion in citrus orchards is based on short-term measurements. Long-term soil erosion measurements are needed to assess the sustainability of dripirrigated citrus production and to design new strategies to control high soil erosion rates. The objective of this study is to assess long-term soil erosion rates in citrus plantations and report the changes in soil bulk density as indicators of land degradation. We applied ISUM (Improved Stock-Unearthing Method) to 67 paired trees in an inter-row of 134 m (802 m(2) plot) with 4080 measurements to determine the changes in soil topography from the plantation (2007) till 2020. Soil core samples (469) were collected (0-6 cm depth) to determine the soil bulk density at the time of plantation (2007) and in 2020. The results demonstrate an increase in soil bulk density from 1.05 g cm(-3) to 1.33 g cm(-3). Changes in soil bulk density were higher in the center of the row as a result of compaction due to passing machinery. Soil erosion was calculated to be 180 Mg ha(-1) y(-1) due to a mean soil lowering of 1.5 cmyearly. The highest soil losseswere found in the center of the inter-rowand the lowest underneath the trees. The extremesoil erosion ratesmeasured in newdrip-irrigated citrus plantations are due to soil lowering in the center of the inter-row and in the lower inter-row position where the incision reached 80 cm in 13 years. The whole field showed a lowering of the soil topography due to extreme soil erosion and no net sedimentation within the plantation. The results show the urgent need for soil erosion control strategies to avoid soil degradation, loss of crop production, and damages to off-site infrastructures. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Citrus orchards suffer from severe soil erosion, with an increase in long-term soil erosion rates and soil bulk density. The highest soil losses occur in the center of the inter-row, and new drip-irrigated citrus plantations exhibit higher soil erosion rates.