Quantifying annual soil and nutrient lost by rill erosion in continuously used semiarid farmlands, North Ethiopia

Berhane Lemma,Lindsey Norgrove,Shimbahri Mesfin,Fassil Kebede,Ibrahim Fitiwy,Zenebe Abraha

doi:10.1007/s12665-017-6506-z

Berhane Lemma, Lindsey Norgrove + Show 4 more

Open Access

https://doi.org/10.1007/s12665-017-6506-z

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Abstract

The loss of soil from land surfaces by erosion is widespread and reduces the productivity of agricultural lands. Concurrently, due to increasing human population, agricultural land expansion and exploitation, soil erosion and nutrient loss are the major environmental problems in Ethiopia. This study was conducted to estimate annual losses of soil, soil nutrients and carbon due to rill erosion. The entire watershed was classified into 12 land mapping units (LMUs). Consequently, the cropland was delineated to estimate soil and nutrient losses. Dimensions of the rills were measured at different parts of the landscape, and rill volume of rill erosions was assessed in the field. Disturbed representative composite soil samples were taken from each LMU to estimate the main soil nutrients, and each soil nutrient was estimated using different methods. The result revealed that the amount of soil lost through rill erosion was found to be 3.17 t ha−1 year−1. The average annual nutrient loss by the rill erosion was 41.4 kg ha−1 soil organic matter content, 2.4 kg ha−1 total N, 0.02 kg ha−1 available P and 0.3 kg ha−1 exchangeable K. The annual estimated cost of the soil nutrient lost (total N and available P) due to rill erosion was found to be 1341 USD. This cost would be used to replace the total N and available P nutrients lost through the addition of mineral fertilizers. Water erosion in the form of rill erosion was severely affecting soil fertility management and crop production in the study watershed. Hence, effective integrated watershed management interventions and farmland managements could combat soil erosion.

Highlights

The loss of soil from land surfaces by erosion is widespread and reduces the productivity of agricultural lands
The entire watershed was classified into 12 land mapping units (LMUs)
The average rill density was 17.33 m ha-1, with the highest rill density observed in LMU 6 (40.8 m ha-1) and the lowest was observed in LMU 12 (4.3 m ha-1)

Summary

Introduction

The loss of soil from land surfaces by erosion is widespread and reduces the productivity of agricultural lands. Due to increasing human population, agricultural land expansion and exploitation, soil erosion and nutrient loss are the major environmental problems in Ethiopia. Loss of soil due to current and historical poor management is the main cause for low crop productivity and inefficient use of cropping inputs It can have significant off-farm adverse impacts on the environment (Meadows 2003). Rill erosion mainly occurs as a result of concentrated overland flow of water leading to development of small well-defined channels (Haile and Fetene 2012) These channels act as sediment sources and transport passages leading to soil loss (Wirtz et al 2012). Hurni (1993) has estimated that average soil loss from Ethiopian croplands is 42 t ha-1 year-1 This resulted in a loss of 1–2% annual crop production. The expansion and intensification of agricultural cultivation using inappropriate practices leads to exhaustion of soil resources, deterioration of soil quality and eventually to a decline in land productivity (Shivakoti 2005)

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