Nutrient and Organic Carbon losses by erosion, and their economic and environmental implications in the drylands of Kenya
Oduor, Nathan O.
Mugwe, Jayne N.
Mugendi, Daniel N.
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Erosion causes soil nutrients and financial losses, and negatively impacts the environment. We sought to assess the effects of integrated soil fertility and soil & water management practices on nutrient losses, their equivalent economic losses, and environmental disturbance in the drylands of Tharaka-Nithi County. An experiment was set in a randomized complete block design with four replications. Six treatments implemented included manure + fertilizer + tied ridging under 120 kg ha-1 and 30 kg ha-1 nitrogen (N) application rate, manure + fertilizer + minimum tillage with crop residue mulch under 120 N kg ha-1 and 30 N kg ha-1, Managing Beneficial Interactions in Legume Intercrops with 60 N kg ha-1, and conventional control. A two (120 N kg ha-1 and 30 N kg ha-1) by two (Minimum tillage with mulch and tied ridges) split-plot arrangement was used to evaluate the interaction effect of soil fertility, and soil & water conservation practices. Soil & water conservation and soil fertility management practices reduced soil nutrients and organic carbon losses, ecosystem disturbance, and monetary nutrient losses when isolated or integrated. Minimum tillage with mulch had a higher reduction in the nutrient loss by 20-165% compared to tied ridges. The 120 N kg ha-1 reduced nutrient loss by 16-19% more than 30 N kg ha-1. The enrichment ratio (ER) under all the treatments was above unity, which indicated ecosystem disturbance. Minimum tillage with mulch reduced ER more than the tied ridges, whereas 30 N kg ha-1 had lower ER than 120 N kg ha-1. The equivalent monetary losses of nutrients were as high as 30 US$ ha-1for soil 2 organic carbon, 28 US$ ha-1 for nitrogen, 73 US$ ha-1 for phosphorus, and 140 US$ ha-1 for potassium per season. The combined treatment with the least economic losses was manure + fertilizer (120 N kg ha-1) + minimum tillage with mulch. Hence, the technology should be promoted for sustainable agricultural productivity.