Effects of soil conservation practices on nutrient loss through surface runoff in mid elevation tea lands of Sri Lanka

Abstract Soil nutrient loss occurs naturally through soil erosion, runoff, leaching and burning of crop residues, but this process has accelerated due to improper land and crop management. Minimizing nutrient loss is important for keeping the soil healthy, productive and sustainable for long term sustain crop production and environmental protection. This study was conducted to evaluate the effectiveness of soil conservation measures (SCM) in reducing nutrient loss in a mature tea field at Kenilworth Estate, Ginigathhena, Sri Lanka (6° 59ʹ N, 80° 29ʹ E), located at mid-elevation with a slope of 60–72%. Erosion plots were arranged in a Randomized Complete Block Design with four treatments; stone terrace (T), stone terrace with Vetiver grass (TV), terrace wall (TW) as SCMs, and tea without conservation (TO) as control. Runoff samples were collected from the sediment tanks attached to the 10 m × 3 m plots to analyze nutrients; dissolved nitrogen (DN), dissolved phosphorus (DP), and dissolved potassium (DK) from October 2020 to November 2021, with total rainfall of 5970 mm. The ammonium-nitrogen and nitrate-nitrogen amounts in runoff water were not significantly different among the SCMs and were significantly lower in the SCMs than in the TO. The amount of DP removed by runoff was not significant. The amount of DK loss through runoff was significantly lower in SCMs compared with TO; the amount of DK removal was 1.27, 2.09, 3.37 and 9.09 kg ha −1 yr −1 in TV, TW, T, and TO, respectively. TV proved to be as the potential nutrient saving measure among the SCMs, reducing DN, DP, and DK losses by 6.9 (78%), 1.6 (80%), and 7.8 (86%) kg ha −1 yr −1 , respectively, due to a combination of physical and biological measures in mid elevation tea lands in Sri Lanka.