Nutrient Losses Through Surface Runoff in Different Soil Conservation Practices in Mid Elvation Tea Lands in Sri Lanka: Implications for Climate Change Adaptation

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 of nutrient loss is crucial under the climate change, especially in steep agricultural lands. This study was conducted to evaluate the effectiveness of soil conservation measures in reducing nutrient loss in a mature tea field at Kenilworth Estate, Ginigathhena, Sri Lanka (6°59' N, 80°29' E), located at mid-elevation. The slope of the study area was 60–72%. Erosion plots were arranged in Randomized Complete Block Design with four treatments; stone terrace (T), stone terrace with Vetiver grass (TV), terrace wall (TW) as soil conservation measures (SCM), and tea without conservation (TO) as control. Runoff were collected to the sediment tanks attached to the plots to analyze nutrients; Available Nitrogen (AN), Available Phosphorous (AP) and Available Potassium (AK) from October 2020 to November 2021 with 5970 mm rainfall. The NO ₃ ^- -N concentration in runoff was not significant in different SCMs and NH ₄ ⁺ -N concentration in runoff was significantly low in TV. The NH ₄ ⁺ -N and NO ₃ ^- -N removal in TV was 1.3 and 0.8 kg ha ^-1 yr ^-1 respectively. The amount of AP removed by runoff was significantly higher in TO (2.1 kg ha ^-1 yr ^-1 ) and 0.9,0.5,0.4 kg ha ^-1 yr ^-1 in T, TV, TW respectively. AK loss through runoff was not significant among treatment and lower in SCMs. TV was the most effective nutrient saving measure, reducing AN, AP and AK losses by 6.9 (78%), 1.7 (80%) and 7.8 (86%) kg ha ^-1 yr ^-1 respectively due to combination of physical and biological measures.