Assessing soil chemical properties and soil respiration amended with Sesbania grandiflora

Y.A. Othman, D.I. Leskovar
The objective of this two-year study was to assess the influence of using a leguminous crop, Sesbania grandiflora, on soil nutrient levels (NO3, P, K, Ca2+, Mg2+, Na and S), pH, EC, soil organic matter (OM) and respiration. Sesbania seeds were planted in a certified organic field in March at a planting density of 50 kg ha-1 in 2015 and 90 kg ha-1 in 2016. In order to determine soil chemical analysis, soil cores were collected from the topsoil layer (0-20 cm) prior to the experimental period in February, 2015, and from 3 soil depths (0-20, 20-40 and 40-60 cm) at the end of 2015 and 2016 growing seasons. Except for soil OM %, soil nutrients (NO3, P, K, Ca2+, Mg2+, and S) and pH were higher in 2015 than 2016. In both years soil P, K, Mg2+, OM% and respiration in the topsoil layer (0-20 cm) was higher than at deeper soil depths (20-40 and 40-60 cm). Conversely, soil Ca2+, S, and Na in the 40-60 cm soil layer were higher than in the topsoil (0-20 cm). No significant differences were found in soil pH, EC and NO3 across soil layers during the study. Additionally, shoot NO3 and total N concentration during the flowering period was similar across both years. Shoot NO3 was 415 and 425 ppm, and total N was 2.98 and 3.06%, in 2015 and 2016, respectively. Interestingly, soil respiration in the topsoil (0-20 cm) increased slightly in 2015, but by 9-fold in 2016 as compared to the baseline level measured in February, 2015. In addition, soil respiration in the 20-40 cm and 40-60 soil depth was 39 and 50% lower than the topsoil (0-20 cm) at the end of the experiment in July 2016. Overall, this study revealed that organic soil amendment using Sesbania grandiflora significantly improved soil respiration, but did not potentially enhanced nutrient levels compared to the baseline soil.
Othman, Y.A. and Leskovar, D.I. (2020). Assessing soil chemical properties and soil respiration amended with Sesbania grandiflora. Acta Hortic. 1286, 55-60
DOI: 10.17660/ActaHortic.2020.1286.9
nitrogen, microorganism, soil health, organic farming, organic matter

Acta Horticulturae