Author(s)

Melissa Quinche Gonzalez¹, Annie Pellerin², Léon E. Parent^1*

¹Département des sols et de génie agroalimentaire, Université Laval, Québec, Canada.
²Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec, Direction de l’agroenvironnement et du développement durable, Saint-Jean-sur-Richelieu, Québec, Canada.

Adjusting the N fertilization to soil potentially mineralizable N in Histosols is required to secure high vegetable yields while mitigating nitrate contamination of surface waters. However, there is still no soil test N (STN) relating the response of Histosol-grown onion (Allium cepa L.) to added N. Compositional data analysis can integrate soil C and N composition into a STN index computed as Mahalanobis distance (M²) across isometric log ratios (ilr) of diagnosed and reference soil C and N compositions. Our objective was to calibrate onion response to added N against a compositional STN index for Histosols. Reference compositions were computed from high N-mineralizing Histosols reported in the literature. Soil analyses were total C and N, and a residual soil mass (F_v) was computed as 100%-%C-%N to close the compositional vector to 100%. The C, N, and F_v proportions were synthesized into two ilrs. We conducted thirteen onion N fertilization trials in Histosols of south-western Quebec showing contrasting C, N, and F_v proportions. Each crop received four N rates broadcast before seeding or split-applied. We derived two STN classes separating weakly to highly responsive crops about the M² value of 5.5. Onion crops grown on soils showing M² values >5.5 required more N and yielded less in control treatments compared with soils showing M² values <5.5. Onions grown in low-(M² < 5.5) and high-(M² > 5.5) soils responded significantly (P < 0.10) to 60 and 180 kg N ha^-1, respectively. Using literature data and the results of this study, we elaborated a provisory N requirement model for Histosol-grown onions in Quebec.

Compositional Data Analysis, Meta-Analysis, Onion, C/N Ratio, Soil Test N

Gonzalez, M. , Pellerin, A. and Parent, L. (2016) Onion Response to Added N in Histosols of Contrasting C and N Contents. American Journal of Plant Sciences, 7, 469-478. doi: 10.4236/ajps.2016.73041.