Genotypic differences in N response, N efficiency traits and spectral reflectance behavior among six common broccoli cultivars
Selection of N efficient cultivars, quantitative knowledge about their N demand and a close match of fertilizer N supply with crop demand are critical issues for decreasing the crop-inherent high N budget surplus of broccoli. Two two-factorial field experiments including six cultivars and three N levels were conducted in 2020 and 2021 under northern German climate conditions to investigate genotypic differences in broccoli N use efficiency (NUE). Nitrogen levels corresponded to soil mineral N (SMN) target values of 230, 310 and 390 kg N ha‑1. To evaluate the potential of different vegetation indices (NDVI, GLI, NDYI, CCCI) for increasing the precision of N top dressings, plots were nadir-scanned in 2020, 24 and 49 days after planting with a 5-channel multispectral camera mounted on a quadcopter drone. Least-squares means of total yield varied between cultivars by up to 2.2 t ha‑1 and increased with N level by up to 3.0 t ha‑1. No significant interaction effects between cultivar and N level were observed neither for total yield nor for NUE. Differences in NUE among cultivars were ascribed to variation in both N uptake efficiency and N utilization efficiency. Yield biomass of heads exceeding 500 g increased with N level by up to 7.2 t ha‑1 and, thus, was much stronger affected by N level than total yield, pointing out the impact of retailer specifications on practical N fertilization decisions. All vegetation indices studied were affected by broccoli cultivar, while only GLI and CCCI showed significant responses to N level. Moreover, CCCI was the only index that was not biased by growth stage.
Besand, F., Mausolf, B. and Katroschan, K.-U. (2023). Genotypic differences in N response, N efficiency traits and spectral reflectance behavior among six common broccoli cultivars. Acta Hortic. 1375, 25-32
Brassica oleracea var. italica, nitrogen use efficiency, N fertilization, vegetation index, private retailer standards