Abstract
Background and Aims Knowing the impact of cultural practices on nitrogen (N) dynamics in perennial crops is critical to promote N use efficiency. This study focused on the impact of crop regulation on the plant N dynamics, on the fruit N composition, and on the N fertilisation use efficiency. Methods and Results A large crop load gradient was set in a homogeneous plot of the grape cultivar Chasselas. Fertilisation in the form of 15N-labelled foliar urea allowed the measurement of N uptake and partitioning among plant fractions. Dry mass, carbon, and N dynamics were assessed over two consecutive seasons. Crop regulation did not affect grape N concentration at harvest. Both N uptake and root N mobilisation were reduced in response to crop regulation. Fertilisation efficiency was higher under high-yield conditions in terms of N uptake and grape N accumulation. The carry-over effects of crop regulation in the following year were highlighted. Conclusions Crop regulation strongly affects the overall plant N cycle, that is, uptake, distribution and release. Crop regulation improves must sugar concentration at harvest, while N concentration remained unchanged. The efficiency of N fertilisation varies greatly with crop load, which limits the interest of fertilisation under low-yield conditions. Significance of the Study These results contribute to the development of accurate nutrition models and sustainable cultural practices.
Highlights
Nitrogen (N) is an essential element for plant development and is required in a larger amount than any other nutrient applied to crops
Photosynthesis (A) activity was generally higher in the period from flowering to veraison [day of the year (DOY) 165– 204, average AJun–Jul = 14.8 μmol CO2/(m2 Á s)] in comparison with the period from veraison to harvest [DOY 214–247, average AAug–Sep = 10.3 μmol CO2/(m2 Á s)] (Table 2)
The Dry mass (DM), C, and N seasonal dynamics were in accordance with other studies on grapevines and other perennial crops (Zapata et al 2004, Zufferey et al 2015, Schreiner 2016, Muhammad et al 2020): C and N content in perennial fractions was greatest from leaf fall to budburst and lowest at flowering
Summary
Nitrogen (N) is an essential element for plant development and is required in a larger amount than any other nutrient applied to crops. Understanding the dynamics behind nutrient uptake, transport, storage, and remobilisation is crucial for quantifying the nutrient budget and adjusting cultural practices, in particular for perennial crops. Knowing the impact of cultural practices on nitrogen (N) dynamics in perennial crops is critical to promote N use efficiency. This study focused on the impact of crop regulation on the plant N dynamics, on the fruit N composition, and on the N fertilisation use efficiency. Crop regulation did not affect grape N concentration at harvest. Both N uptake and root N mobilisation were reduced in response to crop regulation. Fertilisation efficiency was higher under high-yield conditions in terms of N uptake and grape N accumulation. Conclusions: Crop regulation strongly affects the overall plant N cycle, that is, uptake, distribution and release. Significance of the Study: These results contribute to the development of accurate nutrition models and sustainable cultural practices
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