Nitrogen dynamics and fertilisation use efficiency: carry‐over effect of crop limitation

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 15 N-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.

Carryover effects of crop thinning and foliar N fertilisation on grape amino N composition

“…The materials and methods for the entire project are detailed in Verdenal et al (2021b). Only the materials and methods regarding the specific results described in this manuscript are presented.…”

“…The field measurements and sample preparations were conducted as described by Verdenal et al (2021b). Vine fruitfulness was determined before crop thinning and expressed as the number of bunches per shoot.…”

“…A balanced vine can produce fully ripe grapes while building up nutrient reserves for the following year (Howell, 2001). To increase the leaf-to-fruit ratio, one can either increase leaf area or decrease crop load (adapted from Verdenal et al, 2021b).…”

“…There are two ways to increase the leaf-to-fruit ratio: either by increasing canopy size or by limiting crop load. The consequences of these two actions on the total N amount in the whole plant and on the YAN concentration in the grapes are different under the cool-climate conditions of Switzerland (Figure 1; Verdenal et al, 2021b). A leaf-to-fruit ratio in the range of 1.0-1.2 m 2 of exposed leaves per kg of fruits is usually recommended for the cultivar Chasselas under Switzerland's cool climate conditions (Murisier and Zufferey, 1997;Verdenal et al, 2016).…”

“…In a research programme conducted in 2017-2018 at Agroscope, Switzerland, vines were shown to be able to maintain a constant concentration of YAN in the must at harvest, despite variations in crop load (Verdenal et al, 2020). Moreover, the grapevine adjusted N uptake and root mobilisation to its crop load, which had carryover effects on plant N content in the year n + 1 (Verdenal et al, 2021b). The experiment was conducted over two seasons, and the present manuscript addresses the formation of the FAA pool in grape must as a function of crop thinning and fertilisation and their carryover effects in the following year.…”