Annual Urea Nitrogen Contribution to the Nutrition of Cabernet Sauvignon Grapevine Grown in Sandy and Clayey Soil

Abstract

The timing of nitrogen fertilizer application in vineyards can determine the amount of nitrogen (N) absorbed, distributed, and accumulated in grapevine organs. The study aimed to evaluate the annual contribution of N from urea, applied at different times in Cabernet Sauvignon, grown in sandy and clayey soil in a subtropical climate. The sandy soil received 21.42 kg N ha−1 and the clayey soil 30 kg N ha−1, both enriched with 3% excess 15N atoms, applied at different times. The N derived from the fertilizer in grapevines, at all times of N application, and in sandy and clayey soil did not exceed 8%, with the highest values being observed in annual organs, especially in the leaves. The application of N marked at the phenological stages of IBB (50% at beginning of budbreak + 50% at full budbreak) enabled greater absorption of N derived from the fertilizer by the vines grown in both sandy and loamy soil. The N present in the annual organs (leaves, berries, stalks, and shoots) and in the perennial organs (stems and canes) of Cabernet Sauvignon grown in sandy and clayey soil was derived in greater percentages from the soil.

The Fate of Soil-Applied Nitrogen in the Fig Tree

“…This is attributed to the rapid cell division in these organs, which act as nitrogen sinks during the fig tree's vegetative and productive cycle, thereby increasing dry matter production and nutrient demand, including nitrogen (references). Similar phenomena are well documented in other fruit-bearing species, such as grapevines [5,8], peaches [10], and apple trees [23]. However, perennial organs, such as shoots from previous years and stems in fruit-bearing species, serve as transitional nutrient flow areas within the plant during vegetative and productive growth periods [3,18,24].…”

“…It is desirable for perennial organs to serve as nitrogen accumulators, including those derived from fertilizers, as part of the nitrogen can be redistributed to other organs in the subsequent vegetative and productive cycle [25], reducing reliance on soil-applied nitrogen absorption within the same year. A potential reduction in nitrogen fertilizer application frequency or dosage in fig orchards [8,14] can be advantageous, decreasing fertilizer procurement costs and the risk of soil and water contamination in orchards.…”

“…Total N and excess 15 N atoms in the fig tree organs and in the soil were determined by a continuous flow isotope ratio mass spectrometer, Hydra 20/20 (Sercon, Crewe, UK). With the results obtained, the atoms of excess 15 N (Equation (1)) and fertilizer N (Ndff) (Equations ( 2) and ( 3)) in the fig tree organs and in the soil [8,10] were calculated according to the procedure described by [21].…”

“…The fig tree, like other fruit-bearing species, takes up soil N, especially in mineral forms such as nitrate (NO 3 − -N) and ammonium (NH 4 + -N), which is then incorporated into the tree biomass and temporarily accumulated in the growing organs, such as leaves, fruit, and new shoots [7][8][9]. At the end of the cycle, N may be redistributed and accumulated in the form of N compounds in perennial organs, especially the roots, and in the following cycle, N may be mobilized and redistributed to the annual organs [8,10]. Thus, the quantity of N taken up by fruit-bearing species, like the fig tree, should both meet the current season demands and the need for the formation of N reserves.…”

“…However, the distribution of N fertilizer within these organs is not sufficiently understood, particularly in fig trees. The nitrogen isotope ( 15 N) works as an efficient marker for determining the optimal timing and targeted organs for nitrogen (N) fertilizer application and has already been used in grapevines [8,14], peach [10], pears [15], apples [16], and citrus [17]. This technique facilitates the tracking and quantification of labeled N accumulated in the plant's organs, enabling insights into the fate of applied N in the plant [5].…”