Grapevine Nitrogen Research Articles

Developing a rapid method for determining grapevine nitrogen status

Developing a rapid method for determining grapevine nitrogen status

Predicting grapevine canopy nitrogen status using proximal sensors and near‐infrared reflectance spectroscopy

AbstractBackground: The current method employed by industry for tissue analysis to determine grapevine nitrogen (N) status is expensive and time intensive.Aims: This study explored the use of proximal sensors and Fourier transform near infrared spectroscopy (FT‐NIRS) to predict vine (Vitis vinifera L.) canopy N status over two growing seasons in Southern Tasmania, Australia.Methods: The GreenSeeker, Crop Circle ACS‐430 and SPAD‐502 proximal sensors were used to measure vine canopies (cv. Pinot Noir and Chardonnay) at three sampling dates (January, February, March) in the 2017/18 growing season, and two (December & February) in the 2018/19 growing season. For 12 replicates consisting of 5 vines each, a 30‐leaf sample was taken for FT‐NIRS and elemental analysis on dried, ground leaf samples. In addition, measurements with a portable FT‐NIRS were taken on fresh leaf samples (2018/19). All measurements were correlated with leaf N concentration (%) determined via elemental analysis.Results: The reliability of the proximal sensors to predict vine N content was dependent on the vine variety and sampling time. FT‐NIRS demonstrated a strong ability to predict vine N concentration independent of season, sampling time and variety. The benchtop FT‐NIRS showed the strongest predictability over both seasons (r2 = 0.94), yet the portable FT‐NIRS also showed potential (r2 = 0.76).Conclusion: Further investigation of portable FT‐NIRS technology is necessary to provide a robust model for non‐destructive vine N determination in the field.

A Novel Machine Learning Approach to Estimate Grapevine Leaf Nitrogen Concentration Using Aerial Multispectral Imagery

Assessment of the nitrogen status of grapevines with high spatial, temporal resolution offers benefits in fertilizer use efficiency, crop yield and quality, and vineyard uniformity. The primary objective of this study was to develop a robust predictive model for grapevine nitrogen estimation at bloom stage using high-resolution multispectral images captured by an unmanned aerial vehicle (UAV). Aerial imagery and leaf tissue sampling were conducted from 150 grapevines subjected to five rates of nitrogen applications. Subsequent to appropriate pre-processing steps, pixels representing the canopy were segmented from the background per each vine. First, we defined a binary classification problem using pixels of three vines with the minimum (low-N class) and two vines with the maximum (high-N class) nitrogen concentration. Following optimized hyperparameters configuration, we trained five machine learning classifiers, including support vector machine (SVM), random forest, XGBoost, quadratic discriminant analysis (QDA), and deep neural network (DNN) with fully-connected layers. Among the classifiers, SVM offered the highest F1-score (82.24%) on the test dataset at the cost of a very long training time compared to the other classifiers. Alternatively, QDA and XGBoost required the minimum training time with promising F1-score of 80.85% and 80.27%, respectively. Second, we transformed the classification into a regression problem by averaging the posterior probability of high-N class for all pixels within each of 150 vines. XGBoost exhibited a slightly larger coefficient of determination (R2 = 0.56) and lower root mean square error (RMSE) (0.23%) compared to other learning methods in the prediction of nitrogen concentration of all vines. The proposed approach provides values in (i) leveraging high-resolution imagery, (ii) investigating spatial distribution of nitrogen across a vine’s canopy, and (iii) defining spatial zones for nitrogen application and smart sampling.

Utility of dormant season pruning wood to predict nutrient status of grapevines

Grape growers utilize leaf blades or petioles collected during the growing season to monitor vine nutrition. However, an earlier indicator of vine nutrient status is desirable. The pruning wood derived from last season’s fruiting shoots (dormant stems) collected in winter may be a useful tissue to assess vine nutrition before the growing season. The utility of dormant stems to indicate grapevine nitrogen (N), phosphorus (P), and potassium (K) status was tested in Pinot noir grapevines (Vitis vinifera L.) from a microplot vineyard where varying levels of N, P, or K were provided over four years. Dormant stem nutrients were evaluated based on their response to varying nutrient supply and as predictors of vine nutrient status in the upcoming growing season. Concentrations of P and K in dormant stems reflected the amount of P and K supplied to vines, and effects grew larger over time. The concentrations of P and K in dormant stems also correlated well with next season P and K levels in leaf blades and petioles. Relationships between leaf blade and petiole tests and dormant stems were more consistent across three years for P than for K. Nitrogen concentrations in dormant stems did not consistently reflect N inputs and were correlated only weakly to leaf blade and petiole N tests during the growing season. These findings indicate that dormant stems can be useful for diagnosing P and K status of grapevines.

Effects of an Ascophyllum nodosum (L.) Le Jol. extract on grapevine yield and berry composition of a Merlot vineyard

Few publications in the scientific literature document effects of seaweed extracts on winegrape varieties. A 2-year field experiment was conducted to evaluate effects of foliar applications of an Ascophyllum nodosum (L.) Le Jol. extract on vine yield components, canopy chlorophyll content, berry composition and phenolic indices. The split plot experiment allowed for the investigation of extract effects with and without in-season N fertilization in a Merlot vineyard in 2015 and 2016. Great differences in vine productivity and berry composition between years were attributed to hail damage in 2015. Vines were not affected by N supply in any single year other than a decline of some berry quality parameters in 2016. Effects of seaweed extract application were evident in the absence of hail damage in 2016. The greatest vine responses were obtained with 1% extract concentration under in-season N supply by a 26% increase in yield, 35% increase in the number of berries and 21% increase in anthocyanin extractability of berry skins. These beneficial effects came about without a negative impact on other parameters of berry composition or phenolic indices and, in part, appear to be caused by direct effects on berry physiology and grapevine nitrogen status. The lower extract concentration (0.2%) also increased number of berries and anthocyanin extractability, but these were accompanied by a reduction of berry phenols and an increase of seed tannins. The results demonstrate the potential of this extract to increase production and improve wine quality in red winegrape vineyards.

Influence on wine biogenic amine composition of modifications to soil N availability and grapevine N by cover crops.

Vineyard soil management can modify the nitrogen soil availability and, therefore, grape amino acid content. These compounds are precursors of biogenic amines, which have negative effects on wine quality and human health. The objective was to study whether the effect of conventional tillage and two cover crops (barley and clover) on grapevine nitrogen status could be related to wine biogenic amines. Over 4 years, soil NO3- -N, nitrogen content in leaf and wine biogenic amine concentration were determined. Barley reduced soil NO3- -N availability and clover increased it. In 2011, at bloom, nitrogen content decreased with barley treatment in both blade and petiole. In 2012, nitrogen content in both leaf tissues at bloom was greater with clover than with tillage and barley treatments. Also, total biogenic amines decreased in barley with respect to tillage and clover treatments. There were correlations between some individual and total biogenic amine concentrations with respect to nitrogen content in leaf tissues. Wine biogenic amine concentration can be affected by the grapevine nitrogen status, provoked by changes in the soil NO3- -N availability with both cover crop treatments. © 2017 Society of Chemical Industry.

Effect of two doses of urea foliar application on leaves and grape nitrogen composition during two vintages

Nitrogen affects grapevine growth and also yeast metabolism, which have a direct influence on fermentation kinetics and the formation of different volatile compounds. Throughout the grapevine cycle, soil nitrogen availability and grape nitrogen composition can vary because of different factors. Nitrogen foliar applications can contribute toward enhancing grapevine nitrogen status and minimize the problem of leaching that traditional nitrogen-soil applications can provoke. The present study aimed to evaluate the influence of urea foliar applications on grapevine nitrogen status and grape amino acid content. Accordingly, two different doses of urea were applied over the leaves of a 'Tempranillo' vineyard. The highest urea doses affected nitrogen content on blade leaf tissues after veraison. Must amino acid profiles were modified by urea application and some of the compounds increased their concentrations. The effect of year on the increase of must total amino acid concentrations was more important than the effect of the doses applied. Urea foliar applications can be an interesting tool for decreasing grapevine nitrogen deficiencies. This method of nitrogen implementation in the vineyard could avoid sluggish fermentation problems during winemaking, enhance must nitrogen composition, and contribute to improving wine quality. © 2016 Society of Chemical Industry.

Amino acid content in red wines obtained from grapevine nitrogen foliar treatments: consumption during the alcoholic fermentation

Nitrogen is an important element for grapevine and winemaking which affects the development of the plant and yeast, and therefore it is important for wine quality. The aim of this work was to study the influence of foliar application to vineyard of proline, phenylalanine and urea and two commercial nitrogen fertilizers, without and with amino acids in their formulation, on the wine amino acid content and their consumption during the alcoholic fermentation. The results showed that these treatments did not affect the amino acid composition in wines. The differences observed for certain amino acids were so small that the concentration of total amino acids was not significantly different among wines. Moreover, it was observed that the higher the content of amino acids in the medium, the greater their consumption during the alcoholic fermentation.

Amino acid content in red wines obtained from grapevine nitrogen foliar treatments: consumption during the alcoholic fermentation

Nitrogen is an important element for grapevine and winemaking which affects the development of the plant and yeast, and therefore it is important for wine quality. The aim of this work was to study the influence of foliar application to vineyard of proline, phenylalanine and urea and two commercial nitrogen fertilizers, without and with amino acids in their formulation, on the wine amino acid content and their consumption during the alcoholic fermentation. The results showed that these treatments did not affect the amino acid composition in wines. The differences observed for certain amino acids were so small that the concentration of total amino acids was not significantly different among wines. Moreover, it was observed that the higher the content of amino acids in the medium, the greater their consumption during the alcoholic fermentation.

Using active canopy sensors and chlorophyll meters to estimate grapevine nitrogen status and productivity

Effects of nitrogen (Ν) and water supply on grapevine leaf transmittance and canopy reflectance were studied over 2 years (2009–2010) in two vineyards planted with cvs. Cabernet Sauvignon and Xinomavro (Vitis vinifera L.) located in northern Greece. Three N (0, 60 and 120 kg ha−1) and two irrigation (irrigated at 70 % of crop evapotranspiration and non-irrigated) treatments were managed in triplicate in randomized blocks. Measurements with two transmittance-based chlorophyll meters (CM: SPAD-502 and CCM-200) and two active canopy sensors (Crop Circle ACS-210; amber band and Crop Circle ACS-430; red and red edge bands) were conducted on four and two growth stages, respectively. Fertilization increased leaf N and chlorophyll concentrations, as well as CM readings and vegetation indices. The CCM and SPAD values did not vary across growth stages and better estimated leaf N and chlorophyll concentrations in Cabernet Sauvignon than in Xinomavro. The SPAD readings provided better predictions of leaf N concentration. The vegetation indices of the ACS-430 sensor correlated with leaf N and chlorophyll concentrations and dormant wood in Cabernet Sauvignon; the red edge-based indices were generally more efficient than the red-based indices. Consistent relationships were observed for all ACS-430 indices with yield and for red edge-based indices with total phenols early in the season for both vineyards. The correlation between ACS-210 sensor indices and vine properties was low. These results showed that the two technologies examined could provide information on grapevine performance early in the season but have limitations that may restrict their use in vineyards because the acquired relationships were not consistent across vineyards and instruments.

Complete vineyard floor cover crops favorably limit grapevine vegetative growth

Complete vineyard floor cover crops were evaluated in a long-term study for their ability to regulate excessive vegetative growth of the grapevine (Vitis vinifera L.) variety ‘Cabernet Sauvignon’. Treatments were: tall fescue (Festuca arundinacea Shreb.) ‘KY-31′ and ‘Elite II’, hard fescue (Festuca ovina L.) ‘Aurora Gold’, perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata L.), and an under-trellis herbicide strip combined with KY-31 fescue interrows. Compared to herbicide-treated soil strip, Elite II fescue reduced vine pruning weights (kg/vine) 28%, individual cane weight (g) 20%, and canopy leaf layer number 25%. KY-31 fescue produced the greatest biomass and stand density, while perennial ryegrass produced the least biomass and Aurora Gold hard fescue produced the lowest stand density. Elite II fescue produced less biomass but equivalent stand density compared to KY-31 fescue. Treatments minimally impacted vine water potential (Ψmd, Ψstem), indicating that the grasses were not overly competitive with grapevines for soil moisture. All grass treatments tended to depress grapevine nitrogen levels relative to the under-trellis herbicide strip treatment, but no treatment resulted in vine nitrogen levels below the acceptable sufficiency range. Because of its establishment and growth characteristics, desired suppression of vine vegetative growth, and its low impact on crop yield, we considered Elite II fescue the optimal cover crop evaluated.

Competition for nitrogen in an unfertilized intercropping system: The case of an association of grapevine and grass cover in a Mediterranean climate

Cover cropping is currently increasing in vineyards as it provides solutions to some of the problems encountered in vine growing. However, its development is still hampered in Mediterranean regions because of fears of severe competition for water. Recent studies have shown that soil resources other than water may also be restrictive, and particularly nitrogen. Over a three-year period, the effect of introducing a cover crop was studied with respect to the temporal and spatial changes to nitrogen dynamics in a Mediterranean vineyard. The experiment compared the impact of three different types of soil cover management on nitrogen dynamics, and particularly on soil nitrogen mineralization which is the principal source of inorganic nitrogen in situations with no application of N fertilizers which are frequent in viticulture. This experiment provided evidence that the presence of an intercrop significantly reduced nitrogen accumulation in aerial parts of grapevine during the year due to competition for soil resources. This reduction varied markedly between years and treatments, and was more pronounced during dry years. The competition for nitrogen was direct as intercrop deprived grapevine of soil nitrogen beneath the inter-row and caused grapevine uptake to be higher beneath the row. In deep soils, a grapevine can adapt its root system in order to access deeper water resources, but it then partially abandons the mineralization zone containing most inorganic nitrogen. Competition for nitrogen was less marked with a temporary cover crop than with a permanent one, because of the shorter period of uptake with the former and the time needed for an annual cover crop to develop its root system each year. Intercrop also competed indirectly for nitrogen with grapevine as it took up soil water and made inorganic nitrogen less mobile and accessible to grapevine. Intercrop markedly decreased soil nitrogen mineralization. Although it did not significantly affect organic matter characteristics or soil temperature, it clearly modified the water regime. Indeed, under either temporary or perennial cover crops, the upper soil layers dried more rapidly than when there was only evaporation from bare soil. Consequently, nitrogen mineralization decreased faster with intercropped treatments and halted prematurely during the summer. The earliness of the reduction in nitrogen accumulation in intercropped vineyards also suggested that a lower level of nitrogen transfer to perennial reserves was involved. Indeed, grass cover grows and competes for nitrogen during the autumn which is a favourable period for nitrogen accumulation in wood reserves. Although better water infiltration was observed in the presence of a cover crop (notably in the autumn), the favourable conditions for nitrogen mineralization were propitious for grass cover growth and uptake. Consequently, intercrop reduced grapevine growth of the year but also the potential growth for the next year by decreasing grapevine nitrogen perennial reserves.

Implications of nitrogen nutrition for grapes, fermentation and wine

This review discusses the impacts of nitrogen addition in the vineyard and winery, and establishes the effects that nitrogen has on grape berry and wine composition and the sensory attributes of wine. Nitrogen is the most abundant soil-derived macronutrient in a grapevine, and plays a major role in many of the biological functions and processes of both grapevine and fermentative microorganisms. Manipulation of grapevine nitrogen nutrition has the potential to influence quality components in the grape and, ultimately, the wine. In addition, fermentation kinetics and formation of flavour-active metabolites are also affected by the nitrogen status of the must, which can be further manipulated by addition of nitrogen in the winery. The only consistent effect of nitrogen application in the vineyard on grape berry quality components is an increase in the concentration of the major nitrogenous compounds, such as total nitrogen, total amino acids, arginine, proline and ammonium, and consequently yeast-assimilable nitrogen (YAN). Both the form and amount of YAN have significant implications for wine quality. Low must YAN leads to low yeast populations and poor fermentation vigour, increased risk of sluggish/stuck/slow fermentations, increased production of undesirable thiols (e.g. hydrogen sulfide) and higher alcohols, and low production of esters and long chain volatile fatty acids. High must YAN leads to increased biomass and higher maximum heat output due to greater fermentation vigour, and increased formation of ethyl acetate, acetic acid and volatile acidity. Increased concentrations of haze-causing proteins, urea and ethyl carbamate and biogenic amines are also associated with high YAN musts. The risk of microbial instability, potential taint from Botrytis-infected fruit and possibly atypical ageing character is also increased. Intermediate must YAN favours the best balance between desirable and undesirable chemical and sensory wine attributes. ‘Macro tuning’, of berry nitrogen status can be achieved in the vineyard, given genetic constraints, but the final ‘micro tuning’ can be more readily achieved in the winery by the use of nitrogen supplements, such as diammonium phosphate (DAP) and the choice of fermentation conditions. This point highlights the need to monitor nitrogen not only in the vineyard but also in the must immediately before fermentation, so that appropriate additions can be made when required. Overall, optimisation of vineyard and fermentation nitrogen can contribute to quality factors in wine and hence affect its value. However, a better understanding of the effect of nitrogen on grape secondary metabolites and different types of nitrogen sources on yeast flavour metabolism and wine sensory properties is still required.

Application of Spectroscopy for Measuring Leaf Nitrogen, Chlorophyll and the Other Pigments in Pinot Noir Grape

Nitrogen is one of the most important nutrition factors affecting grapevine growth performance and berry quality. Leaf pigments contents and leaf areas are the important indicators of grapevine nitrogen status and plant performance. In order to find a efficient way to nondestructively measure leaf nitrogen and pigments status, the SPAD meter, CCM-200 and CM-1000 chlorophyll meter in comparisons with FOSS NIR system were used in measuring leaf nitrogen, leaf chlorophyll, carotenoids, flavonoids and anthocyanins in 7-year-old Pinot Noir grape with different rate of N treatments. The results indicate that the reading of all these meters have a good relationship with leaf N, leaf chlorophyll and leaf area. But the accuracy among these meters was different, in which the accuracy of FOSS NIR is better than that of the SPAD meter, CCM-200 and CM-1000. There is the good relationship between leaf nitrogen contents, leaf area, leaf chlorophyll and carotenoids contents. Flavonoids and anthocyanins have the inverse relationship with leaf N contents and leaf area. FOSS NIR system can be use for nondestructive assessing nitrogen, leaf chlorophyll, carotenoids, flavonoids and anthocyanins whereas the other meters can only used for nondestructive assessing leaf nitrogen and leaf chlorophyll. These results indicate it is possible to use nondestructive spectral methods as the precision viticulture tools to manage vineyards nitrogen fertilization and grapevine performance.

Grapevine Uptake of15N-Labeled Nitrogen Derived from a Winter-Annual Leguminous Cover-Crop Mix

A winter-annual leguminous cover-crop mix was labeled with ¹⁵N-depleted ammonium sulfate fertilizer and tilled into every other alley of a Chardonnay vineyard on 5-C rootstock. The cover crop-derived nitrogen was detected in the grape leaves four weeks after cover-crop incorporation. There were two main periods of grapevine nitrogen uptake from the decomposing cover crop: from 4 to 6 weeks and again from 16 to 20 weeks following incorporation. The percent of grape-leaf nitrogen derived from labeled cover crop (%Ndfcc) reached 0.28% by the end of the growing season. The results of this preliminary study indicate that leguminous cover crops have the potential to supply nitrogen to grapevines during the times of peak nitrogen demand in early spring and fruit set. In this tilled vineyard, the overall contribution of cover-crop nitrogen to total grape-leaf nitrogen content was small compared to previous studies that have measured cover-crop nitrogen uptake by younger grapevines or annual crops.

Leaf and must nitrogen content two complementary indicators of grapevine nitrogen status

<p style="text-align: justify;">Grapevine nitrogen status was assessed by nitrogen content in leaf blade and petiole at veraison, in must at harvest and in pruned wood in December. The comparison of these indicators were done in vineyards bearing adults plants in the Atlantic and Mediterranean climates. Soil nitrogen offer were changed by soil grass cover, fertilization and irrigation. Leaf blade nitrogen (LBN) content cannot be simply predicted from soil texture, training characteristics and climate. Petiole and wood nitrogen content was less precise indicators compared to LBN content per unit dry weight. LBN content based on unit of leaf area usually constant along the growing season provides a complementary information on the leaf photosynthetic capacity and nitrogen availability for grapevine in summer. LBN content informs on the early growth grapevine access to soil and reserve nitrogen.</p><p style="text-align: justify;">Must and leaf blade nitrogen contents are significantly correlated. But it is shown that must N content is also changed by the yield and the soil capacity to provide nitrogen to the grapevine in summer. A simple predicting model of N in must is proposed. It is based on the availability of N in spring and summer and the positive effect of spring N on berry set up. Leaf blade and must N content considered both provided a complementary information on the grapevine N nutrition along the season.</p><p style="text-align: justify;">Sampling conditions for LBN content was tested. Primary leaves of a rank above 6 are very similar in N content and most representative of the grapevine N status. The LBN content on a leaf area basis is a more versatile expression because less variable along the growing season. The expressions of LBN content on the dry weight and leaf area can be obtained from a simple analysis by sampling leaf disks.</p>