Prediction of Nitrogen Dosage in ‘Alicante Bouschet’ Vineyards with Machine Learning Models

Vineyard soils normally do not provide the amount of nitrogen (N) necessary for red wine production. Traditionally, the N concentration in leaves guides the N fertilization of vineyards to reach high grape yields and chemical composition under the ceteris paribus assumption. Moreover, the carryover effects of nutrients and carbohydrates stored by perennials such as grapevines are neglected. Where a well-documented database is assembled, machine learning (ML) methods can account for key site-specific features and carryover effects, impacting the performance of grapevines. The aim of this study was to predict, using ML tools, N management from local features to reach high berry yield and quality in ‘Alicante Bouschet’ vineyards. The 5-year (2015–2019) fertilizer trial comprised six N doses (0–20–40–60–80–100 kg N ha−1) and three regimes of irrigation. Model features included N dosage, climatic indices, foliar N application, and stem diameter of the preceding season, all of which were indices of the carryover effects. Accuracy of ML models was the highest with a yield cutoff of 14 t ha−1 and a total anthocyanin content (TAC) of 3900 mg L−1. Regression models were more accurate for total soluble solids (TSS), total titratable acidity (TTA), pH, TAC, and total phenolic content (TPC) in the marketable grape yield. The tissue N ranges differed between high marketable yield and TAC, indicating a trade-off about 24 g N kg−1 in the diagnostic leaf. The N dosage predicted varied from 0 to 40 kg N ha−1 depending on target variable, this was calculated from local features and carryover effects but excluded climatic indices. The dataset can increase in size and diversity with the collaboration of growers, which can help to cross over the numerous combinations of features found in vineyards. This research contributes to the rational use of N fertilizers, but with the guarantee that obtaining high productivity must be with adequate composition

Establishment of Potassium Reference Values Using Bayesian Models in Grapevines

Critical levels (CL) of available potassium (K) in soils and leaves and maximum technical efficiency (MTE) doses are relevant information to define the best K fertilization strategies. The aim of this study was to determine reference values of K in leaves and soil, using Bayesian analysis, in order to maximize grape yield and must quality of ‘Chardonnay’ and ‘Pinot Noir’ grown in a subtropical climate. The vines were subjected to applications of 0, 20, 40, 60 and 80 kg K2O ha−1 year−1. The CL and MTE doses of K, in leaves and soils, were determined using Bayesian hierarchical models. The range of probability of the occurrence of CL in leaves was 15.8 to 18.9 g K kg−1 in ‘Chardonnay’ and 16.8 to 19.1 g K kg−1 in ‘Pinot Noir’ at flowering. Moreover, the range was 15.3 to 18.1 g K kg−1 in ‘Chardonnay’ and 16.1 to 18.2 g K kg−1 in ‘Pinot Noir’ at veraison. In the soil, the CL of available K for ‘Chardonnay’ was 27.4 mg K kg−1 and for ‘Pinot Noir’ it was 23.2 mg K kg−1. The increase of K in leaves and soil increased the TSS, while the TTA decreased in both cultivars after sufficiency rate. The MTE was estimated in ‘Pinot Noir’. The proposition of CL and/or MTE doses of K can help increase the efficiency of K fertilization in vineyards

2ª Atualização Recomendação de adubação em videiras em produção para a Campanha Gaúcha do Rio Grande do Sul

A 2º aproximação de recomendação de adubação para videiras cultivadas na Campanha Gaúcha do RS, através da proposição de níveis críticos e faixas de suficiência de nutrientes em solo e folhas, bem como doses de nutrientes, contribui para o aumento e manutenção de elevadas produ- tividades de uva. Mas também, pode contribuir para que o mosto tenha valores de variáveis enológicas adequados, o que favorece a elaboração de vinhos de qualidade. Porém, sempre que necessário, o técnico deve observar as notas de rodapé das tabelas e realizar ajustes nos valores propostosA 2º aproximação de recomendação de adubação para videiras cultivadas na Campanha Gaúcha do RS, através da proposição de níveis críticos e faixas de suficiência de nutrientes em solo e folhas, bem como doses de nutrientes, contribui para o aumento e manutenção de elevadas produ- tividades de uva. Mas também, pode contribuir para que o mosto tenha valores de variáveis enológicas adequados, o que favorece a elaboração de vinhos de qualidade. Porém, sempre que necessário, o técnico deve observar as notas de rodapé das tabelas e realizar ajustes nos valores propostosAgradecemos ao Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS—21/2551-0002232- 9), e Vinícola Família Salton pelo apoio financeiro