Impact of application of urea modes and rates on yield and nitrous oxide emissions in grapevine (Vitis vinifera L.) on sandy soils in subtropical climate

Grapevines subjected to applications of nitrogen (N) doses on the soil surface can use only a small amount of the nutrient, probably because of losses, such as nitrous oxide (N2O) emissions to the atmosphere. An alternative to reduce these N losses may be the application of N via fertigation. The study aimed to evaluate the N2O emissions and grape yield (Vitis vinifera L.), in grapevines submitted to the application of modes and doses of N cultivated in sandy soil in a subtropical climate. 'Alicante Bouschet' grapevines were subjected to a factorial scheme with three N rates: 0, 40 and 80 kg N ha-1 year-1; and two application modes: surface (NS) and via fertigation (NF). Evaluations of N2O emissions and ammonium (NH4+) and nitrate (NO3-) contents in the soil, N concentration in leaves, grape yield, and number of clusters per plant were carried out. Grapevines cultivated with applications of 40 and 80 kg N ha-1 yr-1, in NF and NS modes, respectively, present-ed higher N2O emissions. N2O emission peaks occurred in the first 9 days after N application. Cumulative N2O emissions ranged from 161.74 ± 34.67 to 496.18 ± 37.00 g ha-1 of N2O-N, in soils that received 0 and 40 kg N ha-1 yr-1, respectively, both in NF mode. Accumulated N2O emissions had a linearly positive relation with the mineral N content in the soil (NH4+ and NO3-) and these had a negative relation with grape yield.  

Residual and immediate effect after 16 applications of organic sources on yield and nitrogen use efficiency in black oat and corn

Soils with a long-term history of animal manure application exhibit higher residual effects of nitrogen (N) in soil and can affect the efficiency with which N will be used. This study aimed to evaluate how the immediate and residual effect of 16 applications of animal manure reflects on yields of black oat and corn rotation system, as well as N use efficiency. The study was carried out in no-tillage from 2004 to 2016 in Brazil. The treatments were pig slurry (PS), dairy slurry (DS), pig deep-litter (PL), mineral fertilizer (MF), and control (C). Prior to the sowing of black oat, in which 16 animal manure applications had already been made, an area of the soil was delimited where the treatments were not applied. This area was referred to as unfertilized (U) soil. Applications were carried out in the remaining area and were referred to as fertilized (F) soil. The highest dry matter yield and N accumulation in black oat and corn were found in F soils treated with DS and PL, respectively. In corn, the highest grain yield and N accumulation in grains were found with DS and PS. In U soil, the 16 applications (of DS especially) resulted in yields and N accumulation greater than the control and MF, but lower than those in F. The highest N use efficiency was found with DS. The history of animal manure applications was not enough to rule out additional applications in the following years

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

Nitrogen Critical Level in Leaves in ‘Chardonnay’ and ‘Pinot Noir’ Grapevines to Adequate Yield and Quality Must

The nitrogen (N) critical level in leaves and maximum technical efficiency (MTE) doses contribute to the grape yield, must quality, and fertilizers rationalization. This study aimed to define sufficient ranges and critical levels in leaves and maximum technical efficiency doses to obtain high yields and quality must in grapevines grown in sandy soil in a subtropical climate. ‘Chardonnay’ and ‘Pinot Noir’ grapevines were subjected to the annual application of 0, 10, 20, 40, 60, and 80 kg N ha−1 in a vineyard. The nitrogen concentration in leaves at flowering and veraison, grape yield and grape must chemical parameters (total soluble solids—TSS, total titratable acidity—TTA and total anthocyanins—TA) were evaluated. The N critical level in leaves at flowering was different between grapevines cultivars, but this was not observed in leaves at veraison. It was possible to estimate MTE for ‘Chardonnay’ grapevines, in the evaluated growing seasons. In the range of higher probability of the N critical level in leaves, the TSS and TTA variables showed opposite responses, for both cultivars. This study proposes different N critical levels for red and white grapevines, in a subtropical climate

Trabalhadores temporários para o café: mecanização e núcleos coloniais em São Paulo, 1895-1911

Este artigo examina o problema da mão de obra diante da expansão cafeeira ocorrida em São Paulo e da queda dos preços do café, na virada do século XIX para o século XX. Mais especificamente, este texto trata de alguns aspectos do debate que destacava a necessidade de redução dos custos com mão de obra frente às dificuldades que envolviam a contínua expansão da produção cafeeira naquele momento. As propostas discutidas no artigo privilegiavam a mecanização do cultivo e a flexibilização do trabalho por meio da contratação de trabalhadores temporários. A implantação de núcleos coloniais estrategicamente localizados poderia contribuir para incrementar a oferta desse tipo de trabalhador. A análise deste debate mostra que segmentos da elite econômica paulista tinham clara consciência, já naquele momento, de que somente a garantia de oferta abundante de mão de obra para os momentos de demanda intensa de trabalho na agricultura permitiria a mecanização e a flexibilidade de contratação