Determinants of nitrogen use efficiency in coffee crops. A review

World production of coffee (Coffea spp.) has increased in recent decades due to its growing demand. Nitrogen (N) is one of the most required nutrients by coffee crops and in many cases, the most yield-limiting; nevertheless, a high percentage of supplied N is lost, generating pollution, greenhouse gases, and economic losses. Given this scenario, it is a priority to adopt practices that increase nitrogen use efficiency related to the capacity of plants to absorb and use N to produce biomass. This article provides context about NUE and determining factors in coffee: plant, soil, climate, and management. On the plant side, despite advances in genetics and the results of genotype evaluation, it may be a decade or more before improved coffee varieties with high EUN become available or used in world coffee farming. Both the physical, chemical, and biological properties of the soil and the elements of the climate, mainly temperature, precipitation, and solar radiation, have an influence on coffee growth and many of the processes that intervene in the N cycle and NUE; however, some components of these two factors are not fully controllable. Management of the factors that determine NUE should focus on reducing N losses in the system, increasing its uptake and utilization by plants, and maintaining or increasing productivity

Potassium use efficiency throughout the development of sugarcane cultivars aiming to early selection

A cana-de-açúcar (Saccharum spp.) é uma planta cultivada em praticamente todas as regiões do Brasil, que é o maior produtor mundial. Cerca de 70% da produção brasileira de cana-de-açúcar concentra-se nos estados de São Paulo, Goiás e Minas Gerais. No entanto, para atender à demanda nacional e internacional de etanol, açúcar e bioeletricidade, novas áreas têm sido incorporadas ao sistema produtivo, especialmente as regiões do cerrado, cujos solos apresentam fertilidade natural baixa. Apesar de haver diversos estudos com manejo de K em cana-de-açúcar, pouca atenção tem sido dada à eficiência de uso deste insumo no melhoramento genético, que é o elemento mineral requerido em maior quantidade pela cultura. Objetivou-se com este trabalho avaliar a eficiência de uso de potássio em quatro genótipos ao longo do ciclo produtivo em função de cinco doses de K, e verificar se seria possível fazer seleção precoce para esta característica nas fases iniciais de desenvolvimento da cultura. Para isto, o experimento foi conduzido em condições de campo, onde foram avaliadas doses crescentes de potássio no solo e diferentes genótipos de cana-de-açúcar. Foram realizadas cinco avaliações ao longo do desenvolvimento da cultura, aos 5, 8, 10, 12 e 14 meses após o plantio. Foram avaliadas nas primeiras quatro fases: produção de matéria seca de parte aérea (MSPA), matéria seca do colmo (MSC), teor e acúmulo de nutrientes do colmo (TNC e ANC), eficiência de uso de potássio em função da produção de MSC e TPH (EUK MSC ) e curva de acúmulo de sacarose (°Brix); na fase final foram avaliadas as mesmas variáveis sendo acrescentadas as análises tecnológicas feitas na industrialização da cana-de-açúcar e foi calculada e EUK em função da produção de sacarose aparente (EUK TPH ). Posteriormente, foram comparados os índices de EUK MSC , MSPA, MSC, TKC, AKC e °Brix da última avaliação com as demais variáveis analisadas nas avaliações antecessoras por meio de correlações de Pearson. Verificou-se que o genótipo RB 92579 foi o mais eficiente no uso de K para MSC e TPH. Os genótipos RB 988082 e RB 867515 apresentaram valores intermediários para estas variáveis. Por outro lado, o RB 987935 foi o menos eficiente sendo superado pelo genótipo RB 92579 em 40 e 38% para MSC e TPH, respectivamente. Quanto à possibilidade de se fazer seleção precoce para EUK, observou-se que as correlações entre a EUK nas fases iniciais foram intermediárias e altas, indicando que é possível fazer a seleção para esta característica antes do ciclo completo da cultura. Por outro lado, o teor de K no solo influencia a EUK dos genótipos, o que dificulta uma padronização do processo de seleção precoce. Conclui-se que o genótipo RB 92579 foi o mais eficiente no uso de K para MSC e TPH. A época e dose mais adequadas para se fazer seleção precoce de genótipos de cana- de-açúcar mais eficientes no uso de MSC é aos 8 meses após o plantio e sob condições de baixa disponibilidade de K no solo. viiABSRACT REY, Juan Camilo Sandoval, M.Sc., Universidade Federal de Viçosa, march, 2017.Sugarcane (Saccharum spp.) is a plant cultivated in almost all regions of Brazil, which is the largest producer in the world. About 70% of Brazilian sugarcane production is concentrated in the states of São Paulo, Goiás and Minas Gerais. However, to achieve the national and international demand for ethanol, sugar and bioelectricity, new areas have been incorporated into the production system, especially “cerrado” regions, where soils have low natural fertility. Although there are several studies with K management in sugarcane, little attention has been paid to the use efficiency of this nutrient in plant breeding, which is the mineral element required in greater quantity by the crop. This study aimed to assessing potassium use efficiency of four sugarcane cultivars throughout the productive cycle with five K doses and attempted to verify if it would be possible to make an early selection for this characteristic in the initial stages of crop development. For this, the experiment was planted in field conditions, where increasing potassium doses in the soil and four sugarcane cultivars were evaluated. Five evaluations were carried out during the development of the crop at 5, 8, 10, 12 and 14 months after planting. Since first until forth phases were evaluated: aboveground dry matter (ADM), stem dry matter (SDM), stem nutrient content and accumulation (SNC and SNA), stem potassium use efficiency for SDM (KUE SDM ) and sucrose accumulation curve (° Brix); In the final phase the same variables were evaluated increasing the technological analyzes made in the industrialization of sugarcane and it was calculated KUE for sucrose accumulation yield (KUE SAY ). Subsequently, in the last phase was compared KUE SDM , ADM, SDM. SKC, SKA and ° Brix with the other variables analyzed in the previous phases using Pearson correlations. RB 92579 cultivar was highlighted as more efficient cultivar for SDM and SAY. RB 988082 and RB 867515 cultivars showed intermediate values for these variables. On the other hand, RB 987935 cultivar was the less efficient being overcome by RB 92579 cultivar in 40 and 38% for SDM and SAY, respectively. Regarding the possibility of making early selection for KUE, it was observed that the correlations between the KUE SDM in the initial stages were intermediate and high, indicating that it is possible to make the selection for this characteristic before the complete crop cycle. On the other hand, soil K content influences the KUE cultivars, which makes it difficult to standardize the early selection process. It is concluded that RB 92579 cultivar was the most efficient in the use of K for SDM and SAY. The best stage and K dose to make early selection of sugarcane cultivars more efficient in KUE SDM is at 8 months after planting and under conditions of low soil K availability

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care