A B S T R A C TNitrogen (N) is the nutrient most absorbed by the oat crop. Unfavorable climate conditions decrease its efficiency, generating instability and reduction in yield. The objective of this study was to improve N use efficiency in oat grain yield by the economic value of the product and of the input and by models that scale the stability, considering systems of succession of high and reduced residual-N release in favorable and unfavorable years for cultivation. The study was conducted in the years 2013, 2014 and 2015 in two systems of succession (soybean/oat, maize/oat) in randomized blocks with eight replicates, using the N-fertilizer doses of 0, 30, 60 and 120 kg ha -1 . The N-fertilizer dose for maximum economic efficiency in oats should be considered based on the meteorological trends of the cultivation year. N use optimization by models that determine the stability is an innovative proposal to increase fertilization efficiency on the yield. The N-fertilizer dose of 60 kg ha -1 promotes greater efficiency with predictability and yield, regardless of the agricultural year and the system of succession.A eficiência do nitrogênio em aveia na produtividade de grãos com estabilidade R E S U M O O nitrogênio é o nutriente mais absorvido pela aveia; em condições climáticas desfavoráveis diminui sua eficiência, gerando redução e instabilidade na produtividade. Objetivou-se, no estudo, a melhoria da eficiência de uso do nitrogênio na produtividade de grãos de aveia pelo valor econômico do produto e do insumo e por modelos que dimensionam a estabilidade considerando sistemas de sucessão de alta e reduzida liberação de N-residual em anos favoráveis e desfavoráveis ao cultivo. O estudo foi conduzido nos anos de 2013, 2014 e 2015 em dois sistemas de sucessão (soja/aveia; milho/aveia) em delineamento experimental de blocos casualizados com oito repetições, para as doses de N-fertilizante de 0, 30, 60 e 120 kg ha -1 . A dose de N-fertilizante pela máxima eficiência econômica em aveia deve ser considerada observando-se as tendências meteorológicas do ano de cultivo. A otimização de uso do nitrogênio por modelos que determinam a estabilidade é uma proposta inovadora para aumentar a eficiência de adubação sobre a produtividade. A dose de 60 kg ha -1 de N-fertilizante promove a maior eficiência com previsibilidade e produtividade, independente de ano agrícola e do sistema de sucessão.

The retainers of water in the soil can favor nitrogen (N) use efficiency in oat yield. The aim of the study was to determine if the conditions of use of the biopolymer hydrogel increase the fertilizer-N use efficiency in oat yield in succession systems of high and low residual-N release. In each succession system (soybean/oat, corn/oat), two experiments were conducted in 2014 and 2015, one to quantify biomass yield and the other to estimate grain yield and lodging. The design was randomized blocks with four replicates in a 4 x 4 factorial scheme for hydrogel doses (0, 30, 60 and 120 kg ha-1), added in the furrow with the seed, and N fertilizer doses (0, 30, 60 and 120 kg ha-1) applied in the fourth-expanded-leaf stage. The use of hydrogel increases N use efficiency in oat yield, especially under the conditions of 30 to 60 kg ha-1 of biopolymer; however, this effect is dependent on the succession system and on weather conditions.

A B S T R A C TSingle or split nitrogen (N) supply can maximize the expression of wheat yield indicators. The objective of the study was to evaluate the greater N use efficiency on wheat yield indicators by the single and split N supply under favorable and unfavorable year conditions to the crop in succession system of high and reduced residual N release. The study was conducted in 2014 and 2015, in a randomized complete block design with four replicates in a 4 x 3 factorial, for N-fertilizer doses (0, 30, 60, 120 kg ha -1 ) and supply forms [full dose (100%) in the phenological stage V 3 (third expanded leaf); split dose (70 and 30%) in the phenological stages V 3 /V 6 (third and sixth expanded leaves, respectively) and; split dose (70 and 30%) in the phenological stages V 3 /R 1 (third expanded leaf and early grain filling)], respectively, in soybean/wheat and maize/wheat cultivation systems. The highest N use efficiency for wheat yield was obtained with the single dose supply in favorable year of temperature and rainfall and with the split dose in the V 3 /V 6 stages in unfavorable year, regardless of the succession system of high and reduced residual N release.Dose única e fracionada do nitrogênio nos indicadores de produtividade do trigo R E S U M O O fornecimento único ou fracionado do nitrogênio pode maximizar a expressão dos indicadores de produtividade do trigo. Objetivou-se no estudo avaliar a maior eficiência de uso do nitrogênio sobre os indicadores de produtividade do trigo pelo fornecimento único e fracionado do nutriente em condição de ano favorável e desfavorável ao cultivo, em sistema de sucessão de alta e reduzida liberação de N-residual. O estudo foi conduzido em 2014 e 2015, em delineamento experimental de blocos casualizados com quatro repetições em fatorial 4 x 3, para doses de N-fertilizante (0, 30, 60, 120 kg ha -1 ) e formas de fornecimento [dose única (100%) no estádio fenológico V 3 (terceira folha expandida); fracionada (70 e 30%) no estádio fenológico V 3 /V 6 (terceira e sexta folha expandida) e; fracionada (70 e 30%) no estádio fenológico V 3 /R 1 (terceira folha expandida e início do enchimento de grãos)], respectivamente, no sistema de sucessão soja/trigo e milho/trigo. A maior eficiência do nitrogênio à produtividade do trigo é obtida no fornecimento em dose única em ano favorável de cultivo e com o fracionamento no estádio V 3 /V 6 em ano desfavorável, independente do sistema de sucessão de alta e reduzida liberação de N-residual.

The supply of glutamic acid-based biostimulants may represent an innovative technology to increase oat grain yield and quality. The objective of this study is to measure the effect of different biostimulants based on concentrations of glutamic acid and nutrients and their application on indicators of productivity and industrial and chemical quality of oat grains. The study was conducted in 2016 and 2017 in a randomized block design with four replications, considering 10 combinations of treatments for different application conditions and types of glutamic acid-based biostimulants, which were: 1. Control; 2. Zinplex (seed) + Biomol (grain filling); 3. Zinplex (seed) + Glutamin Extra (grain filling); 4. Zinplex (seed) + Biomol (thinning); 5. Glutamin Extra (1st fungicide application) + Glutamin Extra (2nd fungicide application); 6. Biomol (1st fungicide application) + Biomol (2nd fungicide application); 7. Zinplex (seed) + Vorax (grain filling); 8. Vorax (1st fungicide application) + Vorax (2nd fungicide application); 9. Biomol (thinning) + Vorax (grain filling) and 10. Biomol (thinning) + Glutamin Extra (grain filling). The foliar application of biostimulants with the presence of glutamic acid and nutrients may have positive effects on variables related to productivity and industrial and chemical quality of oat grains, however, depending on the agricultural year conditions. The application of Glutamin Extra in the 1st and 2nd fungicide application shows the best results in the vast majority of grain yield and quality variables, but the costs involving only biostimulants do not guarantee economic viability.

Studies on efficient use of the plant growth regulator can make this technology possible for leveraging oat yield in Brazil. This study aims to define the optimal dose growth regulator in oat, which allows plant lodging at most 5%. Establishing equations describe the yield indicators behavior and by using the optimal growth regulator dose for lodging, simulate the expression of these indicators regardless of reduced, high and very high conditions of nitrogen fertilization and favorable and unfavorable cultivation year. The study was conducted in 2013, 2014 and 2015, in carrying out two experiments, one to quantify the biomass yield and another aiming at estimating grain yield and lodging. The experimental design was a randomized block with four replications, following factorial scheme 4 x 3 to growth regulator doses (0, 200, 400 and 600 mL ha ), respectively. The use of 495 mL ha -1 growth regulator trinexapac-ethyl active principle is shown efficient at the reduction of oat plant lodging, regardless of the agricultural year condition and N-fertilizer rate. In the expression of grain yield and harvest index, quadratic behavior is obtained, however with decreasing linearity on the biomass yield and straw by increasing the growth regulator dose. The optimal dose of growth regulator in reducing oat lodging does not affect grain yield, but it reduces biological yield via biomass straw with elevation on the harvest index.

A B S T R A C TNitrogen use efficiency in wheat biomass and grain yields can be favored by the biopolymer hydrogel. The objective of the study was to analyze the use of the biopolymer hydrogel applied to the seed in the optimization of fertilizer-N on wheat biomass and grain yields, under different conditions of agricultural year and succession systems of high and reduced release of residual-N. In the study, two experiments were conducted, with different farming systems, soybean/wheat and maize/wheat, one to quantify the biomass yield rate and the other to determine grain yield. The experiments were conducted in the years 2014 and 2015, in a randomized block design with four replicates in a 4 x 4 factorial scheme, corresponding to hydrogel doses (0, 30, 60 and 120 kg ha ), applied as top-dressing. It is possible to improve the fertilizer-N efficiency by wheat using the biopolymer hydrogel for the production of biomass and grains. The highest wheat yield per kilogram of N supplied is obtained with 30 and 60 kg ha -1 of hydrogel, regardless of the year and succession system.Eficiência do nitrogênio na produtividade do trigo pelo biopolímero hidrogel ) aplicadas em cobertura, respectivamente, no sistema de sucessão soja/trigo e milho/trigo. É possível melhorar a eficiência de N-fertilizante pelo trigo com o uso do biopolímero hidrogel à produção de biomassa e grãos. A maior produtividade de trigo por quilograma de nitrogênio fornecido é obtida com 30 e 60 kg ha -1 de hidrogel, independente do ano e do sistema de sucessão. R E S U M O IntroductionWheat is one of the most produced cereals in the world (Arenhardt et al., 2015;Brezolin et al., 2017). Nitrogen (N) is essential to guarantee high yield of the wheat crop (Teixeira Filho et al., 2010;Prando et al., 2013), but is easily leached in rainy years (Teixeira Filho et al., 2010; Mantai et al., 2015) or volatilized in dry years (Rojas et al., 2012;Arenhardt et al., 2015). Thus, N use efficiency by wheat is eventually compromised, decreasing the yield and increasing the losses to the environment (Prando et al., 2013. Technologies that allow to improve yield with greater sustainability are necessary, especially in the increase of N use efficiency in the agricultural processes (Pinnow et al., 2013; Mantai et al., 2015).One of the ways to improve N absorption by plants is the maintenance of soil moisture, since the N supply depends, among other factors, on moisture, aeration and temperature, which interact in the cultivation systems (Rocha et al., 2008;Silva et al., 2015). The use of the biopolymer hydrogel may represent a technology to regulate soil water availability to crops, which would favor the efficiency of absorption of nutrients and improve the yield (Azevedo et al., 2008;Mendonça et al., 2013). Hydrogels are biodegradable threedimensional polymeric networks that retain water in their structure, forming a gel, which is capable of hydrating and releasing water over time (Kaewpirom & Boonsang, 2006;Venturoli & Venturoli, 2011).The objective of the study was t...

The use of growth regulator in oats can reduce plant lodging with reflections in biomass and grain yield. The objective of the study was to determine the feasibility and efficiency of using Trinexapac-Ethyl regulator in the growth of white oat under different conditions of N-fertilizer and years favorable and unfavorable for cultivation. In this study, two experiments were conducted in the years 2011, 2012 and 2013, one for quantifying biomass production rate and the other for the determination of grain yield and lodging. The experimental design was randomized blocks with four replicates, in a 4 x 3 factorial scheme, for growth regulator doses (0, 200, 400 and 600 mL ha-1) and nitrogen doses (30, 90 and 150 kg ha-1), respectively. There is a linear reduction of biomass rate with the increase in the growth regulator dose in oat, regardless of the condition of year and use of N-fertilizer. The growth regulator dose of 495 mL ha-1 efficiently reduces lodging with reduced, high and very high use of N-fertilizer, without reducing the yield of oat grains, in favorable, intermediate or unfavorable year for cultivation.

Nitrogen fertilizer management modifies oat (Avena sativa) panicle components and its grain yield. The work aims to study the potential of the variables of oat (A. sativa) panicle with N-fertilizer, and to simulatate its grain yield using multiple linear regression in succession systems of high and reduced Nresidual release. The study was done in 2013 and 2014. The experiment was done in a complete randomized block of 4×2 factorial design, with four replications. The treatments include: nitrogen fertilizer of four doses (0, 30, 60 and 120 kg ha-1), oat (A. sativa) cultivars at two levels (Barbarasul and Brisasul) and succession system at two levels (soybean/oat (A. sativa) and corn/oat (A. sativa). The multiple linear models were efficient in the harvest index of panicle of soybean/oat (A. sativa) system, regardless of the dose evaluated. However, at high doses, the number of grain per panicle was included. In the corn/oat (Avena sativa) system, the harvest index of panicle, the number of grains and spikelets panicle were adjusted based on the model. The multiple linear regression efficiently simulates N-fertilizer to affect the grain yield of oat (Avena sativa) and one or more potential variables of panicle in the succession systems.