ABSTRACT Pisum sativum L. is a multi-purpose crop. The duration of its vegetative and reproductive periods is determined by a combination of temperature and humidity and genotype response to these conditions. To minimize the loss of productivity due to adverse conditions in sensitive periods of the crop, we evaluated the phenological development and production of Pisum sativum L. in different growing seasons. We used a randomized block design, and the experiments were conducted across five growing seasons, with four replications and eight plants per experimental unit. The variables analyzed were as follows: plastochron, number of days to start flowering, full flowering, and beginning of harvest, the accumulated thermal sum to start flowering, full flowering, and beginning of harvest, and the number of pods, pod mass, and total productivity per unit area. The analysis of variance was performed, and the mean values of the data were compared using the Scott-Knott test. Principal component analysis was also performed from Pearson’s correlation matrix of phenological and production variables. In seasons 1, 4, and 5, the plants reached full flowering earlier, and the pod mass was considerably lower, resulting in lower yields. Seasons 2 and 3 were the most productive and showed lower results for plastochron, less thermal sum until full flowering, and a shorter photoperiod, which, combined with low temperatures during the growing season, resulted in a longer cultivation cycle.

RESUMO Pisum sativum L. é uma cultura multiuso, cuja duração de seu período vegetativo e reprodutivo é determinada pela combinação de temperatura, umidade e resposta do genótipo a essas condições. Diante do exposto, visando minimizar as perdas de produtividade por condições adversas em períodos sensíveis da cultura, o objetivo foi avaliar o desenvolvimento fenológico e a produção de Pisum sativum L. em diferentes épocas de cultivo. Utilizou-se o delineamento em blocos casualizados, com cinco estações de cultivo, quatro repetições e oito plantas por unidade experimental. As variáveis analisadas foram: plastocrono, número de dias para início da floração, plena floração e início da colheita, soma térmica acumulada para início da floração, plena floração e início da colheita, número de vagens, massa de vagens e produtividade total por unidade de área. A análise de variância foi realizada e as médias comparadas pelo teste de Scott Knott. Também foi realizada a análise de componentes principais da matriz de correlação de Pearson’s das variáveis fenológicas e de produção. Nas estações 1, 4 e 5, as plantas atingiram a plena floração mais cedo e a massa de vagens foi consideravelmente menor, resultando em menores rendimentos. As estações 2 e 3 foram as mais produtivas e apresentaram menores resultados para o plastocrono, menor soma térmica até a plena floração e fotoperíodo mais curto, o que aliado às baixas temperaturas durante o ciclo vegetativo, resultou em um ciclo de cultivo mais longo.

RESUMO O manejo do nitrogênio analisando indicadores agronômicos e ambientais garante produtividade satisfatória com maior qualidade ambiental. O objetivo neste estudo é propor um manejo mais sustentável de uso do nitrogênio em trigo, considerando o fornecimento em dose cheia e fracionada com estimativa da eficiência técnica, econômica e de expectativa de produtividade. Dois experimentos foram conduzidos, um para quantificar a produtividade de biomassa e outro, para avaliação do rendimento de grãos. O delineamento experimental foi o de blocos casualizados com quatro repetições em fatorial 5 × 3, para doses de N-fertilizante (0, 30, 60, 90 e 120 kg ha-1) e forma de fornecimento do nutriente [condição cheia (100%) no estádio fenológico V3 (terceira folha expandida); fracionada (70/30%) no estádio fenológico V3/V6 (terceira e sexta folha expandida) e; fracionada (70/30%) no estádio fenológico V3/R1 (início da antese)], respectivamente. O manejo mais sustentável do nitrogênio em trigo é obtido com a dose de expectativa de produtividade de 3 t ha-1 pela adubação manual, com o nutriente fornecido em dose cheia no estádio fenológico V3.

ABSTRACT The management of nitrogen by the assessment of agronomic and environmental indicators ensures satisfactory productivity with higher environmental quality. The objective of this study was to propose more sustainable management of nitrogen use in wheat, considering the supply of full and fractioned doses with an estimate of technical, economic efficiency, and expected productivity. Two experiments were conducted, one to quantify biomass productivity and the other to evaluate grain yield. The experimental design consisted of a randomized block with four repetitions in a 5 × 3 factorial, for N-fertilizer doses (0, 30, 60, 90, and 120 kg ha-1) and nutrient supply form [full condition (100%) in the phenological stage V3 (the third leaf expanded); fractionated (70/30%) in the phenological stage V3/V6 (third and sixth leaf expanded) and; fractionated (70/30%) in the phenological stage V3/R1 (beginning of anthesis)], respectively. The most sustainable management of nitrogen in wheat was obtained with the expected yield rate of 3 t ha-1 by manual fertilization, with nitrogen supplied in full dose at the V3 phenological stage.

Abstract The objective of this work was to evaluate the influence of colored shade mesh and plant density on the morphological characteristics of Corymbia citriodora seedlings. The highest radiation efficiency was found in the blue mesh, 7.01 g MJ-1 and 5.72 g MJ-1 for average and high density respectively. For dry matter and leaf area index at high density, the treatment without mesh followed by the red mesh was the best. The chlorophyll index did not differ between treatments, with mean values of 206.4, 59.1 and 262.0 for chlorophyll a, b and total, respectively. Using principal component analysis, we found the total variance to be 70%. The use of colored shade mesh and plant density altered the radiation use efficiency and dry matter accumulation. Leaf area index was affected only by plant density. The red mesh resulted in the most similar values to the treatment without mesh.

RESUMO: O objetivo deste trabalho foi determinar a variável meteorológica com maior contribuição na produtividade de colmos de cana-de-açúcar na região noroeste e central do Rio Grande do Sul. Os genótipos de cana-de-açúcar utilizados foram: UFSM XIKA FW, UFSM LUCI FW, UFSM PRETA FW, UFSM DINA FW, UFSM MARI FW, IAC87-3396. As cultivares UFSM são provenientes do processo de mutação do programa de melhoramento da Universidade Federal de Santa Maria, campus de Frederico Westphalen, e possuem tolerância a baixas temperaturas. Os caracteres morfológicos responsáveis pela produtividade utilizados nos modelos foram diâmetro médio de colmo, número médio de colmos por metro de sulco e estatura média de colmos. As variáveis meteorológicas utilizadas foram a temperatura mínima do ar, precipitação pluviométrica, radiação solar incidente e soma térmica acumulada. Foi realizada a correlação de Pearson, correlações canônicas e regressão de Stepwise entre os caracteres morfológicos e as variáveis meteorológicas, nos quais foi constado que a temperatura mínima do ar é a variável com maior influência na produtividade da cana-de-açúcar nas regiões estudadas e, que a soma térmica acumulada é a variável com maior correlação e contribuição no diâmetro de colmo e estatura média dos colmos. Desse modo, os modelos indicam que o crescimento da cana-de-açúcar responde de forma positiva a soma térmica acumulada, e as regiões em estudo apresentam potencial para o cultivo da cana-de-açúcar.

ABSTRACT: This study determined the meteorological variable that most contribute to the productivity of sugarcane stalks in the northwest and central regions of Rio Grande do Sul. The following sugarcane genotypes were used: UFSM XIKA FW, UFSM LUCI FW, UFSM PRETA FW, UFSM DINA FW, UFSM MARI FW, and IAC87-3396. The UFSM cultivars originate from a mutation process in the breeding program conducted at the Federal University of Santa Maria, Frederico Westphalen campus, and have low temperature tolerance. The productivity-associated morphological characters included in the models were average stem diameter, average stem number per meter of furrow, and average stem height. The following meteorological variables were used: minimum air temperature, precipitation, incident solar radiation, and accumulated thermal sum. Pearson’s correlation, canonical correlations, and Stepwise regression were performed between morphological characters and meteorological variables: minimum air temperature had the greatest influence on sugarcane productivity in the studied regions, and accumulated thermal sum showed the highest correlation and contributed most to stem diameter and average stem height. Thus, the models indicated that the growth of sugarcane is positively associated with the accumulated thermal sum, and sugarcane can be cultivated at the studied regions.

ABSTRACT Agriculture has caused numerous concerns regarding the preservation of natural resources. In this context, agroforestry systems are emerging as a more sustainable alternative. The present study aimed to evaluate growth characteristics, radiation use efficiency, biomass partition, and yield of soybean grown in two agroforestry systems and full sun. A field experiment was conducted in Southern Brazil during the 2014/2015 crop year, in which transmissivity of solar radiation, leaf area index, radiation use efficiency, and yield of soybean were evaluated. The solar radiation dynamics varied among the study factors, mainly due to the agroforestry arrangements. Shading influenced the leaf area index, radiation use efficiency, biomass partition, and soybean yield. Based on the soybean yield values generated in this study, the use of more spaced agroforestry arrangements and Peltophorum dubium forest species is recommended. However, because the yield values were below the expected levels, it is not yet possible to confirm the full potential of soybean crop in agroforestry systems. Thus, new studies should be conducted in order to generate alternatives that make soybean cultivation feasible in agroforestry systems, such as assessing the use of more spaced agroforestry arrangements, the insertion of the soybean crop in the initial years of cultivation of agroforestry, as well as reduce intraspecific competition by decreasing the plant population of the crop.

ABSTRACT Aloysia triphylla is an aromatic plant used in several industrial sectors, owing to the chemical properties of its essential oil. Biosynthesis of organic compounds is influenced by the growth conditions. As such, temporal and spatial variation affect the chemical composition of essential oils. We hypothesized that: i) the chemical composition of A. triphylla essential oil is influenced by differences in irrigation and season; and ii) the major components of A. triphylla essential oil do not vary between treatment conditions. To test these hypotheses, we determined the chemical composition of A. triphylla essential oil as a function of four seasons crossed with four irrigation levels. A completely randomized experimental design with a randomized block in a 4 × 4 factorial scheme, representing the four seasons of the year (summer, autumn, winter, and spring) and four irrigation levels (50%, 75%, 100%, and 125% of the reference evapotranspiration), was used with four replicates. Our results show that the chemical composition of A. triphylla essential oil varied with the two study factors, of which season was the major factor. The highest concentrations of constituents classified as monoterpene and sesquiterpene were observed in the summer season, and the highest constituents of the other group of compounds were observed in winter. In addition, the major components of the essential oil were α-citral, limonene, and β-citral, and their levels were the highest during winter.

Abstract: Despite its economic importance, the microclimate in soybean canopies has not yet been studied in detail. Such a study can yield valuable information regarding the interaction of a crop with its environment. In this context, the aim of this study was to evaluate the solar radiation dynamic and yield responses for each canopy strata for two soybean cultivars with determined and undetermined growth habits. A field study was conducted during the 2013/2014 and 2014/2015 growing seasons in the city of Frederico Westphalen, Rio Grande do Sul, Brazil. The cultivar NA6411, with a determinate growth habit, presented a greater interception of radiation in the middle and lower canopies strata which results in higher soybean yield when compared to the cultivar TEC6029, and thus, can be recommended for cultivation in crop production systems. The contribution of the middle and upper canopy strata to the total yield formation was greater than that observed in the lower canopy strata due to the greater interception of solar radiation by these strata. To increase soybean yields, new studies regarding the microclimatic conditions of the soybean canopy should be developed to improve the maximum potential yield of the new soybean cultivars.

Abstract: The objective of the study was to evaluate the growth and production efficiency of forage-grain dual-purpose wheat in two arrangements and four agroforestry systems (Intercrop-I and Intercrop-II), as well as to evaluate crop management for the wheat crops in two planting seasons (Crop Season I-2014 and Crop Season II-2015. The experiment was conducted in a randomized complete block design, factorial scheme 7x2x2, with seven cultivation systems Eucalyptus urophylla x Eucalyptus grandis Intercrop-II and Intercrop-I; Peltophorum dubium Intercrop-II and Intercrop-I; P. rigida Intercrop-I; S. parahyba Intercrop-I; a wheat monoculture with no tree species present; and two harvest management techniques (with and without harvesting of the forage species). Agroforestry systems generated shading for wheat plants, with a higher phyllochron and lower values of leaf area index of those individuals kept under trees with higher crown shading (non-deciduous trees) due to the lower transmissivity of solar radiation. The systems composed with Schizolobium parahyba in Intercrop-I and Parapiptadenia rigida in Intercrop-I provide a minor phyllochron to the wheat, resulting in a higher leaf area index and dry matter yield. Thus, the cultivation of tree species and dual-skilled agricultural crops, such as wheat, provides promising alternatives for the future use of land in tropical countries.

Abstract Sugarcane (Sacharum officinarum L.) monocropping has had a great socio-economic and environmental impact in Brazil, and agroforestry systems have been considered as an alternative for more sustainable production; however, there is a lack of field research under such conditions. The aim of this study was to evaluate the growth rates, radiation use efficiency and yield traits in sugarcane cultivated in the understory of Aleurites fordii, in two agroforestry arrangements and monocropping systems. A field experiment was conducted from July 2015 to June 2016 in the city of Frederico Westphalen, Rio Grande do Sul, Brazil. The radiation use efficiency, assimilate partitioning, leaf area index, absolute growth rate, net assimilation rate, number of tillers, plant height, % of intercepted solar radiation, extinction coefficient, and yield in each system was evaluated. In agroforestry systems, the dynamic interactions between multiple plant species change with the time and can result in unique microclimates. The use of agroforestry systems in 12 x 12m arrangements should be prioritized because it enables greater yields and radiation availability in the understory. This study sought to provide new sustainable alternatives for farmers in order to increase the diversification of the rural property and maintain the preservation of existing agroecosystems.

Abstract Soybean (Glycine max L.) monocropping have had a great socio-economic and environmental impact on the world and agroforestry systems has been considered an alternative for more sustainable production. The aim of this study was to evaluate the effect of different arrangements of agroforestry systems of the species E. urophylla x E. grandis and P. dubium and the pruning of the trees on the dynamics of solar radiation and soybean yield. A field experiment was conducted in Southern Brazil. In order to achieve the objective of the study, the solar radiation transmissivity and the productive performance of the soybean were evaluated. In this study, the soybean yield was determined by the arrangement of the agroforestry system and forest species utilized. The soybean crop cultivated in the understory of the P. dubium trees showed the highest yield response. The use of silvicultural practices for the management of forest species should be considered to generate the balance of the productive system. In this context, tree pruning is a viable side for agroforestry systems, as it promotes an increase in the incidence of solar radiation in the understory, resulting in an increase in soybean yield, especially when integrated with P. dubium.