No abstract

Agroforestry systems are a more sustainable alternative to food and energy production without compromising existing agroecosystems. In this context, the study aimed to analyze the growth characteristics and the solar radition use efficiency of corn cultivated in different arrangements of agroforestry and monoculture systems. The study was conducted in the experimental area of the Laboratory of Agroclimatology of the Federal University of Santa Maria, Campus of Frederico Westphalen – RS, Brazil. The experimental design was a complete randomized block, arranged in a factorial scheme of 3 × 2 × 2 representing two arrangements of agroforestry systems (Intercrop I and Intercrop II) and the monoculture of corn; two forest species, Peltophorum dubium (Spr.) Taubert, denoted as P. dubium and the hybrid Eucalyptus urophylla S.T. Blake × Eucalyptus grandis Hill ex Maiden, denoted as Eucalyptus; and two crop years (Crop I and Crop II), with four replicates each. The growth rates varied between the different systems, with the highest values recorded for the absolute growth rate in the monoculture system, in both crop years, for the relative growth rate in the Eucalyptus-Intercrop I-Crop I and monoculture system-Crop II plots, and for the net assimilation rate in the Eucalyptus-Intercrop II in both crop years. The solar radiation use efficiency was varied between the different systems, with greater values of efficiency found in the Eucalyptus-Intercrop I-Crop I and in Eucalyptus-Intercrop II-Crop II plots. Therefore, different agroforestry arrangements influence corn growth; however, further studies related to this subject are needed as it is a way to optimize land use.

Soybean (Glycine max) stands out in the agricultural scene, being one of the main sources of protein and oil for human and animal nutrition. The aim of this study was to evaluate the growth, radiation use efficiency, and the yield of soybean, cultivated under four levels of artificial shading to simulate the environment provided by an agroforestry system. A field experiment was conducted in Frederico Westphalen, Rio Grande do Sul, Brazil, from December 2015 to April 2016. The experimental design was completely randomized with four levels of shading (0, 30, 50, and 70%) as treatment, and eight collections of plants at specific growth stages. The growth and yield traits of the soybean crop are influenced differently as a function of shade levels. Thus, the simulation of an agroforestry system from artificial shading allowed the recommendation of soybean cultivation for intercropping systems, provided that the interception of solar radiation by the tree component is less than 30%, in order to enable soybean cultivation. Efeito do sombreamento artificial no crescimento e produtividade da sojaRESUMO: A soja (Glycine max) destaca-se no cenário agrícola mundial, sendo uma das principais fontes de proteína e óleo para nutrição humana e animal. O objetivo deste estudo foi avaliar o crescimento, a eficiência do uso da radiação e a produtividade da soja cultivada sob quatro níveis de sombreamento artificial visando similar o ambiente proporcionado por um Sistema agroflorestal. Um experiment de campo foi conduzido em Frederico Westphalen, Rio Grande do Sul, de dezembro de 2015 a abril de 2016. O delineamento experimental empregado foi o inteiramente casualizado com quatro níveis de sombreamento (0, 30, 50 e 70%) como tratamento, e oito coletas de plantas em estádios específicos de crescimento. As características de crescimento e produtivas da cultura da soja são influenciadas diferentemente em função dos níveis de sombreamento. Assim, a simulação de um Sistema agroflorestal a partir de sombreamento artificial permitiu a recomendação do cultivo da soja para sistemas consorciados, desde que a interceptação da radiação solar pelo componente arbóreo seja inferior a 30%, a fim de viabilizar o cultivo da soja. Palavras-chave: sistemas agroflorestais; Glycine max; análise de crescimento; variáveis meteorológicas; radiação solarEffect of artificial shading on soybean growth and yield Rev. Bras.

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.

Simultaneous cultivation of agricultural and forest species may result in changes in plant community interactions, generating microclimatic changes within the understory and then modifying growth and yield characteristics of the intercropping systems. Thus, this study aimed to assess the radiation use efficiency, growth and yield of bean and soybean cultivated in succession under two arrangements of agroforestry and full sun. To these ends, two field experiments were conducted in Southern Brazil: bean in‐season and soybean off‐season. Absolute and relative growth rates, net assimilation rate, leaf weight ratio, leaf area ratio, specific leaf area, radiation use efficiency and yield of bean and soybean were assessed. The solar radiation flux was modified by plant arrangement and tree canopy characteristics. Shading affected growth and yield characteristics and the radiation use efficiency of the studied crops. From the results obtained in this study, it is possible to recommend crop bean cultivation in agroforestry systems. However, for soybean, due to the reduced yields obtained in agroforestry systems, further research should be conducted in order to study more spaced arrangements and crop insertion in the early years of agroforestry, in order to enable its insertion in agroforestry systems in Southern Brazil.

No abstract

A soja é considerada uma das principais commodities agrícolas, por ser produto base para produção de alimentos. Assim, o objetivo foi analisar a eficiência do uso da radiação solar, crescimento e produtividade da soja submetida a diferentes níveis de sombreamento, e com diferentes densidades de semeadura. O estudo foi realizado em Frederico Westphalen - RS na safra 2016/2017. O delineamento experimental empregado foi em blocos casualizados dispostos em sistema fatorial 4 x 4, caracterizados por quatro níveis de interferência na chegada de radiação no dossel e quatro densidades de semeadura, sendo a densidade ideal (250.000 plantas/ha) e outras 3 variações em função dessa densidade (-40%, +40% e +80%). Melhores resultados para produtividade foram encontrados no nível de 50% de interferência com densidade +40% plantas por hectare. Os tratamentos influenciaram os valores de índice de área foliar, taxa de crescimento absoluto, eficiência de conversão da radiação e produtividade. Sendo, que níveis de radiação com até 50% de interferência e densidade de +40% da densidade ideal a produtividade aumenta, com diferenças significativas para o nível de 0% de interferência e 70% nessa densidade. Portanto, caso a soja seja cultivada em sistemas de consórcio a interferência de radiação deve ser inferior a 50%.

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.