Edson Alves Bastos

Irrigation management is essential for applying the required amount of water to crops. This study evaluated the growth and yield of cowpea cultivars as a function of water regime. The experiment was conducted in Teresina, Piauí State, Brazil, from July to September 2022. The experimental design comprised a randomized block in a split-plot scheme with four replicates. The treatments comprised five water regimes (133.80, 191.70, 249.00, 303.00, and 357.00 mm per cycle) and two cowpea cultivars (BRS Inhuma and BRS Olho Negro). Physiological characteristics, growth, and yield were also evaluated. Decreasing water regimes restricted the relative water content of the leaves, relative chlorophyll index, leaf area index, dry matter accumulation, number and size of pods, and cultivar yield. BRS Inhuma showed greater growth, dry matter accumulation, and yield but was more sensitive to decreasing water regimes. Water regimes of 311.00 and 332.08 mm per cycle maximized the yield of BRS Inhuma and BRS Olho Negro, respectively. BRS Olho Negro was more tolerant to growing conditions under water-deficit conditions, indicating that there were genetic variations among the cultivars. Therefore, identifying cowpea cultivars that are more tolerant to water deficit is fundamental to ensuring high yields in irrigated areas.

Mechanistic models, such as the Agricultural Production Systems Simulator (APSIM), are used to predict the growth of pasture species and grain crops in monoculture and intercropping systems. The objective of this study was to evaluate the performance of the APSIM model in simulating the growth and productivity of maize and Marandu palisadegrass in monoculture and intercropping systems in eastern Maranhão, Brazil. Data on biomass partitioning, climate, and soil properties were collected. Model calibration involved parameterizing the light extinction coefficient and radiation use efficiency, as well as adjustments to the phenological and structural parameters of maize. Additionally, dry biomass, leaf area index, and reproductive structures of maize plants were evaluated. The model satisfactorily simulated Marandu palisadegrass grown in monoculture, with R2 values ranging from 0.95 to 0.97 and Nash-Sutcliffe efficiency (NSE) values ranging from 0.08 to 0.97. However, simulations of intercropped Marandu palisadegrass were inaccurate, with R2 values between 0.09 and 0.87 and NSE values ranging from -1035.25 to -3.33. The model performance ranged from inaccurate to accurate for maize grown in monoculture, with R2 values between 0.11 and 0.90 and NSE values ranging from -0.37 to 0.90, and for intercropped maize, with R2 values between 0.44 and 0.87 and NSE values ranging from -4.39 to 0.68. The APSIM model performed well in simulating Marandu palisadegrass grown in monoculture; however, inaccuracies were evident in simulations of intercropped Marandu palisadegrass. Simulations of maize, both in monoculture and intercropping systems, resulted in performance ranging from satisfactory to reasonable.

The Agricultural Production Systems Simulator (APSIM) has been widely used in studies to simulate the growth and development of pastures and grain crops in single-crop and intercropping cultivation systems. The objective of this study was to parameterize the APSIM and evaluate its effectiveness in estimating the growth and productivity of maize and signalgrass (Urochloa ruziziensis) in single-crop and intercropping systems in northern Piauí State, Brazil. Data were collected from the experimental field of the Brazilian Agricultural Research Corporation (Embrapa Mid-North) in Teresina, Piauí State, Brazil. The photosynthetically active radiation and soil water content were the main measurement parameters to calibrate the light extinction coefficient and radiation use efficiency, with adjustments to the phenological and structural parameters of maize. The leaf, stalk, and total shoot dry weights and leaf area index (LAI) of both crops and maize organs (husk, cob, and grains) were evaluated. The model showed coefficient of determination (R2) values ranging from 0.81 to 0.99 and Nash–Sutcliffe efficiency (NSE) values ranging from 0.72 to 0.99 for single-crop cultivation of signalgrass; R2 values ranging from 0.87 to 0.93 and NSE values ranging from 0.62 to 0.67 for intercropping cultivation of signalgrass; R2 values ranging from 0.43 to 0.97 and NSE values ranging from -3.33 to 0.95 for single-crop cultivation of maize; and R2 values ranging from 0.30 to 0.93 and NSE values ranging from 0.21 to 0.92 for intercropping cultivation of maize. The APSIM model provided an adequate fit for growth simulations of signalgrass and maize in single-crop and intercropping systems. It can simulate the growth and yield of irrigated signalgrass and maize in single-crop and intercropping systems.

O feijão-mungo (Vigna radiata (L.) Wilczek) é um grão da família das fabáceas rico em proteínas, fibras e minerais. Amplamente consumido na Ásia, é semeado em diversas partes do mundo, com destaque para a Índia. Apesar de seu potencial, a produtividade média está em torno de 500 kg ha-1 em comparação com o potencial de 2.000 kg ha-1. O estudo teve por objetivo avaliar o efeito do deficit hídrico sobre o desempenho do feijão-mungo. O experimento foi realizado na Embrapa Meio-Norte, utilizando-se delineamento em blocos casualisados no esquema de parcelas subdivididas. Nas parcelas, avaliaram-se cinco lâminas de irrigação (40, 70, 100, 130 e 160% da ETc) e, nas subparcelas, duas linhagens de feijão-mungo (M19 e M20), com quatro repetições. A imposição das menores lâminas (40 e 70% da ETc) resultou em diferenças significativas em todas as variáveis estudadas. Registrou-se uma redução de 43% na produtividade de grãos entre a maior lâmina L160 e a menor L40. A aplicação da menor lâmina de irrigação L40 (133 mm), resultou em uma produtividade de grãos de 482 kg ha-1. Em contraste, a imposição da maior lâmina de irrigação L160 (357 mm), proporcionou uma produtividade média de grãos de 1.117 kg ha-1.

Key message Climate change can limit yields of naturally resilient crops, like sorghum, challenging global food security. Abstract Agriculture under an erratic climate requires tapping into a reservoir of flexible adaptive loci that can lead to lasting yield stability under multiple abiotic stress conditions. Domesticated in the hot and dry regions of Africa, sorghum is considered a harsh crop, which is adapted to important stress factors closely related to climate change. To investigate the genetic basis of drought stress adaptation in sorghum, we used a multi-environment multi-locus genome-wide association study (MEML-GWAS) in a subset of a diverse sorghum association panel (SAP) phenotyped for performance both under well-watered and water stress conditions. We selected environments in Brazil that foreshadow agriculture where both drought and temperature stresses coincide as in many tropical agricultural frontiers. Drought reduced average grain yield (Gy) by up to 50% and also affected flowering time (Ft) and plant height (Ph). We found 15 markers associated with Gy on all sorghum chromosomes except for chromosomes 7 and 9, in addition to loci associated with phenology traits. Loci associated with Gy strongly interacted with the environment in a complex way, while loci associated with phenology traits were less affected by G × E. Studying environmental covariables potentially underpinning G × E, increases in relative humidity and evapotranspiration favored and disfavored grain yield, respectively. High temperatures influenced G × E and reduced sorghum yields, with a ~ 100 kg ha⁻¹ average decrease in grain yield for each unit increase in maximum temperature between 29 and 38 °C. Extreme G × E for sorghum stress resilience poses an additional challenge to breed crops for moving, erratic weather conditions.

The objective of this work was to evaluate the effect of the application of different doses of hydrogel and irrigation levels on the morphophysiological and productive behavior of a bell pepper cultivar, in a protected environment. Four doses of hydrogel (0.0, 0.6, 1.2, and, 2.4 g per plant) and four irrigation levels (50, 75, 100, and, 125%) were used, on the basis of the daily evapotranspiration of a bell pepper crop grown in a sandy soil. Height, stem diameter, and leaf area were measured at 70 and 100 days. At the end of the experiment, bell pepper yield and water use efficiency were estimated. Hydrogel associated with irrigation increases leaf area, productivity, and irrigation-water use efficiency. The applied water deficit (132.8 and 199.26 mm), associated with the hydrogel doses, does not affect the plants morphologically.

The objective of this work was to evaluate the potential of vegetation indices (VIs), obtained using aerial images from an unmanned aerial vehicle (UAV), for assessing water status of maize hybrids subjected to different water regimes under the soil and climate conditions of Teresina, Piauí, Brazil. Evaluations were carried out considering the application of five water regimes (WR) based on the crop evapotranspiration (ETc) (40%, 60%, 80%, 100%, and 120% of ETc) for three maize hybrids: BRS 3046 (conventional triple hybrid), BRS 2022 (conventional double hybrid), Status VIP3 (transgenic simple hybrid). A randomized block experimental design with four replications was used, in a 5×3 split-plot arrangement, consisting of WRs in the plots and maize hybrids in the subplots. A UAV was used for acquiring multispectral images. Eighteen VIs were evaluated and correlated with stomatal conductance (gs), leaf relative water content (RWC), and grain yield (GY). The VIs TCARI -RE and NDVI presented correlation with gs, whereas MNGRD and GCI presented correlation with RWC; therefore, they were considered promising for assessing the water status of maize plants. NDVI and WDRVI presented correlations with GY. Maps of NDVI, MNGRV, and WDRVI showed spatial correlation with gs, RWC, and GY measurements, respectively, in response to the applied WRs, denoting potential for assessing the water status of maize plants using aerial images from UAV.

The objective of this study was to evaluate the water status of maize cultivars through thermal and vegetation indexes generated from multispectral aerial images obtained from an unmanned aerial vehicle (UAV), and correlate them with physiological indicators and soil water contents. The application of three water regimes based on the reference evapotranspiration (ETo) (30%, 90%, and 150% ETo) was evaluated for two maize cultivars (AG-1051 and BRS-Caatingueiro). An UAV was used to acquire thermal and multispectral images. The indexes evaluated were CWSI, CI-G, CI-RE, CIV, NDVI and OSAVI, which were correlated with gas exchange and soil moisture measures. The CWSI present correlation with physiological indicators (stomatal conductance, transpiration, and net CO2 assimilation rate) that can be used to evaluate water status of maize plants. The multispectral vegetation indexes NDVI and OSAVI can replace the CWSI thermal index in water status evaluations for maize plants.

The objective of this study is to determine the vegetation indices (IV) as a means of identifying the nutritional status of corn, with respect to the soil nitrogen and potassium, using the aerial images received through an RGB camera loaded on an unmanned aerial vehicle. The images were obtained for an experiment of the nitrogen levels (0, 60, 120 and 180 kg ha-1) and potassium levels (0, 50, 100 and 150 kg ha-1), in the random block design, with a factorial scheme of 4 x 4, having three repetitions. Ten leaves were plucked per plot during the flowering phase to assess the total N (NF) and K+ leaf contents. The Pearson’s correlation analysis, as well as the analyses of variance and regression between the IV and the concentrations of N and K2O. NF, K+ and the grain yield, responded only to the soil N levels. A significant correlation was observed for the indices of Red Index, Normalized Difference Index and Visible Atmospherically Resistant Index with the NF, which endorses them as favorable in identifying the nutritional standing of corn, with respect to the N level. Not even a single one of the indices evaluated could detect the nutritional ranking of corn in the context of the potassium level.

PERFORMANCE AGROINDUSTRIAL DE CANA-DE-AÇÚCAR EM DIFERENTES REGIMES HÍDRICOS     EDUARDO MAGNO PEREIRA DA SILVA¹; ADERSON SOARES DE ANDRADE JÚNIOR²; EDSON ALVES BASTOS² E VALDENIR QUEIROZ RIBEIRO^{2   1}Instituto Federal de Educação, Ciência e Tecnologia do Piauí - Campus Uruçuí Rodovia PI 247, S/N - Portal dos Cerrados, CEP: 64860-000, Uruçuí, Piauí, Brasil, e-mail: eduardo.silva@ifpi.edu.br ²Embrapa Meio‑Norte, Avenida Duque de Caxias, n° 5.650, Bairro Buenos Aires, CEP64006‑220, Teresina, Piauí, Brasil, e-mail: aderson.andrade@embrapa.br, edson.bastos@embrapa.br, valdenir.queiroz@embrapa.br 1 RESUMO   O objetivo desta pesquisa foi avaliar a performance agroindustrial de cana-de-açúcar (planta) em resposta a diferentes regimes hídricos aplicados por gotejamento subsuperficial. O experimento foi realizado em um argissolo vermelho amarelo distrófico, na Embrapa Meio-Norte, em Teresina, Piauí, durante o período de outubro de 2015 a setembro de 2016. Modelou-se o experimento em delineamento experimental de blocos casualizados em parcelas subdivididas, com quatro repetições. As parcelas foram constituídas por quatro regimes hídricos (irrigação mais precipitação pluviométrica) baseados em frações da evapotranspiração de cultura (50% ETc = 1.374,3; 80% ETc = 1.534,2; 110% ETc = 1.712,0 e 150% ETc = 1.905,8 mm) e as subparcelas por dez variedades de cana-de-açúcar (RBUFRPE01, RBUFRPE02, RBUFRPE03, RBUFV01, RB036066, RB987935, RB935744, RB943538, RB92579 e RB867515). As características tecnológicas de qualidade do caldo da cana e rendimentos de açúcar e álcool foram alterados pelos regimes hídricos e variedades. Os maiores teores de Brix (22,5%), Fibras (13,3%), Polcaldo (17,5%) e Polcana (13,9%) foram obtidos com as variedades RB867515, RB935744, RB943538 e RB935744, respectivamente. Os rendimentos de açúcar (32,2 Mg ha^-1) e álcool (23 m³ ha^-1) foram alcançados com a variedade RB935744 e reposição hídrica próxima a 110% da ETc. Palavras-chave: Saccharum officinarum, eficiência da água, manejo da irrigação. SILVA, E. M. P.; ANDRADE JÚNIOR, A. S.; BASTOS, E. A.; RIBEIRO, V. Q. AGRO-INDUSTRIAL PERFORMANCE OF SUGARCANE IN DIFFERENT WATER REGIMES   The objective of this research was to evaluate the agro-industrial performance of sugarcane varieties (cane plant) in response to different water regimes applied by subsurface drip irrigation. The experiment was carried out in a dystrophic yellow red acrisol at Embrapa Middle North, Teresina, Piauí State, Brazil, from October 2015 to September 2016. The experiment was designed in a randomized block design in subdivided plots, with four replications. The plots consisted of four water regimes (irrigation plus rainfall) based on crop evapotranspiration fractions (50% ETc = 1,374.3 mm, 80% ETc = 1,534.2 mm, 110% ETc = 1,712.0 mm and 150% ETc = 1,905.8 mm) and the subplots per ten varieties of sugarcane (RBUFRPE01, RBUFRPE02, RBUFRPE03, RBUFV01, RB036066, RB987935, RB935744, RB943538, RB92579 and RB867515). The technological quality characteristics of sugarcane juice and yields of sugar and alcohol were affected by water regimes and varieties. The highest contents of Brix (22.5%), Fibers (13.3%), Pol-juice (17.5%) and Pol-stalk (13.9%) were obtained with varieties RB867515, RB935744, RB943538 and RB935744, respectively. The maxim yields of sugar (32.2 Mg ha^-1) and alcohol (23 m³ ha^-1) were obtained with variety RB935744 and water replenishment close to 110% of the ETc. Keywords: Saccharum officinarum, water efficiency, irrigation management.