One of the most notorious pathogens affecting tobacco production is tobacco bacterial wilt (TBW), caused by Ralstonia solanacearum. Controlling TBW is a global issue, and developing more resistant cultivars is one of the solutions. Therefore, this study investigated the effectiveness of recurrent selection (RS) as a breeding strategy to enhance resistance to R. solanacearum in tobacco. We also aimed to identify the appropriate progeny type for RS. The trials were carried out in an area where the pathogen is known to occur, with seedlings inoculated with R. solanacearum to assure the presence of the pathogen. The incidence of the pathogen was evaluated over two seasons. In the first year, we utilized 100 S-1:2 progeny from the original population (cycle 0) and 108 half-sib progeny of cycle I. In the subsequent year, we evaluated 196 S0:1 progeny of CI and 176 half-sib progeny of cycle II. Additionally, to ensure the presence of the pathogen, we inoculated R. solanacearum 40-45 days after transplanting the seedlings. The incidence of the pathogen was assessed based on the number of plants showing symptoms (%). Although the difference between cycle 0 and cycle II was relatively small, the results suggest that recurrent selection was successful in accumulatingresistance alleles, as reflected in the positive association between disease resistance and agronomic traits.
Soybean monoculture (Glycine max) and second-crop corn succession in the Cerrado reduce soil quality and compromise long-term productivity. Adopting conservation practices such as crop rotation, cover crops, and multifunctional rhizobacteria is essential for sustainable soybean cultivation in the region. This study aimed to determine the effect of mixes of cover crops grown in the second crop in rotation with upland rice and co-inoculation of soybeans with multifunctional rhizobacteria on the physical, chemical, and biological quality of the soil and the nutrient accumulation, biomass production, production components, and yield of the soybean crop. The experiment was conducted in a randomized block design, arranged in a 7x2 factorial scheme, with 14 treatments and four replications. Treatments included five cover crop mixes and two fallows (rice/fallow/soybean and soybean/fallow/soybean), with or without co-inoculation of seeds with Bacillus sp. (BRM 63573) and Serratia marcensces (BRM 32114). Rotation with upland rice and cover crop mixes provided higher P and Zn content in the soil, higher activity of the β-Glycosidase enzyme, lower density, better total porosity, lower incidence of phytopathogenic fungi Fusarium solani and Rhizoctonia solani and greater biomass production, greater macro and micronutrient content in the aerial part, greater number of pods per plant and grain yield of the soybean crop concerning the areas that remained fallow. Fallow 2 (soybean/fallow/soybean) provided the worst results for most of the analyzed variables. Co-inoculation provided higher soil microporosity, lower density of the phytopathogenic fungus (Fusarium oxysporum) in the soil, and greater biomass production and nutrient accumulation in the shoot of soybean plants compared to treatment without co-inoculation.
The use of cover crops during the winter period is the foundation of the no-till system and provides physical, chemical, and biological benefits to the soil. A high biomass input from cover crops and benefits related to nutrient cycling also enhance the presence of beneficial soil microorganisms. Thus, this study aimed to evaluate dry matter phytomass production, the soil coverage curve with cover crops, and the decomposition curve of dry matter phytomass in monoculture and cover crop mixtures in a subtropical environment. The following cover crop treatments were evaluated during the winters of 2022 and 2023 using a randomized block experimental design: black oat, rye, common vetch, forage radish, black oat + common vetch, black oat + forage radish, black oat + common vetch + forage radish, rye + common vetch, rye + forage radish, and rye + common vetch + forage radish. Dry matter phytomass production, soil coverage, and dry matter phytomass decomposition were measured using the litter bag method. Black oat and forage radish in monoculture stood out for their dry matter phytomass production, and forage radish excelled in mixed treatments, presenting values exceeding 50% of the composition in all cases. Soil coverage was adequate for black oat, rye, common vetch, and forage radish in monoculture and their intercropping systems. After 150 days of decomposition, black oat and rye exhibited the lowest decomposition rates, and the cover crop mixtures showed intermediate decomposition rates, confirming their suitability as autumn/winter cover crops in subtropical environments.
The use of nitrogen fertilizers in maize crops must be reduced, and a potential alternative is the use of diazotrophic bacteria of the genus Azospirillum. This research aims to characterize the efficiency of the association with Azospirillum brasilense (Az) among maize genotypes on grain yield. Forty-eight experimental single-cross maize hybrids obtained from the cross in a partial diallel scheme between eight and six inbred lines were used. The maize hybrids were evaluated in seven environments, considering the grain yield (GY) without nitrogen (N) topdressing and without Az inoculation, GY with N topdressing and without Az inoculation, GY without N topdressing but with Az inoculation, and the efficiency to Az. The hybrids’ GY varied in the presence of Az, indicating a differential response to the bacteria and confirming that this association enables the selection of more efficient genotypes since some hybrids maintained similar yield levels when N topdressing was replaced by Az inoculation. Low or medium correlation estimates were obtained among the considered traits, indicating a low correspondence between yields under the different conditions and between yields and the efficiency of the association with Az, suggesting that indirect selection for these traits is not efficient. These results indicate that it is possible to select the most efficient maize genotypes.
Cadmium (Cd) and lead (Pb) contamination in agricultural and urban soils poses significant environmental and human health risks, especially in areas impacted by metallurgical waste. In this study, the efficacy of four biochars produced from rice straw (RSB), sugarcane bagasse (SBB), sewage sludge (SSB), and filter cake (FCB), in immobilizing Cd and Pb and improving soil chemical properties, was assessed. An incubation experiment was conducted using contaminated soil from Santo Amaro, Brazil, a site historically affected by lead smelting. Biochars were applied at 10% (w/w), and their effects on soil pH, nutrient availability, organic matter (SOM), and metal fractionation were evaluated. Compared with the control treatment, the SBB and FCB treatments significantly reduced the availability of Cd (~30%) and Pb (~20%). These biochars also increased phosphorus (P) availability and increased the SOM content. Sequential extraction indicated a shift of Cd and Pb from labile to more stable forms, particularly the reducible and residual fractions, suggesting improved long-term immobilization. The superior performance of SBB and FCB was attributed to their higher SOM and P contents, as well as functional groups that promote metal complexation. Overall, the findings demonstrate the potential of nutrient-rich, waste-derived biochars as a sustainable and cost-effective solution for the remediation of heavy metal-contaminated soils. The results highlight the importance of selecting biochars based on feedstock characteristics and underscore the need for field-based studies to evaluate their long-term stability and the effects on metal uptake by plants.
Citrullus lanatus (mini-watermelon type) ‘Sugar Baby’ seeds were irradiated with Cobalt-60 gamma rays at doses of 0 (control), 100, 200, 300, and 400 Gy to enhance genetic variability. Germination, anomalies, development, flowering, and fruiting were assessed through 29 quantitative and qualitative traits and 79 molecular markers (random amplified polymorphic DNA (RAPD), intersimple sequence repeat (ISSR), and simple sequence repeat (SSR)). Gamma radiation significantly influenced germination (p < 0.001), with low doses showing neutral or positive effects and higher doses reducing germination. The 50% lethal dose (LD50) was determined as 325.81 Gy. Of 25 evaluated traits, most showed highly significant differences (p < 0.001), with developmental improvements at 100 and 200 Gy and deleterious effects at 300 and 400 Gy. Phenotypic diversity increased with the dose, forming distinct clusters: three at 400 Gy, five at 300 Gy, and fewer at lower doses. Molecular analyses revealed changes induced by two RAPD markers, five ISSR markers, and one SSR marker. Seventeen morphotypes that differed from the control were identified. These results confirm the efficiency of gamma radiation in inducing significant phenotypic and genetic variability, enabling LD50 determination and the detection of previously unreported molecular alterations in mini watermelon.
Height–diameter models are widely used to estimate tree height from diameter at breast height (DBH) and play a crucial role in forest inventories by reducing fieldwork effort. However, statistical challenges such as nonlinearity, heteroscedasticity, nonnormality, and outliers can compromise model accuracy. To address these issues, this study proposes a generalization of Scolforo’s height‒diameter model (Scolforo, 1998), which incorporates random effects to improve flexibility and fit. With observational data from Eucalyptus urograndis plantations, we present a step-by-step framework for model fitting, inference, and validation. Our approach considers hierarchical structures and variability across stands to improve predictive performance. To rigorously assess model adequacy, we conducted a simulation study under various scenarios, evaluating goodness-of-fit with deviance, randomized quantile residuals, and least-confounded residuals. These diagnostics identify misspecification and enable robust parameter estimation. Additionally, we provide a detailed tutorial (Appendix B) for implementing the model in R that encompasses (i) inference for fixed and random effects, (ii) local influence analysis to detect sensitive observations, and (iii) residual-based diagnostics adapted to mixed models. Our results reveal the adaptability of the model to complex data structures while maintaining interpretability. The proposed framework provides forest researchers a reliable tool for height prediction that combines theoretical rigor and practical applicability. The accompanying R tutorial increases reproducibility and facilitates the integration of the framework into forest inventory workflows.
In Brazil, Eucalyptus plantations occupy approximately 7.6 million hectares, of which 8% are located in the state of Bahia. In southern Bahia, these plantations are predominantly established on soils with cohesive horizons, characterized by high soil strength when dry and restricted pore connectivity when wet. These conditions reduce water, air, and nutrient fluxes, adversely affecting root development and plant growth. Subsoiling is a management practice commonly employed to mitigate these limitations; however, its effectiveness and persistence in modifying the physical attributes of naturally dense soils remain under debate. This study aimed to assess the effects of subsoiling on the physical quality of cohesive Argissolo Amarelo under Eucalyptus cultivation. Two sites were evaluated: one with Argissolo Amarelo distrófico típico (PA1) and another with Argissolo Amarelo distrocoeso fragipânico (PA2), both subsoiled to 0.60 m prior to planting. Soil samples were collected 6.5 years after planting in PA1 and 1 year after planting in PA2. Sampling was performed in the planting rows (0.20–0.25, 0.35–0.40, and 0.60–0.65 m) and the inter-rows (0.20–0.25 m). The following physical attributes were determined: bulk density, total porosity, the least limiting water range (LLWR), the water retention curve and the pore size distribution. According to the results, subsoiling led to sustained improvements in soil physical quality. The subsoiled layers exhibited lower bulk density, increased macroporosity, and a higher LLWR. Additionally, pore distribution was altered, with a higher proportion of cryptopores in non-subsoiled layers. The surface layers showed greater water retention at high matric potentials in the planting rows and low potentials in the inter-rows. These findings underscore the potential of subsoiling to enhance the physical functionality of cohesive soils under Eucalyptus, with effects that persist for multiple years post-subsoiling.
Despite the improvements in soil properties and grain yield obtained by using cover crops, there is little information on their long-term effects and associated nitrogen topdressing fertilization on subsequent crops grown in the same field. Thus, this study aimed to determine the effects of cover crops and nitrogen topdressing fertilization on the soil chemical and physical properties and yield of subsequent grain crops over eight years. The experiment was conducted on soil classified as Oxisol in southern Brazil using a randomized block design in split plots, with five replications. The main plots were divided by winter cover crop (black oat (Avena strigosa Schreb), and pea (Pisum sativum ssp. arvense)), and the subplots had differing nitrogen topdressing application rates (0, 25, 50, 75, and 100 kg N ha−1) and summer grain crops (bean (Phaseolus vulgaris), maize (Zea mays L.), and soybean (Glycine max (L.) Merr.)). In March 2022, after the eighth year of crop rotation, samples were collected in 0–5, 5–10, 10–20, and 20–30 cm soil layers to determine the chemical properties and in 0–5, 5–10, 10–20, and 20–40 cm layers to determine the physical properties. The pH, phosphorus content, and organic matter values were not influenced by the cover crop. A higher soil potassium content was observed at depths of 0–5, 5–10, and 10–20 cm in oat. Oat also showed increased soil macroporosity compared to pea in the 20–30 cm layer. Pea only increased the grain yield in one season with bean and one season with maize. Nitrogen fertilization increased the yield in only some seasons, two seasons with bean and one season with maize. The results of this study can be used to guide cover crop management in no-tillage cropping systems to maximize the positive effects on soil quality.
Phenological studies are fundamental for species management and conservation and support research into genetic improvement by providing insights into plant life cycles and their relationship with phenophases and environmental conditions. This study aimed to determine the environmental variables and their influence on the vegetative and reproductive phenological patterns of Hymenaea martiana Hayne. Field observations were carried out in five areas located in the municipality of Areia, Paraíba State, Brazil. Between May 2021 and April 2023, the phenological events of budding, senescence, flower bud, flowering, and fruiting were assessed every 30 days. Statistical analyses were circular to verify the occurrence of the phenophase periods, their concentration, seasonality, and duration, and Spearman correlations were used to test the relationships between meteorological variables during the period and the phenophases. The patterns of budding, senescence, flower bud, and flowering phenophases of H. martiana were seasonal, with an annual periodicity and a continuous fruiting pattern. The average dates of occurrence of the budding phenophase were August (area 2), October (areas 1, 4, and 5), and November (area 3). The average date for senescence was July (area 2) and August (areas 1 and 3–5). The average date for the flower bud phase was November (area 5) and December (areas 1–4). Flowering occurred in January (areas 3 and 4), March (area 2), and December (areas 1 and 5). Rainfall and temperature had a significant impact on the period and occurrence of vegetative and reproductive phenological events in H. martiana. Under highland marsh conditions, H. martiana fruit should be collected in October, November, and December.
The purpose of this study is to analyze the genetic and residual variability of the grain yield trait in Coffea canephora using the Bayesian multi-trait model. Thirty-six varieties of conilon coffee were used. The design was randomized blocks, with three replications, nine plants per plot. Data was analyzed using multi-trait Bayesian models with an arbitrary number of random effects, employing a Gibbs sampler. The covariance matrix of the random effects is assigned as a prior Inverse Wishart distribution. A total of 1,800,000 samples were generated, with a burn-in of 5,000 and a thin of 5 interactions, resulting in 1,795,000 samples. The broad-sense heritability, residual and genetic variations were calculated from the posterior distribution. The variance-covariance matrix for the genetic factor shows significant variability among the traits. The 95% credibility intervals for the variances and covariances are narrow, indicating accurate estimates. The data is adequate to provide reliable estimates, indicating significant genetic effects on most traits. The residual variance-covariance matrix reveals heteroscedasticity among the traits. According to the results, accurate estimates of broad-sense heritability obtained by the Bayesian methods can guide breeding programs, in addition to identifying traits with high genetic variability and potential for response to selection. The Bayesian approach provided robust and detailed estimates, aligning with previous studies and offering valuable insights for breeding programs.
Zinc is an essential micronutrient for both humans and plants. In humans, it plays a vital role in various biological functions, as a component of approximately 300 proteins, with a recommended daily intake of 15 mg. About one-third of the global population faces zinc deficiency. In plants, zinc is crucial for phytohormone and carbohydrate pathways. Biofortification of staple crops is an efficient and sustainable method for addressing zinc deficiency. Allium schoenoprasum L., commonly known as chives, is a promising candidate for zinc biofortification due to its widespread use in Brazil and ease of cultivation. This study determined the responsiveness of chives to agronomic biofortification with zinc and the impact of biofortification on biochemical and nutritional parameters. Zinc was applied via foliar fertilization at rates of 0.0, 0.25, 0.5, 1, 1.5, 3, 6, and 12 kg ha-1. The following parameters were assessed: fresh weight, shoot height, collar diameter, root and aerial part dry weight, and contents of selected sugars, free amino acids, macronutrients, micronutrients, chlorophylls, carotenoids, flavonoids, and phenolics. Linear regression and analysis of variance were performed using SigmaPlot software. The application of 6 kg ha⁻¹ resulted in a 248% increase in the zinc content and an average increase of 34% in nitrogen, phosphorus, potassium, calcium, magnesium, manganese, sulfur, copper, and boron compared to the control. An application rate of 0.5 kg ha⁻¹ led to a 26% average increase in plant growth. Thus, 6 kg ha⁻¹ of zinc is recommended for biofortifying Allium schoenoprasum L., as this concentration significantly increased the zinc content without severely impacting plant growth.
Various techniques have been employed to assess the stability and adaptability of crops, where mixed models or BLUP-based indexes like WAASB proving particularly more benefit. We introduce rYWAASB, an open-source R package designed to offer a novel index for quantifying both stability and performance of a biological trait. It quantifies the stability and performance of individuals/genotypes e.g. in plant breeding programs. It simultaneously considers the trait of interest, along with the WAASB index in a new perspective. The package then provides bar plots, PCA diagrams, and optimum cluster number estimate and cluster categorization by MCMC algorithms. For executing the package, a field experiment was conducted on chickpea (Cicer arietinum L.) from 2018 to 2020, evaluating the grain yield and days to maturity in rainfed conditions. The genotypes have put in 7 clusters for grain yield while genotypes 18, 69, and 5 were the most stable, exhibiting the highest grain yields, but genotypes 2, 103, 27, and 88 are identified as the earliest ripening varieties, exhibiting a higher degree of stability. The findings highlighted the effectiveness of the novel rYWAASB index in distinguishing observations in the experiment, suggesting its potential application in agronomic and plant breeding stability and adaptability programs.
Agrobiodiversity can promote food and nutritional security. Agrobiodiverse agricultural systems are frequently found on small family coffee farms with distinct economic, social, and environmental characteristics in Central and South America. Brazil is the world’s largest coffee producer, with the state of Minas Gerais, especially the Zona da Mata mesoregion, being the country’s leading producer, recognized for its small mountainous family coffee farms. The presence and composition of home gardens in Brazilian family coffee farms still lack objective and measurable assessments of species agrobiodiversity. Given the limited knowledge about agrobiodiversity at these properties, this study aimed to: (i) evaluate plant communities and agrobiodiversity in the home gardens of family coffee farms in Zona da Mata of Minas Gerais State, Brazil; and (ii) document the use of plant species in these home garden communities. Evaluations were conducted in the home gardens of five family coffee farms located in the Zona da Mata region of Minas Gerais State, Brazil, with identification, quantification, and determination of Simpson, Shannon–Wiener, Pielou’s equitability, Morisita, alpha diversity, species–individual curve, and species use indices across 0.1-ha plots per farm. Significant variations in the number of individuals were recorded with the presence of fruit-bearing and vegetable species in the evaluated home gardens. There were notable differences in species compositions and agrobiodiversity indices of the home gardens of family coffee farms. Considerable plant diversity and species richness were observed in all home gardens, primarily associated with food, commercial, medicinal, and ornamental uses, contributing to the social function of the land and the preservation of plant diversity.
Approximately 85000 hectares of popcorn, which is a C4 glycophytic and salt-sensitive crop, is cultivated in Brazil. Agricultural land area is decreasing because of increasing population and salinity stress, leading scientists to devise a means to develop salt-tolerant crops using genetic approaches. This study was carried out to determine the most suitable NaCl concentration for screening popcorn inbred lines for salt tolerance. Four NaCl solutions (0, 60, 120, and 180 mmol L-1) were used on four popcorn inbred lines in a completely randomized design. The experimental treatments were replicated four times in a seed-germinating chamber over seven days. Twenty-five seeds from each line were treated with Maxim® before being placed on germination paper and soaked in an appropriate NaCl solution. Significant (p < 0.05) responses of the inbred lines to different NaCl concentrations in terms of shoot length, root length, fresh and dry shoot and root weight, root diameter, root surface area and germination percentage were observed. The salt tolerance index based on dry seedling weight was significantly correlated with the other traits under 60 and 120 mmol L-1 NaCl. The most concentrated NaCl solution (180 mmol L-1) resulted in the greatest reduction in the performance of the inbred lines, indicating that NaCl is toxic to the inbred lines evaluated. Regression analysis indicated that shoot length and root length are the most significant traits for assessing salt stress tolerance in popcorn inbred lines. The results suggest that NaCl solutions of 60 and 120 mmol L-1 could be used for screening salt tolerance in popcorn, as these provide a strong ability to distinguish among the inbred lines studied.
This study aimed to correlate the developmental stages of the embryo sac with the morphometric traits of spikelets and to characterize the expression of the BbrizRan, BbrizSti1, and BbrizAGL6genes in Urochloa ruziziensis(sexual) and U. decumbens(apomictic). Data on the length and diameter of spikelets and anatomical sections were also obtained. Gene expression was determined using RT-qPCR in spikelets at megasporogenesis and megagametogenesis. The spikelet length could be used as a reliable morphological marker to discriminate between the two stages in both species. The embryo sacs observed were of the Polygonumtype in U. ruziziensisand the Panicumtype in U. decumbens. RT-qPCR analysis revealed that the BbrizRan, BbrizSti1, and BbrizAGL6genes were differentially expressed in the studied species during reproductive development. The BbrizSti1gene was more highly expressed in U. decumbens(apomictic) than in U. ruziziensis(sexual) during megasporogenesis, while for BbrizRan, U. decumbensshowed higher expression than U. ruziziensis during both megasporogenesis and megagametogenesis. An increase in the expression level of BbrizAGL6was observed in both species at both developmental stages ofthe embryo sac
The replacement of native vegetation with nonnative vegetation for different land uses, which is a consequence of the intensification and expansion of agricultural production, significantly alters the dynamics of soil organic fractions. The aim of this study was to evaluate the changes in carbon and nitrogen contents and stocks, as well as the chemical fractions of organic matter, caused by different land uses in Cerrado areas. The selected areas were conventional tillage (CTS), no-tillage (NTS), eucalyptus cultivation (EC) and native Cerrado vegetation (NC) in the regions of Barreiras and Luis Eduardo Magalh & atilde;es, Bahia State, Brazil. The highest carbon contents and stocks were found under NTS up to 10 cm, and these values, as well as those of EC, were equal to those found under NC below 10 cm. The same phenomenon was not verified for the nitrogen contents and stocks in the soil up to 20 cm deep. The values of carbon in the fulvic acid fraction (C-FAF) under NTS and EC were equal to those of NC up to 10 cm deep, but only EC was equal to NC below this layer. At the 10-20 cm depth, the C-FAF increased by 1.23 gkg(-1) and 0.95 gkg(-1 )under NTS compared with those under EC and NC, respectively. With respect to the correlations between carbon fractionation and total organic carbon, the nonextractable humic fraction (C-HUM) had the strongest correlation with the TOC content, with r(2) = 96 (p < 0.001). Overtime, the input of residues in the NTS and EC areas contributed to increasing soil carbon stocks and organic matter quality, with a recovery of up to 84% of the carbon in humin.
Rice is a staple food for more than half of the world's population. In Brazil, upland rice cultivation in the southeastern region faces competition from soybean due to its higher profitability in recent years. In this context, developing more competitive rice lines and expanding the sowing window, such as incorporating rice into the second season, can enhance its integration into cropping systems. This study aimed to evaluate the performance of elite upland rice lines under different sowing dates during the second crop season. Field experiments were conducted in Lavras, Minas Gerais State, Brazil, across 4 sowing dates in 7-day intervals, starting on January 28, 2022. Eight genotypes were evaluated in a randomized block design with a two-way factorial scheme (8 genotypes & times; 4 sowing dates). The assessed traits included the number of days to flowering (NDFL), plant height (PH), tolerance to Helminthosporium oryzae, and grain yield (GY). The data were analyzed using mixed models based on the restricted maximum likelihood/best linear unbiased predictor. The results revealed significant genetic variability for NDFL and PH as well as significant sowing date effects on NDFL, PH, and GY. A sharp decline in performance was observed across sowing dates, with an increase of 24 days in NDFL, a 14% reduction in PH, and sterility rates reaching 100% at the last sowing. These findings highlight the importance of genotype selection and optimal sowing timing to sustain upland rice production during the second crop season.
The storage of soybean seeds is a critical aspect of the production process, making it essential for genotypes to show tolerance during this phase to maintain seed quality. This study aimed to examine and correlate lignin content in the seed coat, enzyme activity expression, and morphoanatomical characteristics of soybean cultivars with the preservation of physiological quality and storage tolerance. Eight soybean cultivars were selected, produced, and harvested under uniform edaphoclimatic conditions. Physiological quality assessments were conducted at six storage intervals: 0, 60, 120, 180, 240, and 360 days. Evaluations included tests for germination, emergence, accelerated aging, electrical conductivity, and lignin content in the seed coat. Additionally, biochemical and enzymatic analyses of antioxidant metabolism and morphoanatomical examinations were performed using light microscopy on seeds stored for 0 and 360 days. The experiment used an 8 & times; 6 factorial arrangement, encompassing eight cultivars and six storage periods. For the enzymatic and morphoanatomical analyses, a 4 & times; 2 factorial design was employed, involving four cultivars and two storage durations. The results showed that genotype significantly influenced the tolerance of soybean seeds to extended storage periods. Seeds proving high physiological quality and storage resilience exhibited reduced hydrogen peroxide accumulation and diminished lipid peroxidation. Furthermore, morphoanatomical analyses provide a promising method for selecting genotypes with enhanced physiological quality and storage tolerance.
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 Piau & iacute; State, Brazil. Data were collected from the experimental field of the Brazilian Agricultural Research Corporation (Embrapa Mid-North) in Teresina, Piau & iacute; 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 (R-2) 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; R-2 values ranging from 0.87 to 0.93 and NSE values ranging from 0.62 to 0.67 for intercropping cultivation of signalgrass; R-2 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 R-2 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.
