BRS Tumucumaque Research Articles

Arbuscular mycorrhizal fungi in the rhizosphere of soybean in integrated crop livestock systems with intercropping in the pasture phase

Arbuscular mycorrhizal fungi (AMF) are important microorganisms that act as sensitive soil quality indicators. The increase in plant diversity in Integrated Crop Livestock Systems under no-tillage (ICLS-NT) can also alter the diversity of species of fungi and bring benefits to the system. This study had the objective of evaluating the AMF diversity and its quantitative characteristics in ICLS-NT with intercrop in the pasture phase. The experiment was conducted in a dystrophic red latosol, with plots represented by the grasses Panicum maximun cv. BRS Tamani and Urochloa brizantha cv. Piatã, intercrop with the legumes (subplots): cowpea (Vigna unguiculata) cv. BRS Tumucumaque, pigeon pea (Cajanus cajan) cv. BRS Mandarim and single grass type only. The potential for inoculation was elevated in areas with legume intercrop, with either grass, and about 29% higher in areas with the C. cajan/P. maximun consortium. They may be associated with the benefits that the intercrop with legumes brings, through the relationship of rhizobia and AMF. The spore density and mycorrhizal colonization were higher with the use of grass from the genus Urochloa in relation to Panicum, reaching 92% and 88% higher, respectively, as well as an increase in species richness, being associated with a greater affinity of AMF with intercropped grasses. The insertion of the legumes into the intercrop with the grasses affected soybean productivity, positively correlating (74%) with mycorrhizal colonization. These results are related to the fact that intercrop promote the release of a high diversity of organic compounds, helping in the activity of soil microbiota, including AMF, increasing colonization and species diversity of these fungi. Thus, intercrops of grasses with legumes affected positively the activity and diversity of species of the AMF, reflecting in the increase in productivity of the soybean crop.

Analysis of the phenotypic adaptability and stability of strains of cowpea through the GGE Biplot approach

The cowpea is produced in different environmental conditions in several regions of Brazil. It is crucial to select and develop cultivars that attend to the regional requirements with high productivity, adaptability, and stability, due to the interaction between the genotype and the environment. This research aimed to select strains of cowpea for the simultaneous presence of high genotypic productivity, adaptability, and stability in the North-eastern region of the state of Rio de Janeiro (Brazil) by the GGE-Biplot method. The study assessed 27 genotypes: 23 strains and four cultivars, in six environments of the North-eastern region of the state of Rio de Janeiro, during the years 2016, 2017, and 2018. The experimental design was a randomized block design with four repetitions. The GGE-Biplpot method assessed the genotypic adaptability and stability, by the use of the statistical software R. The interaction between the environment and the genotypes was complex, and the general average for the productivity of the grains was 1231.98 kg/ha. GGE-Biplot method was efficient in identifying the best strains to be suggested for the use in the North-eastern region of the state of Rio de Janeiro. The strains (9), (3), and (6) were classified as ideotypes due to their superior performance compared to the general average, and their stability. Their performance overcame the control cultivars BRS Tumucumaque, BRS Imponente, BRS-Itaim e CB-27.

Dead Cover and Agronomic Characteristics of Cowpea

Dead cover, or mulch, consisting of plant residues, plays an important role for the success of diverse agricultural crops, working as an insulating layer protecting the soil from daytime temperature variations and maintaining the soil moist and rich in organic matter. Cowpea is a source of proteins, carbohydrates, vitamins and minerals. Its importance in the North, Northeast and Midwest regions of the country is associated with economic and social aspects, since it is an important food for low-income populations, supplying their nutritional needs. This study was carried out under greenhouse conditions in Manaus, state of Amazonas, with the purpose of assessing the effect of different dead covers on the agronomic characteristics of cowpea cultivars. It consisted of a completely randomized design in a 4 × 4 factorial arrangement. The treatments comprised four cowpea cultivars (BRS Caldeirão, BRS Tumucumaque, BRS Guariba and BRS Tracuateua) and three species of cover plants (Brachiaria decumbens, Brachiaria ruziziensis and Mucuna pruriens) and one control treatment, without soil cover, in a total of 16 treatments, with four replications and two plants per experimental unit. Analysis of variance was applied to the data, and the means were compared by the Scott-Knott’s test at 5% probability level. The following characteristics were examined: number of pods per plant, pod length, number of seeds per pod, weight of shoot dry matter, and grain yield. Mulching provided better results for all characteristics assessed in the four cultivars when compared to the control. BRS Caldeirão is the recommended cultivar for the state of Amazonas and the other regions with similar edaphoclimatic characteristics (high air temperature, rainfall, air humidity, and low-fertility tropical soils) because it exhibited the greatest number of pods per plant, number of seeds per pod, shoot dry matter, and the highest average grain yield (Freire Filho et al., 2011; Souza et al., 2016).

Resistance of Cowpea Genotypes to Spodoptera frugiperda (Lepidoptera: Noctuidae) and Its Relationship to Resistance-Related Enzymes.

Spodoptera frugiperda (J.E. Smith) can attack cowpea plants (Vigna unguiculata [L.] Walp.) (Fabales: Fabaceae) in any growth stage but attacks primarily in the first days after plant emergence, when the plants are more sensitive to defoliation. This study was carried out to evaluate the resistance to S. frugiperda in six cowpea genotypes, of which four were cultivars (BRS Tapahium, BRS Tumucumaque, Fradinho, and Miranda), and two were landraces (Juti and Nioaque), in three different experiments. In the first experiment, adult emergence, adult weight, adult longevity, larva to adult period, numbers of injured leaves per plant canopy (upper, middle, and lower), and reduction in plant dry matter were assessed. In the second experiment, the oviposition preference of S. frugiperda for the different cowpea genotypes was evaluated under free-choice conditions. In the third experiment, levels of peroxidase (POD), superoxide dismutase (SOD), and protein content in cowpea leaves were assessed. Insects fed on landrace Juti plants showed low adult emergence, yielded a lower fitness index, and caused less plant dry matter reduction. In addition, plants of landrace Juti were less preferred for oviposition. Overall, Juti plants showed higher resistance levels in all three resistance categories and higher levels of POD and SOD in S. frugiperda injured leaves, in addition to a lower protein content. Juti will be tested in field conditions, followed by molecular characterization. This will provide additional information about its potential as an S. frugiperda resistance source in plant breeding programs.

Comportamento de genótipos de feijão-caupi (Vigna unguiculata L. Walp., Fabaceae) sob infestação de Empoasca sp. (Hemiptera: Cicadellidae) e Liriomyza sp. (Diptera: Agromyzidae) em Redenção, Ceará, Brasil

O feijão-caupi (Vigna unguiculata L. Walp.) é uma fabácea utilizada como fonte alimentar em diversos países da África, Ásia e Américas. Objetivou-se, com esta pesquisa, avaliar o comportamento de genótipos de feijão-caupi ao ataque de cigarrinha-verde (Empoasca sp.) e de minador (Liriomyza sp.). O experimento foi conduzido na Fazenda Experimental Piroás da Universidade da Integração Internacional da Lusofonia Afro-Brasileira (Unilab), nos meses de agosto a outubro de 2018, onde se utilizou o delineamento experimental em blocos ao acaso, com 15 tratamentos e quatro repetições. Para a cigarrinha, foi avaliado o número de indivíduos por planta na parcela útil, aleatoriamente, uma vez na semana, ao longo de nove semanas. Já para a minadora, foi avaliada a frequência de minas, na parcela útil e ao acaso, ao longo de quatro semanas. Os dados acumulados na última amostragem foram transformados [(x + 0,5)1/2] e submetidos à análise de variância, sendo as médias comparadas pelo teste Scott-Knott. Os genótipos BRS Juruá, BRS Marataoã, Rabo de Soin, BRS Guariba, BR 17 Gurguéia, BRS Xiquexique, BRS Potengi, BRS Aracê, BRS Cauamé, BRS Imponente, BRS Itaim, BRS Tumucumaque e Vita-7 foram menos suscetíveis ao ataque de Empoasca sp., enquanto que BRS Aracê, Rabo de Soin e Vita-7 foram menos atacados por Liriomyza sp.

PRODUCTION PERFORMANCE OF BRS TUMUCUMAQUE COWPEA UNDER DIFFERENT PLANT DENSITIES AND WATER REGIMES1

ABSTRACT Cowpea is a legume of great socioeconomic importance for the North and Northeast regions of Brazil. However, studies to evaluate its production performance when cultivated under irrigated regime and under different plant densities are necessary. The objective of this work was to evaluate the effects of different water regimes and different plant densities on grain yield, production components and water use efficiency, and on the correlation between grain yield and production components of BRS Tumucumaque cowpea cultivar. The experiment was carried out at Embrapa Meio-Norte experimental area, in Teresina, Piauí State, Brazil, from June to September 2017, in an Argissolo Vermelho-Amarelo eutrófico (Ultisol). A randomized complete block design was used, in a split-plot scheme with four replicates, in which the water regimes occupied the plots (187.7; 233.5; 263.5 and 288.7 mm) and plant densities, the subplots (12; 16; 20 and 24 plants m-2). The number of pods per plant, number of pods per square meter, pod length, dry grain yield and water use efficiency were evaluated. The maximum dry grain yield reached was 1,694.46 kg ha-1, with application of 288.7 mm and density of 20.4 plants m-2. The production component number of pods per square meter was the most correlated with dry grain yield.

Identification and Quantification of Phenolic Compounds in Grains of Biofortified Cowpea Cultivars, Before and After Cooking

Objective:This study aimed to identify and quantify phenolic compounds in the grains of biofortified cowpea (Vigna unguiculata) cultivars before and after cooking.Methods:We analyzed two cultivars of genetically improved cowpeas, namely BRS Aracê and BRS Tumucumaque. Raw and cooked samples of the cultivars were analyzed (in triplicate). The concentrations of phenolics, flavonoids, anthocyanins, and flavanols, as well as the antioxidant activity, were determined. Phenolic compounds were identified and quantified using high-performance liquid chromatography.Results:Grains of cultivar BRS Tumucumaque had higher concentrations of total phenolic compounds before (297.23 ± 4.24 (mean ± standard deviation) mg/100 g) and after (147.15 ± 6.94 mg/100 g) cooking, and higher concentrations of total flavonoids before (49.36 ± 2.02 mg/100 g) and after (23.97± 0.67 mg/100 g) cooking. Anthocyanins were not measured in the grains of either cultivars. There was a statistically significant reduction in the concentration of total flavanols after cooking, with the greater retention in BRS Aracê. Similarly, the antioxidant activity was significantly reduced after cooking, with greater reductions in BRS Tumucumaque than in BRS Aracê. Five phenolic acids were identified and quantified, including gallic, caffeic, and ferulic acids.Conclusion:We conclude that cooking affected the concentrations of phenolic compounds in the cultivars, as well as the antioxidant activity exhibited by these cultivars. The cultivars contained beneficial compounds that can contribute to disease prevention and health maintenance.

Chlorophyll fluorescence as a tool to select salinity-tolerant cowpea genotypes

The use of saline water reduces the growth and productivity of crops, so the need for techniques that make possible the use of this resource such as the use of salinity tolerant genotypes and efficient selection methods are of great importance. Thus, this study aimed to evaluate the tolerance of cowpea (Vigna unguiculata L. Walp.) genotypes to salt stress, through the chlorophyll fluorescence analysis. The experiment was conducted in a protected environment at the Federal University of Campina Grande, Paraíba, Brazil, using a completely randomized design in a 2 x 10 factorial arrangement, with three replications, consisting of two levels of irrigation water salinity (0.6 and 5.1 dS m-1) and ten cowpea genotypes: (G1: MNCO1-649F-2-1, G2: MNCO3-736F-2, G3: PINGO DE OURO-1-2, G4: BRS GURGUÉIA, G5: BRS MARATAOÃ, G6: MNCO2-676F-3, G7: MNCO2-683F-1, G8: MNCO3-737F-5-4, G9: MNCO3-737F-5-9, and G10: BRS TUMUCUMAQUE). The stem length, stem diameter, SPAD index, and chlorophyll fluorescence transients were evaluated. The G2 and G4 genotypes had the lowest reductions in the growth, stem diameter, initial fluorescence, and primary and maximum photochemical efficiency of PSII, proving to be tolerant to salinity. Chlorophyll fluorescence is a tool that can be used in the selection of salinity-tolerant cowpea genotypes.

Arbuscular mycorrhizal fungi in integrated crop livestock systems with intercropping in the pasture phase in the Cerrado

Integrated crop livestock systems under no-tillage (ICLS–NT) with intercropping in the pasture phase can be an alternative for improvements in soil quality, with possible changes in the dynamics of arbuscular mycorrhizal fungi (AMF). This study was aimed at evaluating the diversity of AMF and their quantitative characteristics in ICLS–NT with intercropping between grasses and legumes in the pasture phase of the Cerrado of Mato Grosso, Brazil. The experimental area is located in Itiquira, MT, at Gravataí farm, on a dystrophic Red Latosol. The experimental design was a randomized block design in a split-plot arrangement and three replications, totaling approximately 60 ha. Plots were represented by the grasses Urochloa ruziziensis and Urochloa brizantha cv. BRS Paiaguás intercropped with the legumes (subplots) cowpea (Vigna unguiculata) cv. BRS Tumucumaque, pigeon pea (Cajanus cajan) cv. BRS Mandarin, and grasses in monoculture. Spore density AMF was not influenced by cropping systems. The intercropping with legumes influenced mycorrhizal colonization AMF and inoculum potential in relation to monocropping. The highest diversity of species AMF occurred when grasses were intercropped. The highest yield was observed in the grass U. ruziziensis, regardless of the intercropping. In general, the intercropping of grasses and legumes positively influenced the mycorrhizal colonization, inoculum potential, diversity of AMF species, and yield of the evaluated grasses.

Periods of water deficit after sowing cowpea

The study aimed to evaluate the germination and initial growth of semi-erect cowpea cultivars as a function of water shortfall. The experiment was conducted in experimental area of Federal University of Mato Grosso state, Brazil. Was evaluated the germination rate, foliar area, shoot and root dry matter production and diameter of the stem of the BRS Nova Era, BRS Tumucumaque and BRS Imponente, in function of four different water shortfall (0; 4; 8 and 12 days without water. The experiment delineation adopted was a factorial design 3 x 4. The cultivars BRS Tumucumaque had a higher number to sprouting seeds, shoot and root dry mass production and diameter of the stem. Perhaps the cultivar BRS Tucmucumaque had a growth sharp decline with 12 days in water shortfall.

Physiological Quality of Cowpea Beans (Vigna unguiculata L.) Seeds in the Function of Cultivars and Planting Times

Germination and vigour evaluation of improved cultivars and creole of cowpea bean seeds as a function of different planting seasons. A completely randomized design in a factorial scheme, with six treatments and two planting periods, with four replications, each repetition with 25 seeds. The treatments consisted of six cowpea bean (Vigna unguiculata L.) cultivars, and two improved (BRS Tumucumaque, BRS Guariba) and four creoles, (Governor, Passagem, Chico Joaquim and Espírito Santo). The experiment place and timing was carried out under greenhouse on a riparian zone of the Federal Rural Semi-Arid University (UFERSA), located in the municipality of Mossoró-RN, Brazil. The first sowing season comprised the period from April 3 to April 18, 2017, and the second one from January 15 to 30, 2018. The sowing was done in plastic trays. Was used the sand washed and sterilized as a substrate. The trays were kept in a greenhouse at room temperature. Two irrigations were realized daily. In order to avoid the local effect, the trays were changed position each day. The evaluated characteristics were: Germination percentage, emergence speed index, seedling height, leaf number, root length, stem diameter, fresh and dry mass of seedlings. Creole cultivars showed superior quality to those improved in the second season. In the first season, the cultivars BRS Guariba and BRS Tumucumaque were the most outstanding. It was concluded that the physiological quality of cowpea beans is directly influenced by the cultivars and the planting season, as well as by the interaction of these two factors.

Bromatological characteristics of the cowpea in the resistance to Callosobruchus maculatus

This work aimed to relate the bromatological characteristics of four cowpea cultivars to the preference and development of Callosobruchus maculatus. For this, oviposition preference, choice and no-choice tests were performed in four cowpea genotypes: Bico de Ouro, BRS Novaera, BRS Guariba and BRS Tumucumaque. In the no-choice test were determined: viability of eggs, duration of the immature stage, biological cycle, viability of the immature stage, population growth rate, weight per insect, biomass consumption and consumption per insect. As to the chemical composition, the seeds were characterized concerning the crude protein content, ash, neutral detergent fiber, acid detergent fiber and organic matter. In the evaluation, there were significant differences within the genotypes, except for the viability of eggs and consumption per insect. The BRS Novaera genotype presented antixenosis resistance to C. maculatus, whereas the Bico de Ouro, BRS Guariba and BRS Tumucumaque genotypes revealed to be susceptible. The chemical composition of the seeds affects the development of C. maculatus, and the crude protein and ash contents of the seeds without integument present a positive influence over the insect development.

Simultaneous selection for yield, adaptability, and genotypic stability in immature cowpea using REML/BLUP

Abstract: The objective of this work was to select cowpea genotypes simultaneously for high yield of immature grains, adaptability, and genotypic stability, taking into account genotype x environment interactions. The mixed models restricted maximum likelihood (REML)/best linear unbiased prediction (BLUP) were used. Sixteen cowpea genotypes were evaluated in nine environments, consisting of a combination of location (Pentecoste in the state of Ceará, Acaraú in Ceará, Teresina in Piauí, and Mossoró in Rio Grande do Norte, Brazil) and year (2012, 2013, 2014, 2015, and 2017). In all trials, a randomized complete block design with four replicates was used. Significant differences were observed for effects of genotypes and the genotype x environment interaction. Environmental variance was the largest component of phenotypic variance, followed by the genotype x environment interaction and genotypic variances. The immature grain yield of the evaluated cowpea genotypes interacts strongly with the studied environments, resulting in a low genotypic correlation between environments. The MNC00-595F-27, MNC05-847B-123, and BRS Tumucumaque cowpea genotypes present high yield of immature grains, adaptability, and genotypic stability, being the most suitable for cultivation in the states of Ceará, Piauí, and Rio Grande do Norte or in other environments with similar soil and climatic conditions.

RESPOSTA DO FEIJÃO-CAUPI À INOCULAÇÃO DE Bradyrhizobium japonicum, ADUBAÇÃO NITROGENADA E NITROGÊNIO DO SOLO

O feijão-caupi é uma importante cultura agrícola, apresenta capacidade de associação com bactérias que fixam o nitrogênio atmosférico, podendo reduzir custos com fertilizantes. O objetivo no trabalho foi avaliar a produtividade e crescimento de feijão-caupi submetidos à inoculação de bactérias fixadora de nitrogênio (Bradyrhizobium japonicum), adubação nitrogenada e nitrogênio do solo. O experimento foi desenvolvido na Universidade Federal do Oeste do Pará, campus Santarém-Pará, nos meses de abril a julho de 2017, sob viveiro de mudas, em vasos, em delineamento inteiramente casualizado, com nove tratamentos de cinco repetições cada. Os tratamentos foram: uso de inoculante, adubação nitrogenada e nitrogênio do solo e três tipos de feijão-caupi, Manteiguinha, IPA 207 e BRS Tumucumaque, as variáveis avaliadas foram, diâmetro do caule (DC), comprimento de planta (CP), número de grãos por vagem (NG) e produtividade por hectare (PG). Não houve diferença significativa para as variáveis DC, CP, NG e PG. O Manteiguinha apresentou maiores valores de CP e PG, que foi 1869,5 kg ha-1 quando submetido à adubação nitrogenada. O IPA 207 apresentou menor PG quando inoculada e maior PG com o uso da adubação nitrogenada que foi 2586,1 kg ha-1. Para o BRS Tumucumaque maior CP foram obtidos no tratamento que usou o nitrogênio do solo, no entanto nesse tratamento a PG foi a menor entre os tratamentos, maior produtividade foi obtido pelo uso da inoculação que foi de 2499,9 kg ha-1. A inoculação de Bradyrhizobium japonicum é eficiente para BRS Tumucumaque e ineficiente para IPA 207 em relação à produtividade. PALAVRAS-CHAVE: Fixação biológica de nitrogênio, Fertilidade, Produtividade.

Soil quality and soybean productivity in crop-livestock integrated system in no-tillage

Abstract: The objective of this work was to evaluate the quality of the soil and its relation with soybean (Glycine max) yield in an integrated crop-livestock system (ICLS), with intercropping between grasses and legumes in the pasture phase. The experiment was carried out in the state of Mato Grosso, Brazil, on a dystrophic Oxisol, in which grasses (Megathyrsus maximus 'BRS Tamani' and Urochloa brizantha 'BRS Piatã'), intercropped with cowpea (Vigna unguiculata 'BRS Tumucumaque') and pigeon pea (Cajanus cajan 'BRS Mandarim'), were cultivated after soybean harvest. A randomized complete block design was used, with three replicates, in a split-plot arrangement, in which grasses were considered as plots, and legumes as subplots. Legume intercrops provided increases of C and total N stocks. The intercrops caused the increase of C and N of the microbial biomass, whereas the single cultures contributed to stress in the soil microbiota. The activity of the urease enzyme was sensitive to management changes in the short term, but acid phosphatase and β-glucosidase were poorly sensitive indicators. Soil quality is high with intercropping between grasses and legumes, with positive effects on soybean grain yield.

Sowing Date Effects on Cowpea Cultivars as a Second Crop in Southeastern Brazil

Core Ideas Cowpea sowing until early March has potential as an alternative second crop in southeastern Brazil. Seed yield up to 2746 kg ha−1 was obtained with early February sowing. Lower temperature at pre‐flowering period with sowing delay was the main factor increasing cowpea cycle and decreasing seed yield. Cultivar ranking varied across sowing dates and growing seasons. In southeastern Brazil, there has been increasing interest in cowpea [Vigna unguiculata (L.) Walp.] cultivation as a second crop. A three‐year study was conducted to evaluate the growth, seed yield, and seed protein of cowpea cultivars (BRS Cauamé, BRS Guariba, BRS Itaim, BRS Novaera, BRS Potengi, BRS Tumucumaque, and BRS Xiquexique) as affected by sowing date (from early February to late April) in Botucatu, Brazil. Delay in sowing, especially after early March, delayed the emergence and flowering and increased the cycle of the cowpea cultivars. On average, each day of sowing delay increased the crop cycle by 0.82 d because of the decreasing temperature. The delay in sowing from late March drastically reduced the aboveground dry matter biomass, numbers of lateral branches and pods per plant, 100‐seed weight, and seed yield of cowpea cultivars. There was great variation in the seed yield across growing seasons, but the earliest sowing date (early February) resulted in the greatest seed yields, which could reach up to 2746 kg ha−1. Sowing dates until early March provided sustainable seed yields (on average >800 kg ha−1). Cultivar ranking varied across sowing dates and growing seasons, but with sowing dates from early February to early March, the cultivars BRS Cauamé, BRS Guariba, BRS Novaera, and BRS Potengi were the most productive. Sowing dates later than early March also reduced the crude protein content in the seeds of cowpea cultivars. Cowpea has potential as an alternative second crop in southeastern Brazil since it can be sown until early March.

Demographic parameters of cowpea aphids on advanced semi-erect cowpea lines

Abstract: The objective of this work was to evaluate the resistance of advanced semi-erect cowpea (Vigna unguiculata) lines, by means of a screening assay for resistance and the elaboration of fertility-life tables of Aphis craccivora (Hemiptera: Aphididae). The experiments were carried out in a screenhouse. For the resistance trial, 15 advanced cowpea lines were used, as well as two standard genotypes for resistance and two for susceptibility, which were arranged in six blocks. After resistance was determined, two lines with the highest and lowest resistance were selected for the development of the fertility-life tables which were used to estimate demographic parameters. The MNCO4-762F-03 and MNCO4-762F-09 cowpea lines were classified as resistant, for which cowpea aphids showed the lowest values (in parentheses, respectively) for: net reproductive rate (RO = 3.0 and 2.5), intrinsic rate of increase (rm = 0.16 and 0.15), and finite rate of increase (λ = 1.18 and 1.16). The highest values were obtained for the 'Vita-7', MNCO4-795F-168, and 'BRS Tumucumaque' genotypes. The MNCO4-762F-03 and MNCO4-762F-09 lines show antibiosis-type resistance, which directly affects the reproductive potential of the cowpea aphid population.

Morphophysiological biometry and grain production in cowpea under different phosphorus levels

In tropical and semi-arid regions of Brazil, phosphorus is one of the most limiting elements of cowpea productivity. The aim of this study was to assess the effects of applying five phosphorus doses in the soil on morpho-physiological and production components in three improved cultivars of cowpea. The experiment was carried out at the São Fernando farm located in José de Freitas, PI, Brazil, in a Plinthosol with a low phosphorus content. The experimental design was complete randomized block design with four replications in a 5 × 3 factorial scheme consisting of five phosphorus doses (0, 60, 120, 180, and 240 kg P2O5 ha−1) and three improved cowpea cultivars (BRS Guariba, BRS Tumucumaque, and BRS Cauamé). No interaction was observed between cultivars and phosphorus doses for any of the assessed variables. The cultivar BRS Tumucumaque showed the highest value for one-hundred-grain weight (21.0 g) and, together with BRS Guariba, the highest value of pod length. An increment was observed in growth (stem diameter, main branch length, leaf area, and shoot dry matter) and production characteristics (number of pods per plant, number of grains per pod, one-hundred-grain weight, and grain production per plant) in response to increases in phosphorus doses. The dose of 183.1 kg P2O5 ha−1 provided the maximum technical grain yield, estimated at 2,023.3 kg ha−1.

Production components, grain yield and water use efficiency of irrigated cowpea

Cowpea cultivars, which are indicated for irrigated cropping, are recommended without proper assessment of their productive potential and water use efficiency in response to water regimes in the soil from different production environments. The aim of this study was to evaluate the production components, the yield performance and the efficiency of water use of cowpea cultivars in response to the application of irrigation depths under the soil and climate conditions of Bom Jesus, PI. The experiment was performed from June to August 2011 in a soil classified as sandy-textured Fluvic Neosol. The study was conducted in a randomized blocks design, with four replicates. The treatments were arranged in subdivided plots (irrigation depths in plots and cultivars in subplots). The cultivars BRS Aracê (semi-prostrate) and BRS Tumucumaque (semi-erect) were submitted to five irrigation depths (108.2, 214.7, 287.9, 426.1 and 527.7 mm). The number of pods per plant and the weight of one hundred grains are the main components related to grain yield. The cultivar BRS Tumucumaque presented a better yield performance (1697.2 kg ha-1) than the cultivar BRS Aracê (1233.8 kg ha-1), with the application of the irrigation depths of 527.7 and 522.4 mm, respectively. The highest water use efficiency (0.420 kg m-3) is obtained with the application of the irrigation depth of 108.2 mm in both cultivars.

POPULATION DENSITY ON COWPEA CULTIVARS WITH DIFFERENT GROWTH HABITS IN THE MATOPIBA REGION

ABSTRACT The aim of this study was to assess the productive performance of cowpea cultivars with different growth habits as a function of population density in the MATOPIBA region, Brazil. The experiments were carried out in Magalhães de Almeida, MA in the agricultural season 2014/2015. The cultivars BRS Itaim, BRS Tumucumaque, and BRS Pajeú, which present an erect, semi-erect, and semi-prostrate growth habits, respectively, were assessed. For the erect and semi-erect cultivars, a total of 8, 12, 16, 20, 24, and 28 plants m−2 were used whereas for the semi-prostrate cultivar, a total of 2, 6, 10, 14, 18, and 22 plants m−2 were used. The experimental design was a randomized block design with four replications and treatments composed of plant densities. Grain yield and number of pods per area presented a quadratic response to the increased plant density whereas a decreasing linear response was observed for the number of pods per plant. The maximum grain yield of erect, semi-erect, and semi-prostrate cultivars were 1,076 kg ha−1 (19.5 plants m−2), 1,252 kg ha−1 (18.7 plants m−2), and 755 kg ha−1 (14.5 plants m−2), respectively. The number of pods per area was the character that most correlated (P<0.01) with grain yield, regardless of the plant growth habit.