Hydrogen Peroxide Alleviates Salt Stress Effects on Gas Exchange, Growth, and Production of Naturally Colored Cotton

Cotton is one of the most exploited crops in the world, being one of the most important for the Brazilian Northeast. In this region, the use of irrigation is often necessary to meet the water demand of the crop. Water is often used from underground wells that have a large amount of salt in their constitution, which can compromise the development of crops, so it is vital to adopt strategies that reduce salt stress effects on plants, such as the foliar application of hydrogen peroxide. Thus, the objective of this study was to evaluate the effects of foliar application of hydrogen peroxide on the gas exchange, growth, and production of naturally colored cotton under salt stress in the semi-arid region of Paraíba, Brazil. The experiment was carried out in a randomized block design in a 5 × 5 factorial scheme, with five salinity levels of irrigation water-ECw (0.3, 2.0, 3.7, 5.4 and 7.1 dS m-1)-and five concentrations of hydrogen peroxide-H2O2 (0, 25, 50, 75 and 100 μM), and with three replicates. The naturally colored cotton 'BRS Jade' had its gas exchange, growth, biomass production, and production reduced due to the effects of salt stress, but the plants were able to produce up to the ECw of 3.97 dS m-1. Foliar application of hydrogen peroxide at the estimated concentrations of 56.25 and 37.5 μM reduced the effects of salt stress on the stomatal conductance and CO2 assimilation rate of cotton plants under the estimated ECw levels of 0.73 and 1.58 dS m-1, respectively. In turn, the concentration of 12.5 μM increased water-use efficiency in plants subjected to salinity of 2.43 dS m-1. Absolute and relative growth rates in leaf area increased with foliar application of 100 μM of hydrogen peroxide under ECw of 0.73 and 0.3 dS m-1, respectively. Under conditions of low water salinity (0.3 dS m-1), foliar application of hydrogen peroxide stimulated the biomass formation and production components of cotton.

Irrigation with saline water in the cultivation of mini watermelon under phosphate fertilization

The objective of this study was to evaluate the water status, photosynthetic pigments, and photochemical efficiency of mini watermelon plants under salt stress and phosphate fertilization. The experiment was conducted in pots under greenhouse conditions in Pombal, PB, Brazil. The experimental design used was randomized blocks in a 5 × 4 factorial scheme, with five levels of electrical conductivity of irrigation water - ECw (0.3, 1.3, 2.3, 3.3, and 4.3 dS m-1) and four doses of phosphorus (60, 80, 100, and 120% of the recommendation), with three replicates. The relative water content in the tissues decreased with the increase in ECw levels in all phosphorus doses, with decreases of 7.05, 7.81 and 8.83% per unit increase in ECw, in plants fertilized with 80, 100 and 120% P2O5. On the other hand, ECw levels increased electrolyte leakage, regardless of phosphorus doses of the recommendation. The synthesis of photosynthetic pigments and the quantum efficiency of photosystem II were inhibited by increasing water salinity from 0.3 dS m-1 in plants grown under phosphorus doses above 60% of the recommendation. Water salinity from 0.3 dS m-1 reduced chlorophyll b contents, initial, maximum, and variable fluorescence of mini watermelon plants, with a decrease of 11.86, 4.51, 4.53, and 4.54% per unit increment of ECw, respectively.

Morphology of 'Crioula' guava seedlings under irrigation with increasing salinity water and nitrogen/potassium fertilization

Several studies have been conducted evaluating the management of fertilizers as strategies to mitigate the deleterious effects of salt stress, so the objective of this work was to evaluate the quality of 'Crioula' guava seedlings under irrigation with water of different salinity levels and fertilized with combinations of nitrogen and potassium. The experiment was performed in a protected (screened) environment using a randomized block design and analyzed in a 5 × 4 factorial scheme, with four replicates, with the plot formed by two plants. The treatments were formed from the combination of the factor electrical conductivity of irrigation water (ECw 0.3, 1.1, 1.9, 2.7 and 3.5 dS m-1), with the factor combinations (C) of nitrogen (N) and potassium (K2O) doses, being C1 = 70% N + 50% K2O, C2 = 100% N + 75% K2O, C3= 130% N + 100% K2O and C4= 160% N + 125% K2O. The recommended dose of 100% N and K, respectively, was 541.1 mg N dm-3 soil and 798.6 mg K dm-3 soil. The combinations of N and K fertilization corresponding to 70% N + 50% K2O and 100% N + 75% K2O of the recommended doses promoted greater growth of 'Crioula' guava seedlings. Water with ECw of 2.1 dS m-1 promotes the formation of quality 'Crioula' guava seedlings.

Irrigation Strategies with Controlled Water Deficit in Two Production Cycles of Cotton

Water scarcity is one of the main abiotic factors that limit agricultural production. In this sense, the identification of genotypes tolerant to water deficit associated with irrigation management strategies is extremely important. In this context, the objective of this study was to evaluate the morphology, production, water consumption, and water use efficiency of colored fiber cotton genotypes submitted to irrigation strategies with a water deficit in the phenological phases. Two experiments were conducted in succession. In the first experiment, a randomized block design was used in a 3 × 7 factorial scheme, corresponding to three colored cotton genotypes (BRS Rubi, BRS Jade, and BRS Safira) in seven irrigation management strategies with 40% of the real evapotranspiration (ETr) varying the phenological stages. In the second experiment, the same design was used in a 3 × 10 factorial arrangement (genotypes × irrigation management strategies). The water deficit in the vegetative phase can be used in the first year of cotton cultivation. Among the genotypes, 'BRS Jade' is the most tolerant to water deficit in terms of phytomass accumulation and fiber production.

Production and Fiber Characteristics of Colored Cotton Cultivares under Salt Stress and H2O2

Salt stress reduces the yield and quality of colored fiber cotton production, but this problem can be mitigated by the foliar application of hydrogen peroxide in adequate concentrations. In this context, the objective of the present study was to evaluate the production and characteristics of fibers of naturally colored cotton cultivares under irrigation with low- and high-salinity water and leaf application of hydrogen peroxide. The experiment was carried out in a greenhouse under a randomized block design, arranged in 4 × 3 × 2 factorial scheme, corresponding to four concentrations of hydrogen peroxide (0, 25, 50, and 75 μM), three cultivares of colored fiber cotton ('BRS Rubi', 'BRS Topázio', and 'BRS Verde'), and two electrical conductivities of water (0.8 and 5.3 dS m^-1), with three replicates and one plant per plot. Irrigation with water of 0.8 dS m^-1 associated with a foliar application of 75 μM of hydrogen peroxide favored the lint and seed weight, strength, micronaire index, and maturity of 'BRS Topázio'. The 'BRS Rubi' cotton cultivar showed higher tolerance to salinity, followed by the 'BRS Topázio' and 'BRS Verde' cultivares regarding the yield of seed cotton weight, with reduction below 20% under water of 5.3 dS m^-1.

NPK Accumulation, Physiology, and Production of Sour Passion Fruit under Salt Stress Irrigated with Brackish Water in the Phenological Stages and K Fertilization

This research aimed to evaluate the effects of salt stress, varying the phenological stages, and K fertilization on NPK concentrations, physiology, and production of Passiflora edulis Sims. The research was carried out at the University Farm of São Domingos, Paraíba, Brazil, using a randomized block design with a 6 × 2 factorial arrangement. Six irrigation strategies were evaluated (use of low electrical conductivity water (0.3 dS m^-1) during all stages of development and application of high-salinity water (4.0 dS m^-1) in the following stages: vegetative, flowering, fruiting, successively in the vegetative/flowering, and vegetative/fruiting stages) and two potassium levels (207 and 345 g K₂O per plant), with four replications and three plants per plot. The leaf concentrations of N, P, and K in the sour passion fruit plants found in the present study were below the optimal levels reported in the literature, regardless of the development stage and the cultivation cycle. The relative water content, stomatal conductance, and photosynthesis were reduced by salt stress in the first cycle. However, in the second cycle, irrigation with 4.0 dS m^-1 in the vegetative/flowering stages increased the CO₂ assimilation rate. Passion fruit is sensitive to salt stress in the vegetative/flowering stages of the first cycle. In the second cycle, salt stress in the fruiting stage resulted in higher production per plant.

CRESCIMENTO E PRODUÇÃO DE ALGODOEIRO DE FIBRA COLORIDA CULTIVADO EM SOLO SALINO-SÓDICO E ADUBAÇÃO ORGÂNICA

CRESCIMENTO E PRODUÇÃO DE ALGODOEIRO DE FIBRA COLORIDA CULTIVADO EM SOLO SALINO-SÓDICO E ADUBAÇÃO ORGÂNICA ADAAN SUDÁRIO DIAS1; REGINALDO GOMES NOBRE2; GEOVANI SOARES DE LIMA3; HANS RAJ GHEYI4 E FRANCISCO WESLEY ALVES PINHEIRO5 1Engenheiro Agrônomo – Pós-graduando em Engenharia Agrícola – Unidade Acadêmica de Engenharia Agrícola – Universidade Federal de Campina Grande/UFCG, Campina Grande, PB, Brasil, sudario_dias@hotmail.com;2Engenheiro Agrônomo – Doutor – Unidade Acadêmica de Ciências Agrárias – Universidade Federal de Campina Grande/UFCG, Pombal, PB, Brasil, rgomesnobre@yahoo.com.br;3Engenheiro Agrônomo – Bolsista do Programa Nacional de Pós-Doutorado, PNPD/CAPES,– Unidade Acadêmica de Engenharia Agrícola – Universidade Federal de Campina Grande/UFCG, Campina Grande, PB, Brasil, geovanisoareslima@gmail.com;4Engenheiro Agrônomo – Doutor – Núcleo de Engenharia de Água e Solo, UFRB, Cruz das Almas, BA. Brasil, hans@pq.cnpq.br;5Graduando em Agronomia – Unidade Acadêmica de Ciências Agrárias – Universidade Federal de Campina Grande/UFCG, Pombal, PB, Brasil;wesley.ce@hotmail.com. 1 RESUMO Os solos das regiões áridas e semiáridas podem naturalmente conter sódio trocável em teores suficientes para reduzir significativamente o desenvolvimento e a produtividade das culturas; entretanto, diversos métodos podem ser empregados na recuperação destes solos, sendo a aplicação de melhoradores químicos e material orgânico associado ao emprego de espécies vegetais tolerantes, o meio mais efetivo para amenizar este problema. Neste sentido, objetivou-se com esta pesquisa avaliar a tolerância do algodoeiro de fibra colorida, cv. BRS Topázio, cultivado em solos com distintos percentuais de sódio trocável (PST) e doses de matéria orgânica em experimento conduzido em condição de casa de vegetação do CCTA/UFCG. O delineamento estatístico utilizado foi o de blocos ao acaso, testando-se cinco níveis de PST(13,6; 22,4; 30,1; 39,0 e 48,0%) e quatro doses de matéria orgânica (0; 5; 10 e 15%, base  volume), em esquema fatorial 5 x 4, com três repetições. O algodoeiro colorido cv. BRS Topázio é tolerante ao sódio trocável, podendo ser cultivado em solo com PST de até 30%. Nível de esterco bovino de 10% atenuou o efeito do sódio trocável sobre a área foliar, fitomassa seca da parte aérea e massa de semente do algodoeiro respectivamente, sob PST de 31, 48 e 48. O diâmetro de caule, a altura de planta e a massa de pluma de algodoeiro tiveram incremento até o nível de esterco de 15%, já o maior índice de fiabilidade foi obtido sob 9% de esterco. Palavras-chave: Gossypium hirsutum L..Sodicidade. Esterco bovino.  DIAS, A. S.; NOBRE, R.G.; LIMA, G. S. de; GHEYI, H. R.; PINHEIRO, F. W. A.GROWTH AND PRODUCTION OF COLORED-FIBER COTTON CULTIVATED IN SALINE-SODIC SOIL WITH ORGANIC FERTILIZATION    2 ABSTRACT The soils of arid and semiarid regions naturally contain exchangeable sodium that can significantly reduce development and crop yields, being necessary to treat them to make them productive. Several methods can be employed in the reclamation of these soils, like the introduction of tolerant cultivars, such as cotton and the use of organic material, due to its low cost and availability being the most effective ways to alleviate this problem. Thus, the aim of this study was to evaluate the growth and production colored cotton BRS Topaz, when grown in soil with different exchangeable sodium percentages (ESP) and cattle manure in greenhouse of CCTA/UFCG. A completely randomized block design in factorial 5 x 4, with 3 repetitions was used testing five level of ESP and four levels of cattle manure. The colored cotton cv. BRS Topázio is tolerant to exchangeable sodium and can be grown in soil with ESP up to 30%. Organic manure level of 10% attenuated the effect of exchangeable sodium on leaf area, dry weight of shoot and mass of cotton seed, respectively, under ESP of 31, 48 and 48. The stem diameter, plant height and the mass of cotton lint increased up to 15% manure level although the highest spin ability was obtained in 9% of manure and the use of cattle manure was efficient in cultivation of cotton BRS Topaz in sodic soils. Keywords: Gossypium hirsutum L.. Sodicity. Cattle manure.