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Cover crops have gained attention due to their potential benefits for the soil and physiological performance of subsequent crops. This study aimed to evaluate the physiological and productive aspects of maize grown in succession to cover crops in northeastern Brazil. A randomized complete block design with four repetitions was employed, in which the treatments consisted of the following cover crops: sunn hemp, spectabilis, pigeon pea, Brachiaria sp., jack bean, millet, and fallow. Physiological aspects and production components of maize were evaluated at the tasseling (VT) and smooth grain (R3) phenological stages. Millet cover increased carotenoid content in maize leaves by up to 78% at R3. Maize grown after pigeon pea, millet, and Brachiaria sp. showed up to 42% greater CO2 assimilation efficiency compared to jack bean. Carboxylation efficiency increased by up to 34% in maize grown after millet and Brachiaria sp., while water use efficiency improved by up to 76% in maize after sunn hemp and pigeon pea at R3. Sunn hemp, spectabilis, and jack bean reduced soil temperature by 2 °C compared to fallow. The highest maize yield was observed after jack bean, with an 8% increase over fallow. These findings demonstrate the benefits of incorporating cover crops into maize cultivation systems in the semi-arid region of Brazil.

ABSTRACT The objective of this research was to evaluate leaf temperature, and watermelon yield components under wetted area percentages (PW) in irrigation located in the Agreste region of Northeastern Brazil. Two experiments were carried out in 2018 and 2019. The adopted statistical design was randomized blocks, with six replications and four treatments, in 2018: P1 = 13%, P2 = 14%, P3 = 19%, and P4 = 22%, in 2019: P5 = 12%, P6 = 15%, P7 = 16%, and P8 = 21% of PW. The meteorological variables analyzed were: air temperature (Ta) and rain. The experimental evaluations consisted of measuring the temperature of the plant’s vegetative canopy, tensiometry, mass, and BRIX. Air temperature was not a limiting factor for watermelon growth and development. The average was 195.88 mm, and the average leaf temperature of watermelon is 29.5 °C, a value lower than Ta. There was no statistically significant difference for fruit mass and BRIX, where the overall mean was 10.82 and 10.46 kg, respectively. Therefore, it is feasible to irrigate watermelon with wetted area percentages ranging from 12 to 22%, in localized irrigation systems, without generating physiological damage and reducing agricultural productivity and fruit quality.

Abiotic stresses, such as water limitation, are significant limiting factors in basil production. One alternative to mitigate the harmful effects of this stress on plants is using plant growth regulators. This study’s objective is to evaluate different doses of plant regulators in basil under water deficiency conditions. A randomized block experimental design in a factorial scheme with two factors was used: the first factor referred to the water regimes of 50% and 100% stomatal conductance, the second to different doses of the plant regulator mixture: 0 mL L−1 (control), 3 mL L−1, 6 mL L−1, 9 mL L−1, and 12 mL L−1. Each treatment consisted of 12 pots per repetition. Biometric parameters, chlorophyll a fluorescence, and gas exchange were analyzed. The plant regulator positively influenced basil plants under water deficiency, with the most pronounced effects observed at the 12 mL L−1 dose: a 17% increase in the number of leaves, a fourfold increase in CO2 assimilation and carboxylation efficiency, and a sevenfold increase in water use efficiency. Therefore, the application of plant regulators on basil is recommended to mitigate the negative effects of water stress, with the most significant results observed at a dose of 12 mL L−1.

Water availability is a limiting factor for plant production, especially in Brazilian semi-arid regions. The main aim of the study was to investigate the physiological effects of drought during the fruiting stage of watermelon cultivation. A completely randomized block design with four replications and six treatments varied by the number of lateral drip tapes (1 or 2) and the duration of drought stress (0, 4, and 8 days) was used. The following parameters were evaluated: relative chlorophyll content, relative leaf water content, electrolyte leakage, CO2 assimilation (A), stomatal conductance (gs), internal CO2 concentration, leaf temperature, transpiration (E), water use efficiency (WUE), carboxylation efficiency (CE), yield, thickness, diameter, length, and fruit °brix, at 4 and 8 days of drought. Drought negatively affected photosynthesis, particularly in treatments with a single dripper and 4 days of drought, resulting in reductions of up to 60% in A, 68% in gs, 44% in E, 58% in WUE, and 59% in CE, but did not have a significant effect on watermelon yield after 4 or 8 days of irrigation. It was concluded that drought influences the physiological responses of watermelon plants, mainly in reducing photosynthesis, but does not drastically affect fruit productivity in short periods of stress.

ABSTRACT The objective, in this research, was to evaluate the agricultural productivity and the financial performance of levels of irrigation in the cassava. For this, experiment was carried out, under a randomized block design, with six irrigation levels, as a function of crop evapotranspiration (L0 = 0% (rainfed), L1 = 40%, L2 = 80%, L3 = 120%, L4 = 160% and L5 = 200% of ETC) and four repetitions. Was evaluated: length and mass of roots, productivity of maximum physical and economic efficiency of roots and productivity of the aerial part. The irrigation level L5 or total useful water of 1,023 mm, got greatest productivity of the aerial part, 57 Mg ha-1. With a total useful water of 926 mm, this irrigation level, generated the greatest length and mass of roots per plant and the maximum physical productivity, 94 Mg ha-1. As well as the root yield of maximum economic efficiency, which is achieved with a total usable water, 914 mm. Among the irrigation levels studied, L3 (963 mm) is the one that provides the greatest productivity of roots, 90 Mg ha-1, and gross revenue 167% higher than in areas cultivated under rainfed conditions. Therefore, irrigation of cassava is economically viable.

O objetivo dessa pesquisa foi avaliar o crescimento, produtividade e as respostas fisiológicas da mandioca sob níveis de irrigação na Zona da Mata de Alagoas. O delineamento estatístico utilizado foi blocos casualizados, em esquema de parcelas subdivididas, com quatro repetições. Os tratamentos foram seis níveis de irrigação, em função da evapotranspiração da cultura – ETC (L0 = 0% (sequeiro), L1 = 40%, L2 = 80%, L3 = 120%, L4 = 160% e L5 = 200% da ETC). As variáveis foram divididas em grupos: crescimento e produção (avaliadas em seis períodos bimestrais – 1 ano) e as fisiológicas (taxa fotossintética líquida e transpiratória, temperatura foliar, condutância estomática, eficiência instantânea do uso de água, rendimento quântico potencial, eficiência quântica efetiva do fotossistema II (ΦPSII) e índice SPAD foram avaliadas em cinco períodos bimestrais – 10 meses). O balanço hídrico dos níveis de irrigação, foi realizado em escala decendial. A evapotranspiração anual da cultura da mandioca estimada foi 1.030 mm, e nas áreas de sequeiro, a chuva efetiva somou apenas 522 mm, o que gerou déficit hídrico de 508 mm, e isso torna evidente a importância de utilização da irrigação em cultivos na região. De maneira geral, crescimento, produtividade e as respostas fisiológicas da mandioca são superiores em áreas irrigadas quando comparadas com cultivos de sequeiro e a irrigação proporciona as produtividades de raízes e biomassa total de 97 e 155 t ha-1, sob os níveis de irrigação de 129 e 136% da ETC, respectivamente, na região estudada.

ABSTRACT: This research evaluated the effects of the irrigation on growth and productivity of irrigated cassava in the Coastal Plateaus of Alagoas. The planting was done in randomized blocks, with six treatments and four replications. The treatments were irrigation levels in function of crop evapotranspiration - ETC (L0 = 0% (rainfed), L1 = 40%, L2 = 80%, L3 = 120%, L4 = 160% and L5 = 200% of ETC). The total water applied was defined as the total irrigation plus the effective rain. The annual evapotranspiration of the cassava plantations in the Costal Plateaus of Alagoas, was 1,030 mm. Plant growth increased significantly with irrigation and the maximum values of the following variables are: leaf area index = 7.6, length of commercial roots = 49 cm, maximum productivity (physical and economic) of commercial roots = 94 Mg ha-1 and total biomass = 149 Mg ha-1 and the harvest index = 0.66, all obtained with total irrigation depths (effective rain plus irrigation) between 817 and 963 mm. Finally, it is ratified that understanding the growth, the agricultural and economically viable productivity of irrigated cassava, is an indispensable factor for good management of the crop, especially in regions with irregular rainfall such as the Northeast of Brazil.

Abstract Myrciaria floribunda is a species native to the restinga areas of the Atlantic Forest that presents great phenotypic variation in fruits, great socioeconomic importance in regions of natural occurrence and high productive potential. The characterization of heterogeneous populations is crucial for plant selection and breeding programs, since it allows the distinction of superior individuals. The aim of this study was to characterize the reproductive structure of M. floribunda accessions, and to observe the influence of climate and environment on its reproductive process, through floral biology, floral morphoanatomy and reproductive phenology. Apis mellifera and Trigona spinipes are the main floral visitors of cambuí. Stigma receptivity lasts up to 5 hours after flower opening and pollen viability was above 90%. Regarding the flower structure, the female sexual organ is monocarpic, the ovary is efferent, bilocular, with two ovules per locule, the inflorescence is fascicle-like and consists of small white flowers, actinomorph symmetry, heteroclamid and monoclines. Plants bloomed irregularly throughout the year, concentrating flowering in two periods of the year with the greatest peaks in March and August, while the greatest fruiting peaks were observed in April and September.

A pimenta malagueta possui grande importância econômica e social para produtores devido sua crescente procura por agroindústrias que confeccionam molhos. Apesar disso, estudos sobre o manejo nutricional da pimenta malagueta são escassos, logo a adubação em cultivos é realizada, principalmente, de forma empírica. Diante disso, este trabalho objetivou verificar a influência de doses de nitrogênio na produtividade de pimenta malagueta. O experimento foi conduzido entre agosto de 2016 e maio de 2017 na área experimental do Campus Arapiraca, da Universidade Federal de Alagoas, Arapiraca, AL. O delineamento experimental utilizado foi em blocos casualizados, com quatro repetições, e seis doses de nitrogênio (0, 100, 200, 300, 400 e 500 kg ha-1 N). A aplicação do N ocorreu de forma parcelada aos 108, 142, 172 e 202 dias após o plantio (DAP), utilizou-se ureia como fonte de N. A colheita de frutos iniciou-se 90 DAP, sendo realizada em uma frequência semanal. As variáveis avaliadas foram: altura de planta (m), diâmetro do dossel (cm), índice SPAD, número de frutos e produtividade (t ha-1). As doses não influenciaram na altura de plantas e diâmetro do dossel. O maior índice SPAD (53,11), maior produção de frutos totais ao final do período de colheita (2.773 frutos por planta-1) e maior produtividade (26,25 t ha-1) foram verificados com 500 kg ha-1 de N.

The salinization process at the mouth of the São Francisco River has been caused serious damage to the ecosystem and the quality of life among riverine populations. This study aimed to assess the perception of the riverine populations regarding the effects of water salinization at the mouth of the São Francisco River, and also to analyze the quality of water that is provided to the Potengi community in Piaçabuçu, Alagoas, Brazil. For data collection, semi- tructured interviews were conducted with 22 riverine residents. The analyses of water samples were carried out at four places in the community, in which analyzes of pH, electrical conductivity, determination of salinity, and turbidity of the water were made. It was possible to identify, during the performance of this study, the inefficiency of the public authorities, both concerning the informative and mitigating actions, as the exposure of the population to high levels of sodium and turbid water, leading to changes in the parameters concerning data established by the World Health Organization (WHO). The results revealed that one of the samples analyzed presented a saline level 17 times higher than the limit established by the WHO, and a turbidity index was 15.6 times higher than the technical limit established. Therefore, these changes have affected the health of the community, directly compromising the use of water and the composition of the biota in the region.

ABSTRACT: Determining actual crop evapotranspiration (ETa) is paramount for irrigation management. The principal measurement methods and physical models generally require crop and weather data that are not readily available. We determined the crop coefficient (Kc) of sweet oranges during the initial development stage and evaluated the performance of the Poulovassilis semi-empirical model coupled with a simple soil water balance for estimating the ETa. The ETa was inferred from the variation in the soil water content over time, measured by time-domain reflectometry. In the Poulovassilis model, the ETa is obtained by multiplying the crop evapotranspiration (ETc) by an adjustment coefficient (ca), which accounts for a reduction in the evapotranspiration caused by soil water depletion. Soil water storage was obtained using the daily and 10-day soil water balances, computed by considering inputs and outputs of water from the system. The empirical parameter, ca, was determined using inverse modeling. The optimal ca value obtained through inverse modeling was 0.05 and 0.03 for the daily and 10-day soil water balances, respectively. The model performed better for the daily soil water balance than the 10-day balance, with performance comparable with the other ETa models. Average Kc during the sweet orange initial crop stage was 0.85.