ABSTRACT Black pepper is widely produced in Brazil, though there are few studies related to its water requirements and the effects of water deficit (WD) applied under tropical conditions. The growth, sensitivity to WD, and first-year productivity of irrigated plants from the Bragantina cultivar were evaluated, employing an irrigation system with automatic management. The plants were cultivated in plastic pots installed in the field for 391 days using emitters with different flow rates (2.2 [T1], 3.3 [T2], 4.3 [T3], and 5.3 L h–1 [T4 – control]). Fresh weight of the leaves, stems, and shoots, and dry weight of the leaves, stem, roots, and shoots as well as the total dry weight of the plant, were evaluated. Productivity was determined by evaluating the grains and spikes from a single harvest. Yield results and the actual versus maximum evapotranspiration rate for the entire growing season was used for calculating the Ky coefficient. Despite 1,346 mm of rainfall, the irrigation system was activated 165 times, distributing a mean volume of 19.0 (T1), 28.5 (T2), 37.1 (T3), and 45.8 L per plant (control). All traits were negatively affected by the WD, and the Ky values obtained (from 1.72 to 2.96) indicate the high sensitivity of black pepper to WD. In general, the spikes produced with at least 81 % of the crop water demand were larger and more numerous than those subjected to inferior treatments. WD occurring during the flowering stage severely hampers the size, weight, and quality of the spikes and grains of black pepper.

ABSTRACT. The center of origin and domestication of Piper nigrum L. are in high rainfall regions. But when grown in regions with irregular or insufficient rainfall, irrigation becomes essential. This study evaluated the impact of irrigation levels on the physiological and growth characteristics of black pepper plants, cv. Bragantina. It was carried out from April 2019 to May 2020, using automatic activation irrigation. We used emitters with different flow rates to apply water depths corresponding to 100, 81, 62, and 42% of the crop water requirement. The parameters evaluated comprised main stem length (MSL), stem diameter (SD), number of leaves (NL), leaf area (LA), chlorophyll contents, chlorophyll-a fluorescence, and some photosynthetic parameters. The treatments significantly influenced (p < 0.05, F-test) MSL and NL. Plants submitted to the control treatment showed MSL (65.8%) and NL (123%) greater than those irrigated with the smallest volume (p < 0.05, F-test). However, the treatments had no significant effect on SD. Moreover, chlorophyll b levels decreased by 26% and chlorophyll a/b ratio increased by 22% at 120 and 180 DAT, respectively. Some photosynthetic parameters such as FV/FM, ABS/RC, and DI0/RC were affected by water deficit at 120 DAT. Our results suggest the sensitivity of black peppers to water deficit and contribute to the proper management of this crop.

ABSTRACT Optimization of the use of water and the possibility of using residues as substrate in the black pepper production chain can yield economic and environmental benefits. The objective of this study was to evaluate the biometric and physiological traits of black pepper plantlets (Piper nigrum L.), cv. Bragantina, at different irrigation levels and soilless substrates. Plantlets were grown for 120 days on three substrates [biosolid + crushed coconut fiber (3:1, by volume); biosolid + granitic rock powder (3:1, by volume); and biosolid + crushed coconut fiber + granitic rock powder (2:1:1, by volume)] and at five irrigation levels [36 % (very low); 55 % (low); 85 % (moderate); 100 % (well-irrigated); and 126 % of the reference irrigation level (over-irrigated)]. The biometric traits evaluated increased as the irrigation levels increased, with the exception of root dry mass, which was not influenced by this factor, nor water use efficiency, which decreased as the irrigation levels increased. In general, plants grown with a mixture of the three wastes (biosolid + crushed coconut fiber + granitic rock powder) exhibited higher values for biometric variables and chlorophyll content when they were moderately, well or over-irrigated, in comparison with the other two substrates. It was possible to achieve the plantlet commercial standard using this three waste mixture and the moderate irrigation level.

RESUMO Em razão da quantidade de água utilizada no setor agropecuário, comparada às outras atividades, a irrigação deve ser feita de forma criteriosa e com base no conhecimento das relações hídricas vegetais. O objetivo deste trabalho foi avaliar o comportamento fisiológico de plantas jovens de pimenta-do-reino (Piper nigrum L.), submetidas a restrições hídricas, assim como o potencial de recuperação após o estresse. As plantas, cultivadas em potes de 5 L, foram submetidas a diferentes níveis de irrigação (100; 78; 58 e 32% da lâmina controle), com manejo realizado por acionamento automático a partir de um sensor de tensão da água no solo. Foram avaliados: potencial osmótico foliar (Ψo), conteúdo relativo de água (CRA), condutância estomática (gs) e pigmentos fotossintéticos. Para avaliar a capacidade de recuperação das plantas, houve reidratação do substrato quando cerca de 50% das plantas de um tratamento apresentassem condutância estomática (gs) próxima a zero. Os diferentes níveis de déficit hídrico reduziram os valores de todas as variáveis. No tratamento 32% foram observados valores de −2,39 MPa para Ψo, 60% para CRA e gs próxima a zero no 28º dia de restrição hídrica. Após três dias de reidratação deste tratamento, a recuperação desses valores foi parcial, não atingindo os valores dos tratamentos 100 e 78%. Plantas de pimenta do reino exibiram elevada susceptibilidade a restrições hídricas e baixa capacidade de recuperação após estresse.

ABSTRACT Due to the amount of water used in the agricultural sector, compared to other activities, irrigation must be done carefully and based on knowledge of plant water relations. The aim of this work was to evaluate the physiological behavior of young black pepper plants (Piper nigrum L.), subjected to water deficit, as well as the potential for recovery after stress. In 5 L pots, the plants were subjected to different irrigation levels (100; 78; 58 and 32% of the control depth), with irrigation management performed by an automatic controller from a water tension sensor in the soil. The following traits were evaluated: leaf osmotic potential (Ψo), relative water content (RWC), stomatal conductance (gs) and photosynthetic pigments. To evaluate the plants’ recovery capacity, substrate rehydration was performed when about 50% of the plants in a treatment had stomatal conductance (gs) close to zero. The different levels of water deficit reduced the values of all traits. In the treatment 32%, values of −2.39 MPa for Ψo, 60% for RWC and gs close to zero were observed on the 28 th day of water restriction. After three days of rehydration of this treatment, the recovery of these values was partial, not reaching the values of the treatments 100 and 78%. Black pepper plants showed high susceptibility to water restrictions and low capacity for recovery after stress.

RESUMO Tradicionalmente, viveiros florestais não utilizam manejo da irrigação, comprometendo a eficiência do sistema e a qualidade das mudas. O objetivo desse estudo foi avaliar a qualidade de mudas sob diferentes níveis de irrigação e do substrato composto por biossólido puro, e o crescimento inicial de três espécies arbóreas de Mata Atlântica, produzidas com manejo automático da irrigação. Quatro níveis de irrigação (V1 a V4) foram aplicados por gotejamento em mudas de Schizolobium parahyba (Vell.) Blake, Cytharexyllum myrianthum Chamiáo e Ceiba speciosa Ravenna. Em seguida, as mudas foram plantadas para avaliar seu crescimento inicial em vasos. A água foi aplicada em resposta à necessidade das espécies e os volumes foram medidos por sensores de fluxo de água, conectados a uma placa Arduino MEGA. Medidas de altura, diâmetro do colo, área foliar, massa seca e teor de clorofila foram utilizadas para avaliar o desenvolvimento das plantas na fase de mudas e nos estágios iniciais de crescimento. Mudas que receberam o maior volume médio de água (V4) tiveram maior taxa de crescimento em altura e diâmetro do colo para as três espécies estudadas. Apesar disso, as mudas que receberam menor volume de água (V1) atingem tamanhos semelhantes às do tratamento V4 em vasos. Os dados de crescimento e qualidade das plantas, nas duas fases analisadas, juntamente com a agregação do substrato, indicam que o nível ideal de irrigação está vinculado aos tratamentos que receberam os maiores volumes de água (V3 e V4) na fase de produção de mudas. Os resultados obtidos indicam que é possível economizar água e produzir mudas de espécies florestais com qualidade, garantindo sua sobrevivência no campo.

ABSTRACT Traditionally, irrigation management has not been used in forest nurseries, compromising the efficiency of the system and the quality of seedlings. In this study, we evaluated the quality of seedlings under different irrigation levels and the substrate composed of pure biosolid, and the initial growth of three Atlantic Forest tree species, produced with automated irrigation management. Four irrigation levels (V1 to V4) were applied by dripping on Schizolobium parahyba (Vell.) Blake, Cytharexyllum myrianthum Chamiáo and Ceiba speciosa Ravenna seedlings. After that, the seedlings were planted to evaluate their early growth in pots. The water was applied in response to species requirement and the volume was measured by water flow sensors, connected to an Arduino MEGA board. Height, collar diameter, leaf area, dry mass and chlorophyll content measurements were used to assess plant development on the seedling and early growth stages. Seedlings that received the highest average volume of water (V4) had a higher rate of growth in height and collar diameter for the three species studied. Despite this, the seedlings that received a smaller volume of water (V1) achieve similar size than V4 ones in pots. The plant growth and quality data, in the two phases analyzed, together with the aggregation of the substrate, indicate that the ideal irrigation level is linked to treatments that received the highest volumes of water (V3 and V4) in the seedling production phase. The results obtained indicate that it is possible to save water and produce seedlings of forest species with quality, ensuring their survival in the field.

RESUMO O uso de água produzida torna-se opção na irrigação de culturas não alimentícias e que apresentam potencial para a produção de biocombustível. Contudo, seus efeitos devem ser conhecidos em diferentes fases de desenvolvimento das plantas e, principalmente, na germinação das sementes. O trabalho foi desenvolvido visando avaliar o desempenho de plântulas de girassol submetidas a diferentes tipos de água produzida. Adotando delineamento experimental em esquema fatorial, foram avaliados 3 cultivares (Catissol 01, Embrapa 122 e IAC Iaramã) e 6 tipos de água (água destilada - testemunha, água de abastecimento, água resultante do processo de separação água e óleo - WOS, da filtragem em filtro de areia - SAF, da filtragem em filtro de areia e carvão - SCF, e da filtragem em filtro de areia + osmose - SOF). Também foi usado o umedecimento do substrato com soluções de polietilenoglicol, simulando os potenciais osmóticos das águas avaliadas, e realizado o teste de sensibilidade com sementes de alface sob condições similares às adotadas para girassol. A cv. Catissol apresentou maiores porcentagens de germinação e vigor de plântulas, independente da água utilizada. Houve tendência de redução da germinação e do vigor das plântulas com o uso da água produzida tratada com os sistemas WOS, SAF e SCF. Todos os potenciais hídricos simulados por soluções de PEG reduziram a germinação e vigor das sementes de alface, sendo esta mais acentuada para o sistema WOS. A SOF foi a única capaz de tornar a água produzida não tóxica para as sementes de girassol e plântulas de alface.

ABSTRACT The use of produced water becomes an option in the irrigation of non-food crops with potential for biofuel production. However, its effects on different stages of plant development and mainly on seed germination should be known. The study was conducted to evaluate the performance of sunflower seedlings subjected to different types of produced water. An experimental design in a factorial scheme was adopted to evaluate 3 cultivars (Catissol 01, Embrapa 122 and IAC Iaramã) and 6 types of water (distilled water - control, public-supply water, water resulting from the water and oil separation process - WOS, filtration in sand filter - SAF, filtration in sand + charcoal filter - SCF, and filtration in sand + osmosis filter - SOF). In addition, the substrate was moistened with polyethylene glycol (PEG) solutions, simulating the osmotic potentials of the evaluated waters, and a sensitivity test was conducted with lettuce seeds under conditions similar to those adopted for sunflower. The cv. Catissol showed higher percentages of germination and vigor of seedlings, regardless of the water used. There was a trend of reduction in germination and vigor of seedlings with the use of produced water treated with the WOS, SAF and SCF systems. All water potentials simulated by PEG solutions reduced the germination and vigor of lettuce seeds, and the effect was more pronounced for the WOS system. SOF was the only one capable of making the produced water non-toxic to sunflower seeds and lettuce seedlings.

Resumo: O objetivo deste trabalho foi avaliar cultivares de feijão-caupi (Vigna unguiculata) quanto ao desenvolvimento da planta e à quantidade e à qualidade de proteínas solúveis em seus grãos, com vistas ao melhoramento. O experimento foi conduzido em casa de vegetação, em delineamento experimental inteiramente casualizado, com as cultivares Paulistinha, BRS Novaera, Epace 10 e BR 17-Gurguéia. Avaliaram-se área foliar, peso fresco e seco da parte aérea, conteúdo de proteína foliar, número de nódulos, e massa seca de nódulos e de raiz. Nos grãos maduros, também quantificaram-se as frações solúveis e os aminoácidos solúveis, e a análise eletroforética foi realizada com desnaturação das proteínas. Não houve diferenças entre as cultivares quanto às variáreis do desenvolvimento da planta. No entanto, a quantidade e a qualidade das proteínas nos grãos diferiram entre as cultivares. 'BRS Novaera' e 'BR 17-Gurguéia' apresentaram maior teor de proteína solúvel nos seus grãos. 'BRS Novaera' apresentou maior teor de dois aminoácidos sulfurados solúveis - metionina e cisteína - , não tendo diferido de 'BR 17-Gurguéia' quanto ao conteúdo de metionina. Ambas as cultivares apresentaram polimorfismo de bandas, mas BRS Novaera apresentou uma banda extra para albuminas. As cultivares BRS Novaera e BR 17-Gurguéia apresentam o maior conteúdo de proteínas solúveis nos seus grãos e o maior polimorfismo de proteínas, o que as torna adequadas para o melhoramento nutricional do feijão-caupi.

Abstract: The objective of this work was to evaluate cowpea (Vigna unguiculata) cultivars regarding plant development and the quantity and quality of soluble proteins in their grains, for breeding purposes. The experiment was conducted in a greenhouse, in a completely randomized experimental design, with the Paulistinha, BRS Novaera, Epace 10, and BR 17-Gurguéia cultivars. Leaf area, shoot fresh and dry matter, leaf protein content, number of nodules, and nodule and root dry matter were evaluated. In mature grains, soluble fractions and soluble amino acids were also quantified, and the electrophoretic analysis was performed with protein denaturation. There were no differences between cultivars for the plant development variables. However, protein quantity and quality in the grain differed between cultivars. 'BRS Novaera' and 'BR 17-Gurguéia' showed a higher soluble protein content in their grains. 'BRS Novaera' exhibited higher contents of two soluble sulfur amino acids - methionine and cysteine - , not differing from 'BR 17-Gurguéia' regarding methionine content. Both cultivars presented protein band polymorphism, but BRS Novaera had an extra band for albumins. The BRS Novaera and BR 17-Gurguéia cultivars have the highest content of soluble proteins in their grains and the greatest protein polymorphism, which makes them suitable for improving the nutritional quality of cowpea.

ABSTRACT: Seedling production is an important step in the lettuce production system. However, there is a tendency to apply excessive irrigation at this stage. The aim of this study was to test the use of the Simplified Irrigation Controller (SIC) under two conditions: first, with the sensor installed in the substrate (measuring the soil water tension) and second, in the atmosphere (“atmospheric” - responding to vapor demand in the atmosphere) to control the irrigation of lettuce seedlings. The performance of the SIC was evaluated by monitoring plant traits. The lettuce seeds of the Regina cultivar were sown in styrofoam trays with commercial organic substrate. Both experiments were conducted under greenhouse conditions and evaluated under different SIC activation tensions. Shoot fresh weight and dry weight, height, number of leaves, leaf length, leaf area, water use efficiency (WUE) (ratio between the dry mass of plant produced by the volume of water applied), chlorophyll content, stomatal conductance and chlorophyll a fluorescence were assessed. In the experiment with the substrate sensor, the tension of 11.5 kPa caused death in 94 % of the seedlings and was disregarded in the statistical analysis. All biometric and physiological traits evaluated decreased as the SIC tensions increased. Thus, tensions of 4.0 (substrate sensor) and 3.5 kPa (atmospheric sensor) showed greater potential for producing vigorous seedlings, with WUE average values of 1.86 and 1.37 g L−1, respectively. Cultivation of lettuce seedlings proved viable under both conditions when the SIC was used, with the emergence of a number of practical advantages of the atmospheric sensor over the substrate one.

ABSTRACT: Concerns with water crisis involve all sectors of society and irrigated agriculture remains the main water consumer. This study evaluated an agricultural production system for lettuce cultivation in greenhouse, “organic potponics”, to economize water and manure use, using a Simplified Irrigation Controller (SIC), based on soil matric potential monitoring. Five irrigation volumes were evaluated in pots with 4.8 L, fertilized with 200 g of vermicompost. One of the volumes was controlled with the SIC. The other volumes represented 130, 80, 60 and 33 % of that controlled by the SIC and all treatments received water at the same time. Shoot fresh weight, head diameter and stomatal conductance (gs) increased linearly with irrigation volumes. For shoot dry weight, number of leaves and water use efficiency (WUE), the regression was quadratic with maximum values at 126, 114 and 83 %, respectively. Leaf relative water content did not show variation among treatments and changes in some fluorescence parameters (Reo/RC, Sm, N and φR0) were much more remarkable to drought compared with the FV/ FM ratio, one of the most commonly used stress indicators. The data indicated a tradeoff between WUE and plant growth thus the economic values of water and lettuce should be taken into account to indicate the best SIC irrigation volume. Organic potponics is promising and should be further improved to save on water, labor and fertilizer use.

RESUMO. Foram realizados dois experimentos com objetivo de avaliar o efeito de diferentes doses de torta de mamona (0, 200 e 300 g m-2) e lâminas de irrigação (204, 224, 278 e 321 mm, em 2014 e 278, 302, 397 e 444 mm, em 2015) na produtividade e qualidade de bulbos de cebola, nos anos de 2014 e 2015. Nos experimentos o delineamento experimental foi em blocos casualizados (fatorial 4 x 3), com cinco repetições. O manejo da irrigação foi realizado pelo “Acionador simplificado de irrigação” (ASI), em resposta à tensão de água no solo, no tratamento de maior lâmina. Foram avaliadas a biomassa seca de planta (BSP) e de bulbo (BSP), a produtividade total (PT), o peso médio fresco de bulbo (PMFB), o peso médio seco de bulbo (PMSB), o diâmetro de médio dos bulbos (DMB), a eficiência de uso da água (EUA). As maiores lâminas de irrigação influenciaram positivamente a produção de bulbos de cebola, independente da dose de torta de mamona aplicada. As doses de torta de mamona influenciaram positivamente a produção de bulbos de cebola quando maiores lâminas de irrigação foram aplicadas. A EUA não foi influenciada pelas lâminas.

ABSTRACT. Two experiments were carried out to evaluate the effects that different doses of castor bean (0, 200, and 300 g m-2) and irrigation levels (204, 224, 278, and 321 mm in 2014, and 278, 302, 397, and 444 mm in 2015) have on both the productivity and quality of onion bulbs. In the experiments, the experimental design was randomized blocks (4 x 3 factorial scheme), with five replicates. Irrigation management was performed using a Simplified Irrigation Device (SID) in response to soil water tension in the treatment of highest irrigation depth. The following variables were evaluated: plant dry biomass (PDB), bulb dry biomass (BDB), total yield (TY), mean bulb fresh weight (MBFW), mean bulb dry weight (MBDW), mean bulb diameter (MBD) and water use efficiency (WUE). The highest irrigation depths positively influenced the mean production of onion bulbs, regardless of the applied dose of castor cake. The doses of castor cake positively influenced the production of onion bulbs when higher irrigation depths were applied.

RESUMO. Foram realizados dois experimentos com objetivo de avaliar o efeito da cinza (40, 80 e 120 g por planta), da torta de mamona (140 e 280 g por planta) e de lâminas de irrigação (135, 165, 191 e 213 mm) no crescimento e produção do tomateiro orgânico, cultivado em vaso e ambiente protegido. O delineamento experimental foi em blocos casualizados e o manejo da irrigação realizado pelo acionador automático para irrigação. Foram avaliadas a altura das plantas, os números de folhas, cachos, flores e frutos, as massas de fruto total, comercial e com podridão apical, e os diâmetros de fruto total e comercial. A maioria das variáveis de crescimento obtiveram ganhos com a aplicação de 140 g de cinza e 280 g de torta. A dose de 280 g de torta proporcionou maior massa fresca comercial (1,78 kg por planta), independente da dose de cinza. O déficit hídrico reduziu os valores da maioria das variáveis de crescimento e de produção. A lâmina de 213 mm foi a responsável pela maior massa fresca comercial (4,04 kg por planta). As maiores eficiências de uso de água, 37,00 e 37,93 kg m-3, foram encontradas para as lâminas de 191 e 213 mm, respectivamente.

ABSTRACT. Two experiments were performed to evaluate the effect of ash (40, 80, and 120 g per plant), castor cake (140 and 280 g per plant) and water depth (135, 165, 191, and 213 mm) on the growth and production of organic tomato cultivated in pots in a greenhouse. The experimental design was randomized blocks, and the irrigation was managed using an automatic irrigation device. The following variables were evaluated: plant heights, numbers of leaves, bunches, flowers and fruits, total mass of fruits, mass of marketable fruits, mass of fruits with blossom-end rot, total diameter of fruits, and diameter of marketable fruits. Most of the growth variables showed gains with the application of 140 g of ash and 280 g of cake. The dose of 280 g of castor cake was responsible for the greatest mass of marketable fruits (1.78 kg per plant), regardless of the ash dose. The water deficit reduced values of most of the variables of growth and production. The irrigation depth of 213 mm was responsible for the greatest mass of marketable fruits (4.04 kg per plant). The highest water use efficiencies, 37.00 and 37.93 kg m-3, were observed at irrigation depths of 191 and 213 mm, respectively.

RESUMO O objetivo do trabalho foi avaliar o crescimento e a produtividade de grãos do feijão-caupi nos diferentes sistemas de consórcio com o milheto, na época das águas e da seca. Os experimentos foram conduzidos no campo experimental do Departamento de Fitotecnia, da Universidade Federal Rural do Rio de Janeiro, em delineamento em blocos ao acaso, com três repetições e cinco tratamentos: T1- cultura solteira de milheto; T2- cultura solteira de feijão-caupi; T3- consórcio com uma linha de milheto e uma de feijão-caupi espaçadas de 0,5m (1M x 1C-0,50); T4- consórcio com uma linha de milheto e uma de feijão-caupi espaçadas de 0,75m (1M x 1C-0,75); e T5- consórcio com uma linha de milheto e duas de feijão-caupi espaçadas de 0,5m (1M x 2C-0,50). No feijão-caupi, avaliou-se a massa seca da parte aérea, massa seca de raiz, o número e massa seca de nódulos, a produtividade de grãos e a massa de 1000 grãos; enquanto no milheto, avaliou-se a massa verde, a massa seca da parte aérea, a produtividade de grãos e a massa de 1000 grãos. Pela comparação do índice de equivalência de área (IEA), se verificou diferenças significativas na produção de feijão-caupi por área explorada, no sistema consorciado em relação ao cultivo solteiro, com a maior massa de grãos no consórcio 1M x 2C-0,50, em relação aos outros. Por outro lado, o consórcio 1M x 1C-0,75 não é recomendável para o local.

ABSTRACT The objective of this work was to evaluate the growth and yield of cowpea grains in different intercropping systems with millet, in wet and dry seasons. The experiments were performed in the experimental field of the Department of Plant Science of the Federal Rural University of Rio de Janeiro, Brazil, using a randomized block design with three replications and five treatments: T1- sole crop of millet; T2- sole crop of cowpea; T3- intercrop of millet (1 row) and cowpea (1 row) with 0.5 m between rows (1Mx1C-0.50); T4 - intercrop of millet (1 row) and cowpea (1 row) with 0.75 m between rows (1Mx1C-0.75); and T5 - intercrop of millet (1 row) and cowpea (2 rows) with 0.5 m between rows (1Mx2C-0.50). The cowpea shoot dry weight, root dry weight, number and dry weight of nodules, grain yield and 1000-grain weight, and the millet fresh weight, shoot dry weight, grain yield and 1000-grain weight were evaluated. The land-use efficiency index (LUE) showed significant differences in yield between the sole crop of cowpea and the intercropping system, with greater grain weight in the intercrop 1Mx2C-0.50. On the other hand, the intercrop 1Mx1C-0.75 was not recommended for the study conditions.

O presente estudo teve como objetivo comparar um sistema automático de baixo custo a outras duas técnicas de manejo (sistema Irrigás e tanque classe A) na cultura da alface (Lactuca sativa L.) com relação à operacionalidade dos sistemas, custo dos equipamentos, lâminas aplicadas e dados de produção da cultura. O cultivo foi desenvolvido num delineamento experimental de blocos ao acaso, com quatro tratamentos casualizados em seis blocos. Os tratamentos foram caracterizados pelo sistema Irrigás, tanque Classe A (TCA) e pelo uso de um acionador automático de baixo custo para irrigação (AAI), em duas tensões de água no solo (9,0kPa e 12,0kPa). Foram avaliados dados de lâmina aplicada, eficiência no uso da água e as variáveis de produção, área foliar, massa fresca e seca da parte aérea, diâmetro e altura da cabeça. Não houve diferença significativa entre os tratamentos para nenhuma das variáveis de produção avaliadas(P>0,05) e as lâminas totais referentes aos diferentes métodos de manejo foram próximas à evapotranspiração de referência (ETo) acumulada no período. A eficiência no uso da água nos tratamentos TCA, AAI/9kPa, Irrigás, AAI/12kPa foi, respectivamente, 241,4; 217,9; 205,5 e 267,1kg ha-1 mm-1, enquanto as produtividades foram respectivamente, 32,80; 28,86; 28,80 e 35,45Mg ha-1. Os resultados obtidos são próximos de valores reportados na literatura, permitindo concluir que as metodologias de manejo avaliadas foram eficientes para o cultivo de alface, e que, dessa forma, a escolha do método dependerá da disponibilidade de mão-de-obra e também do nível de treinamento do agricultor.

The objective of the present research was to compare an low cost controller with two other techniques of irrigation management, Irrigas system and Class A pan, in the cultive of lettuce (Lactuca sativa L.),concerning operability of systems, equipment costs, applied depths and crop yield data. The cultivation was developed in a randomized complete blocks design with four treatments randomized in six replicates. The treatments were characterized by the system Irrigás, Class A pan (TCA) and the use of automatic irrigation of low cost device (AAI) in two different soil water tensions (9.0kPa and 12.0kPa). Data of irrigation depth, water use efficiency and production variables leaf area, fresh and dry weight of shoots, diameter and height of the head were evaluated. There wasn't significant difference between treatments for any of the production variables evaluated (P>0.05) and total irrigation depths were related to different management practices and close to the evapotranspiration estimated reference (ETo) accumulated in the period. The water use efficiency in treatments TCA, AAI/9kPa, Irrigás, AAI/12kPa were, respectively, 241.4, 217.9, 205.5 and 267.1kg ha-1 mm-1, while the productivities were, respectively, 32.80, 28.86, 28.80 and 35.45Mg ha-1. The results obtained are close to values reported in the literature, allowing to conclude that the evaluated methodologies were efficient for growing lettuce and thus the method chosen would depend on the availability of skilled manpower and also of the level of farmer training.

O estudo avaliou o crescimento e a fisiologia de mudas de mamoeiros 'Sunrise Golden' e 'Tainung 01' cultivadas em tubetes de 280 mL e irrigadas com sistema de controle automático de baixo custo, ajustado para iniciar a irrigação com tensão de água no substrato (STI) a 3,0; 6,0 e 9,0 kPa. As lâminas aplicadas pelo sistema de gotejamento e as drenagens em cada tratamento foram monitoradas nas fases de germinação e de crescimento das mudas. Foram analisados: porcentagem de germinação, índice de velocidade de emergência (EVI), área foliar, altura de planta, massa de matéria seca da parte aérea e das raízes, condutância estomática, conteúdo relativo de água (RWC) e teor relativo de clorofila (RCC). Os teores de nutrientes do substrato foram estimados pela condutividade elétrica (EC). A eficiência de uso da água (WUE) foi calculada como a razão entre a massa seca da planta inteira e a água aplicada. Os valores testados para a STI não afetaram a porcentagem de germinação e o EVI. As regulagens de 3,0 e de 6,0 kPa apresentaram os maiores volumes de drenagem e os menores valores de EC e RCC, indicando perda de nutrientes no substrato e deficiência nutricional nas plantas. A drenagem foi maior nos tubetes com a variedade 'Tainung 01' que apresentou menor sistema radicular e também menor condutância estomática que a 'Sunrise Golden'. Os maiores valores de massa da parte aérea seca e WEU foram obtidos a 6,0 kPa nas mudas da 'Sunrise Golden' (0,62 g e 0,69 g L-1) e a 9,0 kPa em 'Tainung 01' (0,35 g e 0,82 g L-1). O RWC foi menor na regulagem de 9,0 kPa que a 3,0 kPa em ambas as cultivares. Os dados indicam que a tecnologia de baixo custo para automação da irrigação é promissora. Mesmo assim, novos estudos devem ser realizados para avaliar sistemas de irrigação de baixa vazão bem como as necessidades nutricionais e hídricas das diferentes variedades de mamoeiros.

The study assessed growth and physiological parameters of 'Sunrise Golden' and 'Tainung 01' papaya seedlings grown in 280mL plastic tubes and watered using a low-cost automatic irrigation system adjusted to operate at substrate water tension for starting irrigation (STI) of 3.0, 6.0 or 9.0 kPa. The water depths applied by the dripping system and drainage were monitored during germination and seedling growth. Germination, emergence velocity index (EVI), leaf area, plant height, shoot and root dry weight, stomatal conductance, relative water content (RWC) and relative chlorophyll content (RCC) were evaluated. Soil nutrient levels were determined by electrical conductivity (EC). Water use efficiency (WUE) corresponded to the ratio of plant dry mass to depth of water applied. STI settings did not affect papaya germination or EVI. System configuration to 3.0 and 6.0 kPa STI exhibited the highest drainage and lowest EC and RCC, indicating soil nutrient loss and plant nutrient deficiency. Drainage was greater in tubes planted with the 'Tainung 01' variety, which developed smaller root systems and lower stomatal conductance than 'Sunrise Golden' seedlings. The highest values for shoot dry weight and WEU were obtained at 6.0 kPa STI for 'Sunrise Golden' (0.62 g and 0.69 g L-1) and at 9.0 kPa in 'Tainung 01' (0.35 g and 0.82 g L-1). RWC at 9.0 kPa STI was lower than at 3.0 kPa in both varieties. The results indicate that the low-cost technology developed for irrigation automation is promising. Even so, new studies are needed to evaluate low-flow irrigation systems as well as the nutrient and water needs of different papaya varieties.

A despeito da enorme demanda por água na irrigação de plantas, existem poucos aparelhos para automação deste processo sendo usados na agricultura. Avaliou-se um acionador automático para irrigação, o qual pode ser confeccionado com materiais comerciais de baixo custo, pois são produzidos em larga escala. Este acionador é composto por uma cápsula cerâmica usada em filtros de água domésticos; um tubo plástico com cerca de um metro e meio de comprimento e um pressostato de máquinas de lavar roupas domésticas. A cápsula e o pressostato são conectados pelo tubo de forma que todo o espaço interno seja preenchido com água. A cápsula é o sensor do acionador e deve ser posicionada dentro do substrato das plantas. O pressostato deve ser posicionado abaixo do sensor e quanto mais baixo ele estiver, maior é a tensão da água que aciona a irrigação, pois quanto mais baixo estiver o pressostato, maior é a coluna de água acima do mesmo e, portanto, maior é a tensão na cápsula cerâmica para puxar para cima a coluna de água. O acionador foi avaliado no controle da irrigação por gotejamento em pequenos potes preenchidos com substrato orgânico comercial ou solo. Regressões lineares explicaram a relação entre a posição do pressostato e a tensão máxima no substrato comercial (p < 0,0054) e no solo (p < 0,0001). Entre as posições do pressostato de 0,30 a 0,90 m abaixo do sensor, a tensão da água variou de 1 a 8 kPa para o substrato comercial e de 4 a 13 kPa para o solo. Este simples acionador pode ser útil para cultivar plantas, aplicando água automaticamente em função da tensão da água no substrato das plantas.

Despite the massive demand of water for plant irrigation, there are few devices being used in the automation of this process in agriculture. This work evaluates a simple controller to water plants automatically that can be set up with low cost commercial materials, which are large-scale produced. This controller is composed by a ceramic capsule used in common domestic water filters; a plastic tube around 1.5 m long, and a pressostate used in domestic washing machines. The capsule and the pressostate are connected through the tube so that all parts are filled with water. The ceramic capsule is the sensor of the controller and has to be placed into the plant substrate. The pressostate has to be placed below the sensor and the lower it is, the higher is the water tension to start the irrigation, since the lower is the pressostate the higher is the water column above it and, therefore, the higher is the tension inside the ceramic cup to pull up the water column. The controller was evaluated in the control of drip irrigation for small containers filled with commercial organic substrate or soil. Linear regressions explained the relationship between the position of pressostate and the maximum water tension in the commercial substrate (p < 0.0054) and soil (p < 0.0001). Among the positions of the pressostate from 0.30 to 0.90 m below the sensor, the water tension changed from 1 to 8 kPa for commercial substrate and 4 to 13 kPa for the soil. This simple controller can be useful to grow plants, applying water automatically in function of the water tension of the plant substrate.