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: 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 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.