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High levels of dissolved salts in irrigation water sources limit melon cultivation in northeastern Brazil. In this context, nitrogen fertilization has been employed as one strategy to alleviate the effects of salt stress on plants. This study aimed to evaluate the effect of different nitrogen sources on cantaloupe melon cultivation under fertigation and irrigation with water of the same salinity and different cationic concentrations (Na+ and Ca+). The research consisted of two experiments, each following a randomized complete block design in a 4 × 2 factorial arrangement with four replicates. The treatments included four levels of electrical conductivity of the nutrient solution (2.0; 3.0; 4.0; and 5.0 dS m−1) and two nitrogen sources of different origins: NO3− [Ca(NO3) and KNO3] and NH4+ [CH4N2O and NH4H2PO4]. The following factors were chlorophyll pigments, chlorophyll a fluorescence, and fruit weight. Nitrogen fertilization with NH4+ mitigated salt stress by increasing the synthesis of chlorophyll a and carotenoids in plants irrigated with NaCl-based saline water. Furthermore, there was no influence of nitrogen sources on chlorophyll a fluorescence. Finally, NO3− fertilization reduced the effects of salt stress on the leaf mass ratio, specific leaf area under Ca2+ fertigation, and relative growth rate of leaf area in melons under cationic prevalences of Na+ or Ca2+ (associated with Cl−).

Different soil management systems can change the sugarcane yield and quality parameters for sugar/ethanol production. The objective of this study was to evaluate the effects of subsoiling on the inter-row of sugarcane ratoons after the second harvest on productivity and technological quality. Productivity was estimated in tonnes of sugarcane per hectare (TSH), and technological quality parameters were apparent sucrose percentage (Pol) and total sugar recoverable per hectare (TRS). The apparent sucrose percentage and total recoverable sugar were measured in tonnes per hectare, corresponding to the parameters TSH and total recoverable sugar in tonnes per hectare (TTRSH), respectively. This research was carried out at the Experimental Sugarcane Station at the Federal Rural University of Pernambuco in the northeast region of Brazil. A randomized complete block design was used, with two treatments: conventional tillage and inter-row subsoiling. Subsoiling provided a significant gain of stalk yield of 5.53 tonnes per hectare. The other parameters evaluated did not differ significantly.

The objective was to perform a comparative study of the meteorological elements data that most cause changes in the reference Evapotranspiration (ETo, mm) and its own value, of automatic weather stations AWS and conventional weather stations CWS of the Sertão and Agreste regions of Pernambuco State. The ETo was calculated on a daily scale using the standard method proposed by the Food and Agriculture Organization (FAO), Penman-Monteith (FAO-56). The ETo information obtained from AWS data can be used to update the weather database of stations, since there is a good relationship between the ETo data obtained from CWS and AWS, statistically determined by the Willmott's concordance index (d > 0.7). The observed variations in the weather elements: air temperature, relative humidity, wind speed, and global solar radiation have not caused significant changes in the ETo calculation.

ABSTRACT The production of vegetables in communities of family farmers in semiarid regions is limited due to rudimentary cultivation practices and systems, water scarcity, and excess salts in the water and soil. Thus, the objective of this work was to evaluate the production of rocket (Eruca sativa L. cv. Folha Larga) in a low cost hydroponic system, considering strategies for the use of brackish water in the nutrient solution. The experiments were conducted in complete randomized designs, in 6×2 factorial arrangements, with five replications, using rocket plants grown in different nutrient solutions, consisting of six salinity levels (1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 dS m -1) and two circulation frequencies of the nutrient solution (twice a day, at 8:00h, and 16:00h; and three times a day, at 8:00h, 12:00h, and 16:00h). In Experiment I, the nutrient solution lost by evapotranspiration was replenished with the respective brackish water used in its preparation; and in Experiment II it was replenished with public water (0.12 dS m -1). The shoot and root fresh and dry biomass of the plants and their respective dry weight proportions, and biometric variables were evaluated. Replenishing of the nutrient solution with public water resulted in lower losses in biomass and plant growth. The increases in circulation frequency of the nutrient solution did not affect the biometric variables, however, the plants prioritized shoot biomass development to the detriment of the root when using high circulation frequencies. RESUMO A produção de hortaliças em comunidades de agricultores familiares, residentes em condições semiáridas, são limitadas por práticas e sistemas rudimentares de cultivo, escassez hídrica e problemas de salinidade. Neste sentido, o objetivo do presente trabalho foi analisar a produção de rúcula, cv. Folha larga, em sistema de hidroponia de baixo custo, adotando-se estratégias de uso da água salina no preparo e reposição da solução nutritiva evapotranspirada. Em dois experimentos, plantas de rúcula foram expostas a seis níveis de salinidade da solução nutritiva (1,5; 3,0; 4,5; 6,0; 7,5 e 9,0 dS m -1) aplicadas em duas frequências de circulação (duas vezes ao dia - às 8 e 16 horas; três vezes ao dia - às 8, 12 e 16 horas). O delineamento experimental adotado foi inteiramente casualizado, em esquema fatorial 6 x 2, com cinco repetições, sendo que, no Experimento I a reposição da solução nutritiva foi efetuada com a respectiva água salina utilizada no preparo da solução e, no Experimento II, com água de abastecimento (0,12 dS m -1). Analisou-se a fitomassa fresca e seca da planta, da parte aérea e da raiz, bem como as respectivas partições de matéria seca e variáveis biométricas. A reposição da lâmina evapotranspirada com água de abastecimento resultou em menores perdas de biomassa e no crescimento das plantas e que, o aumento da frequência de circulação não influenciou as variáveis biométricas, no entanto, sob maior frequência de circulação a planta priorizou o desenvolvimento da biomassa da parte aérea em detrimento da raiz.

The present study aimed to evaluate different irrigation scheduling strategies on capsicum growth and yield inprotected environment. The experiment was carried out at the Northeastern of Brazil. Five irrigation scheduling techniques to define water depth (weighing lysimeter, Hargreaves-Samani equation, Piché evaporimeter, tensiometer and soil moisture sensor) andtwo application frequencies (F1-once a day and F2-alternating frequency) were tested. A completely randomized factorial design experiment was installed in a 5 x 2 factorial scheme, with eight replicates. It was observed that the variables stem diameter and leaf area index were influenced by the irrigation scheduling techniques, and treatments based on Hargreaves-Samani and lysimeter scheduling methods led to the lowest values. Fruit biometric parameters were significantly affected only by the Hargreaves-Samani treatment. It can be concluded that both irrigation scheduling techniques and frequencies influenced capsicum growth and yield. Furthermore, irrigation management techniques based on soil sensors caused the highest yields.

With the goal of developing an irrigation system with ultra low flow rate (ULF) of 0.2 L h-1, using microtubes with derivation and operating in a laminar regime, this work began by seeking efficient irrigation and low costs. The experiment consisted of two stages. The first experiment was conducted in the laboratory to determine the actual diameter of the microtubes and irrigation system design. The second stage of the experiment was conducted in an experimental area, where tests were carried out to obtain the uniformity of water application which was evaluated by the coefficient of uniformity statistic that had an initial value exceeding 90%. The proposed irrigation system had economic advantages for small-scale producers. However, the system evaluated presented problems with accumulation of air and emitters obstruction during the study period, causing a reduction in statistical uniformity. It is therefore necessary to conduct further studies to obtain more conclusive results.

Water scarcity in semiarid regions represents a critical challenge for sustainable agriculture, reducing the availability of forage and affecting livestock systems. The reuse of treated wastewater offers an environmentally friendly alternative to meet water and nutrient needs, supporting the principles of the circular economy. Sweet sorghum, with its remarkable tolerance to abiotic stress, represents a resilient crop option. Evaluating its agronomic and industrial responses to different depths of irrigation using reclaimed water is essential for improving resource-efficient agricultural practices in water-limited environments. This study evaluated the effects of different irrigation regimes with treated wastewater on the growth, productivity, and water use efficiency of sweet sorghum grown in a semiarid region of Brazil. The experiment was conducted in a randomized complete block design, with five irrigation regimes ranging from 50% to 150% of crop evapotranspiration (ETc) and four replications. Irrigation was carried out with treated wastewater using a drip irrigation system. Growth parameters, fresh biomass, water use efficiency, and soluble solids content (°Brix) were analyzed in two consecutive harvests (main and ratoon crop). Deficit irrigation regimes (50% and 75% of ETc) resulted in higher water use efficiency and higher °Brix, whereas regimes above 100% of ETc reduced water use efficiency and biomass productivity. The ratoon crop showed greater sensitivity to water management, with significant productivity responses under irrigation around 100% of ETc. The first harvest was more productive in terms of fresh biomass and plant growth. Reclaimed water is a sustainable and efficient strategy for cultivating sweet sorghum in semiarid regions. Deficit irrigation regimes can be technically viable for maximizing water use efficiency and production quality, while proper irrigation management is crucial to avoiding losses associated with excessive water application.

This study aimed to develop a new model, valid for soil with and without expandable characters, to estimate volumetric soil water content (θ) from readings of scaled frequency (SF) acquired with the Diviner 2000® sensor. The analysis was carried out on six soils collected in western Sicily, sieved at 5 mm, and repacked to obtain the maximum and minimum bulk density (ρb). During an air-drying process SF values, the corresponding gravimetric soil water content (U) and ρb were monitored. In shrinking/swelling clay soils, due to the contraction process, the variation of dielectric permittivity was affected by the combination of the mutual proportions between the water volumes and the air present in the soil. Thus, to account for the changes of ρb with U, the proposed model assumed θ as the dependent variable being SF and ρb the independent variables; then the model’s parameters were estimated based on the sand and clay fractions. The model validation was finally carried out based on data acquired in undisturbed monoliths sampled in the same areas. The estimated θ, θestim, was generally close to the corresponding measured, θmeas, with Root Mean Square Errors (RMSE) generally lower than 0.049 cm3 cm−3, quite low Mean Bias Errors (MBE), ranging between −0.028 and 0.045 cm3 cm−3, and always positive Nash-Sutcliffe Efficiency index (NSE), confirming the good performance of the model.

Frequency domain reflectometry (FDR) is widely used to measure the soil water contents. However, the soil composition effects on FDR calibration has to be quantified to reduce the need for further calibration. Our objectives were to (1) evaluate the accuracy of EC-5 for measuring soil water content in sandy soils and (2) develop soil-specific sensor calibration curve. Disturbed and undisturbed soil samples were collected in a Sopossol profile (07º 37’ 30’’ S, 34º 57’ 30’’ W) representative of region sugarcane grown, in northeast of Brazil. Regression statistics analysis showed good accuracy and RMSE = 0.01 m3 m-3, while without specific calibration the RMSE = 0.06 m3 m-3. The EC-5 sensor should be subjected to field-specific calibration in sandy soils due to the low field capacity and water content during the growing season.

In this study, the authors analyzed the consequences of irrigation management strategies as an essential factor to save water and maintain high crop yields. The present research aimed at comparing coriander (Coriandrum sativum L.), cv. Verdão, yields under fertigation via drip irrigation with a continuous application and in pulses, with 40, 60, 80, 100 and 120% of the crop evapotranspiration (ETc) being recovered. These treatments were distributed in randomized blocks in a 2 × 5 factorial scheme, with three replications, in a greenhouse located at the Federal Rural University of Pernambuco, northeast Brazil (08°01′6.50″ S and 34°56′46″ W, average elevation 6.5 m). The continuous irrigation consisted of the application of water depth in a single daily event, while pulsed irrigation comprised the application of the same irrigation depth split up into five events with a 1-hour interval between pulses. Crop evapotranspiration (ETc) was determined via the water balance by lysimetric drainage. The fertilizers were applied in every watering. The biometric and productivity crop pointed that pulsed irrigation to a mean depth of 58% of the ETc corresponds to the results obtained with the application of the depth equivalent to 100% of the ETc by continuous irrigation, consequently with reduced input costs.