The cowpea bean presents low productivity in the Pará state, Brazil, due to low soil fertility and climatic adversity, mainly water deficiency. The aim of this study was to evaluate the yield gap of cowpea bean in northeast of Para state in response to water deficit during its reproductive phase. The experiment was carried out in Castanhal, PA, Brazil, during 2015 and 2016. A randomized block design with six repetitions and four treatments was used; where T1 consisted of 100% replacement of the crop evapotranspiration (ETc), T2 to 50%, T3 to 25% and T4 without irrigation, in the reproductive phase. The yield was determined at R9 stage. The simulations with the SARRAZON model were carried out with different sowing dates. The total deficiencies in the reproductive phase were spatialized considering the 30 locations in order to assess the temporal and spatial seasonality of water availability and the sowing period in the study region. The cowpea bean was sensitive to soil water availability with considerable reductions in productivity due to the increase in water deficit compared to the treatment T1 (100% ETc). When water deficits reached more than 47 mm, there were yield gaps over 20%. According to the spatial variability of simulated water deficiency, the sowing of cowpea bean in regions located above 2° latitude may extend until June 20 without showing high yield gaps.

Cowpea (Vigna unguiculata (L.) Walp.) is a leguminous species widely cultivated in northern and northeastern Brazil. In the state of Pará, this crop still has low productivity due to several factors, such as low soil fertility and climatic adversity, especially the water deficiency. Therefore, the present study aimed at evaluating the physiological parameters and the productivity of cowpea plants under different water depths. The experiment was conducted in Castanhal/Pará between 2015 and 2016. A randomized block design was applied with six replications and four treatments, represented by the replacement of 100%, 50%, 25% and 0% of the water lost during crop evapotranspiration (ETc), starting from the reproductive stage. The rates of net photosynthesis (A), stomatal conductance (gs), leaf transpiration (E_leaf), substomatal CO₂ concentration (Ci), leaf temperature (T_leaf) and leaf water potential (Ψ_w) were determined in four measurements at the R5, R7, R8 and R9 phenological stages. Cowpea was sensitive to the water availability in the soil, showing a significant difference between treatments for physiological variables and productivity. Upon reaching a Ψ_w equal to −0.88 MPa, the studied variables showed important changes, which allows establishing this value as a threshold for the crop regarding water stress under such experimental conditions. The different water levels in the soil directly influenced productivity for both years, indicating that the proper water supply leads to better crop growth and development, increasing productivity.

Understanding the green dwarf coconut palm development is essential to improve its management. This study aimed to characterize and understand the seasonality of the green dwarf coconut palm development and yield under rainfed and irrigated conditions in the northeastern region of the Pará state, Brazil. The longitudinal and transverse diameters, fruit mass and yield, in addition to the number of live leaves, live bunches, fruits of the bunches nº 11 and 14 and female fowers were monitored. The coconuts between the bunches nº 20 and 22 showed larger dimensions and biomass (fresh and dry). The partition of the production components varies according to the time of the year, with the liquid albumen mass, which is a component of greater commercial focus, being higher in the rainy season, with lower percentage losses in the irrigated cultivation. The meteorological seasonality plays a key role in fower dropping and fruit abortion, directly contributing to the amount of produced fruits.

Energy and water dynamics are crucial for citrus development in the Eastern Amazon. This study aimed to determine the energy balance, water demand, and crop coefficient of acid lime in the northeast region of Pará. A micrometeorological tower was installed in the center of the experimental area to monitor meteorological variables between October 2020 and December 2021. The energy balance and water demand were obtained by the Bowen ratio method. Kc was determined by the ratio between crop and reference evapotranspiration. The results obtained indicate that 63% of the available energy was used by latent heat in the rainiest period, while 60% was used during the less rainy period. Sensible heat used 32% and 34% during the most and least rainy periods, respectively. Soil heat presented a low variation, with an average of 5% for the entire period. Water consumption of the acid lime during the experiment was 1599 mm, with a daily mean of 3.70 mm day⁻¹, while the mean value of Kc was 1.4. These results allow for the design of adequate water supply protocols for the crop in the main citrus pole in the Amazon region.

Cowpeas are of high socioeconomic importance in the North and Northeast regions of Brazil, whereby the search for alternatives that offer increased productivity with financial returns has become an important challenge. Thus, the objective of this study was to estimate and evaluate the economic indicators of cowpea production in 2015 and 2016 when applying drip irrigation to different depths. Irrigation treatments were based on crop evapotranspiration (ETc). The experiment was laid in a randomized complete blocks design with four treatments (0, 25, 50, and 100% ETc) and six replications. For economic analysis, the results were extrapolated to an area of one hectare. Productivity in 2015 was lower than that in 2016; however, in all treatments, it was always higher when plants were grown under adequate water supply. In both years, the total operating costs were higher under irrigation than under rainfed conditions. The 100% ETc treatment resulted in a greater number of cowpea bags (60 kg) produced and a higher gross revenue than the rainfed treatment by 17 bags ha-1, equivalent to 1,020 kg ha-1 (gross revenue US$ 711.48) and 16 bags ha-1, equivalent to 960 kg ha-1 (gross revenue US$ 867.12), in 2015 and 2016, respectively. Water deficit limited cowpea yield in both years but made cultivation economically unfeasible only in 2015.

Water availability is a crucial factor in the final productivity of cowpea. The objective of this work was to evaluate the production and productivity components of cowpea under different irrigation depths in Amazonian conditions. The experiment was carried out at the School Farm of the Federal Rural University of Amazonia, in the municipality of Castanhal-PA, using the cultivar BR3 Tracuateua, from September to November 2014, 2015, and 2016. The experimental design was conducted on six blocks and four treatments, where the four irrigation depths of 0, 25, 50, and 100% of crop evapotranspiration were tested. The productivity analysis was performed when 90% of the plants were in the phenological stage R9. The evaluated production components were pod length, number of pods per plant, number of grains per pod, mass of one hundred grains, and harvest index. There was a statistical difference among all treatments for the components of production and among productivities. An average reduction of 827 kg ha⁻¹ in cowpea productivity was observed during the three years of study, when the treatment without irrigation was compared with the treatment irrigated with 100% of the crop’s water demand. It was found in this research that the simple fulfillment of the nutritional and phytosanitary demands of the crop, associated with an adequate planning of when to plant in the region, would already help in the improvement of local production when choosing times where the water deficit in the reproductive phase is less than 33 mm.