No abstract

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 (Eleaf), substomatal CO2 concentration (Ci), leaf temperature (Tleaf) and leaf water potential (Ψw) 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 Ψw 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.

The acai palm (Euterpe oleracea Mart.) is a fruit from the Amazon that is originally found in flooded areas. Over recent years, its marketability has gained significant interest in Brazil and abroad because of its agronomic, nutritional and economic potential. However, there is a lack of technical-scientific information about crop water requirements for irrigation management during the reproductive phase of acai palm. Therefore, the aim of this research was to estimate the water requirements (crop evapotranspiration (ET c ), single (Kc) and dual (Kcb + Ke) crop coefficients) of acai palm in the Eastern Amazon (Brazil) using the Bowen ratio system. A micrometeorological tower was installed in the center of an experimental area to monitor ET c and meteorological variables. Phenological development was monitored during two growing seasons. Soil water evaporation was determined on a daily scale using weighing microlysimeters. Ke and Kcb values were calculated by the ratio of soil surface evaporation and transpiration to reference evapotranspiration (ET o ), respectively. Total water requirements of the acai palms were 1165 mm, with a daily average of 3.49 mm day −1 for the growing season. The average values of Kc, Ke and Kcb for the acai palm were 1.08; 0.21 and 0.84, respectively. The findings will assist the design of irrigation management protocols for acai trees that are better tailored to satisfy crop water requirements. This will allow improved water use efficiency, ensuring tree crop sustainability.

RESUMO:O tomate está entre as hortaliças mais consumidas no mundo, sua produção anual no Brasil é estimada em torno de quatro milhões de toneladas. O objetivo do trabalho foi estudar o efeito de diferentes doses de fósforo e potássio no crescimento de tomateiro, cultivado em sistema hidropônico. O trabalho foi conduzido em casa de vegetação do Instituto de Ciências Agrárias da Universidade Federal Rural da Amazônia, no período de outubro de 2008 a janeiro de 2009, em solução nutritiva. O delineamento experimental utilizado foi inteiramente casualizado em esquema fatorial 3 x 3 (três doses de fosfóro e três doses de potássio) com quatro repetições. Cada parcela foi constituída de uma planta por vaso. Não houve interação significativa para os fatores avaliados. Os tratamentos constituídos pela combinação P1K2 e P2K2 proporcionaram melhor desempenho para altura de planta. Para massa fresca da parte aérea e massa fresca de raiz, P2K1 proporcionou melhor incremento em relação às demais doses. Na massa seca total acumulada, os tratamentos P1K1 e P2K1 proporcionaram maiores incrementos, 62,7 e 71,9 g planta -1 respectivamente. Com base nisso, o tratamento mais eficiente para a produção do tomateiro foi o P2K1, que promoveu maior crescimento em todos os parâmetros avaliados. PALAVRAS-CHAVE:Cultivo sem solo. Fertilizantes. Solanum lycopersicum. CULTURE OF TOMATO (Solanum lycopersicum) HYDROPONIC UNDER DIFFERENT LEVELS OF PHOSPHORUS AND POTASSIUM NUTRIENT SOLUTIONABSTRACT: Tomatoes are among the most consumed vegetables in the world, its annual production in Brazil is estimated at around four million tonnes. The objective was to study the effect of different doses of phosphorus and potassium on the growth of tomato grown hydroponically. The work was conducted in the greenhouse of the Institute of Agricultural Sciences, Federal Rural University of Amazonia, from October 2008 to January 2009, in nutrient solution. The experimental design was completely randomized factorial 3 x 3 (three doses of phosphorus and potassium three doses) with four replications. Each plot consisted of one plant per pot. There was no significant interaction for the factors evaluated. The treatments consisted of the combination P1K2 and P2K2 in better performance for plant height. For fresh weight of shoot and root fresh weight, P2K1 provided better growth compared to the other doses. In the total dry mass accumulation, the P1K1 and P2K1

Cowpea is a culture of great socioeconomic relevance for northern Brazil, but the knowledge about technology that increases productivity, such as irrigation, is still incipient. The objective of this work was to evaluate the stomatal conductance (gs) of cowpea, in different hydric availabilities, Castanhal-PA. For this, it was planted the cv. BR3 Tracuauteua was planted in 0.5 ha in the year 2013, in the center of this area was instrummented a micrometeorological tower for measurements of atmospheric variables. The experimental design was in randomized blocks with 4 treatments, which were: 0%, 25%, 50% and 100% of the water slide as a function of crop evapotranspiration. The treatments started in the reproductive phase. The gs readings were performed at different phenological stages through a porometer, the data were subjected to analysis of variance (Tukey, p < 0.05). In the reproductive phase, the lowest gs values were found in the 0% 0% of ETc, which were 141.08 and 186.80 mmol m-2 s-1, respectively, in the R7 and R8 stages. In contrast, the highest values were observed in T100%, 777.76 mmol m-2 s-1 (R7) and 754.50 mmol m-2 s-1. The ideal water depth for cowpea stage R7 was 25% of ETc, whereas from R8, the ideal water depth was 50% of crop evapotranspiration.