Evapotranspiration, crop coefficient and water use efficiency of onion cultivated under different irrigation depths

ABSTRACT This study aimed to determine crop evapotranspiration through the soil water balance, the crop coefficient and water use efficiency of the onion (Allium cepa L.) in a system with four irrigation regimes, cultivated in the semiarid region of northeastern Brazil. Two field experiments were carried out during the rainy and dry periods of the region in 2018, using the treatments of 100% (T1), 75% (T2), 50% (T3) and 25% (T4) of the reference evapotranspiration for daily water replacement and five replicates for each treatment. It was verified that crop evapotranspiration varies according to the water availability in the soil; however, the highest water use efficiency occurred for the T3 treatment. The T1 treatment obtained the highest estimated yield, 43.86 tons ha-1, while T4 obtained 13.47 tons ha-1, the lowest estimated yield among the treatments, and this difference was statistically significant (p ≤ 0.05) by F test. The crop coefficients obtained were 0.68, 0.89, 0.99 and 0.73 for the initial, vegetative, bulbing and maturation stages, respectively.

Comparison of Crop Evapotranspiration and Water Productivity of Typical Delta Irrigation Areas in Aral Sea Basin

The intensity of agricultural activities and the characteristics of water consumption affect the hydrological processes of inland river basins in Central Asia. The crop water requirements and water productivity are different between the Amu Darya and Syr Darya river basins due to the different water resource development and utilization policies of Uzbekistan and Kazakhstan, which have resulted in more severe agricultural water consumption of the Amu Darya delta than the Syr Darya delta, and the differences in the surface runoff are injected into the Aral Sea. To reveal the difference in water resource dissipation, water productivity, and its influencing factors between the two basins, this study selected the irrigation areas of Amu Darya delta (IAAD) and Syr Darya delta (IASD) as typical examples; the actual evapotranspiration (ETa) was retrieved by using the modified surface energy balance algorithm for land model (SEBAL) based on high spatial resolution Landsat images from 2000 to 2020. Land use and cover change (LUCC) and streamflow data were obtained to analyze the reasons for the spatio-temporal heterogeneity of regional ETa. The water productivity of typical crops in two irrigation areas was compared and combined with statistical data. The results indicate that: (1) the ETa simulated by the SEBAL model matched the crop evapotranspiration (ETc) calculated by the Penman–Monteith method and ground-measured data well, with all the correlation coefficients higher than 0.7. (2) In IAAD, the average ETa was 1150 mm, and the ETa had shown a decreasing trend; for the IASD, the average ETa was 800 mm. The ETa showed an increasing trend with low stability due to a large amount of developable cultivated land. The change of cultivated land dominated the spatio-temporal characteristics of ETa in the two irrigation areas (3). Combined with high spatial resolution ETa inversion results, the water productivity of cotton and rice in IAAD was significantly lower than in IASD, and wheat was not significantly different, but all were far lower than the international average. This study can provide useful information for agricultural water management in the Aral Sea region.

Dry Bean (Phaseolus vulgaris L.) Crop Water Production Functions and Yield Response Factors in an Arid to Semi-Arid Climate

HighlightsDeficit irrigation negatively affected dry bean yield and yield components.Excess irrigation increased crop ETc but not dry bean yield.Soil moisture fluctuation was greater in the top 0.3 m of the soil profile compared to deeper depths.Crop water production function had a slope of 18.9 kg ha-1 mm-1 and threshold crop evapotranspiration of 171 mm.Dry bean crop was found to be sensitive to water stress (yield response factor Ky = 1.94).Abstract. Under changing climate conditions and declining water resources, understanding crop response to water stress is critical for effective irrigation management. The objectives of this study were to quantify dry bean (Phaseolus vulgaris L., cv. Othello) soil moisture dynamics, crop evapotranspiration (ETc), and yield response factor and to develop dry bean irrigation and crop water production functions (IWPF and CWPF). Five irrigation treatments, i.e., full irrigation (FIT), 75% FIT, 50% FIT, 25% FIT, and 125% FIT, were evaluated using a randomized complete block design (RCBD) with three replications for three years (2017, 2018, and 2019) in the arid to semi-arid intermountain region of Powell, Wyoming. The results showed a significant influence of irrigation on dry bean soil moisture dynamics and ETc. The dry bean crop showed a greater soil moisture fluctuation in the top 0.3 m of the soil profile compared to 0.6 m and at 0.9 m. ETc ranged from 187 to 438 mm, from 190 to 409 mm, and from 217 to 398 mm in the 2017, 2018, and 2019 growing seasons, respectively. A positive two-segment relationship was observed between dry bean seed yield and cumulative irrigation water applied. The average cumulative seasonal irrigation of 310 mm resulted in maximum seed yield. For all three years, the seed yield increased linearly with ETc. Combining the data from the three years resulted in a CWPF with a slope of 18.9 kg ha-1 mm-1 and an offset of 171 mm of ETc (i.e., the ETc required for crop establishment before any seed yield is produced, or threshold ETc). Moreover, the dry bean crop was found to be sensitive to water stress (Ky = 1.94). These results indicated that under the typical semi-arid to arid climate conditions of the intermountain region of Wyoming, deficit irrigation of dry bean may not be a viable strategy because the yield loss outweighs water-saving benefits. Keywords: Dry bean, Crop evapotranspiration, Crop production function, Irrigation water production function.

Efficacy of benzyladenine for compensating the reduction in soybean productivity under low water supply

Undoubtedly, drought is a negative consequence of climate change. Farmers have to deal with this issue and may be forced to irrigate their crops with less water than required, however reduction in productivity is anticipated. Thus, two–year field trials were conducted to assess the impact of irrigation regimes (60, 80 and 100% of crop evapotranspiration, denoted ET60, ET80, and ET100, respectively) and benzyladenine rates (0, 50, 100, 150 and 200 mg L−1, symbolized as BA0, BA50, BA100, BA150, BA200, respectively) on soybean. Findings clarified that the maximum increases in plant height and net assimilation rate were obtained with the interactions of ET100 or ET80 x BA200 or BA150 in both seasons. ET80 x BA200 (in both seasons) and ET100 x BA150 (in the first season) were as similar as ET100 x BA200 for enhancing pods number plant−1. Irrigation water use efficiency progressively increased with decreasing irrigation water amount and increasing benzyladenine rate. In conclusion, the reduction in seed yield due to lowering water supply up to 80% of crop evapotranspiration (with saving 20% of irrigation water) could be compensated using benzyladenine, 150 mg L−1, thus it should be involved in soybean irrigation programs.

Modeling Basin-Scale Impacts of Cultivation Practices on Cotton Yield and Water Conservation under Various Hydroclimatic Regimes

The SWAT model equipped with an improved auto-irrigation function was used to assess the impacts of cultivation practices on irrigated and dryland cotton yield and water conservation in the Texas Panhandle. Results showed the largest irrigation depth led to reductions in irrigation and crop evapotranspiration (ETc) with slightly increased cotton yields compared to the baseline scenarios under different hydroclimatic regimes. However, soil water content and surface runoff values were increased when using the largest irrigation depth. The opposite results were observed for the small irrigation depth. Early planting of cotton resulted in decreased irrigation and ETc, and increased cotton yields under both irrigated and dryland conditions, particularly in normal and wet years. By contrast, the late planting scenarios indicated the opposite for those variables. Simulated hydrologic variables were relatively stable using various maturity cultivars. Nevertheless, greater than 10% reductions in irrigated cotton yield under diverse hydroclimatic years and dryland yields during normal and wet years were identified in the long-season cotton. The opposite was determined for the short-season cotton. These outcomes suggest that a larger irrigation depth, earlier planting date, and short-season cultivar are promising cultivation practices for improving cotton yield and water conservation in the Texas Panhandle.

Optimal levels of water and salt in the growth of giant sweet clone cactus forage

Forage cactus is perennial growth plant, resistance to drought adaptation to hot climate regions, being considered important for the development of livestock. In this study objective was estimate the morphometrics measures of forage cactus Giant Sweet clone associate the optimal levels water and salt. Design used was completely randomized, composed of four levels of water replacement, using the crop evapotranspiration (25, 50, 75 and 100%.Etc) and four levels of salinity (0, 2, 4 and 8 dS/m), obtained through the concentrations of (NaCl) salts corresponding to 0, 1.16, 2.32 and 4.64 g/L, respectively. The morphometric measures of cladodes were evaluated 20 times during the experimental period. Response surface was used to estimate the optimal levels water and salt that maximizing the morphometric measures of the cladodes. Water level in range of 54% and 64%, and 3.5 to 5.3 dS/m of saline level promote greater development of the Giant Sweet clone without changing the morphological characteristics of plant, generating greater phytomass yield.

CARACTERIZAÇÃO FÍSICO-QUÍMICA DE SUBSTRATO DE FIBRA DE CASCA DE COCO APÓS O CULTIVO HIDROPÔNICO DE PIMENTÃO COM ÁGUA DE REÚSO E DIFERENTES LÂMINAS DE SOLUÇÃO NUTRITIVA

CARACTERIZAÇÃO FÍSICO-QUÍMICA DE SUBSTRATO DE FIBRA DE CASCA DE COCO APÓS O CULTIVO HIDROPÔNICO DE PIMENTÃO COM ÁGUA DE REÚSO E DIFERENTES LÂMINAS DE SOLUÇÃO NUTRITIVA1 RENATA DA SILVA CUBA DE CARVALHO2; MARA RÚBIA MENDES DE MELO3; fRANCIELLY GUIEIRO GOMES DE SOUSA4; luís roberto almeida gabriel filho5; antonio evaldo klar6 E hélio grassi filho7 1Trabalho originado da tese de doutorado do primeiro autor intitulada: “Cultivo de pimentão em sistema hidropônico com água de reúso em diferentes níveis de disponibilidade de água no substrato”. 2Doutora, Programa de Pós-graduação em Agronomia – Irrigação e Drenagem, Faculdade de Ciências Agronômicas, Universidade Estadual Paulista (UNESP), Avenida Universitária, 3780, CEP 18610-034, Altos do Paraíso, Botucatu-SP, Brasil, [email protected]. 3 Doutoranda, Programa de Pós- graduação em Agronomia, Departamento de Produção e Melhoramento Vegetal. Faculdade de Ciências Agronômica, Universidade Estadual Paulista (UNESP), Rua José Barbosa de Barros, 1780. CEP: 18.610-307, Botucatu-SP - Brasil. E-mail: [email protected]. 4Doutora, Programa de Pós- graduação em Agronomia – Irrigação e Drenagem, Faculdade de Ciências Agronômica, Universidade Estadual Paulista (UNESP), Avenida Universitária, 3780, CEP 18610-034, Altos do Paraíso, Botucatu-SP, [email protected]. 5 Professor Associado do Departamento de Gestão, Desenvolvimento e Tecnologia da Faculdade de Ciências e Engenharia, Universidade Estadual Paulista (UNESP), Avenida Domingos da Costa Lopes,780, Jardim Itaipu, 17602-496, Tupã-SP, Brasil, [email protected]. 6 Professor Emérito do Departamento de Engenharia Rural da Faculdade de Ciências Agronômicas, Universidade Estadual Paulista (UNESP), Avenida Universitária, 3780, CEP 18610-034, Altos do Paraíso, Botucatu-SP, Brasil. E-mail: [email protected]. 7 Professor Titular do Departamento de Solos e Recursos Ambientais da Faculdade de Ciências Agronômicas, Universidade Estadual Paulista (UNESP), Avenida Universitária, 3780, CEP 18610-034, Altos do Paraíso, Botucatu-SP, Brasil, [email protected]. 1 RESUMO Este trabalho objetivou caracterizar a partir de análises físicas e químicas, o substrato de fibra de casca de coco antes e após o seu uso com a cultura do pimentão, cultivada em vasos com solução nutritiva preparada com água de reúso e água potável e diferentes lâminas de reposição dessa solução (100, 75 e 50% da evapotranspiração da cultura). O cultivo foi realizado em ambiente protegido ao longo de 175 dias, em vasos com capacidade volumétrica de 15 L, preenchidos com fibra de casca de coco. A cada 30 dias mediu-se o pH e a condutividade elétrica do substrato em laboratório. Após a colheita das plantas, foram coletadas amostras do substrato, com as quais avaliaram-se as características químicas e físicas: condutividade elétrica, pH, teores de NH4+, NO3-, P, K, Ca, Mg, S, Cl, B, Fe, Mn, Cu, Zn, capacidade de troca catiônica (CTC), capacidade de retenção de água (10kPA) e densidade volumétrica seca. A reposição de solução nutritiva no substrato através da evapotranspiração da cultura proporcionou aumento dos teores de nutrientes, condutividade elétrica, CTC do substrato e densidade. Os maiores valores desses parâmetros foram verificados para os tratamentos cultivados com solução nutritiva preparada com água de reúso. Palavras chave: salinização, nutrientes, água residuária, hidroponia, efluente. CARVALHO, R. S. C.; MELO, M. R. M.; GOMES, F. G.; GABRIEL FILHO, L. R. A.; KLAR, A. E.; GRASSI FILHO, H. PHYSICAL AND CHEMICAL CHARACTERIZATION OF IN COCONUT HUSK FIBER SUBSTRATE AFTER THE CULTIVATION OF PEPPER IN A HYDROPONIC SYSTEM WITH WATER REUSE AND DIFFERENT DEPHTS OF NUTRIENT SOLUTION 2 ABSTRACT This work aimed to characterize the physical and chemical characteristics of the coconut husk fiber substrate before and after its use with the pepper crop, cultivated in pots with a nutritive solution prepared with reuse and drinking water and different depths of this solution replenishment (100, 75 and 50% of crop evapotranspiration). Cultivation was conducted in pots greenhouse with a volumetric capacity of 15 L, filled with coconut husk fiber. The plants were grown for 175 days and every 30 days, the pH and electrical conductivity of the substrate were measured in the laboratory. After the plants were harvested, samples of the substrate were collected and the chemical and physical characteristics were evaluated: electrical conductivity, pH, NH4 +, NO3-, P, K, Ca, Mg, S, Cl, B, Fe, Mn, Cu, Zn, cation exchange capacity (CTC), water retention capacity (10kPA), and dry bulk density. The replacement of the nutrient solution in the substrate through crop evapotranspiration provided an increase in nutrient content, electrical conductivity, CTC of substrate and density. The highest values for theses parameters were verified ​​for the treatments cultivated with nutritive solution prepared with water reuse. Keywords: salinization, nutrients, wastewater, hydroponic, effluent.