RESUMO No semiárido brasileiro o déficit hídrico é um dos principais fatores que compromete o crescimento e o rendimento produtivo das culturas, inclusive do maracujazeiro- amarelo, devido à limitação da assimilação de carbono pela atividade fotossintética dos vegetais. Diante disso, faz-se necessário o manejo do solo com tecnologias que possam reduzir a perda de água no solo e que amenize os efeitos do déficit hídrico às plantas de maracujazeiro-amarelo cultivadas em condições de semiaridez. Objetivou-se avaliar a aplicação no solo de doses de hidrogel e mulching sob os aspectos fisiológicos do cultivo de maracujazeiro-amarelo irrigado. O experimento foi desenvolvido em delineamento em blocos casualizados, no esquema fatorial 5 × 2, referente às cinco doses de hidrogel (0,0, 0,5, 1,0, 1,5 e 2,0 g dm−3 de solo) no solo sem e com cobertura vegetal oriunda braquiária (Brachiaria decumbens L.). As variáveis analisadas foram índices de clorofila, fluorescências (inicial, máxima e variável) e trocas gasosas. O índice de clorofila total foi elevado com a aplicação de 1,5 g dm−3 e uso de mulching, ao se aplicar doses de 2,0 g dm−3 de hidrogel a taxa fotossintética das plantas de maracujazeiro-amarelo aumentou, já a taxa de transpiração das plantas foi incrementada com o uso de cobertura vegetal e doses de hidrogel, como consequência houve redução na eficiência do uso da água.

ABSTRACT In the Brazilian semi-arid region, water deficit is one of the main factors that compromise the growth and productive yield of crops, including yellow passion fruit, due to the limitation of carbon assimilation by the photosynthetic activity of plants. Therefore, it is necessary to manage the soil with technologies that can reduce the loss of water in the soil and mitigate the effects of water deficit on yellow passion fruit plants cultivated under semi-arid conditions. The objective of this study was to evaluate the application of hydrogel doses and mulching to the soil on the physiological aspects of irrigated yellow passion fruit cultivation. The experiment was carried out in a randomized block design, in a 5 × 2 factorial scheme, referring to five doses of hydrogel (0.0, 0.5, 1.0, 1.5 and 2.0 g dm−3 of soil) in soil without and with mulching from signal grass (Brachiaria decumbens L.). The variables analyzed were chlorophyll indices, fluorescence (initial, maximum and variable) and gas exchange. The total chlorophyll index was increased with the application of 1.5 g dm−3 of hydrogel and the use of mulching; when applying hydrogel doses of 2.0 g dm−3 the photosynthetic rate of yellow passion fruit plants increased, whereas their transpiration rate increased with the use of mulching and doses of hydrogel; as a consequence, there was a reduction in water use efficiency.

ABSTRACT The yellow passion fruit is grown under different edaphoclimatic conditions. Irrigation standardizes and increases the development and productivity of the plants. The objective of this study was to evaluate the physiological and productive aspects of yellow passion fruit with application of hydroabsorbent polymer at different irrigation depths. The experimental design was in randomized blocks in a 2 × 5 factorial arrangement. The treatments were soil with and without polymer and five dephts of irrigation (60 to 100% of crop evapotranspiration). Initial, maximum, and variable chlorophyll fluorescence, physiology (photosynthetic rate, internal carbon concentration, transpiration, stomatal conductance, water use efficiency, and instantaneous carboxylation efficiency) and production of yellow passion fruit were the variables analyzed. The hydrogel probably retained water in its structure, reducing the ability to dissipate excess energy. Setting the irrigation depth at an estimated 82% of crop evapotranspiration increased photosynthetic rate, stomatal conductance, and water use efficiency of yellow passion fruit plants. Maximum yield was 17.2 t ha-1 in irrigated plants at 100% evapotranspiration (ETc) in soil without hydrogel.