No abstract

A study was conducted in order to assess the effect of different fertilisation levels of Ca 2+ , K + and NO 3 − on the bioactive nutrient content in red pepper (Capsicum annuum L) fruits. The experiment was carried out in a greenhouse, under hydroponic culture. Lycopene, β-carotene, vitamin C, total phenolic compound, sugar, nitrate and potassium contents and antioxidant activity were determined. Increasing Ca 2+ and NO 3 − concentrations in the root medium increased the lycopene and β-carotene contents in pepper. Antioxidant activity was determined in the hydrophilic (HAA) and lipophilic (LAA) fractions. HAA was increased by intermediate and high Ca 2+ concentrations in the culture medium. However, LAA was raised only by NO 3 − treatments. Vitamin C, sugar and total phenolic acid contents were not affected by Ca 2+ or NO 3 − treatments. K + treatments had no effect on nutritional quality of pepper. An increased supply of Ca 2+ and NO 3 − in the culture medium could constitute a useful practice for improving the nutritional attributes of pepper as well as its commercial quality.

BACKGROUND: There is a need to encourage more sustainable agricultural practices, reducing inputs of water and fertilisers while minimising any negative impact on fruit quality. The effect of irrigation frequency, salinity and potassium and calcium fertilisation on the content of bioactive compounds and quality attributes of green and red peppers grown with and without substrate was evaluated.

The influence of Ca 2+ and K + levels on fruit yield and quality of sweet pepper (Capsicum annuum L. cv. Orlando) plants under hydroponic culture has been investigated. The treatments consisted of three concentrations of Ca 2+ (1.5, 4 and 8 mmol L -1 ) and K + (2.5, 7 and 12 mmol L -1 ) that were imposed separately. Fruit yield parameters and different fruit quality parameters, as well as dry matter production and mineral composition in individual parts of the plant, were determined. The increase of Ca 2+ in the root medium increased the marketable yield from 1.67 to 2.38 kg plant -1 , mainly due to an increase in the number of fruits per plant, while higher K + levels decreased marketable yield from 2.2 to 1.66 kg plant -1 , due to decreases in the number of fruits per plant and the mean fruit weight. With respect to fruit quality, fruit shape index and, therefore, pepper fruit appearance improved with Ca 2+ addition to the root medium. Fertilisation with K + increased fruit acidity and decreased maturity index, which could improve fruit storability. Low Ca 2+ or high K + levels reduced both root and shoot dry matter. Therefore, an adequate management of fertilisation with Ca 2+ and K + could improve the yield and fruit quality of pepper grown in soilless culture.Additional key words: Capsicum annuum L. cv. Orlando, greenhouse, Hoagland nutrient solution, hydroponics, plant nutrition. ResumenRendimiento y calidad de los frutos de pimiento en respuesta a la fertilización con Ca 2+ y K + Se investigó el efecto del Ca 2+ y del K + sobre el rendimiento y la calidad de los frutos en plantas de pimiento (Capsicum annuum L. cv. Orlando) crecidas en cultivo hidropónico. Los tratamientos consistieron en tres concentraciones de Ca 2+ (1,5, 4 y 8 mmol L -1 ) y tres de K + (2,5, 7 and 12 mmol L -1 ), que fueron comparadas de forma separada. Se determinaron los parámetros de rendimiento y la calidad de los frutos, así como la producción de materia seca y composición mineral en la parte aérea, raíces y frutos. El aumento de la concentración de Ca 2+ en la solución nutritiva incrementó el rendimiento comercial de 1,67 a 2,38 kg planta -1 , al aumentar el número de frutos por planta. La mayor concentración de K + ensayada (12 mmol L -1 ) disminuyó el rendimiento de frutos comerciales de 2,2 a 1,66 kg planta -1 , debido al descenso del número de frutos por planta y del peso medio de los frutos. El índice de forma de los frutos, y por tanto, su apariencia, mejoró con la adición de Ca 2+ . Por su parte, el aumento de K + incrementó la acidez de los frutos y disminuyó el índice de madurez, lo que podría facilitar el almacenaje de los frutos. El crecimiento de la parte aérea y de la raíz disminuyó con 1,5 mmol L -1 de Ca 2+ o con 12 mmol L -1 de K + . De esta forma se concluye que un manejo adecuado de la fertilización con Ca 2+ y K + podría mejorar el rendimiento y la calidad de los frutos en pimiento crecido en cultivo sin suelo.Palabras clave adicionales: Capsicum

The objective of the present study was to evaluate the marketable fruit yield of sweet pepper plants (Capsicum annuum cv. Orlando) in function of the management of nutrient solution with training system. Plants were grown on coconut coir dust under greenhouse conditions in the southeast of Spain. A randomized block design in split-split plot with four blocks was used to test the effect of the nutrient solution strength (full or half-strength Hoagland nutrient solution), training system (two and three stems per plant) and water salinity (saline and non-saline) on total and marketable yield, fruit quality, and fruit mineral concentration. Salt treatment decreased fruit yield by decreasing the fruit fresh weight but not the number of fruits per plant. Under saline and non-saline conditions, the higher yield of fruits was obtained in plants watered with half-strength Hoagland solution, and grown with three stems per plant. Blossom end rot incidence increased under saline conditions or using full-strength Hoagland solution, but decreased with the combination of half-strength Hoagland solution and three-stem training system. Salt treatment also decreased fruit quality in all the treatments due to a decrease in PO2-, SO4(2-), Fe2+;3+, Cu1+;2+ and Mn2+ concentrations, and fruit shape index. Likewise, plants exposed to salinity and watered with half-strength Hoagland solution and trained with three stems showed a reduction in juice glucose and fructose concentration. Based on these results, an increase of the marketable fruit yield could be obtained under non or moderate saline conditions with the implementation of suitable culture practices.