Impact of cultivar and grafting on nutrient and water uptake by sweet pepper (capsicum annuum l.) grown hydroponically under mediterranean climatic conditions

In closed-cycle hydroponic systems (CHS), nutrients and water should be delivered to the plants at identical ratios to those they are removed via plant uptake, to avoid their depletion or accumulation in the root zone. For a particular plant species and developmental stage, the nutrient to water uptake ratios, henceforth termed “uptake concentrations” (UC), remain relatively constant over time under similar climatic conditions. Thus, the nutrient to water uptake ratios can be used as nutrient concentrations in the nutrient solution (NS) supplied to CHS to compensate for nutrient and water uptake by plants. In the present study, mean UC of macro- and micronutrients were determined during five developmental stages in different pepper cultivars grown in a closed hydroponic system by measuring the water uptake and the nutrient removal from the recirculating NS. The experiment was conducted in a heated glasshouse located in Athens Mediterranean environment and the tested cultivars were ‘Orangery,’ ‘Bellisa,’ ‘Sondela,’ ‘Sammy,’ self-grafted and ‘Sammy’ grafted onto the commercial rootstock ‘RS10’ (Capsicum annuum). ‘Sondela’ exhibited significantly higher NO3 -, Mg2+, Ca2+ and B UC, while Bellisa exhibited higher K UC in comparison with all other cultivars. The UC of all nutrients were similar in the grafted and the non-grafted ‘Sammy’ plants, which indicates that this Capsicum annum rootstock does not modify the uptake of nutrients and water by the scion. The UC of macronutrients estimated in the present study (mmol L-1) ranged from 2.4 to 3.7 for Ca, 1.0 to 1.5 for Mg, 6.2 to 9.0 for K, 11.7 to 13.7 for N, and 0.7 to 1.1 for P. The UC of N, K, Ca, and Mg were appreciably higher than the corresponding values found in Dutch tomato glasshouse, while that of P was similar in both locations during the vegetative stage and higher in the present study thereafter. The UC of Fe, Zn and B tended to decrease with time, while that of Mn increased initially and subsequently decreased slightly during the reproductive developmental stage. © 2018 Ropokis, Ntatsi, Kittas, Katsoulas and Savvas

Effects of temperature and grafting on yield, nutrient uptake, and water use efficiency of a hydroponic sweet pepper crop

In areas characterized by mild winter climate, pepper is frequently cultivated in unheated greenhouses in which the temperature during the winter may drop to suboptimal levels. Under low temperature (LT) conditions, the uptake of nutrients may be altered in a different manner than that of the water and thus their uptake ratio, known as uptake concentration, may be different than in greenhouses with standard temperature (ST) conditions. In the present study, pepper plants of the cultivars “Sammy” and “Orangery”, self-grafted or grafted onto two commercial rootstocks (“Robusto” and “Terrano”), were cultivated in a greenhouse under either ST or LT temperature conditions. The aim of the study was to test the impact of grafting and greenhouse temperature on total yield, water use efficiency, and nutrient uptake. The LT regime reduced the yield by about 50% in “Sammy” and 33% in “Orangery”, irrespective of the grafting combination. Grafting of “Sammy” onto both “Robusto” and “Terrano” increased the total fruit yield by 39% and 34% compared with the self-grafted control, while grafting of “Orangery” increased the yield only when the rootstock was “Terrano”. The yield increase resulted exclusively from enhancement of the fruit number per plant. Both the water consumption and the water use efficiency were negatively affected by the LT regime, however the temperature effect interacted with the rootstock/scion combination. The LT increased the uptake concentrations (UC) of K, Ca, Mg, N, and Mn, while it decreased strongly that of P and slightly the UC of Fe and Zn. The UC of K and Mg were influenced by the rootstock/scion combination, however this effect interacted with the temperature regime. In contrast, the Ca, N, and P concentrations were not influenced by the grafting combination. The results of the present study show that the impact of grafting on yield and nutrient uptake in pepper depend not merely on the rootstock genotype, however on the rootstock/scion combination. © 2019 by the authors

Responses of sweet pepper (Capsicum annum L.) cultivated in a closed hydroponic system to variable calcium concentrations in the nutrient solution

BACKGROUND: The use of water containing calcium bicarbonate (Ca(HCO3)2) at excessively high concentrations in closed hydroponic crops can cause calcium ion (Ca2+) accumulation in the recycled nutrient solution (NS) and concomitantly negatively affect yield and product quality. The aim of the study was to determine maximum Ca2+ concentrations that do not harm the crop and to simulate the pattern of Ca2+ accumulation when the Ca2+ concentration in the irrigation water, and concomitantly in the replenishment nutrient solution (RNS), is excessive. In the current study, irrigation water containing 1.5, 3.0, 4.5 and 6.0 mmol L−1 Ca2+ was used to prepare the RNS supplied to pepper cultivated in a closed hydroponic system. RESULTS: At 1.5 mmol L−1 Ca2+, no Ca2+ accumulation was observed in the recirculating NS. However, at 3.0, 4.5 and 6.0 mmol L−1 in the irrigation water, the Ca2+ concentration in the recirculating NS, increased by the latter cropping stages to 17, 28 and 37 mmol L−1, corresponding to 6.4, 9.0 and 10.8 dS m−1. The accumulation of Ca2+ in the recirculating NS affected both tissue nutrient concentrations and uptake concentrations of Ca2+, sulphate ion (SO42−) and magnesium ion (Mg2+), but this was not the case for nitrogen (N) or potassium ion (K+). Growth, yield and plant water uptake were restricted at moderate (3.0 and 4.5 mmol L−1) and high (6.0 mmol L−1) external Ca2+ levels. CONCLUSION: In soilless pepper crops with zero discharge of fertigation effluents, the Ca2+ concentration in the irrigation water and the RNS should be lower than 3.0 mmol L−1 to avoid yield restrictions due to salinity. © 2021 Society of Chemical Industry. © 2021 Society of Chemical Industr

Nutrient uptake concentrations of a pepper crop under Mediterranean climate conditions

Knowledge of nutrient to water uptake ratios which are commonly termed "uptake concentrations", are especially important in greenhouse crops when plants are grown in closed-cycle cultivation systems. In such systems, the input ratio between the mass of a nutrient and the volume of water should be equal to the corresponding nutrient to water uptake ratio by the plants, so as to avoid accumulation. Thus, if data about the mean uptake concentrations are known, they can be used to establish nutrient solutions for closed-cycle hydroponic cultivations. Preliminary observations indicated that the nutrient-to-water uptake ratios in crops grown hydroponically in Mediterranean greenhouses may be substantially different than in north-European greenhouses, due to differences in climatic conditions. Furthermore different genotypes or different rootstocks in the case of grafted plants may have an impact on nutrient and water uptake. In the present study, the uptake of water and nutrients was measured in 4 different pepper genotypes ['Orangery', 'Bellisa', 'Sondela', 'Sammy' self-grafted and 'Sammy' grafted onto a commercial rootstock 'RS10' (Capsicum annum L.)]. All plants were grown in a closed NFT system. Mean water uptake ratios (uptake concentrations) of macro- and micronutrients for two time intervals, namely vegetative and 1st reproductive stage, were determined through the estimation of nutrient removal from the recycled nutrient solution. The results of this study indicated that 'Sondela' exhibited the highest uptake concentrations of NO3, Mg nd Ca in comparison with all other treatments In contrast, the uptake concentrations of all nutrients were similar in the grafted and the nongrafted 'Sammy' plants and that must be due to the genotype of the rootstock and the specific combination of the rootstock-scion. © 2017 ISHS

Responses of sweet pepper (Capsicum annum L.) cultivated in a closed hydroponic system to variable calcium concentrations in the nutrient solution

BACKGROUND: The use of water containing calcium bicarbonate (Ca(HCO3)2) at excessively high concentrations in closed hydroponic crops can cause calcium ion (Ca2+) accumulation in the recycled nutrient solution (NS) and concomitantly negatively affect yield and product quality. The aim of the study was to determine maximum Ca2+ concentrations that do not harm the crop and to simulate the pattern of Ca2+ accumulation when the Ca2+ concentration in the irrigation water, and concomitantly in the replenishment nutrient solution (RNS), is excessive. In the current study, irrigation water containing 1.5, 3.0, 4.5 and 6.0 mmol L−1 Ca2+ was used to prepare the RNS supplied to pepper cultivated in a closed hydroponic system. RESULTS: At 1.5 mmol L−1 Ca2+, no Ca2+ accumulation was observed in the recirculating NS. However, at 3.0, 4.5 and 6.0 mmol L−1 in the irrigation water, the Ca2+ concentration in the recirculating NS, increased by the latter cropping stages to 17, 28 and 37 mmol L−1, corresponding to 6.4, 9.0 and 10.8 dS m−1. The accumulation of Ca2+ in the recirculating NS affected both tissue nutrient concentrations and uptake concentrations of Ca2+, sulphate ion (SO42−) and magnesium ion (Mg2+), but this was not the case for nitrogen (N) or potassium ion (K+). Growth, yield and plant water uptake were restricted at moderate (3.0 and 4.5 mmol L−1) and high (6.0 mmol L−1) external Ca2+ levels. CONCLUSION: In soilless pepper crops with zero discharge of fertigation effluents, the Ca2+ concentration in the irrigation water and the RNS should be lower than 3.0 mmol L−1 to avoid yield restrictions due to salinity. © 2021 Society of Chemical Industry