Assessed variables

Foliar concentration of macronutrient: foliar macronutrient content (%) was determined every 20 days to 140 ddt (seven samplings). Total N content was determined by the semi-microkjeldahl method, P by colorimetry, K by flame photometry, Ca and Mg by atomic absorption spectrophotometry (^{Alcantar-Gonzalez and Sandoval-Villa, 1999}).

Accumulated dry biomass: weight of dry biomass for leaves, stems and commercial and noncommercial fruits were recorded. The plant material was dried in a forced air oven at 70 °C for 72 h until constant weight. Quantification was performed using a digital scale Escali model A115B, with capacity of 5 kg with approximation 0.01 g. It was expressed in g plant^-1.

Nutrimental extraction: it is calculated from the nutrient content in dry biomass (fruit, leaf and stem). It was expressed in g plant^-1.

Experimental design

A completely randomized design was used. The experimental unit consisted of a pot that contained a plant and all determinations were made with 5 replications. Extraction curves charts were performed using Microsoft Excel 2010 for Windows.

Foliar macronutrient concentration

A dilution effect of nutrients was observed from 20 to 140 ddt in all elements, except Ca (Table 1). It is inferred that because Ca is a bit variable component compared to N its concentration gradually increased, since one of its functions is to regulate the absorption, besides participating in storage and firmness of fruit (^{Alcántar-González and Trejo-Téllez, 2006}). Also ^{Cruz-Crespo et al. (2014)} reported this upward trend of Ca in plant growth of serrano pepper (Capsicum annuum L.), as for N, the behavior is due to it is an essential mobile element in cell division and expansion, thus in the vegetative growth of structures in such as stems and leaves (^{Sonneveld and Voogt, 2009}).

In P, K and Mg was also a dilution effect, this corresponds to an intense phase of growth, development and cell differentiation, which is when the crop development phases overlap; also, stems, young leaves and growing points are actively growing and contain high amounts of organic P in the form of nucleic acids and phospholipids (^{Mengel et al., 2001}). Potassium works as an osmotic regulator and activator or cofactor of more than 50 enzymes (kinases and oxidoreductase) from carbohydrates and protein metabolism, which is why its importance in plant metabolism (^{Alcántar-González Trejo-Téllez, 2006}).

Regarding Mg, the highest accumulation is in the leaves, as it is where great amount of chlorophyll and other pigments are synthesized. 15 to 30% of total magnesium in plants is associated with chlorophyll molecule, the other 70 or 85% is associated as a cofactor in different enzymatic processes of photosynthesis and respiration (^{Mengel et al., 2001}; ^{Taiz and Zeiger, 2010}).

It is noteworthy that a factor influencing the reduction in concentration of elements in leaf tissue is that when fruits were harvested there were nutrients losses in the plant. In this regard, ^{Terbe et al. (2006)} reported that fruits represent 64 to 84% of total fresh weight in plants of green pepper (Capsicum annuum L.). Foliar nutrient content (Table 1), can be used as reference to establish critical levels and concentration ranges for diagnostic and nutritional monitoring (^{Sonneveld and Voogt, 2009}; ^{Marchner, 2012}).

Nutrient extraction

N, P, K, Ca and Mg extraction in Hungarian pepper plants (Table 2), followed the trend of dry matter accumulation. These results are similar to those obtained by ^{PinedaPineda et al. (2008)}, in red raspberry ‘Malling Autumn Bliss’, where nutrient absorption was proportional to dry matter values gained by the plant. ^{Valentin-Miguel et al. (2013)} also reported the same behavior when assessing nutritional extraction in water pepper plants (Capsicum annuum).

In decreasing order of nutrient extraction was K>N> Ca>P>Mg (Table 2). These trends of nutrient extraction coincides with that reported by ^{Terbe et al. (2006)} who in green pepper (Capsicum annuum L.) indicate that the nutritional requirements are as follows:4 - 5.7 kg of K, 2.4-3.8 kg of N and 0.3- 0.5 kg of P per ton of harvested fruit. K was the nutriment extracted in greater extent due to formation processes and fruit growth, which constitute the main body of demand, with values of 70 to 80% of the total amount extracted by the plant (^{Bugarín-Montoya et al., 2002}).

With the information nutrient content, fruit production per plant (3511 g) and amount of accumulated dry matter in fruits, the amount of nutrients needed to produce a ton of fruit was calculated, which were (in kg t^-1 product harvested): 3.1 N, 0.4 P, 4.2 K, 1.0 Ca and 0.2 Mg (Table 2). To obtain these nutrimental extraction indices was taken as reference the amount of accumulated dry matter in commercial fruits, because if the total amounts of biomass in commercial and non-commercial fruits are taken as reference, nutrient extraction indices are underestimated. This information will allow to count with elements to design fertilization programs in open fields, since knowing the nutrient extraction index of the crop (Table 2), and the yield value expected, it will be possible to calculate nutrient demand of the crop; i.e. nutrient units (kg ha^-1) that the plant must extract from the soil and incorporate into their tissues to achieve a given yield (^{Castro-Brindis et al., 2004}). Extraction indices obtained in this investigation are lower than those obtained by ^{Valentín-Miguel et al. (2013)} who in water pepper (Capsicum annuum L.) reported (kg ha^-1): 7.7 N, 0.5 P, 7.5 K, 1.6 Ca and 0.6 Mg; this indicates that Hungarian pepper is a crop with lower nutrient requirements compared to water pepper.

Nutrimental extraction curves

Figure 1 presents the macronutrient extraction curves in Hungarian pepper plants (Capsicum annuum L.). These curves clearly shows that K and N were the most extracted macronutrients, which coincides with the results from ^{Terbe et al. (2006)} who indicated that for green pepper (Capsicum annuum L.) nutrient requirements are as follows: 4- 5.7 kg of K and 2.4-3.8 kg of N per ton of harvested fruits. The results of this study also agree with those reported by ^{Azofeifa and Moreira (2008)}, who in jalapeno pepper (Capsicum annuum L.) quantified extractions of 79.3 and 60 kg ha^-1 of K and N, respectively; with 20 833 plants ha^-1 and a yield of 15 t ha^-1 of fresh commercial fruits. In this sense, ^{Azofeifa and Moreira (2005)}, in chili pepper (Capsicum annuum L.) reported 180 and 139 kg ha^-1 of K and N, respectively; with 20 833 plants per hectare and a yield of 46.3 t ha^-1 of fresh commercial fruits.

Figure 1 Macronutrient extraction curves in Hungarian pepper plants (Capsicum annuum L.). 

According to nutrient extraction curves of Hungarian pepper it is observed that it is not recommended to apply large amounts of nutrients in the initial stage of crop development, because a significant proportion of nutrients would be out of reach from the root system of the plant.

Conclusions

The indices values of nutrient extraction can be used to determine nutrient demand of Hungarian peppers according to a yield goal, as follows (kg t^-1 product harvested): 3.1 N, 0.4 P, 4.2 K, 1 Ca and 0.2 Mg.

Foliar nutrient concentrations in recently mature leaves of Hungarian pepper plants grown with -0054 MPa osmotic potential in the nutrient solution, provide reference values for nutritional diagnostic purposes.