Characteristics of orchards and tres

Persian lemon orchards of productive age were selected in Nayarit and Veracruz. Some characteristics of the orchards are presented in Table 1.

In Nayarit, 500 g of chemical fertilizer of the composition was applied per tree and to the soil: 12 N, 8 P2O5, 16 K2O, 3 Mg, 0.06 Fe, 0.01 Zn and 0.02 B. In Veracruz, in the Paso Largo orchard, it was applied September 2015 to February 2016 the following fertilization (kg ha^-1) 318 N, 61 P2O5, 42 K2O, 9 de Ca and 11 Mg. The Grupo Exportador garden was fertilized from December 2015 to March 2016 with (kg ha^-1) 54.5 N, 20 P2O5, 20 K2O, 26.2 CaO, 34.5 MgO and 10 SO4. In each orchard, five trees were selected without visible nutrient deficiencies and without damage by pests and diseases.

Selected reproductive flows of the five trees selected by Orchard, were marked with plastic strips, 50 buds of different growth streams. In the orchards of Nayarit, buds of the spring and winter flows were marked and in those of Veracruz, buds of the flows were marked summer and winter.

Harvest of fruits. In all the orchards and for each flow, six fruits were harvested from each tree. The fruits were harvested at physiological maturity according to the provisions of NMX-FF-077 (^{SECOFI, 1996}).

Processing of fruits

Fresh weight was recorded from each fruit and separated in husk and segments to obtain its weight. The tissues were dehydrated in a forced air oven (Lab line 34887 Thomas Scientific, Madison, WI, USA), at 70 °C until constant weight was achieved. Samples composed by tree were prepared separately by fruit component and analyzed in a laboratory accredited by the NAPT program of the Soil Science Society of America.

Nutritional analysis

In the dry matter the concentrations of macronutrients (N, P, K, Ca, Mg, S) and micronutrients (Fe, Cu, Mn, Zn, B) were determined. The determination of N-total was by semi-microKjeldahl digestion (^{Carlson et al., 1990}) and for NO3 the colorimetric method was used (^{Baker and Smith, 1969}). The K was extracted by the atomic absorption method using an ICE 3000 atomic absorption spectrophotometer. P, Ca, Mg, S, Fe, Cu, Mn and Zn were extracted by ICP-optical coupled plasma (^{Haung and Schulte, 1985}) using an ICAP 7200 spectrophotometer (Thermo Scientific). B was determined by colorimetry (^{Wear, 1965}) with a Genesis 20 spectrophotometer (Thermo Scientific, USA).

Nutrient removal

The nutritional composition data were subjected to quality control with the Box-plot procedure of the computer program Minitab 15. The total removal of nutrients per ton of fresh fruit (Rt) was calculated by the following formula, exemplified for nitrogen:

Where: CNc= nutrient concentration in the rind, PSc= dry weight of the rind, CNg= concentration of the nutrient in the segments, PSg= dry weight of the segments, Ft= number of fruits in a ton (obtained from the quotient 1 000 kg between the fresh weight of the complete fruit) (^{Mellado et al., 2012}). With the same procedure, the removal of the other nutrients was calculated.

Statistical analysis

In Nayarit, the four orchards were analyzed together as a completely randomized experimental design with five replications (trees) and treatments (water and flowering flow) in factorial design 22 (water factor: irrigation and temporal, flowering factor flowering: spring and winter). Analysis of variance was performed with the statistical package SAS for Windows V9, with the procedure PROC GLM. The mean comparison was made with the Tukey test (p≤ 0.05). In Veracruz, each orchard was analyzed independently, using a completely randomized experimental design with five replications (trees) and two treatments (flowering flow). Analysis of variance was carried out with the statistical package SAS for Windows V9, with the procedure PROC ANOVA. The mean comparison was made with the Tukey test (p≤ 0.05).

Concentration of nutrients

In Nayarit, the concentration of nutrients in the tissues of the Persian lemon fruit was affected by the water management and the flowering flow. In irrigated orchards the husk had a higher concentration of N, P, K and Zn (1.1, 0.09, 1.08 g 100 g^-1, respectively, and 5.7 mg kg^-1), while Mg had higher concentration in rain orchards (0.18 g 100 g^-1). The peel of fruits of the spring flow had higher concentration of Ca and S (1.2 and 0.1 g 100 g^-1, respectively) and the one of fruit of the winter flow greater concentration of Mn and B (11.1 and 17 mg kg^-1, respectively). The interaction water*flow of flowering, significantly affected the concentration of Pand Ca in shell (Pr> F 0.03 and <0.0001, respectively).

The concentration of nutrients in the segments of the Persian lemon fruits was little affected by the water management and more affected by the flowering flow. Only the concentration of Zn showed an effect due to water management, with a higher concentration in irrigated orchards (7.4 mgkg^-1). The flowering flow affected the concentration of P, K, S, Mn and B, with a higher concentration of K and S in the fruits of the spring flow (1.2 and 0.07 g 100 g-1, respectively) and a higher concentration of P, Mn and B in the fruits of the winter flow (0.1 g 100 g^-1, 6.7 and 14.1 mg kg^-1, respectively). The interaction water*flow was significant for the concentration in segments of P, Ca, Zn and B (Pr> F 0.003, <0.0001, 0.04 and 0.03, respectively).

According to the reported ^{Roccuzzo et al. (2012)}, one of the nutrients present in greater quantity in citrus fruits is K (58%). This assertion coincides for the content of K in the fruit peel of irrigated orchards included in the present study, which was 50%. This could be due to the fact that the soil of these orchards presented higher levels of P and K, in comparison with the levels of the orchards without irrigation. The concentration of K found in the segments of the Persian lemon fruits of Nayarit was similar to that reported by ^{Dirceu et al. (2010)} (1.46 g 100 g^-1). However, the concentration of N and Ca of the fruits of Nayarit, presented values below that reported by the same author, which may be related to the low levels in soil of these nutrients.

In Veracruz, the summer and winter fruits of Orchard Paso Largo showed little difference in their concentration of nutrients. The peel of the summer fruits had higher concentration of Ca (1.9 g 100 g^-1) and Fe (95.5 mg kg^-1) than the winter fruits, while the winter fruits showed a higher concentration of Mn, Zn and B (13.3, 6.7 and 30.5 mg kg^-1, respectively). In the segments of the fruits originated by the winter flow there was a higher concentration of Zn and B (8.3 and 11.6 mg kg^-1, respectively).

In the Export Group Orchard, the fruits of the different flows, showed little differences in the concentration of nutrients in the shell and a greater number of differences in the concentration of nutrients in the segments. The peel of the fruits of the summer flow presented higher concentration of P, S and Fe (0.09 and 0.1 g 100 g^-1 and 61.91 mg kg^-1, respectively), and that of the fruits of the winter flow only showed higher concentration of B (29.05 mg kg^-1). Regarding the segments, the fruits of the summer flow presented higher values of concentration of P, K, S and Cu (0.2, 1 and 2.9 g 100 g^-1 respectively, and 5.4 mg kg^-1), and in the segments of fruits of the winter flow had a higher concentration of Zn and B (8.4 and 11.6 mg kg^-1, respectively).

The data presented show that flowering flow that originated the fruits. It has an effect on the concentration of some nutrients in the tissues of the Persian lemon fruit. A similar situation was reported for orange fruits in Florida, which presented a higher concentration of N, P, K, Ca and Mg in the months of June to August (^{Paramasivam et al., 2000}). Likewise, for orange trees ‘Tarocco’in Italy it was reported that the highest uptake of N, P and Ca is made from April to November, while the net absorption of K and Mg is almost complete in the summer (^{Roccuzzo et al., 2012}).

Nutritional removal

Nayarit The effect of water and flowering factors on the removal of some nutrients by the Persian lemon fruit was found. In irrigated orchards the removal of N, P, K and Zn by the shell was greater. Also, the fruit peel of the winter flow removed more P and Mn. The interaction water*flow of flowering was significant for the removal of Ca by the shell (Table 2).

The removal of nutrients by the segments of Persian lemon fruit was affected by the factors of water management and flowering (Table 3). The removal of N, Ca, Cu and Zn was higher in irrigated orchards and the removal of P, Ca, Mn and B was greater in the fruit segments of the winter flow. The interaction water*flow of flowering was significant for the removal of P, Ca and B by the segments.

The removal of nutrients per ton of Persian lemon fruit was affected by water factors and flowering flow, presenting the largest number of differences due to the water factor (Table 4). Under irrigated conditions, the Persian lemon crop removed more N, P, K, Ca, S, Cu and Zn, while these same nutrients under temporary conditions were less removed. The fruits of the spring flow made greater removal of S and those of the winter flow greater removal of P, Mn and and B. The interaction water*flow of flowering affected the removal of P (Figure 1A) and Ca (Figure 1B) per ton of Persian lemon.

Figure 1A and 1B . Interaction of water management*flowering flow in the removal of P and Ca per ton of Persian lemon in Nayarit orchards. 

The interaction water management*flow of flowering in the removal of P showed that, both in the irrigated orchards and in the temporary orchards, the harvest from the winter flow removed more amount of P. Regarding the removal of Ca, the water management interaction*flow of flowering showed that under irrigation conditions the fruits from the spring flow removed more Ca, while, in temporary orchards, the removal by the fruits of the winter flow was greater.

The greater removal of nutrients in irrigated orchards could be facilitated by the availability of water. In addition to the fact that soil moisture affects the growth of plants and their water potential, it influences the availability of nutrients in the soil solution (^{Sheikh Ashkevari et al., 2013}) and limits transpiration and photosynthesis (^{Seneviratne et al., 2010}). In the same way, the ambient temperature is one of the factors that affect the transpiration of plants (^{Azcón and Talón, 2008}). In previous studies it was reported that the seasonal uptake of K by citrus is very low during the colder months and increases rapidly after the resumption of new growth and flowering in spring (^{Roy et al., 1996}).

The nutrients that reported the greatest removal in the Persian lemon orchards included in the present study were N and K. This coincides with what hasalready been pointed out for other citrus fruits (^{Roccuzzo et al., 2012}). For Persian lemon orchards in Huimalguillo, Tabasco, the removal of nutrients considering a potential yield of 30 t ha^-1 was as follows: (kg t^-1) 1.83 N, 0.27 P, 1.97 K, 1.11 Ca, 0.15 Mg and (g t^-1) 9.7

Fe, 0.53 Cu, 1.06 Mn, 2.06 Zn and 3.05 B (^{Salgado et al., 2016}). Themacronutrientremovalreportedfor Tabasco was similar to that foundinthis study, however, the total removal of Fe, Zn and B was lower in Nayarit.

According to the results of the soil analysis, in the four orchards the pH was classified in the range of acidity, but different magnitude. The main differences in the soil of the four orchards were the content of organic matter and P. The content of organic matter was medium in a single orchard, while the others had low content.

Water management and thedifferences between soils reported by the soil analysis affected the removal of nutrients by the Persian lemon crop. The content of P in the soil was higher in the two irrigated orchards, which could explain that the analysis of the interactions water*flow for the concentration and removal of nutrients, has reported the highest value for the treatment with irrigation in the winter flow.

The removal of nutrients could also be influenced by the K contentinthe soils, which was moderatelyhightoveryhigh. It was reported that the high availability of K in the soil can reduce the absorption of other cations, mainly Mg, Ca, and NH + (^{Ashok et al., 2006}).

Of the factors evaluated in the present study, it was found that water management had the greatest effect on the removal of nutrients. However, to replenish at least the nutrients removed for each crop, the nutrients mostly removed in each production flow must be taken into account.

Veracruz. The tissues of the Persian lemon fruits of the Paso Largo orchard showed differences in the removal of nutrients between flows (Table 5). The peel of the summer fruits removed more P, Ca and Fe, while the peel of the winter fruits removed more Mn, Zn and B. As for the segments, in the summer more Fe was removed and Cu and in winter greater amount of B.

In the Export Group Orchard, the peel and segments of the winter fruits removed more nutrients (Table 6). The peel removed more Ca and B and the segments removed more Ca, Fe, Zn and B.

The nutrient removal data per ton of fruit are presented in Table 7. In the Orchard Paso Largo, differences were found in the removal by harvest of each flow. The fruits from summer removed more P, Ca, Fe and Cu, while the removal of Zn and B was higher in the harvest of the fruits from the winter flow. In the Export Group Garden, the winter harvest removed more nutrients, the nutrients being mostly N, Ca, Zn and B removed. In this orchard, the summer flow harvest had less removal of the nutrients analyzed.

The removal of nutrients in the Persian lemon orchards included in this study was affected by factors such as population density and fertilization. The greatest nutrient removal in the Grupo Exportador orchard was related to the lowest number of trees per hectare (208 trees) compared to the Paso Largo orchard (416 trees), this being due to the fact that plantation density is closely related to the effects it produces on the plant, such as intra-specific competition for nutrients, water and space (^{Mateus and Orduz, 2016}). Regarding fertilization, in the Orchard Paso Largo the application of fertilizer was started 3 months earlier than in the Exporter Group Orchard, for which the Paso Largo Orchard received fertilizer for 6 months and the Grupo Exportador Orchard for 4 months, which could propitiate that trees had access to nutrients in a more timely manner. It is important to note that there was a coincidence in both orchards, in the greater removal of Zn and B by the fruits of the winter flow.

When comparing the removal of nutrients in Persian lemon orchards in Nayarit (^{Mellado et al., 2015}), with that found in the present study, it can be seen that in the Veracruz orchards, the N, S, Fe and Zn were mostly removed by the harvest.