Effects of Winter Foliar Fertilizing and Plant Growth Promoters on Element and Carbohydrate Contents on the Shoot of Navel Orange Sapling

ABSTRACT

The main aims of this paper are to evaluate the effects of winter foliar fertilizer and plant growth promoters on element and carbohydrate contents of the shoot of the navel orange sapling. This study was conducted in the lath house in the Agriculture College in Al-Qasim Green University during the period from 11-1-2014 to 6-1-2015. A factorial experiment (2 × 7) was done within a randomized complete block design with four replications. The first factor represented two foliar application dates of PRO-SOL fertilizer (1 g/L) every 2 weeks during winter–spring season (S1) in 2014–2015 and spring season dates (S2) in 2015). Second factor was foliar application of plant growth promoters in mid-March with indole butyric acid (IBA), 40 and 80 mg/L; forchlorfenuron (CPPU, KT-30), 15 and 30 mg/L; IBA+KT-30 (CPPU), 40 + 15 mg/L consecutively; and IBA+KT-30 (CPPU) 80 + 30 mg/L consecutively. The main effects due to the foliar fertilizing dates (S) were found to be highly significant for nitrogen content (%). While the second main factor plant growth promoter (T) was found to be highly significant for nitrogen and potassium content % and S × T interaction which were found to be significantly different for nitrogen, potassium and ferric content (%), respectively. Foliar fertilizing dates (S) caused a significant increase in nitrogen content (%). The experiment results showed that there different responses with treatments, the S2 with T7 treatment achieved the highest value value with ferric contents % while the same treatments recorded the lowest value in potassium contents %. Therefore, it was concluded from the results of the experiment that potassium uptake percent for in S2 not effective as well as T7: IBA at 80 ppm+ CPPU at 30 ppm.

KEYWORDS:

• Winter foliar fertilizer
• plant growth promoters
• carbohydrate contents
• naval orange sapling

Introduction

Orange (Citrus sinensis L.) can be considered a member of the Rutaceae family and of the genus Citrus (Mohamed Ali, 2018). Moreover, orange has become the most commonly grown tree fruit around the world (Al-Taey et al., 2010). In addition, naval orange can be described as the biggest citrus fruits with good flavor having a navel in the base of the fruit; they are juicy, seedless or have only a few seeds, and are early ripening (Gurab, 1998). Citrus trees require nutritional feeding with nutrients to power the movement of biological process and are necessary for the metabolism process and many functions of the plant since nutrient deficiencies can cause physiological confusion and negatively affect plant growth and yield (Abbas and Hasan, 2018). Utilization of chemical fertilizers frequently decays soil fertility and the resultant harvest efficiency because of supplement irregularity in the soil (Al-Taey et al., 2018). As a result, foliar fertilizing or foliar feeding with nutrients can be absorbed by leaves or other parts of the plant like fruits and stems to provide the plant with the nutrients it needs, entering through the cell envelope by water, and diffusion (Alexander, 1986). Brayan (1999) reported that the major role of foliar fertilizing was the fast absorption of nutrients and visually fixes the leaves’ deficiencies because of one or more nutrients.

Plant growth promoters play an important role in vegetative and reproductive growth (Hasan and Jumaa, 2013a). Cytokinins are one of the most important plant hormones and can significantly improve the growth of crop plants, leaves enlargement, seed germination, synthesis of chlorophyll (Al-Taey and Majid, 2018; Hasan and Jumaa, 2013b; Mok, 1994), yield increase, cell division, plant development, and delayed senescence (Ashikari et al., 2005; Gan and Amasion, 1995). KT-30 (CPPU) or forchlorfenuron is a synthesis cytokinin that is more active than benzyl adenine by about 10–100 times. Many types of research indicate that the foliar application of KT-30 improves plant growth and enhances vegetative and reproductive characteristics in many species of plants like Cyclamen persicum (Kabayashi and Matsukawa, 1984), potato (El-shraiy et al., 2010), and Calendula officinalis L. (Cocu et al., 2004).

Auxin is one of the plant’s hormones which regulate many developmental processes and morphogenesis like environmental response, photo and geotropism, cell enlargements, apical dominance, and root primordial initiation (Camolesi et al., 2007; Singh and Khan, 2009; Woodward and Bartel, 2005). Indole butyric acid (IBA) is a synthesis auxin used for root cuttings (Blythe et al., 2003). A few types of research refer to its ability in the foliar application on the vegetative parts of ornamental crops for rooting stem cutting which was similar or less than in its effect compared to immersing the base of a stem cutting in IBA (Li et al., 2011). Other studies showed that foliar application of IBA on pine plants improved seedling growth (Abd El- Gayed, 2013; Xu et al., 2012), yield, and growth of cotton plants (Felixloh and Nina, 2000).

In this study, we have discussed and compared the different plant hormones and winter foliar fertilizing. Thus, the aims of this study were to evaluate the effects of winter foliar fertilizing and plant growth promoters on element and carbohydrate contents on the shoot of naval orange sapling.

Materials and Methods

Experiment Site

The research was conducted in the lath house of the Agriculture College, Al-Qasim Green University in spraying irrigation system conditions during theperiod from 11-1-2014 to 6-1-2015.

Plant Materials

One-year-and-a-half naval orange sapling budded on sour orange rootstocks planting in plastic pots (diameter 23.5 cm). The saplings were brought from the Center of Citrus researches of Karbala governorate.

Experiment Design and Treatments

A factorial experiment (2 × 7) was done within a randomized complete block design (RCBD) with four replications. The first factor represented two foliar application date (S) of PRO-SOL fertilizer that contains macroelements and microelements as shown in Table 1, used (1 g/L) every 2 weeks during winter–spring season (2014–2015) that represented first foliar application date treatment (S1), and the second foliar application date was in the spring (S2) season (2015). Second factor was foliar application of plant growth promoters with seven treatments and assigned as follows: T1: control; T2 and T3 (T) in mid-March with IBA 40 and 80 mg/L; T4 and T5: KT-30 (CPPU), 15 and 30 mg/L; T6: IBA+KT-30 (CPPU), 40 + 15 mg/L consecutively; and last T7: IBA+KT-30 (CPPU) 80 + 30 mg/L consecutively.

Table 1. PRO-SOL foliar fertilizer components (PRO-SOL Company, USA).

Macroelements	Percentage
Total nitrogen	20
Nitrogen (ammonia)	3.9
Nitrogen (nitrate)	5.8
Nitrogen (urea)	10.3
Ammonium phosphate(P2O5)	20
Potassium nitrate (K2O3)	20
Microelements	ppm
Sodium borate (B)	200
Cu (EDTA)	500
Fe (EDTA)	1000
Mn (EDTA)	500
Zn (EDTA)	500
Sodium molybdate (Mo)	5

According to Table 1, the composition of the foliar application of PRO-SOL fertilizer contains macroelements and microelements. Total nitrogen, ammonium phosphate (P₂O₅), and potassium nitrate (K₂O) have the highest rate of by 20%. The nitrogen contents in form ammonia (NH4), nitrate (NO3-), and urea (CH₄N₂O) were 3.9%, 5.8%, and 10.3%, respectively. The microelement component has (Sodium Borate, 200 ppm), (Cu EDTA, 500 ppm), (Fe EDTA, 1000 ppm), (Mn EDTA, 500 ppm), and (Zn EDTA, 500 ppm) and the lowest content was in (Mo, 5 ppm) by Sodium molybdate.

Element Content

The Samples were digestion according to Johnson and Ulrich (1959), Nitrogen was calculated by Microkjeldahl device according to Chapman and Pratt (1961), phosphorous determined using ammonium molybdate by spectrophotometer device on 882 nm wavelength according to Page et al. (1982), potassium was determined by flame photometer according to Johnson and Ulrich (1959).

Irrigation System

Plants were irrigated when needed by adding 1 L of water for each plant beside sprinkler irrigation. A handy sprinkler (1.5 L capacity) was used for foliar application till runoff, and the saplings were established at a distance of 60 cm between saplings and 1 m between plots; there were 14 plants in each plot.

Statistical Analysis

Analysis of variance (ANOVA) was determined using two factorial completely randomized designs.

The mean data for all observations were compiled by taking average value over randomly selected plants from all the replications. The data were subjected to ANOVA to determine the level of variation of all observed parameters using the Statistical Analysis System program (version 9.4, SAS Institute Inc. Cary, NC, USA). Results were expressed as mean, while means were compared using the LSD (Least Significant difference) test at α = 5% and the effect on quality parameters was considered at 5% significance level).

Results and Discussion

The combined ANOVA for content percent of nitrogen, phosphorus, potassium, ferric and carbohydrate of shoots of naval orange sapling is presented in Table 2. The main effects due to the foliar fertilizing dates (S) were found to be highly significant for nitrogen content (%). While the second Factor which represented (Plant Growth Prompters) achieved highly significant  value in nitrogen and potassium content (%), the interaction between the Foliar fertilizing date S and plant growth promoter T  where found to be a significant, different for nitrogen, potassium and ferric content %, respectively. Foliar fertilizing dates (S) caused a significant increase in nitrogen content (%) and there is no significant effect on the other parameters (Table 3).

Table 2. Combined analysis of variance (ANOVA) for treatments for percentage of nitrogen, phosphorus, potassium, ferric and carbohydrate contents of shoots of naval orange sapling.

		Mean squares
Source of variation	df	Nitrogen content (%)	Phosphorus content (%)	Potassium content (%)	Ferric content (%)	Carbohydrate content (%)
Foliar fertilizing dates (S)	1	0.105a	0.003	0.010	0.001	0.074
Plant growth promoters (T)	6	0.092a	0.002	0.056*	0.604	0.062
S*T	6	0.210a	0.002	0.023a	0.188a	0.073
Error	39	0.011	0.002	0.009	0.123	0.080

^a* indicate significance at p ≤ 0.01 or p ≤ 0.05, respectively; df indicates degree of freedom.

Table 3. Effect of foliar application dates (S) of PRO-SOL fertilizer on the percentage of nitrogen, phosphorus, potassium, ferric, and carbohydrate contents of shoots of naval orange sapling.

Foliar fertilizing dates (S)	Nitrogen content (%)	Phosphorus content (%)	Potassium content (%)	Ferric content (%)	Carbohydrate content
Winter–spring (S1)	1.211a	0.241a	1.516a	5.37a	0.239
Spring (S2)	1.125b	0.256a	1.543a	5.37a	0.311
LSD	0.0574	0.0271	0.0516	0.1898	0.1525
Significance	**	ns	ns	ns	ns

In the column, means followed by equal letters are not significantly different (ns) for p ≤ 0.05 (LSD); *p ≤ 0.05; **p ≤ 0.01.

Data presented in Table 4 displayed that there were significant differences in foliar fertilizing application of plant growth promoters (T) in the percentage of nitrogen and potassium contents of shoots of naval orange sapling. This result agreement with Brayan (1999) which he reported major role of foliar fertilizing was fast absorption of nutrients. The Plant growth promoters increase the nitrogen and potassium contents this results were in accordance with the findings of both studies Mok (1994) and Al-Taey and Majid (2018) whose reported their results about important plant hormones and it is had a significantly improvement for the growth of crop plants, leaves enlargements. However, other treatments did not have any significance (Table 4). The highest nitrogen shoot content (1.356) was achieved using (T7) IBA at 80 ppm+ CPPU at 30 ppm. While the lowest nitrogen content (0.995) was recorded using (T4) CPPU at 15 ppm (Table 4). The highest values of potassium content were recorded using T1: control, T3: IBA at 80 ppm and T4: CPPU at 15 ppm and T4, and the values were 1.650, 1.594, and 1.603) (Table 4), respectively. While the lowest potassium value was achieved in other four treatments.

Table 4. Effect of foliar application of plant growth promoters (T) on the percentage of nitrogen, phosphorus, potassium, and ferric contents of shoots of naval orange sapling.

Plant growth promoters (T)	Nitrogen content (%)	Phosphorus content (%)	Potassium content (%)	Ferric content (%)	Carbohydrate content
T1	1.11625b	0.258a	1.650a	5.46abc	0.218a
T2	1.17b	0.225a	1.448b	5.08d	0.240a
T3	1.196b	0.268a	1.594a	5.36bcd	0.248a
T4	0.995c	0.240a	1.603a	5.02d	0.473a
T5	1.159b	0.258a	1.478b	5.69ab	0.240a
T6	1.182b	0.243a	1.494b	5.27cd	0.249a
T7	1.356a	0.250a	1.443b	5.72a	0.258a
LSD	0.1073	0.0507	0.0966	0.355	0.2853
Significance	**	ns	*	ns	ns

In the column, means followed by equal letters are not significantly different (ns) for P≤0.05 (LSD); *P ≤ 0.05; **P ≤ 0.01. where treatments assigned as T1: Control, T2: IBA at 40 ppm, T3: IBA at 80 ppm, T4: CPPU at 15 ppm, T5: CPPU at 30 ppm, T6: IBA at 40 ppm+ CPPU at 15 ppm, T7: IBA at 80 ppm+ CPPU at 30 ppm.

The Table 5 show up there were highly significant differences among interactions of foliar fertilizing dates (S) and plant growth promoters (T) treatments in the shoots of naval orange saplings for nitrogen, potassium, and ferric content. However, there are no significant differences in the interaction of foliar fertilizing dates (S) and plant growth promoters (T) treatments on phosphorus and carbohydrate contents. The highest nitrogen rate in shoot was (1.755%) with interaction S1 ˣ T7 Treatment and this result agree with other studies showed that foliar application of IBA on pines plants improved seedling growth (Abd El- Gayed, 2013; Xu et al., 2012) yield and growth of cotton plants (Felixloh and Nina, 2000). While the lowest value (0.958%) was recorded for interaction S1 ˣ T7.

Table 5. Effect of interaction between dates (S) of foliar application and plant growth promoters (T) on the percentage of nitrogen, phosphorus, potassium, and ferric contents of shoots of naval orange sapling.

Foliar fertilizing dates (S)	Plant growth promoters (T)	Nitrogen content (%)	Phosphorus content (%)	Potassium content (%)	Ferric content (%)	Carbohydrate content (%)
	T1	1.078bc	0.265a	1.578bcd	5.620ab	0.208b
	T2	1.135b	0.225a	1.410e	5.030cd	0.260ab
	T3	1.215b	0.258a	1.595abc	5.284bcd	0.263ab
Winter – spring(S1)	T4	0.918d	0.253a	1.690ab	4.805d	0.223abcd
	T5	1.205b	0.255a	1.418e	5.795a	0.215cb
	T6	1.173b	0.218a	1.473cde	5.468abc	0.248abcd
	T7	1.755a	0.218a	1.450de	5.613ab	0.255abc
	T1	1.155b	0.250a	1.723a	5.293bcd	0.228abcd
	T2	1.205b	0.225a	1.485cde	5.123bcd	0.220bcd
	T3	1.178b	0.278a	1.593abc	5.433abc	0.233abcd
Spring(S2)	T4	1.073bc	0.228a	1.515cde	5.228bcd	0. 0.223abcd
	T5	1.113b	0.260a	1.538cde	5.580ab	0.265a
	T6	1.193b	0.268a	1.515cde	5.073cd	0.250abcd
	T7	0.958cd	0.283a	1.435e	5.830a	0.260ab
LSD		0.1518	0.0717	0.1366	0.502	0.4035
Significant		**	ns	**	**	ns

In the column, means followed by equal letters are not significantly different (ns) for P ≤ 0.05 (LSD); *P ≤ 0.05; **P ≤ 0.01. where treatments assigned as T1: Control, T2: IBA at 40 ppm, T3: IBA at 80 ppm, T4: CPPU at 15 ppm, T5: CPPU at 30 ppm, T6: IBA at 40 ppm+ CPPU at 15 ppm, T7: IBA at 80 ppm+ CPPU at 30 ppm

However, the data presented in Table 5 displayed that the highest contents of potassium (1.723%) were recorded at interaction spring (S2) and T1: control and may be related to the highest effect of weather on uptake the plant to potassium. This result indicated that the foliar application of plant growth promoters may not have any effects on potassium content, and for uptake, the nutrient such as potassium (K) must be applied through drip irrigation or other methods for more nutrient use efficiency. Moreover, the lowest K content (1.435%) was tested under at interaction spring (S2) and T7: IBA at 80 ppm+ CPPU at 30 ppm. This result can be explained due to the weather conditions that have a major effect on absorb the leaves the nutrient when the foliar application applied.

On the other hand, the data displayed in Table 5 investigated that the highest contents of ferric (5.795 and 5.830%) were recorded at interaction of S1 with T5: CPPU at 30 ppm and interaction of spring (S2) with T7: IBA at 80 ppm+ CPPU at 30 ppm. While the lowest ferric content (5.030%) was tested under at interaction S1 with T2: IBA at 40 ppm. This result can be explained due to the weather conditions that have major effect on absorb the leaves the nutrient when the foliar application applied. Although the carbohydrate content was not affected by treatment interaction, data in Table 5 showed that the higher content of carbohydrate was achieved under the treatment contain high concentration CPPU. The higher values of total carbohydrates (%) were obtained from (T5) CPPU at 30 ppm. In general, Table 5 shows that there were trends for increase carbohydrate CPPU work alone without mixed with other plant growth promoters and this agrees with those reported by Bhat et al. (2012).

Orange trees are evergreen trees which hold their foliage over the year. In winter, the leaves continue doing their biological jobs, like photosynthesis, transpiration, and respiration, but metabolism slows down as the plant enters a dormant state, with no new shoot growth. Winter fertilizing is useful and used in evergreen landscape plants (Hasselkus, 1998), ryegrass, and small grains (Hancock, 2016). Lavatt (2013) documented that foliar low-biuret urea application in winter prebloom increase the  total yield of both navel and Valencia orange cultivars, this results agreed with current study as for nitrogen contents (Table 5), but  its disagreement with current study results which we find no significant effects between winter and spring  fertilization maybe because orange sapling dose not has fruits that become a sink to absorb nutrients from leaves so the osmotic potential in leaves dose not much change and be helpful for more nutrients absorption like (Lavatt, 2013) had been found. Nickell (1985) reported the role of growth regulator (CPPU) which plays a role in cell division and cell wall elongation.

Conclusion

In this study, plant growth promoters showed a significant effect in some Nutrients content due to their effect in division and elongation of cells which induced the leaves to consume more nutrients and increase their absorption. There are cross results from current study, for example the Ferric content (%) was highest value recorded under interactions S1 ˣ T7 Treatment, but the same treatments give lowest values for potassium content %. Therefore, it was concluded from the results of the experiment that potassium uptake percent for in S2 not effective as for T7: IBA at 80 ppm+ CPPU at 30 ppm. The reduction of Potassium ratio due to the role of IBA and CPPU to promoting uptake the potassium nutrient to another active parts in the plant during fruit set.

Author’s contribution

Ahmed Mohammad Hasan and Tahani J. Mohamed Ali designed the research and conducted in lath house as well as performed all the lab works. Tahani J. Mohamed Ali and Duraid K.A.Al-Taey also performed the review and statistical analysis and wrote the manuscript with comments from all authors and finalized the manuscript.

Acknowledgments

We thank Al-Qasim Green University for providing lath house and extend our thanks to the Iraq and Agriculture College in Al-Qasim Green University for supporting and providing research facilities for this study during the period from 11-1-2014 to 6-1-2015.