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Effects of different forms of nitrogen application on yield response of corn under saline conditions.

Introduction

Soil salinity and sodicity are one of the main agricultural problems limiting plant growth and development in the world especially in arid and semiarid regions [11]. Osmotic osmotic,
adj pertaining to osmosis.

osmotic pressure,
n See pressure, osmotic.



osmotic

emanating from or pertaining to the pressure of osmosis.
 effect, ionic i·on·ic
adj.
Of, containing, or involving an ion or ions.



ionic

pertaining to an ion or ions.


ionic medication
iontophoresis.
 imbalance, and specific ion toxicity are the main harmful salinity effects that can be inhibited plant growth and development [4]. Agricultural production in these soils to a large extent suffers from insufficient organic matter. It is well established that the growth inhibition Growth inhibition (GI) is a medical term pertaining to cancer therapy and the specific reduction in growth of tumors and oncogene cells by a chemical compound, mechanical therapy (e.g.  and the adverse effects induced by salinity can be alleviated by proper fertilization and water management [4]. Investigations have found there is a positive correlation Noun 1. positive correlation - a correlation in which large values of one variable are associated with large values of the other and small with small; the correlation coefficient is between 0 and +1
direct correlation
 between soil salinity levels and nitrogen application. Therefore, excessive N application leads to soil salinization. Hence, proper rate and timing of N application are critical factors in saline soils.

Nitrogen has been recognized as an extremely essential nutrient An essential nutrient is a nutrient required for normal body functioning that cannot be synthesized by the body and must be obtained from a dietary source. Some categories of essential nutrient include vitamins, dietary minerals, essential fatty acids, and essential amino acids.  for plant growth. Both ammonium-N (N[O.sub.3.sup.-]) and nitrate-N (N[H.sub.4.sup.+]) are readily taken up by plants. But N[O.sub.3.sup.-]is the preferred form in flooding or anaerobic anaerobic /an·aer·o·bic/ (an?ah-ro´bik)
1. lacking molecular oxygen.

2. growing, living, or occurring in the absence of molecular oxygen; pertaining to an anaerobe.
 conditions. Fageria [6] reported that plants supplied with equal proportions of N[H.sub.4.sup.+] and N[O.sub.3.sup.-] grew as well as those supplied with any single amount of N form. The more or less favorable effect of N[H.sub.4.sup.+] or N[O.sub.3.sup.-] in individual cases varies among species and is dependent on the concentration, as well as on the pH value, the buffer capacity, and the content of other nutrients in the medium. It has been claimed that N[H.sub.4.sup.+]absorption is faster than N[O.sub.3.sup.-]. The reason for such a differences between absorption rate can be due to more energy required to assimilate N[O.sub.3.sup.-] compared with N[H.sub.4.sup.+] (20 ATP ATP: see adenosine triphosphate.
ATP
 in full adenosine triphosphate

Organic compound, substrate in many enzyme-catalyzed reactions (see catalysis) in the cells of animals, plants, and microorganisms.
 vs. 5 ATP), as well as oxygen demand to absorption of N[O.sub.3.sup.-].

Forms of N fertilizer varied widely and select the appropriate form of nitrogen should be of principal concern and depends up on various factors such as type of crop, soil status and rotation. In salt-affected soil, N[O.sub.3.sup.-] assimilation is low. There is no agreement that which type of N is the best form under saline conditions. Cations such as K, Ca and Mg decreased by increasing N[H.sub.4.sup.+], while N[O.sub.3.sup.-] has incremental effect on these cations. It is believed that for most plant species, N[O.sub.3.sup.-] is preferred form of N under saline conditions, while a small number of plant prefer N[H.sub.4.sup.+]. Few workers have reported, however, mixtures of ammonium ammonium /am·mo·ni·um/ (ah-mo´ne-um) the hypothetical radical, NH4, forming salts analogous to those of the alkaline metals.

ammonium carbonate
 and nitrate at ratio of 50:50 resulted in consistently positive effects on greater grain and biological yields. These beneficial effects have been attributed to the antagonism effects of N[O.sub.3.sup.-] on [Cl.sup.-] [3].

Irshad et al. [8] studied the influence of nitrogen and saline water Saline water is a general term for water that contains a significant concentration of dissolved salts (NaCl). The concentration is usually expressed in parts per million (ppm) of salt.  on the growth and partitioning of mineral concentration in corn and reported that leaf, stem and root dry matter was significantly reduced by saline water. Saline water had significant effect on plant N concentration. Nitrogen application increased Na to K ratio, whereas ratios of Na to Ca and Na to Mg had greatest value in control. Their result indicated that interaction of saline water and nitrogen has mixed effects on the partitioning of mineral elements in corn. Response of sorghum sorghum, tall, coarse annual (Sorghum vulgare) of the family Gramineae (grass family), somewhat similar in appearance to corn (but having the grain in a panicle rather than an ear) and used for much the same purposes.  plants to different sources and amounts of fertilizer at different levels of salinity also investigated. In sorghum, a study results showed that increasing salinity significantly decreased at 1% level of probability emergence, stem height, fresh and dry weight as well as leaf area index The Leaf Area Index or LAI is the ratio of total upper leaf surface of a crop divided by the surface area of the land on which the crop grows.

The LAI is a dimensionless number.
.

The effect of three forms of N, at a uniform rate equivalent to 100 kg N [ha.sup.-1] namely: urea, nitrate-N, 50% urea + 50% nitrate-N (mixed-N) and no N application (control) on corn under saline and non-saline conditions was studied by Irshad et al. [9]. The biomass (shoot and root) of corn was significantly greater in mixed-N treatment than in single sources in saline condition, whereas it varied in the order of urea > mixed-N > nitrate-N > control in non-saline soil. Nitrogen use efficiency in non-saline soil improved by 15% compared with saline soil. Zhi-Wei et al. [14] showed that salinity had no effect on nitrogen content in the roots or shoots of corn, whereas it significantly reduces leaf area index, stem height, dry matter accumulation, root length and total N uptake. Shenker et al. [12] studied sweet corn response to combination of nitrogen levels and salinity stresses. At low salinities, the leaf N content, N uptake, and yield increased with increasing N fertilizer up to 45% of local N-fertilization recommendations. Azevedo Neto and Tabosa [2] evaluated the effect of different salinity levels on N, P and K nutrient efficiency in corn at seedlings stage. The salt stress reduced the N, P and K nutrient efficiency in both studied cultivars. Tolerant cultivar cultivar

Any variety of a plant, originating through cloning or hybridization (see clone, hybrid), known only in cultivation. In asexually propagated plants, a cultivar is a clone considered valuable enough to have its own name; in sexually propagated plants, a
 (Cv. P-305) had greater nutrient efficiency than sensitive cultivar (Cv. BR-5011) in high salinity conditions. Khalifa et al. [10] showed that the high concentrations of N[H.sub.4.sup.+] reduced dry matter yield of corn in saline condition and N[O.sub.3.sup.-] was more effective in increasing total N content of plant tissues than the same concentration of N[H.sub.4.sup.+]. Concomitant using of N[H.sub.4.sup.+] along with N[O.sub.3.sup.-] always induced higher yields and tissues N content than individual consumption of N[H.sub.4.sup.+].

As an important macronutrient macronutrient /mac·ro·nu·tri·ent/ (-noo´tre-ent) an essential nutrient required in relatively large amounts, such as carbohydrates, fats, proteins, or water; sometimes certain minerals are included, such as calcium, chloride, or sodium. , N form may possibly influence growth and dry matter accumulation in corn under saline conditions. In the present experiment, we investigated the effects of N fertilizers in different forms on the growth and yield response of corn in salt-affected soil.

Materials and Methods

The experiment was conducted at agricultural research center of Islamic Azad University-Sabzevar Branch, Iran during 2010. In this study, a randomized ran·dom·ize  
tr.v. ran·dom·ized, ran·dom·iz·ing, ran·dom·iz·es
To make random in arrangement, especially in order to control the variables in an experiment.
 complete block design with four replications was used. Treatments were N form (urea, ammonium nitrate ammonium nitrate, chemical compound, NH4NO3, that exists as colorless, rhombohedral crystals at room temperature but changes to monoclinic crystals when heated above 32°C;. , ammonium sulfate ammonium sulfate, chemical compound, (NH4)2SO4, a colorless-to-gray, rhombohedral crystalline substance that occurs in nature as the mineral mascagnite. It is soluble in water and insoluble in alcohol or liquid ammonia.  and mixed 50:50 and mixed equally with all three fertilizer). Each of fertilizers was applied based on soil tests and the need of corn (200 kg N [ha.sup.-1]). Soil characteristicis given in Table 3-1.

The treatments were laid out in 3*6 m plots. Crops were sown at a spacing of 0.60 m between rows and 0.20 m within rows. Seeds of crops were sown by hand. Sowing date was last week of June 2010. Preplant N fertilizer as ammonium nitrate (containing 34% N) and urea (containing 46% N) and ammonium sulfate (containing 21% N) were broadcasted manually and incorporated into the soil at planting. Nitrogen side-dress fertilizer was applied at seedling stage. Irrigation irrigation, in agriculture, artificial watering of the land. Although used chiefly in regions with annual rainfall of less than 20 in. (51 cm), it is also used in wetter areas to grow certain crops, e.g., rice.  was done with saline water (Ec= 2.45 ds [m.sup.-1]) in 10-day intervals according convention water scheme for corn in the region. The other fertilizers were applied based on soil analysis results. During the growth period all plots were weeded manually. No serious incidence of insect or disease was observed and no pesticide or fungicide fungicide (fŭn`jəsīd', fŭng`gə–), any substance used to destroy fungi. Some fungi are extremely damaging to crops (see diseases of plants), and others cause diseases in humans and other animals (see fungal infection).  was applied.

At harvesting time one meter from the beginning and a half meter around each plot was removed as a marginal effect. The remaining area was harvested by hand. To evaluate yield components of corn including ear numbers per plant, grain numbers per ear, row numbers per ear, grain numbers and one-hundred grain weight, 10 plants were selected randomly from final harvest area.

Sodium and K were determined by flameemission method (FP640, Shanghai Precision & Scientific Instrument Inc., Shanghai, China). Nitrogen content was analyzed using an Auto-Kjeldahl Unit (B-339, BuchiLabortechnik AG, Switzerland). Nitrogen use efficiency was calculated according;

NUE NUE Nitrogen Use Efficiency
NUE Nuremberg, Germany - Nuremberg (Airport Code)
NUE Non-Upset Ends (piping) 
 = [N.sub.a] - [N.sub.b] / [N.sub.r]

Where [N.sub.a] and [N.sub.b] represent absorbed N in grain for applied N plots and control, respectively and [N.sub.r] is nitrogen application rate for each plot.

Data collected were subjected to the analysis of variance (ANOVA anova

see analysis of variance.

ANOVA Analysis of variance, see there
). Test of significance of the treatment difference was done on a basis of a t-test. The significant differences between treatments were compared with the critical difference at 5% and 1% level of probability.

Results:

Analysis of variance showed that nitrogen form had significant effects on economic and biological yields (p<0.01, Table2). The effects of N Form on economic yield is illustrated in Fig. 1. Ammonium had more effect on yield compared with other forms of N, although there was no significant difference between ammonium nitrate and ammonium sulfate, but nitrogen as urea could not produce desirable yield. Orthogonal comparisons showed that use of mixture fertilization had more effect on yield than single form of N. Among combination form of N, 50:50 combination of ammonium nitrate: ammonium sulfate had greatest economic yield. The greatest biological yield was observed at combination of threeforms of N (Fig 2). The lowest biological yield was achieved in control treatment. There are no difference among urea and combination of urea along with ammonium sulfate and ammonium nitrate. Biological yield had less sensitive to N form than economic yield.

Yield Components:

Analysis of variance showed that nitrogen source had significant effect on row numbers ([ear.sup.-1]), grain numbers ([row.sup.-1]), grain numbers ([ear.sup.-1]) and one-thousand grain weight at 1% level of probability, while sodium was not affected by nitrogen form and the type of fertilizer had significant effect on potassium and nitrogen efficiency at 5% level of probability (Table2).

The highest row numbers ([ear.sup.-1]) were observed in ammonium nitrate form, which had no significance difference with ammonium sulfate and 50:50 combination of ammonium nitrate and ammonium sulfate. The less significance difference among treatment in row numbers ([ear.sup.-1])may be due to sensitivity to amount of nitrogen than nitrogen form. As shown in table 3 maximum grain numbers ([row.sup.-1]) was achieved in plant receiving nitrogen in ammonium nitrate form and minimum grain numbers ([row.sup.-1]) was observed in control treatment. There was no significant difference between nitrogen supply as ammonium sulfate and ammonium nitrate whereas combination of these cannot produce desirable grain numbers ([row.sup.-1]). Grain numbers ([ear.sup.-1])that multiply of row numbers ([ear.sup.-1]) and grain numbers ([row.sup.-1])had similar trend to nitrogen form as rows per was and the highest grain numbers ([ear.sup.-1]) were observed in ammonium nitrate or ammonium sulfate than other nitrogen sources.

Control had the lowest grain weight and fertilization with ammonium nitrate had the highest grain weight. Fewer statistical differences among treatments for grain weight compared with other yield's components were due to compensation by other components. In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke"
put differently
, no significant difference in the treatments of urea and a combination of different sources due to low grain numbers ([row.sup.-1]) and row numbers ([ear.sup.-1]) that caused each individual grain receive more assimilate. Therefore, one-thousand grain weight increased. The least potassium concentration was observed at combination of urea and ammonium nitrate whereas the highest potassium concentration was obtained in ammonium sulfate form. Maximum nitrogen use efficiency (NUE) was observed when plate feed by ammonium nitrate that had significant difference with the consumption of fertilizers as urea or urea + sulfate sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl).  form (Table 3). The least potassium concentration was observed at combination of urea and ammonium nitrate whereas the highest potassium concentration was obtained as ammonium sulfate. Maximum NUE was obtained when plate feed by ammonium nitrate that had significant difference with the consumption of fertilizers as urea or urea + sulfate form (Table 3).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Discussion:

Nitrogen source had significant effect on yield and yield components of corn. It seems that corn prefer ammonium up take under salinity conditions. No significant difference between ammonium nitrate and ammonium sulfate on yield may be due to the ammonium sulfate had sulfur in its structure that has provided sulfur as essential nutrient. Also, in saline soil high pH decreased availability and absorption other essential elements for growth. Addition of sulfate in soil reduces pH, decreasing of pH increased availability of other elements. Farmarzi et al. [7] also showed that nitrogen as ammonium nitrate was better than urea for corn growth. In this study, yield reduction was due to loss nitrogen from soil and leaching nitrogen due to irrigation. In cotton has also been reported that nitrogen can reduce the effects of salinity on the plan [4]. On sugar beet sugar beet, variety of beet used commercially as a source of sugar.
sugar beet

Variety of beet (Beta vulgaris) that accounts for about two-fifths of global sugar production, making it second only to sugarcane as a source of the world's sugar.
 has also been reported that the impact of nitrate or ammonium form of nitrogen on root fresh weight was different. In saline conditions use of nitrogen as nitrate form reduced fresh weight, while in normal conditions
This article is about the philosophical argument; for normal conditions in the sense of standards see the corresponding articles, e.g. Standard conditions for temperature and pressure.
 this form increased root fresh weight of sugar beets. Both in saline conditions and normal conditions, however, ammonium nitrogen form increased fresh weight of sugar beet [13]. Number of rows per ear and kernel per ear was the most important components in corn that was affect by nitrogen form in saline condition. That this indicates that nitrogen plays an important role in determining the number of rows is in the ear. In the urea treatment was also observed that providing nitrogen increased the number of rows per ear. Increasing of kernel per ear may be due to increasing of ear length or increasing of rows per ear also. In Faramarzi et al. [7] study the number of rows per ear was not influenced by type of nitrogen source, although the amount of nitrogen fertilizer affected row number per ear. Alizadeh et al [1] reported that kernel per ear is dependent on availability or accumulation of nitrogen in different organs.

Moreover, time and amount of N grains can also affect the kernel per ear.

It is reported that chlorine ions in saline soils had antagonistic effects on nitrate uptake therefore appears reduction of kernel per ear in urea treatment was due to antagonistic effects of [Cl.sup.-]. Orthogonal comparison among treatment showed that the combined consumption of fertilizer (urea +ammonium nitrate, ammonium sulfate + ammonium nitrate + ammonium sulfate + urea) more beat than single form (ammonium nitrate, ammonium sulfate and urea).

Greater amount of potassium in ammonium sulfate treatments may be due to the exchange element of S[O.sub.4.sup.-] and [k.sup.+] in the root environment. When PH decreased beside root, ore potassium entered in root so increased value of this element in the shoot. On the other hand, in the other sources of nitrogen competition between elements had negative effects on potassium uptake so the amount of potassium absorbed has been less than ammonium sulfate form. Esmaili et al. [5] in sorghum showed that increasing salinity levels increases potassium percentage in dry matter. Potassium percentage in dry matter when plant received nitrogen urea was more than ammonium nitrate. Higher NUE for ammonium nitrate also seems due to prepare both form of nitrate or ammonium that allowed plant absorbs more nitrogen. High NUE in saline condition when urea was used indicated that this form of nitrogen in not suitable. Combination of different form of nitrogen may be appropriate than single form.

Acknowledgment

This work has been supported by grant from Islamic Azad University Islamic Azad University (Persian: دانشگاه آزاد اسلامی , Dāneshgāh-e Āzād-e Eslāmi) is a private chain of universities in Iran. , Sabzevar Branch. We thank for valuable collaborative work at several key stages of this study.

References

[1.] Alizadeh, A., A. Majidi, H. Nadian, Gh. Normohammadi and M.R. Ameryan, 2006. Effects of Drought Stress and Different Amounts of Nitrogen on the Phenology phe·nol·o·gy  
n.
1. The scientific study of periodic biological phenomena, such as flowering, breeding, and migration, in relation to climatic conditions.

2.
 and Growth of Maize. Agricultural Sciences and Natural Resources, 14(5): 45-68, (in Persian).

[2.] Azevedo Neto, A.D. and J.N. Tabosa, 2000. Nutritional Efficiency for NPK NPK Nitrogen, Phosphorous, Potassium
NPK Non-Player Killer
 on Corn Seedlings under Salt Stress. Ecossistema, 25(2): 194-198.

[3.] Bybordi, A., 2009. Study Effect of NaCl Salinity and Nitrogen Form on Composition of Canola (Brassica napus L.). Notulae Scientia Biologicae, 2(1): 113-116.

[4.] Chen, W., Z. Hou, L. Wu, Y. Liang and C. Wei, 2010. Effects of Salinity and Nitrogen on Cotton Growth in Arid Environment. Plant Soil, 32(6): 61-73.

[5.] Esmaili, E., S.A. Kapourchal, M.J. Malakouti, and M. Homaee, 2008. Interactive Effect of Salinity and two Nitrogen Fertilizers on Growth and Composition of Sorghum. Plant Soil Environment, 54(12): 537-546.

[6.] Fageria, N.K., 2006. The Use of Nutrients in Crop Plants. CRC (Cyclical Redundancy Checking) An error checking technique used to ensure the accuracy of transmitting digital data. The transmitted messages are divided into predetermined lengths which, used as dividends, are divided by a fixed divisor.  Press.

[7.] Faramarzi, A., S. Jamshidi and K. Siamei, 2006. The Effect of Amount and Source of Nitrogen on Yield and Yield Components of Corn. Modern Agricultural Science Agricultural science is a broad multidisciplinary field that encompasses the parts of exact, natural, economic and social sciences that are used in the practice and understanding of agriculture. (Veterinary science, but not animal science, is often excluded from the definition. , 1(2): 65-73. (in Persian).

[8.] Irshad, M., A.E. Eneji, R.A. Khattak and A. Khan, 2009. Influence of Nitrogen and Saline Water on the Growth and Partitioning of Mineral Content in Maize. Journal of Plant Nutrition Plant nutrition is the study of the chemical elements that are necessary for plant growth. There are several principles that apply to plant nutrition.

Some elements are essential, meaning that the absence of a given mineral element will cause the plant to fail to complete
, 32(3): 458-469.

[9.] Irshad, M.A.E. Eneji, and H. Yasuda, 2008. Comparative Effect of Nitrogen Sources on Maize Under Saline and Non-saline Conditions. Journal of Agronomy agronomy (əgrŏn`əmē), branch of agriculture dealing with various physical and biological factors—including soil management, tillage, crop rotation, breeding, weed control, and climate—related to crop production.  and Crop Science, 194(4): 256-261.

[10.] Khalifa, K. and A. Zidan, 2001. Effect of Nitrate addition on Efficient Use of Ammonium Sulfate Fertilizer on Corn under Saline Conditions. II. Field experiment. Communications in Soil Science and Plant Analysis, 32(15): 2373-2393.

[11.] Pessarakli, M., 2010. Handbook of Plant and Crop Stress. Third Edition. CRC Press.

[12.] Shenker, M., A. Ben-Gal and U. Shani, 2003. Sweet Corn Response to Combined Nitrogen and Salinity Environmental Stresses. Plant and Soil. 256(1): 139-147.

[13.] Yazdani, M. and S. Ashtiani Farahani, 2005. Effect of Nitrogen Form on Sucrose content in Two Sensitive and Tolerant Sugar beet. Journal of Plant and Soil, 18(1): 50-60. (in Persian).

[14.] Zhi Wei, L. and H. Guan guan: see curassow.  Hua, 2004. Effect of Different Concentrations of NaCl on Plant Growth of and Nitrogen Uptake by Summer Maize. Plant Nutrition and Fertilizer Science, 10(2): 132-136.

(1) Ali A.Absalan, (2) Mohammad Armin, (3) Mohammad R. Asghripour and (4) Sara Karimi-Yazdi

(1) Islamic Azad University, Sabzevar Branch, Department of Agronomy, Sabzevar, Iran

(2) Islamic Azad University, Sabzevar Branch, Sabzevar, Iran

(3) University of Zabol, Zabol, Iran

(4) Islamic Azad University, Shirvan Branch, Shirvan, Iran

Corresponding Author

Ali Asghare Absalan, Islamic Azad University, Sabzevar Branch, Department of Agronomy, Sabzevar, Iran

E-mail: aliasgharabsalan@yahoo.com
Table 1: Physicochemical characteristic of soil

Clay   Silt   Sand   Soil      EC               N         Available
                     acidity   ds. [m.sup.-1]   total *   phosphorus *

50     11     39     7.8       3.5              0.014     3.35

Potassium *   Boron *   Na *   Calcium *   Mg *   Organic
                                                  matter

175           0.34      35     8.27        5.09   0.12

* Mg [Kg.sup.-1]

Table 2: Analysis of variance of yield and yield components of corn.

Source of variation        Economic   Biological   Rows      Seed
                           yield      yield        per ear   row

Replication                ns         ns           0         ns
Fertilizer                 **         **           **        **
Orthogonal comparison      **         **           ns        0
Coefficient of variation   16.52      13.62        16.20     13.58

Source of variation        Kernel   Kernel   Potassium   Nitrogen
                           in ear   weight               uptake
                                                         efficiency

Replication                ns       ns       ns          ns
Fertilizer                 **       **       0           0
Orthogonal comparison      **       ns       0           **
Coefficient of variation   9.35     15.82    3.5         8.32

ns not significant; (*) and (**) represent significant
difference over control at P < 0.05 and P < 0.01, respectively.

Table 3: Effects of different forms of nitrogenon Rows per
ear, Kernel per Rows, Kernel in ear, Kernel weight, Potassium
and Nitrogen uptake efficiency

Treatment                     Rows     Kernel    Kernel    Kernel
                              per ear  per Rows  in ear    weight(gr)

Ammonium sulfate              16 (ab)  50 (ab)   798 (b)   302.71 (a)
Urea                          10 (d)   34 (d)    336 (f)   209.61 (bc)
A. nitrate+ Urea              12 (dc)  42 (c)    510 (de)  236.86 (abc)
Urea+ A. nitrate+ A. sulfate  14 (bc)  46 (bc)   640 (dc)  258.11 (ab)
Ammonium nitrate              18 (a)   54 (a)    972 (a)   309.06 (a)
A. nitrate+ A. sulfate        16 (ab)  48 (b)    766 (bc)  285.81 (ab)
Urea+ A. sulfate              12 (dc)  32 (d)    386 (fe)  226.06 (abc)
Control                       6 (e)    15 (e)    102 (e)   163.2 (c)

Treatment                     Potassium  Nitrogen uptake
                              (mg.g-1)   efficiency

Ammonium sulfate              4.75 (a)   17 (ab)
Urea                          4.53 (b)   15.5 (b)
A. nitrate+ Urea              4.22 (c)   16.25 (ab)
Urea+ A. nitrate+ A. sulfate  4.56 (ab)  16.35 (ab)
Ammonium nitrate              4.68 (sb)  17.5 (a)
A. nitrate+ A. sulfate        4.6 (ab)   16.75 (ab)
Urea+ A. sulfate              4.44 (bc)  15.75 (b)
Control                       4.25 (c)   --

Values followed by the same letter within the same columns
do not differ significantly at P = 5% according to DMRT
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Title Annotation:Original Article
Author:A.Absalan, Ali; Armin, Mohammad; Asghripour, Mohammad R.; Karimi-Yazdi, Sara
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:7IRAN
Date:Mar 1, 2011
Words:3395
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