Nitrogen Response Curve and Nitrogen Use ...

J. Agric. Res. Kafer El-Sheikh Univ., 37(1) 2011

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NITROGEN RESPONSE CURVE AND NITROGEN USE EFFICIENCY OF EGYPTIAN HYBRID RICE. Metwally, T.F.; E.E. Gewaily and S. S. Naeem Rice Research & Training Center, Field Crops Research Institute, Agricultural Research Center, 33717 Sakha - Kafr El-Sheikh, Egypt.

ABSTRACT Nitrogen (N) deficiency is one of the most important nutritional disorders in lowland rice producing areas around the world. The objectives of this study were to evaluate the response of Egyptian hybrid rice 1 ‘H1’ to nitrogen fertilizer beside the determination of N use efficiency and N uptake by rice grain and straw. A field experiment was conducted during 2008 and 2009 growing seasons at the experimental farm of Rice Research and Training Center, Sakha, Kafer El-Sheikh, Egypt. Nitrogen levels were 0, 50, 100, 150, 200, 250, 300, 350, and 400 kg N ha-1. Nitrogen fertilization significantly increased grain yield. The maximum grain yield was obtained with the _1 application of 200 kg N ha . Yield components were also significantly affected by N treatments. Nutrient use efficiencies were classified as agronomic efficiency, physiological efficiency, agrophysiological efficiency, apparent recovery efficiency, and utilization efficiency. Increasing N level up to -1 200 kg N ha increased N use efficiency . Further, increasing the N levels, decreased N use efficiencies. Key words: Hybrid Rice, Nitrogen Response Curve, Nitrogen Use Efficiency.

INTRODUCTION Rice is the staple food for nearly half of the world‘s population, most of whom live in developing countries. The crop occupies onethird of the world‘s total area planted to cereals and provides 35–60% of the calories consumed by 2.7 billion people (Guerra et al. 1998). Introduction of hybrid rice is an important step towards augmentation of rice yield. Hybrid rice yields about 15-20% more than the promising high-yielding commercial varieties (Chaturvedi 2005). Modern production agriculture requires efficient, sustainable, and environmentally sound management practices. Nitrogen is normally a key factor in achieving optimum lowland rice grain yields (Fageria et al. 1997). It is, however, one of the most expensive inputs and if used improperly, can pollute the ground water. Although rice is grown in different ecosystems, 78% of the world’s rice is grown under irrigated or rainfed lowland conditions (IRRI 1997). Soils under these conditions are saturated, flooded, and anaerobic and N use efficiency is low. Under these situations, increasing rice yield per unit area

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through use of appropriate N management practices has become an essential component of modern rice production technology (Fageria and Baligar 2001). Traditionally, the optimum rate of N-fertilization has been the rate that results in maximum economic yield. Required optimum N rate varies with soil type, yield potential of cultivar, levels of phosphorus (P) and K in the soil, water management practices, and intensity of diseases, insects, and weeds. However, rate of fertilizer application is also governed by socio-economic factors. Such factors are production cost, economic situation of the farmers, efficiency of extension service, and availability of credit to the growers. Use of adequate N rate is important not only for obtaining maximum economic return, but also to reduce environmental pollution ( Fageria and Baligar 2003).

MATERIALS AND METHODS The field experiment was conducted at the experimental farm of Rice Research and Training Center, Sakha, Kafer El-Sheikh, Egypt, in 2008 and 2009 rice growing seasons to evaluate the response of Egyptian hybrid rice 1 ‘H1’ to nitrogen fertilizer beside the determination of N use efficiency and N uptake by rice grain and straw. Soil texture of experimental field was clay. Chemical properties of the soil were measured by the standard methods of soil chemical analysis (Black et al. 1982) and listed in Table 1. Table 1. Soil chemical properties of experimental sites during 2008 and 2009 seasons. -1

Cation and anion meq L (soil paste) Season

pH

EC dSm 1

OM %

N %

P ppm

Ca

Mg

2008

8.20

2.30

1.60

0.065

18.8

5.40

2.10

0.50

2009

8.09

3.15

1.51

0.052

14.20

10.04

7.42

1.40

2+

2+

K

+

Na

+

-

-

2-

HCO3

Cl

12.30

3.90

15.10

2.20

14.10

9.40

19.34

3.22

The experiment was laid out in randomized complete block design with four replications. Nine rates of nitrogen fertilizer namely 0, -1 50, 100, 150, 200, 250, 300, 350 and 400 kg N ha were used. Nitrogen fertilizer at each level in form of urea (46.5% N) was applied in three equal splits (basal, panicle initiation stage and late booting stage). Egyptian hybrid rice 1 ‘H1’ variety was transplanted at spacing of 20 cm × 20 cm. The plot size was kept as 3 x 4 meter. Plots received identical cultural treatments in terms of ploughing, cultivation,

SO4


75

seed rate, P and K fertilizers, and disease control. Chemical herbicides were employed against different weeds during the course of study. The net plots area was harvested and sun-dried for 5 days in the field and the total biomass yield was recorded. After threshing, cleaning and drying the grain and straw, yields were recorded and yield-attributes viz panicle weight, panicle length, panicles hill-1, filled and unfilled grains panicle-1 and 1000-grain weight were recorded from plant samples. Straw yield was obtained by subtracting grain yield from total biomass yield. Nitrogen content was measured in grain and straw samples which taken at harvest time according to micro-Kjeldahl mothed (Yoshida et al., 1976). Nitrogen uptake by grain and straw yields were calculated. The Nitrogen use efficiency can be defined as the maximum economic yield produced per unit of nutrient applied, absorbed or utilized by the plant to produce grain and straw (Fageria and Baligar 2003). However, in the literature, nutrient use efficiency has been defined in several ways. Nutrient use are grouped or classified as agronomic efficiency, physiological efficiency, agrophysiological efficiency, apparent recovery efficiency, and utilization efficiency and are calculated by using the following formulas according to Fageria et al. 1997: Agronomic efficiency (AE) Physiological efficiency (PE) Agrophysiological efficiency (APE) Apparent recovery efficiency (ARE) Utilization efficiency (EU)

-1

= (Gf - Gu /Na) = kg kg -1 = (Yf - Yu / Nf - Nu) = kg kg -1 = (Gf - Gu / Nf - Nu) = kg kg = (Nf - Nu / Na) X 100 = % -1 = PE X ARE = kg kg

Where Gf is the grain yield of the fertilized plot (kg), G u is the grain yield of the unfertilized plot (kg), Na is the quantity of N applied (kg), Yf is the total biological yield (grain plus straw) of the fertilized plot (kg), Yu is the total biological yield of the unfertilized plot (kg), Nf is the nutrient accumulation by the total biological yield in the fertilized plot (kg), Nu is the nutrient accumulation by the total biological yield in the unfertilized plot (kg). The data were analyzed statistically with Fisher’s analysis of variance technique at 5% probability level; treatments were compared using a protected LSD test (Gomez and Gomez 1984).

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RESULTS AND DISCUSSION The analysis of variance showed significant responses of panicle weight, panicle length, number of panicles per hill and 1000grain weight to N rates (Table 2). Increasing the rate of nitrogen application increased significantly the panicle weight. The heaviest panicles were recorded when nitrogen was applied at the rate of 200 -1 kg N ha . This trend might be due to the role of nitrogen in crop maturation, flowering and fruiting including seed formation. These results are in accordance with those of Chaturvedi (2005). Rice plants gave the longest panicles with the application of -1 200 kg N ha . The shortest panicles were observed with the untreated control (Table 2). The longest panicles obtained in treatments receiving optimum nitrogen rates were probably due to better nitrogen status of plant during panicle growth period. Rice plants produced the highest value of number of panicles hill-1 when 200 kg nitrogen per hectare was applied. Minimum panicles hill-1 were recorded in untreated control (Table 2). More panicles hill-1 in experiment might be due to the more availability of nitrogen that played a vital role in cell division. These results are in accordance with the findings of (Manzoor et al. 2006). Also, according to Yoshida et al. (1972), increases the amount of nitrogen absorbed by the crop, increased the number of panicles per square meter. -1

Table 2. Panicle weight (g), length (cm), panicles hill and 1000-grain weight (g) of Egyptian hybrid rice1 (H1) as affected by different N levels. -1

Kg N ha

0 50 100 150 200 250 300 350 400 L.S.D.0.05

Panicle weight g 2008 3.17 3.13 3.53 3.41 4.14 3.95 3.86 3.80 3.64 0.24

2009 3.11 3.33 3.60 3.61 4.33 4.09 3.60 3.55 3.56 0.33

Panicle length cm 2008 2009 20.37 20.73 20.65 20.35 21.18 21.35 21.63 21.15 22.77 22.70 22.72 22.39 22.20 21.83 21.87 21.43 21.75 21.26 1.09 0.87

Panicles hill 2008 19.58 23.61 24.58 23.38 26.59 26.29 22.25 21.67 22.38 1.05

-1

2009 20.08 23.66 25.08 23.13 26.42 26.21 23.08 23.00 22.13 1.07

1000-grain weight g 2008 2009 24.10 24.21 23.50 24.19 23.76 23.44 23.59 23.51 23.48 23.32 22.83 23.66 22.65 23.54 22.00 23.38 22.15 22.93 1.06 1.09

The highest number of filled grains per panicle were obtained at 200 and 250 kg N ha-1. The lowest value of this parameter was recorded in untreated control (Table 3). Similar finding has been


77

obtained by (Manzoor et al. 2006 and Nawaz 2002). There was a marked increase in spikelet sterility when high rates of N were applied. Low spikelets fertility at high N rate is considered one of the important selection criteria for N responsive rice cultivars (Fageria and Baligar 2001). Gunawardena and Fukai 2004, reported that increased spikelet sterility was associated with greater panicle density and application of N significantly increased panicle density. Increasing rates of N application influenced straw yield with a linear trend. More straw yield could be explained as higher capability of hybrid rice to utilize more N through the expression of better growth by accumulating more dry matter. The results confirm the findings of Padmavathi 1997 and Chaturvedi 2005. Higher harvest index -1 apparently was recorded when 150 kg N ha was applied. The harvest index (HI) significantly decreased with the application of high rates of nitrogen (Table 3). This may have been due to an excessive supply of N that produced excessive vegetative growth, as indicated by the high straw yield and low HI. This shift to greater early vegetative growth resulted in lodging of the crop and perhaps was the cause for reduction in rice grain yield. -1

-1

Table 3. Filled grains panicle , sterility %, grain yield (t ha ), straw yield (t ha-1) and harvest index of Egyptian hybrid rice1 (H1) as affected by different N levels. -1

Kg N ha

0 50 100 150 200 250 300 350 400 L.S.D.0.05

Filled grains -1 panicle 2008 2009 134.2 142.1 135.9 143.7 141.0 165.7 167.1 171.9 178.3 184.3 180.3 182.1 152.4 155.7 146.3 146.8 137.0 143.2 9.1 8.2

Sterility % 2008 9.51 9.33 9.34 7.88 7.35 9.30 13.63 15.1 20.66 1.13

2009 9.28 9.01 8.55 8.18 7.27 9.07 14.34 15.37 19.40 0.94

Grain yield t -1 ha 2008 2009 6.98 7.36 7.29 7.51 8.05 8.28 9.59 9.34 10.74 11.35 10.63 11.00 9.85 10.61 9.72 9.96 9.40 9.55 0.46 0.49

Straw yield t -1 ha 2008 2009 9.42 9.92 9.58 10.03 10.60 11.12 11.30 11.19 13.69 13.47 14.49 14.65 14.61 14.56 14.90 14.69 14.75 14.70 0.42 0.58

Harvest index 2008 0.426 0.432 0.432 0.459 0.440 0.423 0.403 0.395 0.391 0.013

2009 0.426 0.428 0.424 0.455 0.456 0.424 0.413 0.404 0.389 0.018

The application of nitrogen fertilizer increased rice grain yield during the both seasons (Fig. 1). Paddy yield was higher in 200 kg N -1 level which was statistically similar to 250 kg N ha . The lowest paddy yield was recorded in control. Manzoor et al. (2006) noted that higher paddy yield with 150 and 250 kg N ha-1, respectively. The higher paddy yield at higher nitrogen rates was also reported by other workers (Dixit and Patro 1994 and Meena et al. 2003).


78

Fig. 1. Trend analysis for grain yield of Egyptian hybrid rice1 (H1) as affected by different N levels. The highest paddy yield at 200 kg N per hectare might be due to higher number of grains per panicle and 1000-grain weight at this


79

nitrogen rate. A decline in paddy yield at the higher levels might be due to reduction in yield components at these N levels. At harvest, grain and straw N contents were significantly affected by N treatment. N content increased significantly with each level of increase in N fertilization and was the highest with 400 kg N ha-1 (Table 4). Several researchers have reported an increased N concentration in rice plant tissue and grain due to N fertilization (Panda et al. 1993 and Kumar and Prasad 2004). The higher N content of nitrogen in treated plants could be connected with the positive effect of nitrogen in some important physiological processes. The lower N content of the straw at maturity in comparison with the content in the grain clearly indicates N remobilization from the vegetative parts. Mae and Shoji (1984) reported that remobilized N from the vegetative organs to the panicles accounted for 70%–90% of the total N, with the leaf blade alone contributing 60% of the remobilized N. Table 4. Nitrogen content % and uptake (kg ha-1) by grain and straw of Egyptian hybrid rice1 (H1) as affected by different N levels. -1

Kg N ha

0 50 100 150 200 250 300 350 400 L.S.D.0.05

Nitrogen content % Grain Straw 2008 2009 2008 2009 1.027 0.973 0.336 0.300 1.130 1.000 0.380 0.360 1.177 1.123 0.431 0.370 1.207 1.170 0.462 0.483 1.277 1.241 0.522 0.553 1.327 1.300 0.537 0.567 1.377 1.347 0.551 0.597 1.400 1.427 0.581 0.660 1.407 1.473 0.557 0.661 0.077 0.081 0.065 0.082

-1

Nitrogen uptake kg ha Grain Straw 2008 2009 2008 2009 71.7 71.6 31.76 29.80 82.4 75.1 36.40 36.11 94.8 93.0 45.59 41.22 115.7 109.3 51.96 54.13 137.1 140.9 71.17 74.54 141.1 143.0 77.72 83.01 135.6 142.9 80.34 86.79 136.1 142.1 86.37 96.90 132.3 140.7 82.02 97.12 10.77 11.79 8.00 12.27

Nitrogen uptake at harvest by grain and straw kg ha-1 were significantly affected by nitrogen application (Table 4.). Nitrogen uptake by grains increased significantly with the increase in the rate of applied nitrogen up to 250 kg ha-1. Under the high rates of nitrogen (more than 250 kg N ha-1), the nitrogen uptake by grains was reduced. Nitrogen uptake by straw increased by nitrogen application up to 350 -1 and 400 kg N ha in the first and second season, respectively. This increase in N uptake is related to biomass production. Agronomic efficiency (AE) was significantly affected by nitrogen application (Fig. 2). AE increased significantly with increasing N levels up to 200 kg N ha-1. Such reduction in AE has been obtained by increasing N levels from 200 up to 400 kg N ha-1. Saleque et al.


80

(2004) reported that AE is usually greater at low dose of N fertilizer application that obtained with the high dose.

25

kg kg-1

20 15

2008

10

2009

5 0 0

50

100

150

200

250

300

350

400

-1

Kg N ha

Fig. 2. Agronomic efficiency (AE) kg kg-1 of Egyptian hybrid rice1 as affected by nitrogen application. Physiological efficiency (PE) kg kg-1 was markedly affected by nitrogen application (Table 5.). Highest values of PE were obtained where N was applied at the rate of 200 and 250 kg N ha-1 in the first and second season, respectively. However, 200 and 250 kg N ha-1 produced statistically similar values of PE in the tow seasons. Nitrogen application significantly increased agrophysiological efficiency (APE) up to 200 kg N ha-1 (Table 5). Application of 150 and 200 kg N ha-1 gave statistically similar and highest APE. Higher PE as compared to APE across the N rates was due to inclusion of dry matter in calculating this efficiency (Fagira and Bligar 2003). Apparent Recovery efficiency (ARE) was significantly varied among nitrogen levels and it ranged from 27.72 to 52.41 % in 2008 and from 19.63 to 57.02 % in 2009 (Table 5.). The highest percentage of ARE were found with the application of 200 kg N ha-1. The utilization efficiency (EU) was affected by nitrogen application. EU -1 -1 values ranged from 9.2 to 40 kg kg and from 5.2 to 37.8 kg kg in the two seasons, respectively. The highest values were obtained when 200 kg N ha-1 was applied.


81

Table 5. Physiological efficiency, agrophysiological efficiency, apparent recovery efficiency, and utilization efficiency of Egyptian hybrid rice1 (H1) as affected by different N levels. -1

Kg N ha

50 100 150 200 250 300 350 400 L.S.D.0.05

Physiological efficiency (PE) 2008 2009 29.98 26.50 60.93 52.71 69.78 52.72 76.52 66.29 75.42 67.25 71.66 61.66 68.99 53.63 70.27 51.17 5.53 5.32

Agrophysiological efficiency (APE) 2008 2009 19.56 15.29 28.97 28.34 40.50 32.24 35.78 35.16 31.47 29.29 25.52 25.49 18.57 18.97 22.19 16.13 5.44 4.01

Apparent recovery efficiency (ARE) 2008 2009 30.68 19.62 36.93 32.82 42.80 41.35 52.41 57.02 46.14 49.84 37.49 42.76 34.00 39.31 27.72 34.11 3.16 3.30

Utilization efficiency (UE) 2008 2009 9.2 5.20 22.50 17.30 29.87 21.80 40.10 37.80 34.80 33.52 26.87 26.37 23.46 21.09 19.48 17.45 3.12 2.93

Generally among the different N levels, increasing the N level up to 200 kg N ha-1, the N use efficiency was increased. Further, increasing the N levels, the N use efficiency was decreased. It may be due to the application of excess nitrogen, which was not effectively utilized by the crop and the rate of production was lesser per unit of N application. The variation in the level of efficiency for the rice tested is in good agreement with the results reported by Lu et al. 1998 and Bindu 2002.

CONCLUSION Based on the findings of the present investigation, fertilizer -1 dose of 200 kg N ha was found to be optimum for Egyptian hybrid rice 1 (H1) and any addition after this rate reduce the grain yield and nitrogen use efficiency.

REFERENCES Bindu, C.J., 2002. Nitrogen management for hybrid rice based on chlorophyll meter and leaf colour chart. M.Sc. Thesis, Tamil Nadu Agric. Univ., Coimbatore, India. Black, C.A.; D.D. Evans; L.E. Ensminger and F.E. Clark. 1982. Methods of Soil Analysis. Part 2- Chemical and microbiological properties. American Soc. of Agronomy, Inc., Publisher, Madison, Wisconsin, USA. Chaturvedi, Indira. 2005. Effect of nitrogen fertilizers on growth, yield and quality of hybrid rice (Oryza Sativa). Journal of Central European Agriculture. 6(4):611-618.


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Dixit,U. C. and N. Patro. 1994. Effect of NPK levels, zinc and plant density on yied attributes and yield of summer rice. Environment and Ecology. 12(1):72-74. Fageria, N. K. and V. C. Baligar. 2001. Lowland Rice Response to Nitrogen Fertilization. Commun. Soil Sci. Plant Anal., 32(9&10): 1405–1429. Fageria, N.K. and V.C. Baligar. 2003. Methodology for evaluation of lowland rice genotypes for nitrogen use efficincy. J. Plant Nutr. 26:1315-1333. Fageria, N.K. and V.C.Baligar; C.A. Jones. 1997. Growth and Mineral Nutrition of Field Crops, 2nd Ed.; Marcel Dekker, Inc.: New York. Gomez, K.A. and A.A. Gomez,. 1984. Statistical Procedures for nd Agricultural Research. 2 ed. Jahn Wiley Sons, New York, USA. Guerra, L.C.; S.I. Bhuiyan; T.P. Tuong,; R. Baker,. 1998. Producing More Rice with Less Water from Irrigated Systems; International Rice Research Institute: Manila, Philippines, Discussion Paper Series No. 29, 18 pp. Gunawardena, Thusitha A. and Shu Fukai. 2004. The effects of nitrogen application and assimilate availability on engorged pollen production and spikelet sterility in rice. New directions for a diverse planet: Proceedings of the 4th International Crop Science Congress Brisbane, Australia, 26 Sep – 1 Oct 2004. IRRI (International Rice Research Institute). 1997. Rice Almanac, 2nd Ed.; IRRI in association with the West Africa Rice Development Association and the Centro Internacional de Agricultura Tropical: Manila, Philippines. Kumar N. and R. Prasad 2004. Effect of levels and sources of nitrogen on concentration and uptake of nitrogen by a high yielding variety and a hybrid of rice. Archives of Agronomy and Soil Science.50:447–454 Lu, W.; C.W. Lindan and W.H. Jr. Patrick, 1998. Supply and 15 uptake of urea N by rice. IRRN., 13: 25-26. Mae,T. and S.Shoji. 1984. Studies on the fate of fertilizer nitrogen in rice plant and paddy soil susing 16N as a tracer in Northeastern Japan. In Soil science and plant nutrition in Northeastern Japan, Special Issue, 77–94. Sendai, Japan: Northeastern Section of the Japanese Society of Soil Science and Plant Nutrition. Mahabari, M. B.; D. S. Patil and S. D. Kalke. 1996. Yield and uptake of nutrients as influenced by the method and time of application of nitrogen fertilizer under floodproone rice. Soils and Crops. 6(1):27-30


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Manzoor, Zaheen; Tahir Hussain Awan; M. Ehsan Safdar; Rana Inayat Ali; Mirza M. Ashraf and Mushtaq Ahmad .2006. Effect of Nitrogen Levels on Yield and Yield Components of Basmati 2000. J. Agric. Res., 2006, 44(2). Meena, S. L.; S. Surendra; Y. S. Shivay and S. Singh. 2003. Response of hybrid rice (Orytza Sativa) to nitrogen and potassium application in sandy clay loam soils. Indian J Agric. Sci. 73(1): 8-11. Nawaz, H. M. A. 2002. Effect of various Levels and Methods of Nitrogen Application on Nitrogen Use Efficiency in Rice Super Basmati. M. Sc. Thesis, Deptt. Agron, Univ. Agric., Faisalabad. Padmavathi, P., 1997. ‘Studies on relative performance of conventional and hybrid rice varieties under various levels of nitrogen, plant population and planting patterns. Ph. D thesis, Indian Agricultural Research Institute, New Delhi. Panda, N.C.; R.N.Samantha Ray; P. Mahapatra and S.K. Mohanty, 1993. Effect of optimum and suboptimum nutrient management on nutrient changes, yield and nutrient uptake. Soil Sci. 41, 90–95. Saleque, M.A.; U.A. Naher; N.N. Choudhury and A.T.M.S. Hossain. 2004. Variety-Specific Nitrogen Fertilizer Recommendation for Low Land Rice. Communications in Soil Science and Plant Analysis. 35(13&14) 1891-1903. Yoshida S.; J.H. Cock and Parao F.T., 1972. Physiological aspects of high yield. Int. Rice Res. Inst. Rice breeding, pp. 455-469. Yoshida, S.; D. A. Forno; J. H. Cock and K. A.Gomez 1976. Laboratory Manual for Physiological Studies of Rice (Third Edn.) International Rice Research Institute, Manila, Philippines. pp.14-22.

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‫‪J. Agric. Res. Kafer El-Sheikh Univ., 37(1) 2011‬‬

‫الملخص العربي‬

‫منحنى استجابة األرز الهجين للتسميد النيتروجيني وكفاءة استخدامه‬ ‫تامر فاروق متولي والسيد السيد جويلي و السيد سعد نعيم‬ ‫مركز البحوث والتدرٌب فً االرز‪ -‬معهد بحوث المحاصٌل الحقلٌة – مركز البحوث الزراعٌة‬ ‫أجرٌت تجربتان حقلٌتان بمزرعة مركز البحوث والتدرٌب فً األرز‪ ,‬سخا‪ ,‬كفرالشٌخ‬ ‫لدراسة استجابة محصول األرز الهجٌن إلضافة السماد النٌتروجٌنً‪ .‬تم إضافة السماد النٌتروجٌنً‬ ‫فً صورة ٌورٌا (‪ %64‬نٌتروجٌن) بالمعدالت االتٌه ‪,000 ,000 ,000 ,000 ,000 ,00 ,0‬‬ ‫‪ 600 , 000‬كجم نٌتروجٌن للهكتار‪ .‬وقد أوضحت النتائج أن زٌادة مستوٌات السماد النٌتروجٌنً‬ ‫حتى معدل ‪ 000‬كجم نٌتروجٌن للهكتار اعطً اعلى محصول ومكوناته‪ .‬ولم ٌكن هناك فروق‬ ‫معنوٌة بٌن اضافة ‪ 000‬او ‪ 000‬كجم نٌتروجٌن للهكتار‪ .‬زادت كفاءة السماد النٌتروجٌنً بصفة‬ ‫عامة بزٌادة مستوي اضافة السماد النٌتروجٌنً حتى ‪ 000‬كجم نٌتروجٌن للهكتار‪ ,‬بٌنما ادت زٌادة‬ ‫اي وحدات اضافٌة عن هذا المعدل الى انخفاض كفاءة استخدام السماد النٌتروجٌنً‪ .‬مما سبق‪,‬‬ ‫للحصول على اعلً كفاءة الستخدام النٌتروجٌن بواسطة االرز الهجٌن ٌتضح ان أفضل معدل للسماد‬ ‫النٌتروجٌنً لمحصول االرز الهجٌن هو ‪ 000‬كجم نتروجٌن للهكتار‪.‬‬