Analysis of Nitrogen Dynamics and Fertilizer Use Efficiency in Rice using the Nitrogen-15 Isotope

method following the application of Biogas Slurry or Chemical Fertilizer

طريقة باستخدام االرز في السماد كفاءة و النيتروجين دينامكية تحليلالمعلم - اضافة 15النيتروجين بعد

المعدني السماد و البيوجاز

Adel Ghoneim, H. Ueno, A. Ebid, N. Asagi and I.Abou El-darag

International Journal of Soil Science 3 (1): 11-19, 2008

Introduction

Biogas slurry is a by-product of the biological breakdown of organic wastes such plants, crop residue, food waste, human and animal manure under anaerobic conditions. Biogas slurry is a valuable source of crop nutrients and organic matter and improve soil physical properties.

Use of 15N tracer is the most powerful tool to distinguish between the fate of particular N source and background soil N.

ObjectivesTo determine the impact of 15N labeled biogas slurry

and chemical fertilizer on N uptake, N distribution and fertilizer use efficiency.

Nitrogen fertilizer is the most costly input element.

Therefore, it is important to maximize N use efficiency and

minimize N losses to the environment. These losses occur from

the soil-plant system via denitrification, volatilization and by

leaching.

By understanding N movement in the soil, we can characterize

how these losses occur and seek to increase N use efficiency.

Problem Statements

• Utilization of large amounts of chemical fertilizer

in paddy field.

• Low nitrogen use efficiency.

• Large quantity of post harvest rice residues.

Treatments

• Chemical fertilizer @ 80 Kg N ha-1 labeled with 1.0 atom% 15N. Nitrogen fertilizer applied 3

splits (40, 20, and 20) during transplanting, 30 and 60 DAT.

• Soil amended with biogas slurry @80 Kg N ha-1 applied at different growth stages

Soil samples and analysis

• Collected at 0, 2, 4, 6 and 8 days after BS application. Samples were categorized as 0-2 and 2-5 cm depth.

• Soil pH and soil mineral N were determined• Rice growth parameters were measured

Nitrogen Dynamics and 15N Recovery Calculation

• Atom% 15N excess was calculated as the difference between 15N atom% in plant – natural abundance in the atmosphere

• Fertilizer N Use Efficiency (FUE)FUE CF = (atom% 15N excess plant )/ (atom% 15N excess CF) x

N plant / N applied CF x 100.

FUE BS = N plant BS /N BS

• Relative efficiency (%) = FUE BS/ FUE CF x100

Materials and Methods

Properties ValuepH 6.7EC 0.37 dS m-1

CEC 9.24 cmol kg-1

Total C 14.6 g kg-1

Total N 1.5 g kg-1

Clay 13.4 %Sand 58.5 %Silt 18.1 %

Table 1. Soil chemical properties

Characteristic Mean (n, 3)pH 7.6EC 1.7 dS m-1

Total C 14 g kg-1

Organic N 1.10 g kg-1

Total Volatile Acids 70.6 %C/N ratio 7.6Phosphate 180 mg kg-1

Exchangeable K 0.57 mg kg-1

SO4-2 380 mg kg-1

Table 2. Chemical properties of biogas slurry

Treatment Yield g pot-1

No of panicle pot-1

1000-grain wt. g

Chemical Fertilizer (CF) 24.6 18.5 23.2Biogas Slurry (BS) 23.1 16.5 22.1F test NS NS NS

Table 3. Yield and yield component

Treatment Rice part DW (g pot-1)Chemical fertilizer 25.9 aBiogas slurry grain 28.5 aChemical fertilizer 37.6 a

Biogas slurry straw 34.7 aChemical fertilizer 14.9 a

Biogas slurry root 10.8 aChemical fertilizer 78.4 aBiogas slurry Whole plant 74.0 a

Table. Dry weight

Means in a column followed by the same letter were not significantly different (Tukey-Kramer test: P =0.05)

Treatment N uptake (mg pot-1)Rice part Ndf Ndfs Total

Chemical Fertilizer (CF)

63.9 (16.8)a 316.9 (3.2)a 380.8a

Biogas slurry (BS)

grain 26.9 (8.93)b 274.2 (9.1)a 303.1a

CF 48.3 (14.7)a 280.9 (88.3)a 329.9a

BS straw 27.3 (9.7)b 257.6 (90.2)a 285.9a

CF 20.8 (14.1)a 127.2 (85.9)a 148.0a

BS root 14.7 (11.4) b 113.9 (88.6)a 128.6a

CF 133.0 (15.5)a 725.0 (84.5)a 858.0a

BS whole plant 68.9 (9.64)b 65.7 (90.4)a 714.6a

Table. N uptake from chemical fertilizer and biogas slurry

Treatment NUE (%)

Relative Efficiency (%)

N distribution (%)

Soil Uptake Loss

Chemical Fertilizer

70.3 a 100 6.2 a 70.3 a 23.5 a

Biogas Slurry

50.5 b 71.8 13.2 b 50.5 b 50.5 b

Means in a column followed by the same letter were not significantly different (Tukey-Kramer test: P =0.05)

Table. Nitrogen use efficiency, relative efficiency and N distribution

Conclusion

N uptake was highest in chemical fertilizer treatment

compared with biogas slurry

The highest proportion of N uptake by rice was from soil

About 6.2 and 13.3% of applied N remained in the soil

treated with chemical fertilizer and biogas slurry,

respectively

Significant amount of N was lost from the soil-plant

system