The document examines the effects of split potassium fertilizer applications and straw on optimum potassium levels in rice plants grown in Sri Lanka's low country intermediate zone. Key findings include: 1) Applying potassium fertilizer in split doses and adding rice straw increased soil exchangeable and non-exchangeable potassium levels compared to control plots without potassium additions. 2) Plants receiving both potassium fertilizer and straw had the highest potassium uptake and content in leaves and stems. 3) While tillering and panicle numbers were unaffected, treatments with both potassium fertilizer and straw yielded significantly more than control plots without added potassium.

1. EFFECT OF POTASSIUM FERTILIZER SPLIT
APPLICATIONS TOGETHER WITH STRAW ON
OPTIMUM POTASSIUM LEVEL IN LEAF AND STEM OF
RICE IN LOW COUNTRY INTERMEDIATE ZONE (LCIZ)

2. Dr. H.M.S.K. Herath
Senior Lecturer
Faculty of Animal Science and Export
agriculture,
Uva Wellassa University,
Badulla
External Supervisor:
Mr. D.N. Sirisena
Deputy Director ( Rice Research and Development)
Rice Research and Development Institute
Bathalagoda
SUPPERVISOR DETAILS
Internal Supervisor:

3. INTRODUCTION
• Potassium – A major nutrient for rice production
• Essential Functions of Potassium in paddy nutrition:
– Osmo-regulation
– Enzyme activation
– Regulation of cellular cation-anion balance
– Regulation of transpiration by stomata
– The transport of assimilates
• Rice- removes more K than N and P
• Usually, 5 tons of rice,
• removes 85kg of K2O/ha

4. RESEARCH PROBLEM
• MOP- price is high and not produced locally
• Insufficient amount of K fertilizer will lead to
many plant diseases
• Response to K application is poor in dry and
intermediate zones
When applying K Yield increase is low
Waste of the applied K fertilizer
• Required amount of K added
availability for plant is low
Leaching
Fixed forms of K in the soil (non-exchangeable K)
4

5. Effect of Potassium application on soil K
• Soil K
• Exchangeable K
 LCDZ and LCIZ – 31-331 mgkg-1 of exchangeable K
 MCWZ – 51-175 mgkg-1 of exchangeable K
 LCWZ – 27-94 mgkg-1 of exchangeable K
(Weerasinghe, 1991)
• Non exchangeable K
No available literature

6. Effect of Potassium on Pest and Disease
Resistance in Rice Plants
Potassium deficiency induces susceptibility of rice
to pest , disease and lodging

7. Sources of K
• Rice Straw
• Chemical fertilizer
MOP
K2SO4

8. Introduction…
Benefits of Paddy Straw:
• Rich in Potassium
• Improve water retention of soil
• Supply of other nutrients
• Improve soil structure
• Slightly less N fertilizer required(20-25 kg/ha)
• More resistant - insect pest and disease attacks

9. OBJECTIVES
General Objective:-
• To find out the effect of potassium fertilizer split
applications on optimum potassium content in
leaf and stem of rice in low country intermediate
zone
9

10. Objectives…
Specific Objectives:-
• To study the ways of reducing the amount of K
fertilizer application
• To find out the changes of exchangeable and
non-exchangeable potassium content in paddy
fields over the cultivation period with different K
fertilizer application
• To find out the relationship between non-
exchangeable K with plant potassium uptake
10

11. METHODOLOGY
• Location:
Rice Research and Development Institute (RRDI),
Batalagoda
• Experimental Design:
Randomized Complete Block Design (RCBD)
• Test variety : Bg 300 (3 months age variety)
• 6 treatments in 4 replicates

12. Methodology….
12
T6 T1 T4 T2 T3 T5
T3 T4 T5 T1 T2 T6
T1 T2 T3 T5 T6 T4
T4 T6 T5 T3 T1 T2
R2
R3
R4
R1
4.5 m
5 m
Field Layout

13. Treatments
1. T1- Control -K0 (only N, P)
2. T2- Straw + N + P
3. T3- Straw + 20 kg K2O ha–1of K (Basal-K) + 20 kg K2O ha–1of K
(PI Stage-K) + N+ P
4. T4- Straw + 20 kg K2O ha–1of K (Basal-K) + N + P
5. T5- Straw +20 kg K2O ha–1of K (PI Stage-K) + N + P
6. T6- 20 kg K2O ha–1of K (Basal-K) + 20 kg K2O ha–1of K (PI
Stage-K) + N + P
13
Methodology….

14. Methodology….
Fertilizer Recommendation for Rice
Yield Level : 140 bushels/ Ac
Paddy Straw Application
Recommendation - 500 g/ m2
(DOA recommended procedure)
Time Fertilizer per 4000 m2(Ac)
Urea TSP MOP
Basal Dressing - 5Kg 45Kg 20Kg
1st Top Dressing 2 WAP 35Kg - -
2nd Top Dressing 5 WAP 55Kg - -
3rd Top Dressing 7 WAP 30Kg - 20Kg

15. Methodology….
Sample Collection
• Soil
Initial soil sampling before ploughing
Planting to maturity at weekly interval
• Plant - 100% flowering stage

16. Parameters
 Soil Chemical Parameters:
• Exchangeable potassium content by Atomic
Absorption Spectrophotometer(AAS) method
• Non-exchangeable potassium content by Atomic
Absorption SpectroPhotometer(AAS) method
 Plant Parameters:
Leaf and Stem K
Dry weight of shoots
Plant K uptake
Methodology…

17. Methodology…
• Plant Growth Parameters:
• Plant height by ruler (cm)
• Number of tillers per hill – by Hand counting
method
• Yield Parameters:
• Number of panicles per hill
• Grain Yield

18. Methodology…
Method of Data Analysis
• Relationship - Correlation analysis
• SAS software package
• Mean separation – Duncan's New Multiple Range
Test

19. Results and Discussion
Exchangeable Soil Potassium Content:
• The Exchangeable K in Initial soil-28.46 mg/kg
• comparative with the finding of Panabokke and
Nagarajah (1964) - <39mg/kg
• After rice straw application,
• soil exchangeable K content in rice straw treated plots –
40.35 mg/kg
• non treated plots – 30.37 mg/kg

20. Results and Discussion…
Treatments Initial 2 WAP 4 WAP 6 WAP 8 WAP
T1 19.33 c 25.39 d 30.39 c 35.87 c 31.73 c
T2 25.70 bc 33.40 c 35.09 bc 39.79c 37.37 bc
T3 34.53 a 46.29 a 48.22 a 58.94 a 51.72 a
T4 32.40 ab 42.98 ab 46.93 a 50.84 ab 47.98 a
T5 29.46 ab 38.73 abc 39.99 ab 45.86 bc 42.98 ab
T6 29.36 ab 35.34 bc 35.72 bc 40.43 c 36.38 bc
Table 1: Mean values of soil exchangeable K (ppm).

21. Results and Discussion…
• The highest Exchangeable K content,
Treatment received K fertilizer at 40 Kg with rice straw
• Soil K content in control plot- significantly low
throughout the growing season
comparison to K fertilizer or straw treated plots
• This showed,
The K in rice straw is present in soluble form and its
available to plant is comparable to that in MOP

22. Results and Discussion…
Soil Non-exchangeable Potassium Content
• The Non exchangeable K in Initial soil-137.67 mg/kg
• After rice straw application,
• soil non exchangeable K content in rice straw treated plots
– 183.03 mg/kg
• non treated plots – 139.88 mg/kg
• The highest Non exchangeable K content,
• Treatment received K fertilizer at 40 Kg with rice straw

23. Results and Discussion…
Treatments Initial 2 WAP 4 WAP 6 WAP 8 WAP
T1 116.80 b 141.80 b 206.70 a 219.10 a 197.95 a
T2 131.05 ab 172.30 a 176.75 a 233.55 a 204.25 a
T3 160.20 a 211.25 a 260.70 a 319.05 a 246.25 a
T4 158.75 ab 204.85 ab 188.45 a 243.9 a 222.05 a
T5 132.45 ab 143.70 b 184.40 a 236.65 a 213.30 a
T6 126.75 ab 137.95 ab 162.45 a 226.45 a 200.80 a
Table 2: Mean values of soil non-exchangeable K.

24. Results and Discussion…
• Higher amount of non exchangeable K content
in rice straw treated plots
• Straw can be a good source of K even in the non-
exchangeable K pool

25. Dry Weight of Shoots
• No significant change in dry weight of shoots among treatments
• Rice straw and fertilizer application had not affected to the
dry weight of the shoots
a
a
a
a
a a
0
5
10
15
20
25
T1 T2 T3 T4 T5 T6
Plantdryweight(g)
Treatments
Figure 01: Dry weight of shoots at eight weeks after planting.

26. Results and Discussion…
Plant Potassium Content
• The K content in rice plant was significantly higher in
leaf part compared to the stem part
• K fertilizer treated plots depict higher K content in
leaf and stem
• compare to the other with or without straw added
plots
• This may be due to the loss of K in rice straw
- submergence in rain water or the K in the straw will get
leached and the K requirement will be met quickly after
decomposition

27. Results and Discussion…
d
c
b
bc bc
a
e
d
b
c c
a
0.0
0.2
0.4
0.6
0.8
1.0
1.2
T1 T2 T3 T4 T5 T6
KContent(%)
Treatments
Leaf K
Stem K
Figure 02: Plant K content.
Means followed by the same letter at the same coloured column are not
significantly different by Duncans post-hoc test at P< 0.05.

28. Results and Discussion…
Plant Potassium Uptake
• Plant K content – Significantly higher in K fertilizer
treated plots compared to the non treated plots
• Lowest K uptake in control plots
• As a result
• Higher K uptake by rice plants was recorded from plots
treated with K fertilizer

29. Results and Discussion…
c
b
ab
ab
b
a
0
40
80
120
160
200
T1 T2 T3 T4 T5 T6
Kuptake(kg/ha)
Treatments
Figure 03: K uptake by plants (kg ha–1)

30. Results and Discussion…
• Due to increment of dry weight of the shoots of rice
plants
• K uptake of the dry matter was noticeably increased in
relation to the added K fertilizer and rice straw
• In 100% flowering stage total K uptake ,
• K fertilizer added – 169.72 Kg/ha
• not added plots - 101.34 Kg/ha

31. Results and Discussion…
Agronomic Parameters and Grain Yield
• The Maximum plant height - which were treated
with K fertilizer (PI stage) and straw
• Lowest plant height - control plots which was not
treated with K fertilizer
• No significant difference in number of tillers per hill
among treatments
• It is relative with finding of Dobermann and
Fairhurst (2000) have reported that unlike N and P, K
does not have a pronounced effect on tillering

32. Results and Discussion…
Table 04: Mean number of tillers, plant height, number of panicles and grain yield as affected
by rice straw and K fertilizer treatments.
At maximum tillering stage At harvesting stage
Treatments Plant height (cm) No of tillers Number of panicles per hill Grain yield
(kg/hill)
T1 92.3 b 10.0 a 6.80 a 7.5 c
T2 95.4 ab 10.0 a 6.70 a 7.6 bc
T3 97.8 ab 11.0 a 7.20 a 8.3 a
T4 98.5 a 11.0 a 6.75 a 7.9 abc
T5 99.6 a 9.0 a 6.50 a 8.1 ab
T6 95.8 ab 11.0 a 6.70 a 7.9 abc

33. 33
• No any statistically significant difference in
panicle number among the treatments
• Maximum number of panicles per hill - T3
(Straw + K fertilizer)
• But the grain yields are significantly higher
with application of rice straw and K fertilizer
(T3)
−contribution the number of panicles per hill
−The higher biomass production with increased
available K content

34. CONCLUSIONS
• Application of rice straw and K fertilizer increased the soil
exchangeable K content and non- exchangeable K content
• Exchangeable and non-exchangeable K contents in all six
treatments were significantly low (P<0.05) at planting and
harvesting
• Rice straw can be used as a source of K, which maintains the
exchangeable K content and as well as the non-exchangeable
K pools in paddy fields in the initial stage
• Significant differences in total grain yield and K concentration
of plant parts among treatments were observed
• Plant K uptake in relation to the non-exchangeable K, there
was a positive relationship irrespective of the treatments
applied and number of weeks after planting
• Though chemical K fertilizer is an important K source for
paddy cultivation, rice straw plays a significant role in
maintaining soil K as well as plant K content
34

35. REFERENCES
• Anon (1956). Plant Potassium Analysis, Analytical Methods Committee,
Analyst,London.
• Bandara, W.M.J., Wickramasinghe, W.M.A.D.B., Sirisena, D.N. and Wijewardana,
J.D.H. (2009). Response of Rice to Applied Potassium in Soils of Sri Lanka, In: Use of
phosphorus and Potassium Fertilizers in Sri Lankan Agriculture, Kumaragamage, D.,
Satyanarayana, T., Singh, H. and Majnmdar, K., International Plant Nutrition
Institute India Programme, 354, Sector-21,HUDA. Pp 89-102.
• Dobermann, A. and Fairhurst, T.H. (2000). Nutrient disorders and nutrient
management in rice, International Rice Research Institute and Potash and
Phosphate Institute of Canada. Pp 72-83.
• Panabokke, C.R. and Nagarajah, S. (1964): The fertility characteristics of rice
growing soils of Ceylon. Tropical Agriculturist 120: 3-30.
• Weerasinghe, P. (1991). Response of irrigated Lowland rice to addition of N, P and
K fertilizers in Non-calcic Brown Soils. Tropical Agriculturist 147: 75-84.