Managing plant population and competition in Field Crops

Plant population is defined as the total number of plants present at unit area of land (Baker, 1964). The number of plants per unit area that would give maximum yield is termed as optimum plant population (Willey & Heath, 1969). Competition is generally refer to the negative effects on plant growth caused by the presence of neighbors, usually by reducing the availability of resources (Paul & James, 2019).

1. MANAGING PLANT POPULATION AND
COMPETITION IN FIELD CROPS

Presenter
Chudamani Pant
Department of Agronomy
Roll no.: WS-01M-2019
Agriculture and Forestry University
Rampur, Chitwan

2. Outline of presentation
Introduction
Objectives
Methodology
Discussion
Conclusion

3. Introduction

Plant population is defined as the total number
of plants present at unit area of land (Baker, 1964).
The number of plants per unit area that would give maximum
yield is termed as optimum plant population (Willey & Heath,
1969).
Competition is generally refer to the negative effects
on plant growth caused by the presence of neighbors, usually by
reducing the availability of resources (Paul & James, 2019).

4. Objectives
•To review and collect information related to managing
plant population and competition in field crops.
•To know about the factor affecting plant population.
•To know about the competition in field crops
•To find out the ways of managing plant population.

5. Methodology
•Review of Literature from Central Library, AFU
•Articles in journals and periodicals
•Internet
•Class note

6. Factors affecting plant population
Genetic/ Crop Factor Input/Environmental Factor Managerial Factor
Seed quality Irrigation Method of planting
Size of plant Nutrient supply Crop geometry
Dry matter Partitioning Seed rate Early/late planting etc
Tillering etc Season
Temperature
Sunlight
Discussion
Source: (Voughan, 2005)

7. Optimum plant population of some crops
Crop Spacing Optimum plant population
Rice 20cm*20cm 300-350 ET/m
2
Wheat 25cm*5cm 250-300 ET/m
2
Maize 75cm*25cm 53,333 plant/ha
Cowpea 120cm*30cm 27777 plant/ha
Cotton 90cm*30cm 37037 plant/ha
Potato 60cm*20cm 83333 plant/ha
Sugarcane 90cm*20cm 55555 plant/ha
Rapeseed 30cm*10cm 333333 plant/ha
Sunflower 60cm*20cm 83333 plant/ha

8. Impact of Low Plant population
•Low Resource Use Efficiency
•Higher tiller or branching
•Yield per plant is higher
•Too much space left between plants, weed growth is promoted,
which could increase weeding costs (Mathiew, 2011).

9. Impact of high plant population
•Plant height is increased because of the competition for light.
•Lower weed competition.
•Greater light interception.
•Increase in stand uniformity.
•Thickness of leaves may be also reduced
•Stem become long and weak resulting in lodging and low yield
•Increase in intraspecific competition.
•Reduction in numbers of ears in indeterminate plants
•Reduction in size of ear in determinate plants.
•Increased sterility of crop

10. Plant population and Yield
0
1
2
3
4
5
6
7
0
50
100
150
200
250
10 20 30 40 50 60
Per plant yield (g/plant
)

Yield per plant (g/ha)Yield per unit area (t/ha)
Plant Population (000 maize/ha)
Yield per unit area(t/ha)

Fig: Relation between plant population and Yield Maize

11. Crop response towards plant density
Parabolic Response
•Eg.Crops, like rice, wheat, maize and several other

Asymptotic Response
•All biological yield used as economic yield
•Eg. Tobacco, leafy vegetables and fodder crops
0
10
20
30
40
50
60
70
80
Relative Yield (%) of seed

Plant Population increases
Parabolic response
Asymptotic Response

12. Plant Population Management

13. 1. Method of sowing
Source: (FAO, 2003)
In wheat, optimum seed rate for broadcast crops can be twice
that of drilled crops
Due to rough seedbeds, poor seed covering and poor contact
between seed and moist soil.

14. 2. Soil

Good soil physical property favors good germination of seeds
Hard and cracked soil surface.
Source: (Harper, 1961)
Figure : Effects of compaction level on crop yield response
Source: (Jodi DeJong, 2018)

15. 3. Seed quality and seed rate
Table: Effects of seed quality on plant population, seed yield of soybean
Dead seed rate(%) Planting Density Seed Yield(kg)
0 143229 3056
10 128900 3219
20 115473 2964
50 72247 2338
Source: (Bihter , Halis & Mehmet, 2004)
Quantity of seed sown/unit area, viability and establishment rate
The best seed rate is that which maximizes grain yield.
Size of seeds and the viability percentage.
In Wheat size is 25 to 50 mg and crop establishment varies 40-95%.
(Source: FAO, 2003

16. 4.Sowing depth
Source: (FAO, 2003)
In wheat, 12% less yield in
deeper planting.
Crop Depth of sowing(cm)
Wheat 2-4
Maize 3-5
Cotton 2-4
Sunflower 2-4
Source: (Pratley & Stanton, 2002)

17. 5.Plant Architecture
•Narrow leaf angle crops and
dwarf varieties planted more
densely
•Hybrid cultivars are planted
closely than local cultivars.
Source: (Kaggwa, Sanchez
& Wang, 2013)
Fig: Cotton lint yield response to plant population for a columnar type variety DP164 and a bush
type variety ST4498

18. 6.Size of the plant
The volume occupied by the plant at the time of flowering decides the
spacing of the crop.
Cotton, sugarcane occupy larger space in the field compared to rice, wheat
Highly spaced crop has comparatively lower number of plant population

19. 7.Tillering/Branching

Wheat, rice has high tillering capacity as compare to maize.
Yield of sugarcane is higher in ring method of planting
8.Weeds and plant population
Weeds and plant population has
inverse relationship.
Weeds growth and population in field
is more means less plant populations.
Source: (FAO, 2003)

20. 9. Fertilizer application
Higher plant density is necessary to fully utilize higher level of nutrients in
the soil to realize higher yield.
Nutrient uptake increases.
Nutrient deficiency symptoms.
10.Rainfall/irrigation
OPP is less under rain-fed.
Under high PP more water
is lost through transpiration.
Source: seedcogroup.com

21. •After germination, gap filling transplanting of seeds/seeding
•Germination lower than 50%, then re-seeding
•Gap transplanting rice seedling maintaining 20 cm after 20 days.
(Akbar, Jabran, & Habib, 2007)
12.Proper plant pest Management
Preventive and curative measures along
with integrated approach.
11.Gap Filling/Re-seeding

22. 13. Over-seeding and Thinning
Maize and Rapeseed in 7-10 days
14. Double Transplanting of Rice
15. Growing of submergence and Drought tolerant variety
Submergence tolerant: Sworna sub-1, Sambha mahasuri sub-1, sheherang sub-1
Drought tolerant: Sukkha-1, Sukkha-2, Sukkha-3, Sukkha-4
Treatment Grain yield(t/ha)
Double transplanting 5.5
Normal transplanting 5.0
Source: (Satapathy, Singh, Pun & Rautaray, 2015)

23. Crop plant competition
Inter plant competition
•Competition of plant with the neighboring plant
•Affects growth and yield of crop
•More taller the plant- more chance to lodge
•More population- the leaf orientation is vertical and the leaf is thinner, the more
thinner is leaf, less is the photosynthesis, seed size decreases.
Intra plant competition
•Competition within the plants
•Competition in the sink for the accumulation of assimilates.
•Results in fruit drop due to source limited.
•Sterility % increases.
•More wider spacing result in intra plant competition

24. Conclusion
•Plant density is an important agronomic factor and affects the
growth, development and yield formation of crops.
•Competition has negative effect on plant growth which increases
with higher plant population.
•Optimum plant population, efficient utilization of resource.
•Optimum plant population provides highest crop yield and profit.
•crop factors, input factor and management factor affects the OPP
•Careful consideration on those factors right from seeding to
harvesting, gap filling, defoliation, thinning, weeding must be done
for managing plant population and competition.