Effect of Deficit irrigation on physio-chemical properties of soil

1. TOPIC
EFFECT OF DEFICIT IRRIGATION ON SOIL PROPERTIES,
PHYSIOLOGY AND NUTRIENT ASSIMLATION OF SWEET
PEPPER (Capsicum annuum)
BY
TABITHA MENSAH

2. INTRODUCTION
 Water supplies are limited worldwide (Postel, 1998) and there is an
urgent need to identify and adopt better irrigation management
strategies.
 Low moisture in the soil may however lead to problems of reduced
growth rate, metabolic activities, development and yield of crops.
 Low soil moisture could also result in total loss of a farmer’s whole
crop or make his crops vulnerable to both biotic and abiotic
complications (Ware and McCollum, 1975).

3. INTRODUCTION CONT’D
 Deficit irrigation, is a practice of reducing the amount of water
supplied to a crop or reducing the frequency of water application.
 It ensures optimum yield in times of drought or make proper use of
irrigation water to achieve the maximum potential yield in times and
areas of abundant and almost free water for irrigation
 The application of less water reduces the leaching effects of
nutrients from the root-zone and agrochemicals and the groundwater
quality is preserved (Pandey et al., 2000)..

4. BENEFITS OF SWEET PEPPER
SWEET
PEPPER
Beautification, taste, flavour
Vitamins(thiamin
e, carotene, B12)
Spices, sauce, pickles
Phytochemical
properties

5. BOTANY OF SWEET PEPPER
S.N:
Soil:
Temp:
Rainfall:

6. PROBLEM STATEMENT
 Relative abundance or scarcity of water as well as the lack of
irrigation knowledge leads to over irrigation or under irrigation.
 This results in leaching of plant nutrients, saturation of soil to create
anaerobic conditions which can result in root damage, reduced root
respiration, and lime hydrolysis as well as denitrification of nitrate
fertilizers.

7. PROBLEM STATEMENT CONT’
 Therefore, there is the need to consider measuring the amount of
water applied to crop like sweet pepper which has an extensive
shallow root system, and is susceptible to water logging.
 Efficient use of water by irrigation is becoming increasingly
important. (Oweis, 2000).
 Deficit irrigation (DI) has been used as a water saving irrigation
technique in horticultural production.

8. GENERAL OBJECTIVE
 The general objective of the study was to examine the effect of
deficit irrigation on soil properties, physiology and nutrient
uptake of sweet pepper.

9. SPECIFIC OBJECTIVES
There specific objectives of the study were:
 To assess the effect of deficit irrigation on the harvest index and dry
matter accumulation of sweet pepper .
 To assess the effect of nitrogen, phosphorus, potassium uptake by
sweet pepper.
 To access the effect of deficit irrigation on the root system
architecture of sweet pepper.

10. JUSTIFICATION
 Several researches have been carried out on deficit irrigation with
resulting indicating 10-15% reduction of crop water requirement had
no significant effect on the yield.
 The interest of the research was to investigate the effect of deficit
irrigation on important soil properties such as bulk density, particle
density, infiltration rate, soil salinity.
 Finally the study would seek to examine the effect of deficit irrigation
on nutrient uptake and utilization by sweet pepper.

11. STUDY AREA
The study was conducted at the engineering field of the School of
Agriculture Teaching and Research Farm at University of Cape Coast.
AREA FEATURES
 Annual temperature of 23.2-33.2 ºC with an annual mean of 27.6 ºc
 Relative humidity is 81.3-84.4% (Owusu-Sekyere et al 2011).
 The annual rainfall is between 650 and 1100 mm (Alhassan, 2009).
 Soil: sandy clayey loam of the benya series classified by Asamoah
(1973)
 Location : central region of Ghana

12. EXPERIMENTAL DESIGN
 Completely Randomized Block Design (CRBD) with three (3)
treatments (T1-T3) and three (3) replications (R1- R3).
 Each replication had 4 (four) plants. In this study, sweet pepper
plants were grown in containers and placed under a transparent rain
shelter.
 Two blocks were used for the study (morning and evening block)

13. TREATMENTS
 After determining the crop water requirement (CWR) for the day,
the plots were subjected to different amounts of water, the
following treatments were imposed: T1, 100% of CWR; T2, 90% of
CWR; T3, and 80% of CWR. These treatments were applied both
for the morning and evening blocks.

14. DETERMINATION OF CROP WATER
REQUIREMENT(ETc)
 Crop evapotranspiration (ETc) was calculated as the product of
reference evapotranspiration (ETo) and the dual crop coefficient
(Kc). Thus;
ETc = ETo ( Kcb + Ke) ……………..(1)
Where;
ETc - is the crop evapotranspiration(mm),
ETo - the reference evapotranspiration (mm),
Kcb - the basal crop coefficient
Ke - the evaporation coefficient.

15. PLANTING OF SWEET PEPPER
Sweet pepper seeds were nursed on the …………. and the healthy
seedlings were transplanted into the container under the rain shed on
………….. All the 72 plants comprising the treatment combination
were given equal volume of water (………) for eight days to ensure
uniformity among the seedlings before the various treatments were
administered.

16. IRRIGATION OF CROPS
 A three day irrigation interval was employed.
 The volume of water applied to each treatment was obtained by the
computation of weight loss by each container with the plants of the
treatment.
 Weight of plant pot was determined using CAMARY 150kg
capacity electronic scale with a graduation of 500g.

17. IRRIGATION CONT’D
 Density (kg/m3) = weight (kg)/volume (m3)
 Density x volume = weight
 Since the density of water is 1kg/m3 then
 Volume = weight

18. FIELD LAYOUT

19. DATA PARAMETERS
Data was collected on the following parameters
 Soil physical properties ; bulk density, particle density and
porosity
 Soil chemical properties ; Nitrogen %, potassium and
phosphorus content
 Vegetative parameters ; dry matter accumulation and harvest
index

20. DRY MATTER ACCUMULATION
 Leaves from the top, middle and down part of data plants randomly
selected after harvest were taken.
 Fresh weight of the leaves was taken by weighing with an
electronic balance.
 Samples were oven-dried at 105 ºC to constant weight to determine
their total dry weight.
 Total dry matter of plant was the sum of total vegetative dry weight
and total fresh weight of fruit per plant.

21. Dm= Total dry weight of sample ×100
Total fresh weight of sample
(Patel & Rajput, 2013)
HARVEST INDEX
 Harvest index was calculated by dividing total dry weight of fruit by
total dry weight of plant.

22. BULK DENSITY
Bulk density of soil was determined using the method as described by
(McKenzie et al., 2004).
 Representative soil samples were collected from both surface,
subsurface and bottom using a standard metal ring cylinder with a
known volume.
 Samples were then transferred into a weighed beaker (W1).
 Weight of both beaker and soil samples were measured using an
electronic balance.

23. BULK DENSITY CONT’D
 The samples were then oven dried for 24hrs at 105oC.
 Samples were weighed (W2) and used to determine the dry weight.
 Bulk density was calculated using the following formula;
Bulk density (g/cm3) = (𝐷𝑟𝑦 𝑠𝑜𝑖𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 (𝑔))/(𝑆𝑜𝑖𝑙 𝑣𝑜𝑙𝑢𝑚𝑒 (𝑐𝑚3))
Dry soil weight (g) = W2 – W1
Soil volume (cm3) = 3.14 x r2 x ring height.

24. PARTICLE DENSITY
 A 100ml graduated cylinder was weighed and its weight recorded.
 The cylinder was then filled with a sieved oven dried soil sample to
the 25ml mark then compacted.
 Additional soil sample was added and compacted until soil reached
the 70ml mark of the cylinder.
 A spatula was then used to scoop soil sample from the cylinder to
the 50ml mark.
 The cylinder containing soil sample was weighed and the weight
recorded.

25. PARTICLE DENSITY CONT’D
 Soil was then transferred from the cylinder to a weighed beaker.
 The cylinder was then filled with water to the 50ml mark to make
the initial volume of soil.
 The soil in the beaker was gradually transferred into the cylinder
while stirring to remove all forms of air bubbles.
 The sample was allowed to settle after which water suspension was
recorded.

26. PARTICLE DENSITY CONT’D
Particle density was calculated as follows;
 Volume of soil solids = final volume of soil – initial water volume
(50ml)
 Particle density = oven-dry soil weight / volume of soil solids

27. POROSITY
 Porosity of each sample was calculated by finding the ratio of bulk
density to particle density and multiplying by 100 to give the %
solid space. 100 were then subtracted from the % solid space to
obtain the porosity for each sample.
 % solid space = (bulk density / particle density) x 100
 % porosity = 100 - (% solid space)

28. PERCENTAGE NITROGEN
 Micro-Kjedahl method was used for nitrogen determination.
 Steps involved in nitrogen determination are;
 Digestion, Distillation and Titration
 𝑁 (%) = (𝑆−𝐵)𝑋 𝑆𝑂𝐿𝑈𝑇𝐼𝑂𝑁 𝑉𝑂𝐿𝑈𝑀𝐸)
(100 𝑋 𝐴𝐿𝐼𝐺𝑈𝑂𝑇 𝑋 𝑆𝐴𝑀𝑃𝐿𝐸 𝑊𝐸𝐼𝐺𝐻𝑇)
Where
 S - sample titre value
 B – Blank titre value

29. PHOSPHORUS DETERMINATION
 Bray No 1 method (with Ascorbic Acid) was used.
 About 1g of soil sample was weighed into 15ml centrifuge tube
and 100ml extraction solution was added was added.
 The content was centrifuge for 10minutes and then filtered.
 2ml of the aliquot of the extract was pipette into 25ml volumetric
flask from the stock solution. 100ml of 5µgP/ml was prepared.
 A set of working standards of P containing 0.0, 0.1, 0.2, 0.4, 0.6,
0.8, and 1.0µgP was prepared from the stock solution of 5µgP/ml

30.  From this point, all the standards were treated in the same way by
adding 10ml of distilled water to each flask and 4ml of ascorbic
acid. Colour was allowed to develop by allowing the solution to
stand for 15minutes. Their respective absorbance was determined
with spectrophotometer at 882nm.
µ𝒈𝑷/𝒈 =
𝒄𝒐𝒏𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏 𝑷 𝒙𝒅𝒊𝒍𝒖𝒕𝒊𝒐𝒏 𝒇𝒂𝒄𝒕𝒐𝒓
𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒔𝒐𝒊𝒍 𝒔𝒂𝒎𝒑𝒍𝒆

31. POTASSIUM DETERMINATION
 About 5g of soil sample was weighed and transferred into a 100ml
extraction bottle. 20ml ammonium acetate was added and the
content was stirred and allowed to stand overnight.
 The suspension was transferred into a 100ml volumetric flask fitted
with funnel filter and filter paper. The soil was leached 4 times with
successive ammonium acetate while allowing the funnel to drain
between each addition.

32. POTASSIUM CONT’D
 The process continued until 100ml of filtrate has been collected.
The mark was made-up with ammonium acetate. Aliquot of the
extract was used for the determination of potassium by flame
photometry.

33. STATISTICAL ANALYSIS
 The various results obtained were subjected to the analysis of
variance (ANOVA) using Genstat statistical software.
 Mean comparisons were done using least significance difference
test at a probability level of 5%.

34. RESULTS

35. DISCUSSIONS
SOIL PHYSIOCHEMICAL PROPERTIES
NITROGEN
 The amount of water applied to a soil has a significant effect on the
nutrient uptake of a plant. From the results obtained, it can be
deduced that the T1 had the highest uptake of nitrogen however the
difference between T1 and T2 is not significant.
 The results correlate with that of Vincenzo Candido et al., (2009)
who stated that, nitrogen absorption, partitioning and translocation
is affected by water availability.

36. PHOSPHORUS
 Unlike nitrogen and potassium, the uptake of phosphorus is not
significantly affected by the availability of water. K. Nahar and R.
Gretzmacher, (2002) reported that, moisture stress did not influence
significantly the uptake of phosphorous.
 Shapiro et al. (1956) pointed out that translocation of phosphorus
increases when there is improvement in aeration.

37. POTASSIUM
 The decrease in uptake of potassium with increasing moisture stress
at the end of the study can be as a result of the fact that uptake of
potassium like nitrogen increases with increasing moisture
availability.
 Adequate amount of water in the soil tend to enhance aeration and
this according to Cline and Erickson (1956), would improve
potassium and nitrogen uptake.

38. DRY MATTER ACCUMULATION
 Dry matter production decreased with increasing water stress
condition. The interaction effect of water deficit and sweet pepper
was highly significant in dry matter production under various
treatments.
 According to Busso et al (1997) during their work reported that,
water stress had a greater effect on the stems, leaves and peduncles
compared to roots.

39. ROOT STRUCTURE
 Root water uptake increases with increasing moisture availability at
the root zone of crops and decrease with increasing rate of deficit.
 . Results from Marouelli and Silva, (2007), confirmed that, the
occurrence of moderate water deficits during the vegetative stage
favours deeper rooting allowing the plants to draw water from the
deeper soil layers

40. CONCLUSION

41. RECOMMENDATION