TOPIC

EFFECT OF DEFICIT IRRIGATION ON SOIL PROPERTIES,

PHYSIOLOGY AND NUTRIENT ASSIMLATION OF SWEET

PEPPER (Capsicum annuum)

BY

TABITHA MENSAH

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).

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.

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)..

BENEFITS OF SWEET PEPPER

SWEET PEPPER

Beautification, taste, flavour

Vitamins(thiamine, carotene, B12)

Spices, sauce, pickles

Phytochemical properties

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.

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.

OBJECTIVE

General objective

To examine the effect of deficit irrigation on soil properties,

physiology and nutrient uptake of sweet pepper.

Specific objective

To assess the effect of deficit irrigation on the harvest index and dry

matter accumulation.

To assess the effect of nitrogen, phosphorus, potassium uptake by

sweet pepper.

To assess the effect of deficit irrigation on soil physical properties.

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 soil physical & chemical properties and physiology of

sweet pepper which have a direct effect of the yield.

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).

EXPERIMENTAL DESIGN

Design

Completely Randomized Block Design (CRBD) with three (3)

treatments (T1-T3) and three (3) replications (R1- R3). Each

replication had 4 (four) plants.

Treatment

T1, 100% of CWR; T2, 90% of CWR; T3, and 80% of CWR.

Planting

Sweet pepper seeds were nursed, and the healthy seedlings were

transplanted into the plastic pots under a rain shed on.

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

DRY MATTER ACCUMULATION

Fresh leaves from the top, middle and down part of data plants

randomly selected and weighed.

Samples were oven-dried at 105 ºC to constant weight to determine

their total dry weight.

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.

BULK DENSITY

Bulk density of soil was determined using the method as described by

(McKenzie et al., 2004).

Bulk density (g/cm3) = ( ( ))/( 𝐷𝑟𝑦 𝑠𝑜𝑖𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 𝑔 𝑆𝑜𝑖𝑙 𝑣𝑜𝑙𝑢𝑚𝑒( 3)) 𝑐𝑚

Dry soil weight (g) = W2 – W1

Soil volume (cm3) = 3.14 x r2 x ring height.

PARTICLE DENSITY

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

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)

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 𝑆𝐴𝑀𝑃𝐿𝐸𝑊𝐸𝐼𝐺𝐻𝑇

Where

S - sample titre value

B – Blank titre value

PHOSPHORUS DETERMINATION

Bray No 1 method (with Ascorbic Acid) was used.

POTASSIUM CONT’D

Flame photometry was used to determine potassium.

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%.

RESULTS

Treatment Bulk density (g/cm3) Particle density (g/cm3) Porosity %

T1 1.333 a 2.530 a 45.53 a

T2 1.357 b 2.610 b 47.83 b

T3 1.387 c 2.630 b 49.30 b

Lsd0.05

Treatment Harvest index Dry matter accumulated

T1 1.333 a 733.7 a

T2 1.357 b 786.8 ab

T3 1.387 c 811.3 c

Lsd0.05

EFFECT OF DEFICIT IRRIGATION ON NITROGEN UPTAKE

NB NA NB NA NB NAT1 T2 T3

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

(Nitr

ogen

leve

l %)

Source; field data 2015

EFFECT OF DEFICIT IRRIGATION ON POTASSIUM UPTAKE

KB KA KB KA KB KAT1 T2 T3

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Pota

ssiu

m le

vels

(K C

mol

/kg

Source; field data 2015

EFFECT OF DEFICIT IRRIGATION ON PHOSPHORUS UPTAKE

PB PA PB PA PB PAT1 T2 T3

0

5

10

15

20

25

30

35

40

45

Phos

phor

us le

vels

(P g

p/g

)

Source; field data 2015

CONCLUSION

From the results on the study it could be concluded that

Although deficit irrigation affects soil physical properties but its

effect is not significant. However increasing water deficit has

increasing effect on soil physical properties.

Also the higher available moisture content the higher the rate of

nutrient uptake. However excessive application of water could lead to

leaching effect on certain soil nutrients.

RECOMMENDATION

From the study it could be recommended that;

A comprehensive study should be carried out on the effect of deficit

irrigation on other micro nutrients uptake in the soil (Ca, Mg)

Also a study on the salinity rate of soil under deficit irrigation must be

carried.

Also other varying levels of water deficit on soil physiochemical

properties can be researched.

END OF PRESENTATION

THANK YOU