ABSTRACT

Two field experiments were conducted at the Michael Okpara University of Agriculture Research Farm. Umudike in 2005 and 2006 cropping seasons to determine the responses of two sweetpotato (Ipomoea batatas (L.) Lam) TIS 87/0087 and TIS 8164 to time of potassium (K) fertilizer application in a humid forest zone of south eastern Nigeria. In 2005 cropping season the experiment was a 2x4 factorial laid out in a randomized complete block design with four replications. Potassium treatments comprised of no K application, 100 kg K/ha at 4 WAP, 100 kg K/ha at 8 WAP. 50 kg K/ha at 4 WAP + 50 kg K/ha at 8 WAP. Time of K application had no significant effect on the growth attributes of the varieties, but these were higher with split K application at 4 WAR and 8 WAR in TIS 87/0087. TIS 87/0087 were significantly (p <0.05) higher in total tuber yield when 100 kg K/ha was applied at 4 WAP and also with split application of 50 kg Klha at 4 WAP + 50 kg K/ha 8 WAP. n 2006 cropping SG2SOfl, a 2x8 factorial in a randomized complete block design with three replications was conducted at the same location as in 2005. The treatments comprised of no K application, 100kg K/ha at 2 WAR, 100 kg K/ha at 4 WAR, 100 kg K/ha at 6 WAR, 100 kg K/ha at 8 WAR, 50 kg K/ha at 2 WAR + 50 kg K/ha at 6 WAP. 50 kg K/ha at 2 WAR + 50kg K/ha at 8 WAR and 50 kg K/ha at 4 WAP + 50 kg K/ha at 8 WAP. Dry weights of plant parts were highest with TIS 87/0087 when split K application was applied at 4 WAR + 8 WAR and was lowest when K was applied whole at 8 WAR. TIS 87/0087 were significantly (p < 0.05) higher in total tuber yield when K was applied split at 2 WAP i- 6 WAP or 50 kg K/ha at 4 WAP + 50 kg K/ha at 8 WAP apphcation. TIS 87/0087 'which was a higher yielding variety should be recommended for the study area with split application of K at 2 WAR + 6 WAR or with 4 WAP + 8 WAR.

TABLE OF CONTENT

Title page

Certification Ii

Dedication lii

Declaration Iv

Acknowledgement V

Table of content vi-vii

Listof tables Viii

Abstract Ix

CHAPTER 1

INTRODUCTION 1

1.1 Objectives of the study 3

CHAPTER 2

LITERATURE REVIEW 4

2.1 Potassium effects 4

CHAPTER 3

MATERIALS AND METHODS 9

3.1 Land preparation 9

3.2 Planting Materials 9

3.3 Field layout and treatments allocation 10

3.4 Planting and maintenance of experimental plots 11

3.5 Record of agronomic measurements 11

3.6 Statistical analysis 12

CHAPTER 4

RESULTS AND DISCUSSION 13

4.3 Experiment 1, 2005 13

4.3.1 Growth

4.3.2 Yield and components 17

4.4 Experiment 2, 2006 18

4.4.1 Growth 18

4.4.2 Yield and yield components 22

CHAPTER 5

CONCLUSION AND RECOMMENDATION 29

References 30

Appendices 34