CHAPTER ONE
1.0 INTRODUCTION
Soybean [Glycine max (L.) Merrill] is a
member of the Fabaceae family, rich in nutrients. Soybean is not only
seen as an oil plant but also used for various purposes. Among grain
legumes, soybean is an economically important crop that is grown in
diverse environments throughout the world. Its adaptation to tropical
and subtropical regions is still involving extensive breeding work. To
use land continuously for crop cultivation, incorporating organic and
inorganic fertilizers to soil would provide multiple benefits for
improving the chemical and physical status of the soil which results in
improved crop yield (Ferguson et al.,2006).
Both organic and inorganic
fertilizers are sources of mineral elements, which plants require for
effective growth and development (Ferguson et al.,2006).
Essential mineral elements are required in optimum amounts and are
classified into micro and macro nutrients. Nitrogen, phosphorus, and
potassium have great effects in plant growth and development. Their
deficiencies or excesses result in marked effects on the growth and
yield of crops. Nitrogen is a chlorophyll component, and it promotes
vegetative growth and green colouration of foliage. Phosphorus plays a
major role in photosynthesis, respiration, energy storage, cell
division, and maturation.According to Fageriaet al., (1995)
large quantity of P fertilizer may be required for successful soybean
production. Potassium is important in plant metabolism, protein
synthesis, and chlorophyll development. The most important crop
nutrients in agricultural systems are nitrogen (N), phosphorus (P), and
potassium (K) (Chiezey2001). Most compound fertilizers will contain
three elements essential for plant growth: NPK which stands for nitrogen
(promotes leaf growth), phosphorus (root, flower, and fruit), and
potassium (stem and root growth and protein analysis). Soybean nitrogen
(N) requirements are met in a complex manner, as this crop is capable of
utilizing both soil N (mostly in the form of nitrate) and atmospheric N
(through symbiotic nitrogen fixation) (Kakaret al., 2002).
The use of fertilizer is
considered to be one of the most important factors to increase crop
yield. Legumes require P for adequate growth and N fixation and their
effectiveness in soil improvement can be hindered by P deficiency
(Giller and Cadisch, 1995). Phosphorous has been shown to be an
essential element, and its application has been shown to be important
for growth, development, and yield of soybean (Kakaret al., 2002). Phosphorus deficiency is probably one of the greatest constraints for agriculture. Fageriaet al., (1995) had earlier reported that large quantity of P fertilizer may be required for successful soybean production.
1.1 Objective
The objective
of this work is to investigate the effect of phosphorus level on
the grain yield and yield components of soybean.