Soybean, like any other legume can fix atmospheric N through symbiotic association with native rhizobia but, the amount of N2 fixed is usually not enough due to existence of ineffective population of native rhizobia. A field experiment was conducted in 2015 at CSIR-CRI demonstration field to study the interactive effect of inoculation and nitrogen fertilization effect on the growth, nodulation and nitrogen fixation, grain yield and protein content, as well as remobilization of N using three soybean varieties. The experiment was a 3x6 factorial experiment laid out in a Randomized Complete Block Design with three replications. The factors were: soybean varieties (Anidaso, Quarshie and Salentuya 1) and the nitrogen sources: (control, 30 and 60 kg N/ha, inoculation alone, inoculation+30 kg N/ha and inoculation + 60 kg N/ha. The seeds were inoculated before sowing. All cultural practices were carried out when needed. The results showed that, inoculated plants of all three varieties established better than their corresponding uninoculated plants. Again, inoculation resulted in significantly greater nodule numbers, nodule dry weight and nitrogen fixation. Also growth, grain yield and protein content were all enhanced following seed inoculation. Application of fertilizer N at grain filling period increased seed yield, especially at the rate of 30 kg N/ha. Lastly, remobilization of N occurred in all treatments, but was greater in treatments with greater availability of N.


1.1 Objectives

2.1 Origin and history
2.2 Botany
2.3 Morphological description
2.4 Climate and soil
2.4.1 Soil
2.4.2 Moisture supply
2.4.3 Photoperiod and temperature
2.5 Soil available nitrogen
2.6 Why N application in soybean is necessary
2.7 Inoculation
2.8 Nodulation, biological nitrogen fixation (BNF) and factors affecting BNF
2.9 Rate of nitrogen application on soybean yield
2.10 Nitrogen application and remobilization on yield of soybean
2.11 Inoculation and nitrogen effect on soybean growth and yield
2.12 Inoculation and nitrogen effect on crude protein content of soybean growth and yield
2.13 Importance and uses of soybean

3.1 Description of experimental site
3.1.1 Land preparation
3.2 Enumeration of population of soil rhizobia
3.3 Inoculation
3.4 Planting
3.5 Experimental design and treatments
3.6 Data collection
3.6.1. Seedling emergence
3.6.2 Plant height
3.6.3 Canopy spread
3.6.4 Number of leaves
3.6.5 Number of branches
3.6.6 Nodule count and effectiveness
3.6.7 Nodule dry weight
3.6.8 Number of pods per plant
3.6.9 Pod length
3.6.10 Number of seeds per pod
3.6.11 Seed width
3.6.12 100 Seed weight
3.6.13 Grain yield
3.6.14 Harvest index
3.6.15 Haulm weight
3.6.16 Total N fixation
3.6.17 N Remobilization between R1 and R5
3.6.18 Seed and residue N
3.6.19 Crude protein content
3.7 Cultural practices
3.7.1 Irrigation
3.7.2 Thinning
3.7.3 Weeding
3.7.4 Pest management
3.7.5 Harvesting
3.8 Statistical analysis

4.1 Crop establishment
4.2 Plant height
4.3 Canopy spread
4.4 Number of leaves
4.5 Number of branches
4.6 Number of pods
4.7 Pod weight
4.8 Pod length
4.9 Number of seeds per pod
4.10 One hundred seed weight
4.11 Seed N
4.12 Residue N
4.13 Total N
4.14 Number of nodules
4.15 Nodule dry weight
4.16 Crude protein
4.17 Total grain yield
4.18 Remobilized N

5.1 Response of soybean growth to N
5.2 Response of soybean grain yield and yield components
5.3 Variety, N and crude protein content of soybean
5.4 Nodulation and nitrogen fixation
5.5 Variety and treatment effect on N remobilization

6.1 Conclusion
6.2 Recommendations

Soybean (Glycine max L) is an annual herbaceous plant in the Fabaceae (legume or bean family) (Tefera, 2011). It is an economically important leguminous crop on a worldwide scale and also the most important legume in China. Among the important food crops grown in every part of the continent is soybean. The crop can be cultivated in many places with low level of agricultural inputs (Gan et al., 2003; Dugde et al., 2009). Soybean is an important protein source in the diet of humans and ration of animals; containing considerable amounts of all essential minerals, oils, vitamins and amino acids (Tefera, 2011).

The protein content of soybean is around 40% and the oil content is approximately 20% which is also 85% unsaturated and cholesterol-free and also the main source of vegetable oil worldwide. It is recorded as the legume with the highest protein content and vegetable oil among the other crops produced (IITA, 2009). Thirty percent of the oil produced worldwide is from soybean and it also serves as bio-fuel source (Graham and Vance, 2003).

Biological nitrogen fixation (BNF) occurs in many legumes due to symbiotic association with soil rhizobia. Soybeans like other legumes are also able to establish associations with other rhizobia specifically Bradyrhizobium japonicuin (Paulo et al., 2009). It is widely known that inoculation of legumes with effective compatible rhizobia can enhance yields through biological nitrogen fixation and this accounts for a substitute and sustainable source of nitrogen for inorganic fertilizers. Introduction of rhizobia in the soil is a practice that has been used over decades in the absence of compatible rhizobia or when native rhizobia population is low or inefficient to fix nitrogen (Catroux et al., 2001; Deaker et al., 2004; Stephens and Rask, 2000).

Most farmers take advantage of legume-rhizobia associations by applying rhizobia inoculant to seeds or soils. Rhizobial inoculants are available in many formulations: granular inoculants are applied over the soil after sowing (Lupwayi et al., 2006); liquid inoculants are mostly used in large areas, mainly with soybean, in South America (Paulo et al., 2009). However, commercial inoculants are available as solid- in powder from peat or in granular form or as liquid formulation (Stephen and Rask, 2000). Inoculant use accounts for greater root biomass and an increase in nodulation, which increases plant vigour and yield. Even though the cost of inoculation is relatively low, nodule failure is very expensive, as without root nodulation with effective rhizobia, the plants will use soil nitrogen for their growth making the soil nitrogen deficient (Bowen and Hogg, 2010).

Soybean can fix between 50-80% of the nitrogen required (Solomon et al., 2012) but most soybean varieties cannot meet all the N required for growth and development of seeds only through fixation. Bradyrhizobium japonicum has been reported to be rarely available in Ghanaian soils because soybean does not originate from Ghana (Okogun and Sanginga, 2003). Moreover, in soils with no previous record of soybean production, bradyrhizobia populations are often not present, and therefore for successful nodule formation, it may require clearly identified bradyrhizobium species for N2 fixation to be effective (Abaidoo et al., 2007). The success of inoculation however, does not only depend on the inoculant quality and proper inoculation practice but also on the achievement of efficient and effective BNF by considering factors that affect the performance of the rhizobia species such as climatic, edaphic, management factors and legume genotype (Giller, 2001; Sanginga et al.,1995; Giller and Wilson, 1991).

In soybean, nitrogen obtained from nodule and fertilizer is the most crucial element for ensuring good growth rate of the source (photosynthetic organs) and also ensuring growth of flower buds at vegetative stage. In effect, nitrogen translocation efficiency from vegetative to reproductive organs has influence on yield at pod filling stage (Nakamura et al., 2010). Reduction of N from the vegetative parts enhances leaf fall and thus limits the photosynthetic ability of the leaf canopy. This results in reduced yield by cutting short the seed filling period (Kumudini et al., 2002).

Several studies have shown that nitrogen fertilizer applied during the reproductive stage (R1 to R5) is likely to increase the capacity and duration of inorganic N utilization periods. Supplying N to soybean plant during the peak of seed demand may supplement N existing resources, thus overcoming premature senescence and increase seed yield (Barker and Sawyer, 2005; Freeborn et al., 2001).

1.1 Objectives 
The main objective of this research was to determine the response of soybean to inoculation and different nitrogen fertilizer levels on the growth and yield of soybean.

The specific objectives of the study were to determine the;

response of soybean to inoculation and their effect on nodulation and nitrogen fixation,

effect of inoculation on growth, grain yield and crude protein content of soybean,

effect of nitrogen availability on nitrogen remobilization between R1 and R5 growth stages in soybean.

The above objectives were based on the hypothesis that;

inoculation of soybean will increase nodulation and nitrogen fixation,

inoculation will increase growth, grain yield and crude protein content of soybean,

nitrogen availability on nitrogen remobilization between R1 and R5 growth stages in soybean will positively be affected.

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Item Type: Ghanaian Topic  |  Size: 89 pages  |  Chapters: 1-5
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