Growth and yield response of soybean varieties to inoculation and nitrogen levels

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Soybean, like any other legume can fix atmospheric N through symbiotic association with native rhizobia but, the amount of N 2 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.
A thesis submitted to the Department of Crop and Soil Sciences, Faculty of Agriculture, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the degree of Master of Philosophy in Agronomy, 2016