Effects of lime and phosphorus on biological nitrogen fixation by soybeans (Glycine max (L.) Merrill) in an Ultisol, Morogoro, Tanzania
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Date
2017
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Sokoine University of Agriculture
Abstract
Low soil pH and phosphorus are among the major soil constraints which limit BNF and
soybean production in sub-Saharan Africa. Most Probable Number (MPN) plant infection
technique and glasshouse pot experiment were conducted at SUA to estimate the
population of native Bradyhizobium japonicum and determine the effect of lime and
phosphorus on soil pH and BNF by soybean in an Ultisol. The pot experiment was a 33
factorial in a split plot experimental design replicated two times. The main plots were
inoculation, non-inoculation and inorganic N fertilizer at the rate of 200 kg N ha-1.
The levels of lime were 0, 5 and 10 ton/ha and the levels of phosphorus were 0, 50 and
100 kg/ha, whose combinations constituted the sub-plots. The soil was acidic (pH 4.6)
and contained 2-79 cells of indigenous Bradyhizobium japonicum per gram of soil, which
is low and appeared to limit BNF by soybean. The soil pH and N content in soybean
plants increased significantly (P < 0.05) with increase in liming rate. The interaction of
lime and phosphorus on nodulation, N2 fixed, DMYs, P content in inoculated plot and on
Ca contents of soybean plants in inorganic N applied plot was significant. It was
concluded that for soybean to be grown in the studied area should be inoculated before
planting due to the low Bradyhizobium japonicum population. The application of 5 tons
lime/ha and 100 kg P/ha would serve as the optimum rates for the Ultisol used in this
study. It is recommended that the study be validated under field conditions before
conclusive decisions can be made.
Description
A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE
REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN SOIL
SCIENCE AND LAND MANAGEMENT OF SOKOINE UNIVERSITY OF
AGRICULTURE. MOROGORO, TANZANIA. 2017
Keywords
Lime - phosphorus effects, Biological nitrogen fixation, Soybeans, Glycine max (L.) Merrill, Ultisol, Morogoro, Tanzania