Effect of Rhizobium-inoculated pueraria phaseolides green manure on soil nitrogen

Abstract

Efforts have been made to improve agricultural productivity through improving the overall agronomic practices yet yields are still below the expected potentials. This could be attributed to soil fertility exhaustion, especially soil nitrogen, which is highly removed through harvesting of high yielding varieties. A study to evaluate the potential of Pueraria phaseolides as a green manure in improving soil nitrogen status and the use of locally available techniques like Rhizobium inoculation, phosphate rock and wood ash in enhancing the performance of Pueraria phaseolides, was conducted at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK). A soil characterisation of the experimental site prior to incorporation of the green manure revealed that the soil had very low levels of phosphorus while nitrogen and potassium were near to the nutrient limiting values. Results showed that application of phosphate rock significantly increased total soil nitrogen after incorporation of Rhizobium inoculated legume the green manure. There was significant increase in nodule numbers, nodule weight, above ground biomass yield and its nitrogen content (kg ha) and high total soil nitrogen where phosphate rock was added to the inoculated legume. This was attributed to the ability of the phosphorus to enhance better early root development; thereby stimulating legume growth and increasing the capacity to absorb other nutrients from the soil improved nodulation hence high nitrogen fixation.