The response to phosphorus of white clover and lotus inoculated with rhizobia or given KNO₃

Abstract

White clover and lotus were grown in a controlled environment at P levels of 50, 500, and 1500 ppm and either inoculated with rhizobia (N₂) or given KNO₃(NO₃). N2 plants of lotus and white clover had different responses to P. The response of NO₃ plants to P was the same in both species. This implies that the reason(s) for the difference in response between N₂ plants lie in differences in the structure and function of the symbiotic association. Lotus plants had a greater proportion of plant dry weight, P, and N in their nodules than did white clover. White clover nodules had higher relative growth rates and relative rates of accumulation of P and N than those of lotus and, in the early stages of growth, were more efficient. At 1500 ppm P, the yield of NO₃ plants was greater than that of N₂ plants in both species. It is suggested that the growth of N2 plants at the high P level was limited by N. These plants appear to have been unable to fix sufficient N for them to have yields similar to NO₃ plants.

Keywords:

• lotus
• nitrate
• nitrogen (nutrient)
• nitrogen fixation
• root nodules
• phosphorus (nutrient)
• rhizobia
• white clover
• plant growth
• plant nutrient absorption
• plant nutrient deficiencies
• nutrients (plant)