Significance of mass flow in nitrate-nitrogen supply to plant roots

Abstract

Abstract Young corn plants (Zea mays L.) were grown in pots with Nishinosato loamy sand by moisturing with Ca(NO3)2 solution at different concentrations, in order to check the effect of the NO3-N concentration of the soil solution on the plant growth without quantitative limita tion of NO3-N supply. Eight treatments were established according to the NO3 concentration supplied. The dry weights of the plants increased with increase in the NO3-N concentration for moisturing and reached a maximum at 12.9 me per liter NO3-N in the supplied solution (treatment No. 4). NACP (the amount of N absorbed by the plants divided by the amount of H2O transpired in a given period, converted to me per liter) coincided with the NO3-N concentration of the rhizosphere soil solution at around 20 me per liter, where transport of NO3-N to the plant roots was limited in mass flow. The minimum NO3-N concentration of the rhizosphere soil solution to give a maximum yield was found in No. 4. The values were 115 and 9.3 me per liter i...