ChileanJAR

Critical levels for boron and phosphorus were determined on the Mountain Papaw. The plants grew on Hoagland N° 2 solution with the following P and B concentrations:

Phosphorus: 0,5 - 1 - 2 - 4 - 16 - 32 - 64 - 128 ppm.
Boron: 0,05 - 0,5 - 1 - 1,5 - 1 - 2,5 - 3 - 4 ppm.

The plants were weekly measured for height; B and P analyses were made in leaves (petioles and leaf blades separately) harvested 35 days after the treatments started and 78 days aftel the first sampling. Fresh and dry weight of leaves and roots were also made.
The following are the main conclusions:
Total height of the plant was not affected by the P levels on the nutrient solution. Nevertheless, incleasing concentrations of B on the solution gave highel plants.
Fresh and dry weight of leaves and roots increased with higher P concentrations, but fresh and dry weight of roots decreased with the highel concentrations.
Fresh and dry weight of roots dimished with increased B concentration in the solution.
Concentrations of P and B in petioles and leaf blades increased with increasing levels of P and B in the solutions.
The critical level for P seems to be found 0,100 - 0,125% in petioles and between 20 - 30 ppm in petioles for B.