The soil/organic matter mixtures were carefully homogenized and
incubated for 20 days while maintaining 60% water holding capacity
(WHC). Triple superphosphate was added to themixtures, to a content
of 200 mg kg−1 P, and the samples were homogenized and incubated
for an additional 15 days after sowing the seeds. Pots were weighed
daily, and water was added to maintain 60% WHC in the mixtures. Nitrogen
was applied (as ammonium nitrate; 15mg kg−1) at seedling
emergence and again 15 days later.