Answering the riddle of poor safflower after rice … banded phosphorus may be the solution

Abstract

Field studies reported here have shown that poor growth of safflower after years of rice tends to be associated with acute phosphorus deficiency. Applications of treble superphosphate, 11–48 and 10–50 ammonium phosphate dramatically increased seedling growth and yield of grain when placed with, or 1 inch below seed. Applications of 200 lbs of 11–48 or 10–50 one inch below the seed were found safe and economic under conditions of these Colusa County experiments. Applications of 100 lbs of 11–48 or 10–50 in the seed row were also found to be safe and effective, as shown in tests in both Colusa and Glenn counties. Generalizations are not yet possible on such questions as: (1) why some rice soils are phosphorus-deficient for safflower; (2) the critical soil phosphorus level for safflower the year following rice; (3) the amount of P required for maximum yields; and (4) other nutrients or soil conditions affecting safflower performance on old rice lands.