The unavailability of phosphorus in rock phosphate to some southern crops
1928
Bartholomew, R.P.
Eleven crops commonly found in southern states were grown in quartz cultures with different phosphorus treatments in order to determine their ability to use rock phosphate as a source of phosphorus for plant growth. Analyses were made on the plant tissue for calcium and phosphorus to see if they had relation to the feeding power of plants for rock phosphate. The results may be summarized as follows: Cotton, cowpeas, sorghum, seredella, beggarweed, lespedeza, bur clover, rice, and velvet beans made very little growth when phosphorus was supplied as rock phosphate. Vetch made about one-third and sweet clover about three-fourths as much growth from rock phosphate as with superphosphate (acid phosphate). There was no definite relation between the calcium-phosphorus ratio in the plants and their ability to feed upon rock phosphate. Other factors than the calcium content of the plants seem to play an important part in determining the ability of plants to use rock phosphate as a source of phosphorus.
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