Get reliable rangeland science

A glass?house study on two Oxisols revealed a marked response by trudan (Sorghum sudanense) to phosphate (P) placement. Plant response to water?soluble forms of P (superphosphate and superphosphate lime mixture) was greater when this phosphale was granulated or when it was banded than when the powdered form was broadcast. Granulation or banding did not, however, affect plant responses to rock phosphate or thermophos. This response to granulation of P was strong in the Farningham soil, but weak in the Clovelly soil which had a lower P fixing capacity. Although both the soils studied can fix large proportions of added P, the considerable difference in their ability to fix P explains why, for Oxisols, fertilizer recommendations based only on estimates of available P in the soil could be unsatisfactory. Growth responses to amelioration by lime occurred until exchangeable Al was eliminated (except on the Clovelly soil when treated with rock phosphate). Additional lime significantly reduced yields where P was banded even when a water soluble P carrier was used. High levels of lime drastically reduced yield where rock phosphate was used, even when P was broadcast. With insufficient lime, root growth and proliferation was severely restricted.