Responses of cassava (Manihot esculenta Crantz) to phosphorus fertilisation when grown on a range of soil types

Rate-of-phosphorus trials were performed concurrently on 5 contrasting soils (yellow podsolic, lateritic podsolic, podsol, alluvial, krasnozem) in southeastern Queensland, to provide information on the phosphorus (P) requirements of cassava (Manihot esculenta Crantz). The study also examined the productivity of cassava when grown under conditions appropriate to commercial production. These conditions included the use of mainly infertile soils, with no irrigation after establishment. The yellow podsolic site of low initial P status (Colwell P of 4.1 �g/g) was the most responsive to P application, with yield (dry weight of storage organs) being increased by 170% with 120 kg/ha of broadcast P. Above that rate there were no further significant increases in yield. A strong response (96% yield increase with 10 kg/ha of P) was also obtained on the podsol site (Colwell P of 3.0 �g/g). For the lateritic podsolic and krasnozem sites, which were higher in Colwell-P, the responses to P were not significant, but deficiencies of other nutrients contributed to the lack of response at the lateritic podsolic site. Although the alluvial site was highest in P (Colwell P of 49 �g/g), a 15% increase in yield was obtained with 20 kg/ha of P. Banded P and broadcast P were also compared over most sites, but the differences between the methods of application were generally small. Yields of 9.0-13.6 t/ha were obtained at the optimum rate of P for each site, with the exception of the podsol where yield was only 3.0 t/ha because of low availability of water and nutrients from the sandy profile.