COMPARATIVE EVALUATIONS OF RICE AND A SORGHUM-SUDANGRASS HYBRID AS CRAWFISH FORAGE CROPS

Comparisons were made among experimental ponds of red swamp crawfish P rocambarus clarkii that were planted with either rice Oryza sativa, a sorghum-sudangrass hybrid Sorghum bicolor x S. sudanense, or a mixture of rice and sorghum-sudangrass. Sorghum-sudangrass produced the great est forage biomass and also exhibited the best biomass persistence. Po nds planted in rice, the industry standard, had the highest dissolved oxygen, but were depleted of forage by the end of the production seaso n. The rice and sorghum-sudangrass mixture maintained an intermediate profile of standing forage over the crawfish production season and exh ibited the lowest dissolved oxygen values. Crawfish production was sim ilar among all treatments and averaged 1,185; 1,135; and 1,107 kg/ha f or ponds planted in rice, sorghum-sudangrass, and the rice and sorghum -sudangrass mixture, respectively. Size grade distributions of harvest ed crawfish were also similar. Crawfish growth trials conducted in enc losures placed over forage substrates provided corroborative evidence as to the suitability of sorghum-sudangrass in comparison with rice. C rawfish weights and condition after two 12-week growth trials were sim ilar among the three forage regimes when crawfish were cultured at a d ensity of 2 crawfish/m(2), but at 10 crawfish/m(2), a mixture of rice and sorghum-sudangrass appeared to be slightly advantageous. However, logistical problems with forage management might hinder the coculture of both crops. Sorghum-sudangrass performed satisfactorily as a crawfi sh forage, and because of its growth rate, production potential, and d rought hardiness, it may be preferable to rice in some circumstances.