Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 14, 2000
Publication Date: N/A
Technical Abstract: A double cropping system of berseem clover and grain sorghum was tested for nutrient management under heavy fertilization with swine effluent. The effects of bean yellow mosaic virus (BYMV) infection in the clover were examined. `Bigbee' berseem was seeded into minimally tilled plots in mid Oct. Four systems (BYMV-inoculated berseem followed by sorghum, noninoculated berseem followed by sorghum, grass followed by sorghum, and continuous grass) were compared from Oct. 1997 to Oct. 1999. Systems were replicated four times in a randomized complete block design. Plots were irrigated with effluent from Apr. to Sept. Virus inoculations were done in mid-Apr., 1 wk after the first spring harvest of berseem. Clover was cut for hay in early April, May and June. Samples from each harvest were analyzed for nutrients. Soil samples were collected at 0-2.5, 2.5-5, 5-10, and 10-20cm in June and Oct. Pioneer 8305 Hybrid grain sorghum was no-till planted in 0.75m(30-in) rows in early June. Grain and stover were harvested in early Oct. and sampled for nutrients. A preliminary summary of phosphorus (P) removal by the double crop showed: little difference in dry weights due to BYMV in either clover or sorghum; a slight increase in P content of BYMV-infected clover; greater dry matter production of sorghum following clover than following grass; and total P removal of 54 kg/ha/yr(48lb/A/yr). Annual component contributions toward P removal were: clover hay (17 kg/ha); sorghum grain (13 kg/ha); and sorghum stover (24 kg/ha). Soil tests showed P levels: were consistently higher in the upper soil profile in all plots; increased in all samples and treatments from June to Oct.; and were lower in clover and sorghum plots than in continuous grass plots.