The distribution of sicklepod (Cassia obtusifoliaL.) and coffee senna (Cassia occidentalisL.) in the United States is similar and both species are increasing as problems within their range. Sicklepod is a problem in 11 southern states and increasing in 12 while coffee senna is a problem in 7 states and increasing in 8 states. Both species germinated over a wide range of temperature. Germination characteristics were similar in the range of 15 to 36 C. Germination of coffee senna was drastically reduced at 39 C byRhizopussp. Seedling growth was similar for both species and was maximum from 30 to 36 C. Both species have a hard seedcoat. Abrasion for 5, 10, or 15 s, puncturing with a needle, and sulfuric acid were all effective in initiating germination. Both species emerged from a soil depth of 12.5 cm; however, emergence of sicklepod was more rapid than coffee senna with 63% of the sicklepod seedlings emerging from 2.5 cm after only 3 days.

Responses of six morningglories (Ipomoeaspp.) and twoCassiaspp. to 13 preemergence applied herbicides were determined at two locations in southern Alabama. Pitted (I. lacunosaL.), cypressvine (I.quamoclitL.), and willowleaf morningglories (I. wrightiiGray) were readily controlled with metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one]; entireleaf [I. hederacea(L.) Jacq. var.integriusculaGray], tall [I. purpurea(L.) Roth.], and ivyleaf morningglories [I. hederacea(L.) Jacq.] were not controlled. Norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] controlled cypressvine morningglory, but did not adequately control the other morningglory species. Perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide} gave acceptable control of cypressvine and willowleaf morningglories, but gave poor control of other morningglory species. Sicklepod (C.obtusifoliaL.) was controlled better than coffee senna (C.occidentalisL.) with 2.2 kg/ha diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and 2.2 kg/ha cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methylpropionitrile} controlled sicklepod better than coffee senna at one location each. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] was more effective in controlling coffee senna than sicklepod. Induction of population shifts toward incidental species of these genera seems unlikely based on the herbicides included in these experiments. In most cases the incidental species were more readily controlled than the prominent weed species.

Primary root elongation of prickly sida (Sida spinosaL.) at pH 5.5 was similar to that at pH 6.5 while sicklepod (Cassia obtusifoliaL.) was reduced to 62% and tall morningglory [Ipomoea purpurea(L.) Roth] to 87% of that at pH 6.5. At pH 5.1, root elongation of prickly sida was reduced to 77% of that at pH 5.5. Some elongation was observed in the pH range of 5.1 to 6.5 for all species. Maximum primary root growth of tall morningglory, sicklepod, and prickly sida occurred at approximately 32° which was similar to that for cotton (Gossypium hirsutumL. ‘Empire’). Temperature as high as 39° did not significantly reduce root elongation of sicklepod. Tall morningglory root growth was reduced approximately 50% by 0.2 ppm of trifluralin (α,α,α-trifluro-2,6-dinitro-N,N-dipropyl-p-toluidine). In contrast, sicklepod and prickly sida root growth was reduced only slightly by 1 ppm of trifluralin.

In areas with a relatively long growing season, a doublecropping system of soybeans (Glycine max (L.) Merr.) planted after corn (Zea mays L.) harvested for silage or grain is gaining acceptance. One problem which has arisen involves the potential injury to the soybean crop from atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] residue remaining in the soil after the corn is harevsted. Field studies were conducted during 1977 on an Arrendondo fine sand (Grossarenic Paleudult) at Gainesville, Florida and during 1978 and 1979 on a Tifton fine sandy loam (Plinthic Paleudult) at Jay, Florida to determine the persistence of atrazine in such a doublecropping system. Soybeans were no‐till planted at various intervals (4 to 19 weeks) after atrazine (0 to 4.48 kg/ha) was applied preemergence to corn. Soybean yields were not significantly affected by 1.12 or 2.24 kg/ha atrazine when the interval between corn herbicide application and soybean planting was 8 weeks. An Interval of 10 weeks was required before 4.48 kg/ha atrazine had no significant affect on soybean yield. The yield loss observed with shorter planting intervals appeared to be the result of a reduction in soybean stand. These results indicate that under conditions of warm temperatures, relatively high rainfall amounts, and sandy soils soybeans can be safely planted after corn harvested for silage or grain (approximately 14 and 20 weeks, respectively, after atrazine application) when rates of atrazine normally recommended for annual weed control in corn (1.12 to 4.48 kg/ha) are used.

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