Rice by-products were evaluated in the greenhouse for herbicidal activity on various weeds and crops. Rice by-products and corn gluten meal (CG) were applied at 0, 125, 250, 500, and 750 g m−2 preemergence (PRE) and preplant incorporated (PPI). The efficacy of rice by-products and CG in reducing weed emergence and shoot weight of broadleaf species was in the order of medium-grain fatty rice bran (MF) > long-grain fatty rice bran (LF) > CG > defatted rice bran (DF) > long-grain hull (LH) > medium-grain hull (MH). For reducing grass emergence, MF = CG > LF > DF > LH > MH, and for shoot weight reduction, CG > MF > LF > LH > DF = MH. Palmer amaranth and ivyleaf morningglory were the most susceptible weeds (91 and 82%) followed by sicklepod, hemp sesbania, and prickly sida (65 to 70%). Velvetleaf was the most tolerant broadleaf weed. Grasses were not as susceptible to rice bran as broadleaf weeds. In general, MF was the best material for reducing weed emergence and its efficacy was not affected by application method. Cotton and corn were the most tolerant direct-seeded crops to MF (6% reduction in plant stand), and soybean, Italian ryegrass, tomato, and rice had intermediate tolerances (30 to 86% stand reduction). Mustard, cucumber, and lettuce were the most susceptible crops (71 to 98% reduction in plant survival). The minimum effective rate was 250 g m−2 MF PPI or PRE.
Nomenclature: Corn, Zea mays L.; cotton, Gossypium hirsutum L.; cucumber, Cucumis sativus L.; hemp sesbania, Sesbania exaltata Raf. SEBEX; Italian ryegrass, Lolium multiflorum L. LOLMU; ivyleaf morningglory, Ipomoea hederacea (L.) Jaq. IPOHE; lettuce, Lactuca sativa L.; mustard, Brassica arvensis L.; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; prickly sida, Sida spinosa L. SIDSP; rice, Oryza sativa L.; sicklepod, Cassia obtusifolia L. CASOB; soybean, Glycine max L.; tomato, Lycopersicon esculentum Mill.; velvetleaf, Abutilon theophrasti Medic. ABUTH.
