Cover crop residues

Hairy vetch (V. villosa Roth) Cover crop Residue or living mulch Cover crop residues... 

Annual cover crops are usually killed before planting a cash crop and then either incorporated as a cover crop residue into the soil or left as a mulch on the surface of the soil. A trend towards more reduced weed growth was observed where residues were not incorporated into soil but they were retained on the soil surface (Jones et al. 1999). 

Rasmussen IA (2004) The effect of sowing date, stale seedbed, row width and mechanical control on weeds and yields of organic winter wheat. Weed Res 44 12-20 Reddy KC (2001) Effects of cereal and legume cover crop residues on weeds yield, and net return in soybean (Glycine max),. Weed Tech 15 660-668 Reynolds LB, Potter JW, Ball-Coelho BR (2000) Crop rotation with Tagetes sp. is an alternative to chemical fumigation for control of root-lesion nematodes. Agron J 92 957-966 Rice EL (1984) Allelopathy. Academic, New York, p 317... 

Teasdale JR, Mohler CL (1993) Light transmittance soil temperature, and soil moisture under residue of hairy vetch and rye. Agronomy J 85 673-680 Teasdale JR, Mohler CL (2000) The quantitative relationship between weed emergence and the physical properties of mulches. Weed Sci 48 385-392 Teasdale JR, Pillai P (2005) Contribution of ammonium to stimulation of smooth pigweed germination by extracts of hairy vetch residue. Weed Biol Manag 5 19-25 Teasdale JR, Beste CE, Potts WE (1991) Response of weeds to tillage and cover crop residue. Weed Sci 39 195-199... 

The purpose of this paper is to describe the GLP compliance system developed for the Residue Chemistry Field Trials Program at ICI Americas Inc. This program covers crop residue and environmental fate studies. 

Reddy K.N. Effects of cereal and legume cover crop residues on weeds, yield, and net return in soybean (Glycine max). Weed Technol 2001 15 660-668. 

Yenish, J. P., Worsham, A. D. and Chilton, W. S., 1995. Disappearance of DIBOA-glucoside, DIBOA, and BOA from rye (Secale cereale L.) cover crop residue. Weed Sci. 43, 18-20... 

To characterize how cover crop residues in no-till systems affect early emergence of broadleaf weeds and to establish and characterize potential relationships between early broadleaf weed seedling emergence and the physical and chemical environments resulting from the presence of cover crop residues. 

To characterize cover crops and cover crop residues and how these may potentially modify the soil environment. 

To determine under controlled conditions how effects of shoot cover crop residues taken from the field change with time after desiccation and how such effects are modified by temperature, moisture, and nitrogen levels. 

Characterize Cover Crops and Cover Crop Residues and How These May Potentially Modify the Soil Environment (Blum etal. (1997) Henry A Wallace Institute for Alternative Agriculture Inc, Summarized with Permission of Cambridge University Press)... 

Lehman and Blum (1997) found that the mean C/N ratios of cover crop residues were 51, 32, 15, and 12 for rye, wheat, crimson clover and subterranean clover, respectively. The C/N ratios of the soils, however, were not significantly modified in 1993 (only year determined). The values ranged from 9 to 19 with a mean of 13.5 0.13 (Blum et al. 1997). Both Iritani and Arnold (1960) and Hannsen and Van Schreven (1955) have suggested that a C/N ratio of 20 is the approximate threshold between mineralization and immobilization of N in soil by nucroorgan-isms. The mean value of 13.5 for these soils suggests that in most instances the soils in 1993 were probably not nitrogen limited. 

Total phenolic acid content of the cover crops taken at monthly intervals from the field after glyphosate desiccation declined over time. However, the decline of total phenolic acid content for rye and wheat residues was not evident until 2 months after glyphosate desiccation (Lehman 1993). After 4 months the total phenolic acid content of the cover crops had declined by 31, 36, 38, and 56% for wheat, crimson clover, rye, and subterranean clover, respectively (Lehman 1993). Estimates of ferulic acid for sterilized (autoclaved) cover crop residues extracted with 0.25 M... 

Blum et al. (1997) found that soil pH values of no-till systems were not significantly modified by the presence of glyphosate-desiccated rye, wheat, crimson clover and subterranean clover cover crops. In this field study a substantial portion (estimated to be roughly 50%) of the cover crop residues was located on the soil surface and thus only had an indirect impact on soil pH by way of leachates generated... 

Adding Hoagland s solution in addition to sunflower tissues eliminated the inhibitory effects of sunflower tissues on pigweed seedling biomass. Thus, it would appear that nutrients in plant tissues mixed into soil might modify plant-plant allelo-pathic interactions differently than nutrients/fertilizer directly applied to surface of the soil or mixed into the soil. The functional role of nutrients in small grain and clover cover crop residues is presently not known. 

Fig. 3.16 The effects of soil moisture, and wheat and crimson clover cover crop residues on percent pigweed seedling emergence in Cecil A soil, where C equals crimson. Wheat inhibitory, C-clover inhibitory, and C-clover non-inhibitory were collected 2,1, and 4 months after glyphosate desiccation, respectively. The absence of standard error bars indicates that the error bars are too small to be visible. Figures adapted from Lehman and Blum (1997). Figures used with permission of International Allelopathy Foundation...

Effects of Cover Crop Residues on the Physicochemical Environment of the Soil... 

Cover crop residues provided only very weak control of broadleaf signal grass suggesting that control of monocotyledonous species may be a serious problem. 

To Characterize How Cover Crop Residues in No-Till Systems Affect Early Emergence of Broadleaf Weeds and to Establish and Characterize Potential Relationships Between Early Broadleaf Weed Seedling Emergence and the Physical and Chemical Environments Resulting from the Presence of Cover Crop Residues (Section 3.4.3)... 

---