Evaluation of Winter-killed Cover Crops Preceding Snap Pea Orion P. Grimmer and John B. Masiunas1 ADDITIONAL INDEX WORDS. barley, Hor- deum vulgare, oat, Avena sativa, snap pea, Pisum sativum var. macrocarpon, white mustard, Brassica hirta, weed control SUMMARY. Winter-killed cover crops may protect the soil surface from ero- sion and reduce herbicide use in an early planted crop such as pea (Pisum sativum). Our objective was to deter- mine the potential of winter-killed cover crops in a snap pea produc- tion system. White mustard (Brassica hirta) produced the most residue in the fall but retained only 37% of that residue into the spring. Barley (Hor- deum vulgare) and oats (Avena sativa) produced less fall residue but had more residue and ground cover in the spring. Greater ground cover in the spring facilitated higher soil moisture, contributing to higher weed numbers and weight and lower pea yields for oat and barley compared with a bare ground treatment. White mustard had weed populations and pea yields similar to the bare ground treat- ment. Within the weed-free subplot, no differences in pea yields existed among cover crop treatments, indicat- ing no direct interference with pea growth by the residues. In greenhouse experiments, fi eld-grown oat and barley residue suppressed greater than 50% of the germination of common lambsquarters (Chenopodium album) and shepherd’s-purse (Capsella bursa- pastoris), while in the fi eld none of the cover crop provided better weed control than the fallow. Department of Natural Resources and Environmen- tal Sciences, University of Illinois, 260 Edward R. Madigan Laboratory, 1201 W. Gregory Dr., Urbana, IL 61801. This paper is a portion of a thesis submitted by Orion Grimmer in partial fulfi llment of the requirements for a Master of Science degree. We thank Fred Kolb for supplying many of the oat cultivars. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the University of Illinois and does not imply its approval to the exclusion of other products or vendors that also may be suitable. 1To whom reprint requests should be addressed. E-mail address: [email protected] ● July–September 2004 14(3) 349 July04HT.indb 343499 6/7/04 1:19:03 PM RESEARCH REPORTS over crops may be grown to Oat and mustard residue may help dall) at Dixon Springs. The experiment increase soil fertility, reduce to control pea root rot (Aphanomyces was a split-plot design, the whole-plot Csoil erosion (Hoyt et al., 1994), euteiches). Studies have shown oat to treatment was cover crop, and the suppress diseases (Muehlchen et al., decrease disease organism density and subplot treatment was weed manage- 1990), and reduce weeds (Teasdale, increase pea yield in root rot infected ment. There were fi ve replications at 1996). Because spring snap pea is an soils (Fritz et al., 1995; Purdue Uni- Champaign and four replications at early season crop, it could follow a versity, 1999; WilliamsWoodward et Dixon Springs. Each whole-plot was fall-planted, winter-killed cover crop. al., 1997). White mustard reduced pea 3.0 × 15.2 m (10 × 50 ft). Managing a cover crop residue mulch stand loss due to root rot (Lewis and ‘Cayuse’ oats, ‘UC-603’ barley, by winter-kill is simple and economical. Papavizas, 1971; Muehlchen et al., and white mustard were planted at Winter-kill requires no application of 1990; Papavizas, 1966) and reduced Champaign on 31 Aug. 2002 and at herbicide, mowing, or use of special- root rot inoculum density in soil and Dixon Springs on 30 Sept. 2002. A seed ized machinery, such as crimping pea disease incidence in greenhouse ex- supplier (Peaceful Valley Farm Supply, rollers (Ogutu, 2000) or undercutters periments (Chan and Close, 1987). Grass Valley, Calif.) had selected the (Creamer et al., 1995), and is compat- Cover crop residues release alle- cultivars used in this experiment for ible with organic production systems. lopathic chemicals that suppress both high biomass production. At both The main disadvantage of winter-kill weeds and diseases. Barley contains the locations a bare ground control treat- is the potentially high loss of residue allelochemicals gramine and hordenine ment was included. Oats and barley biomass due to decomposition over (Liu and Lovett, 1994; Overland, were drilled at 100.9 and 134.5 kg·ha–1 the winter (Stivers-Young, 1998). In 1966). Oat tissue contains the allelo- (90 and 120 lb/acre), respectively, in the event of a mild winter, an alterna- chemicals scopoletin (Fay and Duke, 20.3-cm (8 inches) rows at 3.56-cm tive means of management may be 1977; Martin and Rademacher, 1960) (1.4 inch) depth. White mustard was needed. and L-tryptophan, along with coumar- hand broadcast at 11.2 kg·ha–1 (10 Barley, white mustard, and oats ic, ferulic, p-hydroxybenzoic, syringic, lb/acre) and raked into the top 1.52 have been observed to winter-kill in and vanillic acids (Guenzi and McCalla, cm (0.6 inch) of soil. central Illinois (Biazzo and Masiunas, 1966; Kato-Noguchi et al., 1994). Low winter temperatures killed 2000; Sustainable Agriculture Net- Mustard contains glucosinolates that all cover crops at Champaign. Mustard work, 1998). Both barley and oats have decay into allelopathic isothiocyanates, was the only cover crop to winter-kill been successfully intercropped with nitriles, and thiocyanates (Al-Khatib at Dixon Springs, and all plots were pea in forage mixes (Carr et al., 1998; et al., 1997; Boydston and Hang, sprayed with 841 g·ha–1 (0.75 lb/acre) Chapko et al., 1991; Hauggaard-Niel- 1995; Vaughn and Boydston, 1997). glyphosate the day of pea planting. son and Jenson, 2001) while mustard Even pea produces the allelochemical On 24 Mar. 2003 at Champaign and has been successfully intercropped with β-(3-isoxazolinon-5-on-2-yl)-alanine 27 Mar. 2003 snap pea cultivar Mega pea in Canada (Waterer et al., 1994). (Akemo et al., 2000). (Territorial Seed Co., Cottage Grove, No-till planting of ‘Sparkle’ snap Many questions remain regarding Ore.) was planted, without tillage, into pea into glyphosate-killed cover crop pea planted into winter-killed cover the winter-killed cover crop residue at residue was investigated in Kentucky. crops. Cover crop residue may be lost 112.1 kg·ha–1 (100 lb/acre) of seed Oats and barley interfered with snap during an Illinois winter, with its lim- in rows spaced 38.1 cm (15 inches) pea establishment similarly to wheat ited snowfall. Surface residues of win- apart at a depth of 5.1 cm (2 inches). (Triticum aestivum) and rye (Secale ter-killed barley, white mustard, and oat At Champaign, four 15.2-m rows of cereale) and less than dutch white clover could interact differently with weeds peas per whole-plot were seeded. At (Trifolium repens), tall fescue (Festuca and peas compared with unweathered Dixon Springs, only three 7.3-m (24 arundinacea), perennial ryegrass (Lo- herbicide-killed cover crop residues ft) rows of peas were planted. lium perene), and creeping red fescue and incorporated green manures. The Following the planting of snap (Festuca rubra) (Weston, 1990). objectives of this study were to test pea, the plots were split into weedy Unfortunately, those cover crops that cover crops for their ability to produce control, hand-cultivated, and herbi- interfered least with pea establish- residue in the fall, retain that residue cide subplots. Each subplot was 4.9 ment also suppressed weed growth through spring, and suppress weeds m (16 ft) long at Champaign and 2.4 the least. without impacting pea yields. m (8 ft) long at Dixon Springs. In the White mustard was identifi ed as herbicide subplot, imazethapyr at 70.1 a good incorporated green manure Materials and methods g·ha–1 (1 oz/acre) was applied the day preceding pea (Al-Khatib et al. 1997). FIELD STUDY. The experiments of planting peas at Dixon Springs and 1 In cultivated and untreated plots, white were conducted in central Illinois at d after planting at Champaign. On 14 mustard green manure yielded higher the Cruise Tract Irrigated Vegetable May 2003, at Champaign, bentazon at pea populations than canola (Brassica Research Farm in Champaign County 280 g·ha–1 (0.25 lb/acre) was applied napus), rye, and wheat green manures. (Champaign) and in far-southern to control broadleaf weeds less then 5.1 Cultivated and untreated mustard Illinois at Dixon Springs Agricul- cm tall in the herbicide subplots. plots yielded similarly to rye plots and tural Research Center in Pope County The hand-cultivated subplots signifi cantly higher than wheat and (Dixon Springs). The soil types were were hoed weekly with a colinear-type canola plots. However, another study Flanagan silt-loam (fi ne montimor- hoe from the appearance of weeds until found that incorporated white mustard rillontic, mesic, Aquic Arguidoll) at the week before the fi rst harvest (23 signifi cantly reduced pea emergence Champaign and Grantsburg silt loam Apr. to 28 May), at Champaign. At (Muehlchen et al., 1990). (fi ne-silty, mixed, mesic Typic Fragiu- Dixon Springs, the cultivated subplots 350 ● July–September 2004 14(3) JJuly04HT.indbuly04HT.indb 335050 66/7/04/7/04 11:19:04:19:04 PPMM were hoed once on 19 May. The fewer by Fisher’s protected least signifi cant (40 d); 8 Jan. to 12 Feb. (35 d), and hoeings at Dixon Springs were due to difference (LSD) test at the comparison- 18 Feb. to 20 Mar. (30 d). slower weed emergence and less avail- wise α = 0.05 using the standard error Data were analyzed using SAS. able labor. The single hoeing at Dixon from SAS and an appropriate tabular Analysis of variance was conducted Spring did not affect the yield because t-value.