Cover Crop Response to Late-Season Planting and Nitrogen Application

Cover crops aid in reducing precipitation runoff, soil erosion, and N losses in highly sloped, mountainous regions. Corn (Zea mays L.) producers in states with late spring warmup and early winters have limited success when planting cover crops following harvest. Studies were conducted from 1992 through 1995 in southern and northern West Virginia to evaluate the groundcover ability of several late-planted cover crops and their dry weight response to fall N application. In most years, vetch (Viciu villosu Roth cv. Common) and Austrian winter pea (Pisum sutivum var. arvense L. Poir cv. Austrian winter) produced the least groundcover and dry matter of all species evaluated. Rye (Secule cereule L. ‘Abruzzi’ and ‘Wheeler’) was the most reliable and winter-hardy cover crop, regardless of location. Initial soil nitrate-N concentrations at planting averaged 12 ppm in soils with continuous corn-production and no history of manure application (southern experiment) and 40 ppm in soils with similar rotation and a history of manure application (northern experiment). Nitrogen application did not consistently increase the likelihood of cover crop survival, but increased dry matter for some cover crops on soils with low initial N levels. At the southern location, Abruzzi rye planted alone and common rye in combination with common vetch responded positively to additional N application in 3 out of 3 and 2 out of 3 yr, respectively. ‘Pastar’ rye (1992–1993), common rye (1993–1994), wheat (Triticum aestivum L.) (1994–1995), and barley (Hordeum vulgure L. ‘Barsoy’) (1994–1995) also responded positively to N application at the southern location. Cover crops did not respond to additional N application at the northern location on soils high in initial N fertility. Corn producers in mountainous, highly sloped land should consider methods for planting cover crops earlier to ensure plant survival and to protect soil during the winter. Research QuestionCover crops are used in most of the corn-producing areas of the USA to improve soil conditions and protect the soil during the winter. Producers in highly sloped, mountainous areas with short fall seasons and severe winters have variable success when establishing cover crops following corn harvest. The objectives of this study were to evaluate percentage ground coverage of cover crops planted late following corn harvest and to evaluate the effectiveness of late-season N application for extending the cover crops planting window. Literature SummaryCover crops planted in the early fall in mountainous regions can provide adequate cover to protect the soil during the winter. Cereal cover crops have been shown to respond to N application. Studies have not been conducted to determine whether N application can effectively extend the window of opportunity to allow successful late planting of cover crops. Study DescriptionTwo experiments (groundcover potential by cover crops and cover crop response to N rates) were conducted in both the southern and northern regions in West Virginia each year from 1992 through 1995. Southern experiments were conducted on a corn producer's field located near Lewisburg, and northern experiments were conducted on a corn producer's field located near Bruceton Mills in 1992–1993 and 1994–1995, and on the West Virginia University Animal Science farm located near Morgantown in 1993–1994. Nine cover crop cultivars and mixtures and four rates of N were evaluated each year. Cover crops: rye, triticale, wheat, barley, common vetch, barley plus vetch, and Austrian winter pea plus triticale. N treatments: 0, 20, 40, and 60 lb/acre N equivalent from ammonium nitrate. Experimental design: randomized complete block (RCB) for the groundcover potential experiment and RCB in a split plot arrangement for the N-response experiment. Applied QuestionWhat cover crops provide the most consistent groundcover when planted late? The potential for successful late-season cover crop establishment following corn harvest in mountainous regions is highest with cereal cover crops. Late-sown legumes have little chance for survival. Ryes survived better and were more reliable as cover crops regardless of the N concentration in the soil. Barley and triticale generally provided good groundcover and yielded well on soils with high initial N concentration. Mixtures of cereal cover crops with vetch did not increase cover or dry matter over the cereal planted alone at a higher rate. Can N applied in the fall at planting increase the dry matter produced the following spring, thus increasing groundcover and extending the planting window? Nitrogen application at the time of planting did not consistently increase dry matter production except for ‘Abruzzi’ rye planted alone (3 out of 3 yr) and common rye planted with and without vetch (2 out of 3 yr) on soils with low initial N (nitrate) concentration in southern West Virginia. Nitrogen application at planting cannot consistently overcome the disadvantages resulting from late-planting cover crops in harsh winter environments.