Winter Cover Crops in Illinois: Evaluation of Ecophysiological Characteristics of Corn

Understanding ecophysiological characteristics of corn (Zea mays L.) under winter cover crops (WCCs) can improve management and farmers’ acceptance by increasing the positive effects and decreasing the negative effects associated with their use. This study was conducted to quantify the effects of WCC on corn development, growth, and yield through the evaluation of ecophysiological characteristics. No-till corn planted after hairy vetch (Vicia villosa Roth), cereal rye (Secale cereale L.), and hairy vetch–cereal rye biculture and with four levels of N fertilizer (0, 90, 180, and 270 kg ha) was evaluated in 2002 and 2003 at Urbana, IL. Number of leaves, height, leaf area, chlorophyll meter readings (CMRs), light interception (LI), leaf carbon dioxide exchange rate (CER), grain yield, and yield components were measured. At 0 kg ha, rye had significant detrimental effects on corn ecophysiological characteristics. However, most of the detrimental effects were overcome by adding 90 kg N ha. Overall, hairy vetch provided benefits to corn that resulted in higher corn grain yield and was significantly better than all other treatments when no N fertilizer was used. Corn yield following hairy vetch–rye was intermediate between no cover and rye. As long as N rates are at least 90 kg ha, incorporating WCC in a corn–soybean [Glycine max (L.) Merr.] rotation in Illinois does not affect corn ecophysiological characteristics and yield potential. INTEGRATING WINTER COVER CROPS in a cropping system provides benefits that can result in enhanced crop yield (Snapp et al., 2005). Although it is important to recognize that WCC can increase corn yield and provide environmental benefits, management practices need to be adapted to specific regions and cropping systems to increase the positive effects of WCC on corn yield and the environment. Correspondingly, in cropping systems where use of WCC may result in lower corn yields, possible negative effects need to be decreased. In Illinois, a statewide average of 4 300 000 ha of corn were planted annually between 1993 and 2002, and each year at least 175 kg ha of N fertilizer was used in 94% of the planted area (National Agricultural Statistics Service, 2004). AlthoughWCCs have been recognized as an effective strategy for reducing potential N leaching and maintaining N within the cropping system (Dinnes et al., 2002), until recently very little information was available in this region. Bollero and Bullock (1994) showed that corn yield increase due to hairy vetch did not compensate economically for the cost of the seed, planting operations, and herbicide application. Further research showed that hairy vetch and/or rye alone do not provide sufficient N to optimize corn grain yields (Ruffo and Bollero, 2003a, 2003b). However, the previous studies indicated that management tools such as fertilization and WCCkill date need to be adapted to a specific region and cropping system. Ruffo and Bollero (2003b) concluded that in this region killing cereal rye 1 wk before planting corn was not optimal for adequate synchronization between N release from the residue and N demand for corn. Crandall et al. (2005) evaluated kill date and fertilization strategies with the goal of improving the synchronization of N demand for corn and supply from the cropping system while minimizing N losses. They concluded that applying N fertilizer at planting and killing cereal rye 2 wk before planting corn produced yields comparable to corn following no cover. Most importantly, Crandall et al. (2005) showed that, through adequate management practices, crop productivity can be maintained and negative effects to the environment can be reduced, thus suggesting that these are not conflicting goals. Many studies have focused on describing the decomposition of WCC residues (Wagger, 1989a, 1989b; Ruffo and Bollero, 2003a, 2003b) and quantifying N pools in the cropping system (Varco et al., 1989). However, there is little information about the effects of WCCs on corn beyond grain yield data. Evaluating ecophysiological characteristics of corn under WCCs can lead to improved management decisions that maximize positive effects and minimize negative effects associated with the use of WCCs. In the future, this may promote a greater acceptance of WCCs among Illinois farmers who may need to comply with state laws to reduce the use of fertilizer, address soil erosion, and/or reduce the use of other agrochemicals (Dinnes et al., 2002). The objective of this study was to examine corn development, growth, and yield through the evaluation of ecophysiological characteristics (i.e., morphological characteristics, development, LI, carbon exchange, chlorophyll readings, and yield components) of corn following WCC and a no-cover control. MATERIALS AND METHODS Field Site and Methods This 2-yr field experiment was conducted at Urbana, IL, during 2002 and 2003. The soil is a Drummer silty clay loam (fine-silty, mixed, superactive, mesic Typic Endoaquoll). The experiment was conducted using no-till practices in plots that have been previously in corn–soybean rotation for at least 7 yr. Winter cover crops were drilled on soybean stubble in adjacent fields each year. Corn was planted using 76-cm row spacing on 1 May 2002 and 29 Apr. 2003. The experimental design was a split-plot arrangement in a randomized complete block with four replications. Whole-plot treatments wereWCC (rye, hairy vetch, and hairy vetch–rye biculture) and no cover (control). Dep. of Crop Sciences, Univ. of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801. Received 8 Sept. 2005. *Corresponding author (gbollero@ uiuc.edu). Published in Crop Sci. 46:1536–1545 (2006). Crop Ecology, Management & Quality doi:10.2135/cropsci2005.09.0306 a Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: CER, carbon dioxide exchange rate; CMR, chlorophyll meter reading; GDD, growing degree days; LI, light interception; NFR, nitrogen fertilizer rate; PAR, photosynthetic active radiation; PPFD, photosynthetic photon flux density; SED, standard error of the differences of means; WCC, winter cover crop. R e p ro d u c e d fr o m C ro p S c ie n c e . P u b lis h e d b y C ro p S c ie n c e S o c ie ty o f A m e ri c a . A ll c o p y ri g h ts re s e rv e d . 1536 Published online May 18, 2006