Constituent determination of biomass for theoretical ethanol yield (TEY) estimation requires the removal of nonstructural carbohydrates prior to analysis to prevent interference with the analytical procedure. According to the accepted US Department of Energy-National Renewable Energy Laboratory (NREL) method, biomass extractives in corn stover should be removed by a two-step extraction process. Alternatively, Neutral Detergent Fiber method (NDF) is a fast and cost-effective method used to determine structural carbohydrates of forage biomass. The objective of this study was to determine whether the NDF method can be used as an alternative to the NREL extraction procedure for corn (Zea mays L.) stover biomass. Arabinan content varied between the two methods. However, glucan, xylan, and TEYs were not statistically different. Furthermore, the average TEYs per unit of mass and unit of area varied by 2.0 and 1.9%, respectively. Additionally, the NDF extraction procedure was faster and less expensive than the NREL procedure.

In M.S. Reiter (ed.) A multidisciplinary approach to conservation. Proc. 31st Southern Conservation Agric. Systems Conf., Melfa, VA. 20-23 July 2009. Extension Publ. 2910-1417. Dep. Crop and Soil Environ. Sci., Eastern Shore Agric. Res. Ext. Cntr., Virginia Polytechnic Inst. and State Univ., Painter, VA. Available at: http://pubs.ext.vt.edu/2910/2910-1417/2910-1407.html. EFFECT OF CONSERVATION SYSTEMS AND IRRIGATION ON POTENTIAL BIOENERGY CROPS

Recent research in Alabama found that contract grazing of stocker cattle in winter-ea rly spring (100 to 140 days) offers re­ turns from $70 to $225 per acre (Bransby et al., 1999). Such a system is ideal for small farmers with limited capital and offe rs potential for added income for producer's doublecropping cotton behind winter grazing of annual pastures. Soil management strategies that improve soil quality include conservation tillage, cropping intensification, and inclusion of sod-based rotations. Crop rotation is critical to cropping intensification and has long been recognized as being agronomically and economically beneficial (Bayer et al ., Reeves, 1994). Short-term forage rotations with cotton not only offer reduced eco­ nomic risks for producers but also could increase soil organic carbon, improving soil quality and productivity and enhancing profitability for producers. However, winter-annual grazing results in excessive soil compaction, which can severely limit yields of double-cropped cash crops (Miller et al., 19 97). Although, in-row subsoiling at planting is frequently used to allevi­ ate soil compaction for cotton grown on sandy coastal plain soils (Raper et al., 1994), tillage requirements for cotton follow­ ing winter-annual grazing have not been researched or developed. The objective of the study was: compare two winter pasture forages under grazing and their residual effect on cotton, deter­ mine depth and degree of compaction from grazing, and determine an optimal tillage system for establishment, growth, yield and quality of cotton grown following winter annual grazing. The experiment was conduced in 2001 and 2002 at the Alabama Agricultural Experiment Station's Wiregrass Research and Ex­ tension Center in southeastern Alabama. The soil was a loamy sandy (Plinthic Paleudults). Winter forage and tillage were evalu­ ated in a strip plot design with four replications. Winter forage (main plots) were oat (Avena sativa L.) and ryegrass (Lolium multiflorum L.) planted with a no-till drill. G razing was continuous as contract grazing from January to April at a stocking rate of two head/acre. Tillage systems for cotton (subplots) included: moldboard with disk leveling, chisel and disk; and non- inversion deep tillage (none, in-row subsoiling or paratilling) with and without disking. We evaluated soil cover after grazing, plant population, cotton lint yield for 2001 and 2002, cotton quality parameters for 2001, and soil compaction in 2002. Gross returns from grazing averaged between $141 to $160/acre/year; annual production costs averaged around $75. Rye­ grass and no-tillage systems (averaged over deep tillage treatments) provided the greatest residue cover (average of 2001 and 2002 = 77%). Conventional tillage systems (moldboard, chisel and disking) resulted in the lowest residue cover. Grazing in­ creased soil compaction in the first 4 inches (9% more soil strength averaged all treatments after 60 da ys grazing) but con­ ventional tillage or non-inversion deep tillage conservation tillage systems alleviated this problem at planting. Cotton popula­ tions were 17% greater following oat than ryegrass. Strict no-tillage had the lowest plant stand, but strip-tillage, i.e., subsoiling alleviated this problem. Cotton lint yields were affected by forage species and tillage system interactions, how­ ever, strict no-tillage (934 lb cotton lint/acre averaged over years) resulted in the lowest lint yields (18% less than the mean) for both species and subsoiling was necessary to maximize yields. Cotton required more intensive tillage or more aggressive non-inversion deep disturbance (paratilling) to maximize lint yield following grazing of ryegrass compared to grazing of oat (1006 and 1120 lb acre -1 in ryegrass and 1131 and 1097 acre -1 in oat for no intensive tillage and intensive tillage respectively). With respect to fiber quality, tillage system affected only micronaire, and strict no-tillage resulted in the lowest value (38.3 vs. 40.5 averaged over treatments). There were minor effects of forage species on strength and color grade.

Integrating livestock into cotton (Gossypium hirsutum L.)- peanut (Arachis hypogaea L.) rotations offers alternatives for grazing and crop management, but could result in excessive soil compaction, which can severely limit yields. We began a study in fall 2000 at the Alabama Agricultural Experiment Station's Wiregrass Research and Extension Center in southeastern Alabama on a Dothan sandy loam (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) to develop a conservation tillage system for integrating cotton and peanut production with winter annual grazing of stocker cattle under dryland conditions. Results from the 2000-2001 and 2001- 2002 seasons are presented in this paper. Winter forages and summer tillage were evaluated in a strip plot design with four replications. Winter pastures were oat (Avena sativa L.) and ryegrass (Lolium mutiflorum L.) for grazing and tillage systems were: 1) Moldboard plow +disking, 2) in- row subsoiling with a KMC subsoiler (14-16 in. depth) +disking, 3) No-till with KMC subsoiling 4) Paratill (18-20 in. depth) +disking, 5) No-till with Paratilling 6) strict No-till, 7) Disking, 8) Chisel plow + Disking. We evaluated biomass forage production, animal gain, soil strength, soil cover, plant population, and cotton lint and peanut yield. There were only minor differences in forage produced and animal gain. Soil compaction was increased by grazing to the 4-6 in. depth but conventional tillage or conservation tillage with non-inversion deep tillage alleviated this problem. Strict no-till following ryegrass had the highest soil cover (74%). Cotton and peanut plant populations were better following oat than ryegrass (cotton: 34,800 and 27,800 plants acre-1 for oat and ryegrass, respectively; peanut: 34,200 and 31,100 plants acre-1 for oat and ryegrass, respectively). Strict no-till had the lowest plant stand for both crops, but deep tillage (in row subsoiling or paratill) eliminated this problem. Cotton and peanut yields were affected by pasture and tillage systems interactions; however, peanut yield following oat was greater in all tillage systems except for the moldboard treatment. Strict no-till resulted in the lowest yields (<17% and <42% than the overall mean for lint cotton yield and peanut yield, respectively), and deep tillage was necessary to maximize yields in no-till. Oat appears less risky than ryegrass due to better