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Sustainable cotton (Gossypium hirsutum L.) production will require systems that maintain or augment yields without degrading the soil. Our study was undertaken to determine profitability and fertilizer N rate optimization associated with winter cover management in no‐tillage cotton. This study was conducted beginning the fall of 1988 and continued through the 1992 growing season in a producer's field on a Caledonia loam (fine, loamy, siliceous, thermic, Typic Paleudalfs) soil with 0 to 2% slope. Winter cover treatments were fallow, rye (Secale cereale L.), and hairy vetch (Vicia villosa Roth), each combined with 0, 45, 90, and 135 lb N/acre. Profit maximizing N rates as influenced by varying fertilizer N and lint prices ranged from 81 to 94 lb/acre for winter fallow, 105 to 117 lb/acre for rye, and 54 to 68 lb/acre for hairy vetch. Lint yield at the profit‐maximizing N rate varied only slightly in response to changes in fertilizer N and lint prices for each winter cover treatment. Both cover crop systems were found to be more profitable at all fertilizer N and lint prices, with rye averaging $24 to $44/acre and hairy vetch $33 to $51/acre greater returns than for winter fallow. Marginal profitability of rye compared with winter fallow was greatest at a fertilizer N‐to‐lint price ratio of 0.125, while for vetch it was at 0.375. Inclusion of cover crops in no‐tillage cotton production systems can result in greater profitability as a result of increased lint yield and in the case of the legume lower fertilizer N inputs, but yearly variability in yield as well as profit may increase. Research Question Sustainable cotton production will require systems that maintain or augment yields without degrading soil. Implementation of conservation tillage practices helps to reduce soil loss by erosion. Cotton is considered a low residue crop compared with corn or sorghum and cover crops could provide supplemental residue. The use of cover crops from a producer's perspective must be justified economically by substitution of legume N for fertilizer N or increased productivity. This research was undertaken to determine profitability and fertilizer N rate optimization associated with winter cover management in no‐tillage cotton production on a producer's farm. Literature Summary Comparisons between no‐tillage and conventional tillage production practices for cotton have shown comparable economic benefits. Legume cover crop evaluation with no‐tillage corn has shown greater yields,but not necessarily lower fertilizer N requirements. Limited work with cotton has shown reduced fertilizer N requirements; however, economic evaluations of winter cover and fertilizer N management practices in producers fields are lacking. Study Description Winter cover and fertilizer N management practices were evaluated from 1989 through 1992 on a producer's farm in Lowndes County, MS. Profitability and optimum N rates using a range in lint and fertilizer N prices were determined. Soil type: Caledonia loam Experimental design: Randomized complete block i...

Field studies were conducted from 1987 through 1990 on Sharkey clay to determine effect of weed control treatment (WTRT) on yield and net return from soybean grown with no irrigation (NI) or irrigation (I) during reproductive development. Weed control treatments were: 1) PRE glyphosate plus metribuzin plus metolachlor or pendimethalin, followed by POST bentazon plus acifluorfen or 2,4-DB plus linuron (high WTRT); 2) PRE glyphosate at a rate to kill existing weeds at planting (medium WTRT); or 3) PRE paraquat at a rate to desiccate but not necessarily kill existing weeds at planting (low WTRT). POST cultivation was used in all treatments. Weed ground cover in the high, medium, and low WTRT's was composed of annual grass and moderately competitive broadleaf species, and averaged 7, 25, and 49%, respectively, at harvest in 1990. Yield declined with decreasing weed control in the I treatment after the first year, but average net returns from the high and medium WTRT's were not different, and both exceeded average returns from the low WTRT. Yields from the high and medium WTRT's in the NI treatment were not different, and both exceeded yield from the low WTRT. Average net returns from the medium WTRT were greater than those from the high and low WTRT's in all years. Yield increase from irrigation and difference in average net returns between I and NI declined with decreasing weed control.

almost always made before the onset of drought and without knowledge of ensuing moisture status for subse-Management inputs that maximize economic return from the early quent crop and weed development. This presents a chalsoybean [Glycine max (L.) Merr.] production system have not been evaluated fully. The objective was to determine the effect of weed man-lenge, especially in NI production systems that often agement on yield and net return from early planted maturity group result in low yield in the midsouthern USA. (MG) IV and MG V glyphosate [N-(phosphonomethyl)-glycine]-resis-A majority of the soybean hectarage in the midsouthtant (GR) and conventional (CONV) soybean cultivars grown in the ern USA is NI even though past research has shown early soybean production system with (IRR) and without (NI) irrigathat yield and net return will increase from irrigation tion. Field studies were conducted from 1996 through 1999 on Sharkey (Heatherly, 1999a). The small profit margin and large clay (very-fine, smectitic, thermic Chromic Epiaquert) at Stoneville, start-up costs associated with land leveling to accommo-MS (33؇26 N lat). Weed management systems were (i) pre-emergent date furrow or flood irrigation, or the initial purchase (PRE) broadleaf followed by postemergent (POST) broadleaf and cost associated with overhead irrigation systems, can grass weed management (PRE ϩ POST) and (ii) POST broadleaf make capitalization of irrigation capability prohibitive. and grass weed management (POST). Use of POST-only weed management was cheaper, yielded more, and resulted in greater net returns Thus, most land used for soybean production in the than did use of PRE ϩ POST weed management with both CONV midsouthern USA presently is committed to either an and GR cultivars. Under the conditions of this study, use of GR vs. IRR (start-up costs absorbed in past) or NI production CONV cultivars in an NI or low-yield environment resulted in greater system. Management of NI and IRR plantings of soyprofit ($52 vs. Ϫ$17 ha Ϫ1 3-yr average, respectively). Use of CONV vs. bean in the midsouthern USA entails different sets of GR cultivars resulted in greater profit in an IRR or high yield environproduction practices, especially for weed management ment ($382 vs. $266 ha Ϫ1 3-yr average, respectively). These results (Heatherly et al., 2002), because the opportunity for indicate that use of GR cultivars with POST-only weed management profit is different between the two systems (Heatherly will result in greater profit in an NI environment while use of CONV and Spurlock, 1999). cultivars with POST-only weed management will result in greater Many weed management systems (WMSs) provide profit in an IRR environment.is a nonselective herbicide that kills both annual and

1994a, 1994b, 1995). Cotton, grain sorghum, and rice (Oryza sativa L.) are also adapted to these soils, butDeep tillage (subsoiling) of clayey soils in the fall when the profile they're planted on fewer hectares. is dry is a new concept that results in increased yields and net returns from soybean [Glycine max (L). Merr.] grown without irrigation.The use of large, heavy field equipment early in the Crop rotation may also result in increased crop yields. Field studies season when the soil is wet may compact soil or reduce were conducted on Tunica clay (clayey over loamy, smectitic, nonacid, its productivity (Phillips and Kirkham, 1962; Gameda thermic, Vertic Haplaquept) near Stoneville, MS (33؇26 N lat) to et al., 1987; Voorhees, 1985). When soil is compacted, determine the individual and combined effects of fall deep tillage and its particles are rearranged such that the total pore space crop rotations on crop yields and net returns. Treatments included is decreased, whereas bulk density is increased (Singer monocrop cotton [Gossypium hirsutum (L.)], soybean, and grain sorand Munns, 1987). In most cases, the larger soil pores ghum [Sorghum bicolor (L.) Moench], and biennial rotations of cotton (macropores) are destroyed by the compactive force with grain sorghum and soybean with grain sorghum grown without exerted on the soil, which results in reduced content irrigation and in either a conventional-till (CT) or deep-till (DT) and movement of air, water, heat and nutrients in the production system. Yields from all cotton and soybean crop sequences grown in the DT respectively averaged 541 kg ha Ϫ1 and 525 kg ha Ϫ1 soil. Compaction also increases soil strength, thereby greater than comparable cotton (2184 kg ha Ϫ1 ) and soybean (2983 kg increasing the resistance to root penetration. When ha Ϫ1 ) crop sequences grown in the CT. Net returns from monocrop plant roots cannot explore the entire soil structure, plant cotton ($552 ha Ϫ1 ) and soybean ($462 ha Ϫ1 ) in the DT respectively nutrients become positionally unavailable. averaged $392 ha Ϫ1 and $121 ha Ϫ1 more than similar crop sequences Studies conducted by Akram and Kemper (1979) indiin the CT. Rotations increased cotton and soybean yields but not net cated that soil water content determined the degree of returns because of the low value of the grain sorghum component. R.A. Wesley and C.D. Elmore, USDA-ARS Application and Produciness, 1977). Soybean yields from DTs averaged 2892 tion Technical Res. Unit, Stoneville, MS 38776; and S.R. Spurlock, Dep. of Agric. Economics, Mississippi State Univ., Mississippi State, kg ha Ϫ1 and were significantly higher than the 1950 kg MS 39762.