1980), the BBCH system (Lancashire et al., 1991), andHaun (1973). Zadoks et al. (1974) is an adaptation of The large area of rice (Oryza sativa L.) production worldwide is Feekes' (1941) scale (with 23 subdivisions) but further critical to the well being of large numbers of the world's people. Yet delineated. The IRRI (1980) scale is a 10-point system for rice, the most important single plant species for human nutrition, there is not a widely used growth staging system. Despite good points Paul A. Counce, University of Arkansas, Rice Research and Extensionrather than an arbitrary number (e.g., 10, 11, 99, or Center,

Yield component analysis provides a framework for identifying potentially useful traits for yield improvement. Consideration of how population density affects other yield components has not been addressed specifically for short‐season soybean [Glycine max (L.) Merr.] production. We assessed the direct and indirect contributions of population density for short‐season soybean yield and its components over a wide range of population densities (6–134 plants m−2) using path‐coefficient analysis. Data were from field tests conducted in 1997, 1998, and 1999 at Keiser, AR. Although population density had a large inverse association with pods plant−1, the large direct effect of population density on yield was greater than its negative indirect effect via pods plant−1. The direct effects of pod number plant−1 and seeds pod−1 on yield were positive, whereas mass seed−1 had a negligible effect. Pods fertile‐node−1 differed between cultivars, and it was reduced by increasing population density. For early sowing, the contribution of population density to yield was less because pods m−2 could be achieved at low population densities by a large number of fertile‐nodes plant−1 and pods fertile‐node−1. In contrast, at late sowing, the decreased potential for fertile‐nodes plant−1 was compensated by increasing plant population density. In short seasons, maximizing nodes m−2 and pods m−2 can be achieved by high population densities and early canopy closure, rather than the conventional system of larger plants with greater numbers of pods plant−1 and pods fertile‐node−1

Winter cover crop studies were conducted for 17 years with cotton grown on a Dubbs-Dundee soil complex at the University of Arkansas Delta Branch Experiment Station. This experiment was established in 1972 to investigate the changes induced by winter cover crops of rye, vetch, and lupine. The rye and lupine were later changed to rye + vetch and rye + crimson clover, resp. Cotton yield responses to cover crops were found to be highly dependent on the growing season. Although the cover crops averaged a seedcotton yield increase, certain years had drastic yield reductions. This experiment was not designed with sufficient scope to address why yield responses occurred as they did. Soil physical properties of hydraulic conductivity, water retention, porosity, and proportion of large pores were found to be measurable changed by having winter cover crops. In general the change in soil physical properties resulting from the cover crops would result in faster infiltration and transmission of water, more 1. Published with the approval of the

on yield-enhancing production practices such as tillage system, planting date, and cultivar selection. Soybean [Glycine max (L.) Merr.] yields from nonirrigated fieldsTillage systems can impact soil moisture status bein the midsouthern USA have consistently lagged behind those from cause tillage influences infiltration, runoff, evaporation, irrigated fields. Nonetheless, nonirrigated fields still attract a larger and soil water storage. With conventional tillage, weeds share of soybean acreage in this region. This is likely due to various irrigation constraints, which include land-leasing arrangements, water that compete with crops for moisture and other growth shortage, lack of management time, and low levels of operating capital.resources are mechanically removed. On the other hand, The objective of this study was to identify production system compoconventional tillage can promote drought stress through nents consisting of tillage, cultivar selection, and planting-date stratelow residue cover, increased runoff, and reduced water gies for a soil series that are most suitable for enhancing economic infiltration (Dao, 1993;Unger and Cassel, 1991; Unger returns to dryland soybean. Data from field experiments in three and Fulton, 1989). By contrast, no-till and other conser-Arkansas locations in 1995 and 1996 were used for the study. Leading vation strategies affect soil water content through reproduction systems were identified on the basis of their net returns.duced runoff or erosion and improved residue cover. Results of the study show that the performance of the productionHowever, development of soil crusts that increase runoff systems in terms of crop yields and net returns is influenced by location and impede infiltration is more prevalent with conservaand production year. While the evidence on pure planting-date effects AR 72701; and C.R. Dillon,

Conservation tillage offers an alternative approach for managing clayey soils in the midsouthern United States. This study compared conservation tillage seedbed preparation vs. conventional tillage main plots with subplots of (i) nonirrigated soybean (Glycine max L. Merr.), (ii) irrigated soybean, (iii) irrigated grain sorghum (Sorghum vulgare L.), (iv) irrigated soybean followed by irrigated grain sorghum, (v) irrigated soybean followed by irrigated corn (Zea mays L.), and (vi) continuous irrigated cotton (Gossypium hirsutum L.) for the years 1986 to 1991 at Keiser, AR. Cropping practices were similar to those used by producers in the area. Grain sorghum yielded better in a soybean rotation than in monoculture and also in conventionally tilled seedbed than in conservation tillage. For other crops, yield did not differ significantly by tillage. Except for cotton, conventional tillage resulted in higher average net returns (NR) than conservation tillage. Although the most profitable system was continuous cotton with conservation tillage, NR varied widely across years, and there were fewer observations for cotton than for other systems in the study. Among conventional tillage seedbed preparation, nonirrigated continuous soybean was more profitable than any of the irrigated systems, including irrigated soybean. However, irrigated soybean resulted in NR that were less variable than nonirrigated soybean. The study confirmed the increased variable costs and decreased equipment costs that accompany conservation tillage systems. Even with the dramatic changes in burndown herbicide costs that have occurred since the study was conducted, the rankings of the cropping systems for profitability would not change.