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The understanding, prediction, and modeling efficacy of soil organic carbon (SOC) distribution across fields and larger regions requires a large number of samples that are cosdy to analyze. The objective of this study was to evaluate soil color measurements to predict SOC for agriculture and prairie land uses. Munsell soil color book (B) and chroma meter (C) color readings were taken at the midpoint depth of each horizon (HB and HC) and predetermined depth increments (IB and IC) on 125 cores. Horizon matrix (HD) colors were determined by standard description. A chroma meter was used to determine the color of prepared samples, ground to Abbreviations: HB, Munsell color book readings by horizon; HC, chroma meter readings by horizon; IB, Munsell color book readings by depth increment; IC, chroma meter readings by depth increment; SCd, chroma meter readings on dry samples; SCm, chroma meter readings on moist samples; SOC, soil organic carbon.

The productivity of grasslands depends in part on their diversity of species and functional composition. Our objective was to examine the effects of three landscape positions (summit, backslope, and toeslope) and three stocking systems (continuous, rotational, and nongrazed) on species diversity and percentage of cover of grass, legume, and weed species functional types in southeastern Iowa pastures. Data were collected in 0.2-[m.sup.2] plots randomly distributed throughout each of four replicate pastures in spring and summer 2000 and 2001. Backslope landscape positions within pastures managed with either continuous or rotational stocking contained the greatest overall diversity of species. Across years, overall species richness under grazing averaged 4.8 on backslopes, 3.5 on summits, and 2.9 on toeslopes. Legume cover was greatest within the rotational stocking system, averaging 21% on backslopes, 10% on summits, and 3% on toeslopes across years. Cool-season grasses dominated summits and toeslopes, consisting of 88 to 94% of the cover. Weed species diversity and cover were greatest on backslopes within the continuous stocking system. Our results showed that rotational stocking had more desirable effects through greater legume cover and less weed cover on backslopes than continuous stocking. This research suggested that spatial components of pastures should be considered to optimize the production and quality of forage for grazing livestock., THE PRODUCTIVITY AND STABILITY of aboveground biomass in grassland ecosystems depends inpart on the functional composition and diversity of plant species. Recent experiments showed that species-rich grasslands have greater productivity [...]

Samples of 255 noncalcareous A, Ap, and AB horizons from selected major land resource areas (MLRA) in the north central USA were used to develop equations for predicting organic C content, as determined with a Leco C analyzer, from weight loss-on-ignition (LOI). Organic C concentrations of the samples ranged from 1.09 to 114.6 g [kg.sup.-1]. Within each MLRA, strong linear relationships were observed between LOI and organic C measured by the Leco instrument, with [r.sup.2] ranging from 0.94 to 0.98. Predictive equations developed by least-squares regression were significantly different for individual MLRA's. Loss-on-ignition is a rapid, inexpensive, and accurate for estimating organic C concentration in soils of the north central USA. We recommend that unique predictive equations be developed for individual soil-geographic regions.

Afforestation trends were compared between two continentally-distinct, yet similar ecoregions to characterize similarities or differences in forest advancement due to natural and anthropogenic forcings. Temporal changes in forest cover were analyzed using high resolution aerial and satellite photographs for Southeast Iowa, USA, and satellite photographs for the western Belgorod Oblast, Russia. An increase in forested area was shown to occur over a 44-year period from 1970-2014 in Iowa where afforestation was reflected by the aggregation of smaller forest units. In the Belgorod region the opposite occurred in that there was an increase in the number of smaller forested units. The rate of forest expansion into open grassland areas, previously used as haying lands and pastures, was 14 m decade-1 and 8 m decade-1 in Iowa and the Belgorod Oblast, respectively. Based on current trends, predicted times for complete forest coverage in the study areas was estimated to be 80 years in Iowa and 300 years in the Belgorod Oblast. In both the Iowa and Belgorod Oblast, there was an increase in annual precipitation at the end of the 20th and the beginning of the 21st centuries, thus providing a contributing mechanism to forest advancement in the study regions and implications for future management practices. [ABSTRACT FROM AUTHOR]

Despite a large body of scientific research that shows that soils change on relatively short time scales under different management regimes, classical pedological theory states that we should expect these changes to occur only in the surface few centimeters and that they are not of adequate magnitude to suggest fundamental changes in pedon character over short periods of time. In fact, rarely, do the scientists that make these comparisons report on any properties deeper than 30 to 45 cm in the soil profile. With this study, we evaluate soil transformation to a depth of 150 cm after 50 yr of intensive row-crop agricultural land use in a temperate, humid, continental climate (Iowa, United States), by resampling sites that were initially described by the United States soil survey between 1943 and 1963. We find that, through agricultural land use, humans are accelerating soil formation and transformation to a depth of 100 cm or more by accelerating erosion, sedimentation, acidification, and mineral weathering, and degrading soil structure, while deepening dark-colored, organic-matter rich surface horizons, translocating and accumulating organic matter deeper in the soil proile and lowering the water table. Some of these changes can be considered positive improvements, but many of these changes may have negative effects on the soils' future productive capacity. [ABSTRACT FROM AUTHOR]

Renewable bioenergy could be supplied by high yielding grass crops, such as switchgrass (Panicum virgatum L.). Successful development of a bioenergy industry will depend on identifying cultivars with high yield potential and acceptable biofuel quality. The objective of this study was to evaluate 20 switchgrass populations in a field study planted in May 1997 in southern Iowa, USA. The populations included released cultivars and experimental germplasm of both upland and lowland ecotypes. Yield, plant height, stand, lodging, leaf:stem ratio, cell wall fiber, total plant nitrogen, and ash were determined on all entries between 1998 and 2001. Ultimate and proximate analyses together with chlorine and major oxide determinations were made on three cultivars in 2000 and 2001. Biomass yield was determined from a single autumn harvest each year. The lowland cultivars ‘Alamo’ and ‘Kanlow’ produced the most biomass, exceeding the production of the widely recommended upland cultivar ‘Cave-In-Rock’. Other traits differed among the cultivars, although the range was less than that for yield. The differences among years were substantially greater for the ultimate, proximate, and major oxide analyses than differences among cultivars. The highest yielding cultivars had low ash, slightly lower fiber concentrations, and moderate levels of important minerals, suggesting that excellent germplasm is available for biofuel production. The persistence of the lowland cultivars in southern Iowa may need more research because the winters during the experiment were mild. [Copyright &y& Elsevier]