Manure management effects on grass production, nutritive content, and soil nitrogen for a grass silage-based dairy farm

Legislation in the United States has recently focused on improving water quality by establishing management practices that limit the quantities of nutrients entering the water supply. Timely application and quantification of the amount of manure applied throughout the grass-growing season can reduce the loss of nutrients into ground or surface water while improving the quality and quantity of grass harvested. During the 2001 and 2002 growing seasons, we measured the effects of different manure application rates on grass yields, grass nutritive value, and soil chemistry on a dairy farm. On-farm estimates of manure N were combined with yield estimates and forage quality measures to evaluate the effects of varying levels of manure application. Yield estimates, N content of grass, and the amount of N in soil and manure were monitored at each cutting for plots amended at different manure application rates. There are three major outcomes of this evaluation: (i) new grass seedings were at higher risk of elevated levels of nitrate N in forage; (ii) increased forage nitrate N at harvest was associated with malfermented silage and increased levels of ammonia N, which resulted in less efficient use of metabolizable protein for milk production; and (iii) increased understanding of N cycling between manure, soil, and plant provided an opportunity to reduce purchased fertilizer.     

RED ALDER LEAF LITTER AND STREAMWATER QUALITY IN WESTERN OREGON1

ABSTRACT: Streamside red alder (Alnus rubra Bong.) stands are common in western Oregon, and they have been suspected of causing water quality problems in domestic supplies during autumn leaf fall. Studies in the Seaside municipal watershed showed potential water quality effects (particularly increased color) from alder leaves, but stream sampling during 1981–82 revealed no chronic problems. The few observed short-term increases in water color occurred near the onset of storm flows, which suggested a flushing of organic matter storage sites. An extended period of unusually low flows and high leaf fall are probably necessary to produce significant water quality problems in this stream system. Laboratory leaching of alder leaves in filtered stream water indicated a fairly constant release of colored organic matter over time, and running water leached this matter more efficiently than still water. Water color increased linearly with increasing leaf mass added to still water, and for a given leaf mass there appeared to be a limit to the amount of colored matter that could be removed in the first 48 hours of leaching. Other laboratory tests showed that ultraviolet absorbance (254 mm) may provide a reasonable estimate of dissolved organic carbon concentrations in systems dominated by alder leaf inputs.     

CHLOROPHYLL-BIOMASS-NUTRIENT RELATIONSHIPS FOR NATURAL ASSEMBLAGES OF FLORIDA PHYTOPLANKTON1

Parallel determination of phytoplankton biomass and chlorophyll a concentration were made on spring and summer phytoplankton samples collected from 165 Florida lakes. There was a significant correlation between chlorophyll a concentration and phytoplankton biomass (r=0.80; P < 0.01). Chlorophyll content per unit phytoplankton biomass ranged over two orders of magnitude. Nitrogen seemed to be a major factor influencing the chlorophyll content of Florida algae. Multiple regression analyses indicated that phytoplankton biomass was dependent on both the total phosphorus and total nitrogen concentration. Nutrient-phytoplankton and Secchi-phytoplankton relationships for the Florida lakes had higher coefficients of determination if chlorophyll a concentrations rather than phytoplankton biomass data were used in regression analyses.     

RELATIONS BETWEEN COLOR AND SOME LIMNOLOGICAL CHARACTERISTICS OF FLORIDA LAKES1

Data obtained from a limnological survey of 165 Florida lakes were analyzed to determine regional differences in lake color (Pt-Co units) and relations between color and various physical, chemical, and biological parameters. Average color measurements for the different lakes ranged from 0 to 416 Pt-Co units with individual measurements being as high as 600 Pt-Co units. With the exception of extreme south Florida, lake color concentrations were found to increase from north to south and from inland highlands to lowlands. Central Florida had the greatest heterogeneity in lake color because of an extremely diverse geology and physiography. Color was inversely related to Secchi disc transparency and positively related to total iron concentrations. Color was not strongly related to pH, total alkalinity, nutrients, chlorophyll a, and many other limnological parameters. Although lakes having color concentrations greater than 20 Pt-Co units can often be visually identified as colored lakes, the limnological processes in these are not necessarily different from those of lakes having clear water.     

Aerial Monitoring of Marine Waterfowl in the Alaskan Beaufort Sea

The purpose of this study was to design and test a monitoring protocol for marine waterfowl in the central Alaskan Beaufort Sea. The study provides an important case-study of how a long-term monitoring program may be affected by unanticipated human disturbances.Because of its overwhelming and widespread abundance, relatively sedentary behavior, ease in counting, and the extensive historical database, the long-tailed duck (Clangula hyemalis) was selected as the focal species. Two null hypotheses were formulated concerning potential changes in the numbers and distribution of long-tailed ducks in relation to disturbance in an industrial study area, compared to a reference study area located about 50 km to the east.A 9-year historical database (1977–1984, 1989) of long-tailed duck densities and other important data recorded during systematic aerial surveys was analyzed retrospectively using multiple regression techniques. The retrospective analyses determined which of several predictor variables recorded were significantly related to long-tailed duck density. Separate analyses were conducted for two periods: (1) the overall period when long-tailed ducks were present in the lagoon study areas, and (2) the shorter adult male molt period. The results of the two analyses indicated that 57% and 68%, respectively, of the total variation in long-tailed duck density during the two periods could be explained by variables recorded during the surveys. Predictor variables representing habitat, day of the year, time of day, amount of ice, and wave height recorded on-transect during surveys were most closely associated with long-tailed duck density. Measurement error during the surveys, and influences outside the study area such as nesting success in tundra habitats and mortality during migration and in over-wintering areas likely also had strong influences on the results, but these factors were not measurable in our study.Based on results of the retrospective analyses, a long-term monitoring protocol consisting of a program of systematic aerial surveys and an analyses of variance and covariance (ANOVA and ANCOVA) statistical procedure was designed and initially tested in 1990 and 1991. This 2-year testing phase resulted in several revisions to the monitoring protocol. Refinements were made to the original sampling procedures, to the survey schedule, and to the recommended statistical analysis procedures. Results of the ANOVA and ANCOVA indicated that there was no evidence of a change in long-tailed duck densities that could be attributable to disturbance (from any source) in the industrial study area relative to a reference area with no industrial development. Other analyses indicated that the sampling and analysis procedures would be adequate to detect long-term trends in long-tailed duck density and localized disturbance effects, but that the monitoring program should be continued well beyond two years to detect statistically significant changes. As a result, additional aerial surveys of both study areas were conducted again during 1999–2001.Results of the revised ANOVA and ANCOVA of the 1990–1991 and 1999–2001 survey data indicated that the density of long-tailed ducks had significantly declined in coastal lagoons along the central Alaskan Beaufort Sea coast during the study period. In addition, disturbances throughout the barrier island-lagoon systems used by these ducks, including both the industrial and the reference study areas, had significantly increased over the same period. However, because unanticipated disturbances from a variety of anthropogenic sources, and not just industry sources, increased in both study areas, the reference study area was not an effective statistical control. As a result, the decline in long-tailed duck density in both study areas was not attributable to industry-related activities. Although the monitoring protocol described here is an effective method to detect statistically significant changes in long-tailed duck distribution and abundance in the nearshore Alaskan Beaufort Sea, many more years of sampling would be necessary to attribute observed changes to industry-related disturbances.     

Environmental implications of adopting a dominant factor approach to salinity management

Additive or multiplicative models of crop response on which salinity management theory have been developed may lead to an erroneous perception regarding compensative interaction among salinity and other growth factors. We present results from studies of biomass production and transpiration of corn (Zea mays L. cv. Jubilee), melon (Cucumis melo L. subsp. melo cv. Galia), tomato (Lycopersicon esculentum Mill. cv. 5656), onion (Allium cepa L. cv. HA 944), and date palms (Phoenix dactylifera L. cv. Medjool) under salinity combined with water or nitrate (growth promoters) or with boron (growth inhibitor). The measured crop responses were to the more severe stress rather than to combinations of the individual effects of the various stresses. Consequences of shifting management of saline water to a dominant factor approach include reduction of environmental contamination and conservation of water resources.     

WATER QUALITY IMPACTS OF CONSERVATION AGRICULTURAL PRACTICES IN THE MISSISSIPPI DELTA1

ABSTRACT: Nonpoint pollution in the form of runoff generated by conventional agricultural practices is one of the major sources of environmental degradation of surface water bodies. Agricultural conservation practices including no‐tillage operations have been introduced as alternatives to cope with such challenges. This study attempts to examine the economic and environmental impacts of no‐tillage as compared to conventional agricultural practices for cotton, soybeans and corn cultivated in the Mississippi Delta. Impacts in the form of sediment, nutrient and pesticide runoff at farm level are investigated, using the Erosion Productivity Impact Calculator (EPIC).