Litter Type and Number of Flocks Affect Sex Hormones in Broiler Litter.

Broiler litter contains 17ß-estradiol, estrone, and testosterone, which can contaminate surface waters when surface applied to grasslands and no-till fields. The objective of this study was to evaluate the effects of litter type (full or cake cleanout), litter treatment (none or sodium bisulfate), and number of flocks raised on the litter (1-5) on sex hormone concentrations. Our results showed that in untreated broiler litter, cake cleanout had greater concentrations of 17ß-estradiol, estrone, and testosterone than full cleanout, whereas in litter treated with sodium bisulfate, only the concentration of 17ß-estradiol was greater in cake than in full cleanout. The concentrations of 17ß-estradiol and estrone in untreated broiler litter increased as the number of flocks increased from one to three, with the largest increase observed for estrone in cake cleanout. We also sampled three broiler houses in brooding and nonbrooding sections during the growout period. We found no differences in hormone concentrations between sections of each house, but changes in hormone concentrations during growout varied depending on broiler litter water content. Water contents corresponding to ∼60% water-filled porosity favored a decrease in hormone concentrations with time, whereas a water-filled porosity of 44% was associated with increases in hormone concentration, probably due to slow decomposition rates. Our results suggest that cake cleanout of untreated litter, as well as all cleanouts from houses that have raised several flocks on the same bedding, may be good targets for treatments that can reduce hormone concentrations before the litter is surface applied to fields.

Influence of aeration implements, phosphorus fertilizers, and soil taxa on phosphorus losses from grasslands.

Attenuation of rainfall within the solum may help to move contaminants and nutrients into the soil to be better sequestered or utilized by crops. Surface application of phosphorus (P) amendments to grasslands may lead to elevated concentrations of P in surface runoff and eutrophication of surface waters. Aeration of grasslands has been proposed as a treatment to reduce losses of applied P. Here, results from two small-plot aeration studies and two field-scale, paired-watershed studies are supplemented with previously unpublished soil P data and synthesized. The overall objective of these studies was to determine the impact of aeration on soil P, runoff volume, and runoff P losses from mixed tall fescue [Lolium arundinaceum (Schreb.) Darbysh.]-bermudagrass (Cynodon dactylon L.) grasslands fertilized with P. Small-scale rainfall simulations were conducted on two soil taxa using three types of aeration implements: spikes, disks, and cores. The-field scale study was conducted on four soil taxa with slit and knife aeration. Small-plot studies showed that core aeration reduced loads of total P and dissolved reactive P (DRP) in runoff from plots fertilized with broiler litter and that aeration was effective in reducing P export when it increased soil P in the upper 5 cm. In the field-scale study, slit aeration reduced DRP losses by 35% in fields with well-drained soils but not in poorly drained soils. Flow-weighted concentrations of DRP in aerated fields were related to water-soluble P applied in amendments and soil test P in the upper 5 cm. These studies show that the overall effectiveness of mechanical soil aeration on runoff volume and P losses is controlled by the interaction of soil characteristics such as internal drainage and compaction, soil P, type of surface-applied manure, and type of aeration implement.

Aerating grasslands: effects on runoff and phosphorus losses from applied broiler litter.

Aeration has been promoted as improving infiltration of rainfall and extending grass or forage productivity, but research on the impact of this practice on P losses from grasslands has had mixed results. We designed a study to determine at the field scale, using a paired watershed approach, the impact of slit aeration on runoff volume and P losses in runoff from fescue (Festuca arundinacea Schreb.)/bermudagrass (Cynodon dactylon L.) hay fields fertilized with broiler litter. Three pairs of 0.8-ha fields, each with similar soils (Typic Kanhapludults, Aquic Hapludults, and Aquultic Hapludalfs), were fertilized with broiler litter and monitored under similar management from 1995 through 1998, then one field in each pair received aeration treatment from 2001 through 2003. In the field with mostly well-drained soils, grassland aeration reduced surface runoff volume and mass losses of dissolved reactive P (DRP) in runoff by approximately 35%. In contrast, when poorly drained soils dominated, grassland aeration increased runoff volume (4.8 mm/runoff event) and mass losses of DRP and total P (0.25 kg TP ha-1 per runoff event). This implies that aeration of well-drained soils in the top poultry-producing counties of Georgia (0.2 million ha) could decrease dissolved phosphorus losses by more than 500 Mg P each year. This is not the case if soils are poorly drained.