Estimating the contribution of nitrogen and phosphorus to waterbodies by colonial nesting waterbirds.

Fecal deposition by colonial nesting waterbirds is a potential source of nutrient enrichment and pollution of nearby waterways. Excess concentrations of nitrogen (N) and phosphorus (P) can cause water quality concerns or impairment. We estimated concentrations of N and P deposited to waterbodies by birds nesting in four colonies in east-central Texas during 2011-2013, and developed an age-structured compartment model to estimate the amount of fecal N and P material deposited by birds during the entire breeding season. There was a seasonal variation in the accumulation of N and P in waterbodies where heronries were located with a significant increase from June to July at the peak of the breeding season. Also, there was a significant positive correlation in concentrations of N (P=0.023) in fecal material and water samples from one of the colonies (Murphy Park), suggesting a significant contribution of N from feces to water. Concentrations of N in water near the colonies were also significantly correlated (P=0.004, R2=0.22) with the average amount of precipitation recorded for each region. The simulation model results indicated that total N and P deposition increased proportionally with heronry size, and daily deposition rates varied due to the shifting daily activity budgets of the birds as the breeding season progressed. The total estimated loads from the model reached a maximum of 2170kg N and 240kg P for a given colony, with daily deposition estimated at 22.8kg N, and 2.5kg P. Based on the model, one bird can release about 1mg of N and 0.115mg of P on a daily basis to the soil substrate or directly over water. Results from this study could be useful to estimate the contribution of N and P from wildlife to waterbodies, and for watershed management plans.

An Evaluation of the Contribution of Macro- and Microelements from Colonial Nesting Waterbirds to Surface Water.

Macro- and microelements contained in the feces of cattle egrets () and other colonial birds in heronries can be sources of contamination of nearby waterways. Concentrations of the macroelements potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), sulfur (S) and the microelements zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), and boron (B) were measured in water and fecal samples collected from four locations containing heronries during the breeding seasons of 2011, 2012, and 2013. Nitrogen and phosphorus were measured but not reported in this study. Concentrations of K in feces ranged from 8.19 × 10 ± 4.38 × 10 to 4.88 × 10 ± 7.57 × 10 mg kg, and concentrations in water ranged from 3.92 ± 0.05 to 17.93 ± 0.37 mg L. Similarly, concentrations of Ca in feces ranged from 4.17 × 10 ± 1.84 × 10 to 1.16 × 10 ± 4.14 × 10 mg L, and concentrations in water ranged from 25.28 ± 0.89 to 67.88 ± 2.02 mg L. When birds nested directly over water, concentrations of K, Ca, and Mg in water were significantly higher ( < 0.05) than concentrations in water adjacent to birds nesting on islands. The results from this study show that macroelements from avian feces have the potential to enrich surface water and to negatively affect surface water quality. These results provide information regarding the contribution of nutrients from heronries (comprised primarily by cattle egrets) to watersheds.

Capacity of biochar application to maintain energy crop productivity: soil chemistry, sorghum growth, and runoff water quality effects.

Pyrolysis of crop biomass generates a by-product, biochar, which can be recycled to sustain nutrient and organic C concentrations in biomass production fields. We evaluated effects of biochar rate and application method on soil properties, nutrient balance, biomass production, and water quality. Three replications of eight sorghum [ (L.) Moench] treatments were installed in box lysimeters under greenhouse conditions. Treatments comprised increasing rates (0, 1.5, and 3.0 Mg ha) of topdressed or incorporated biochar supplemented with N fertilizer or N, P, and K fertilizer. Simulated rain was applied at 21 and 34 d after planting, and mass runoff loss of N, P, and K was measured. A mass balance of total N, P, and K was performed after 45 d. Returning 3.0 Mg ha of biochar did not affect sorghum biomass, soil total, or Mehlich-3-extractable nutrients compared to control soil. Yet, biochar contributed to increased concentration of dissolved reactive phosphorus (DRP) and mass loss of total phosphorus (TP) in simulated runoff, especially if topdressed. It was estimated that up to 20% of TP in topdressed biochar was lost in surface runoff after two rain events. Poor recovery of nutrients during pyrolysis and excessive runoff loss of nutrients for topdressed biochar, especially K, resulted in negative nutrient balances. Efforts to conserve nutrients during pyrolysis and incorporation of biochar at rates derived from annual biomass yields will be necessary for biochar use in sustainable energy crop production.

Shifts in microbial community structure along an ecological gradient of hypersaline soils and sediments.

Studies of hypersaline ecosystems often yield novel organisms and contribute to our understanding of extreme environments. Soils and sediments from La Sal del Rey, a previously uncharacterized, hypersaline lake located in southern Texas, USA, were surveyed to characterize the structure and diversity of their microbial communities. Samples were collected along a transect that spanned vegetated uplands, exposed lakebed sediments, and water-logged locations, capturing a wide range of environments and physical and chemical gradients. Community quantitative PCR (qPCR) was used in combination with tag-encoded pyrosequencing, 16S rRNA gene cloning, and Sanger sequencing to characterize the lake's soil and sediment microbial communities. Further, we used multivariate statistics to identify the relationships shared between sequence diversity and heterogeneity in the soil environment. The overall microbial communities were surprisingly diverse, harboring a wide variety of taxa, and sharing significant correlations with site water content, phosphorus and total organic carbon concentrations, and pH. Some individual populations, especially of Archaea, also correlated with sodium concentration and electrical conductivity salinity. Across the transect, Bacteria were numerically dominant relative to Archaea, and among them, three phyla--the Proteobacteria, Bacteroidetes, and Firmicutes--accounted for the majority of taxa detected. Although these taxa were detected with similar abundances to those described in other hypersaline ecosystems, the greater depth of sequencing achieved here resulted in the detection of taxa not described previously in hypersaline sediments. The results of this study provide new information regarding a previously uncharacterized ecosystem and show the value of high-throughput sequencing in the study of complex ecosystems.

Effect of turfgrass establishment practices and composted biosolids on water quality.

Land application of composted municipal biosolids (CMB) enhances soil physical properties and turf establishment. Yet large, volume-based rates of CMB can increase nonpoint source losses of sediment and nutrients from urban soils to surface waters. The objectives were (i) to compare runoff losses of sediment, N, P, and organic C among contrasting establishment treatments for bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy, var. Tifway] and (ii) to evaluate relationships between runoff and soil measurements of N, P, and organic C. Three replications of seven establishment treatments were installed on an excavated slope (8.5%) under field conditions. Five treatments comprised sod transplanted from Tifway bermudagrass grown with and without CMB on soil with and without incorporation of CMB. Two other treatments were composed of Tifway sprigged in soil with and without CMB. Runoff from seven natural rain events was channeled into collection tanks for sampling and analysis. Runoff concentrations and mass loss of dissolved P and organic C forms were greater for CMB-amended sod than for sprigs planted in soil with or without CMB or treatments comprising sod established without CMB. In addition, a linear relationship (R(2) = 0.87) was observed between water extractable soil P of sodded and sprigged treatments and concentrations and mass losses of dissolved P in runoff. Transplanted sod reduced sediment loss compared with sprigged treatments and incorporation of CMB reduced sediment loss from sprigged treatments. Incorporation of CMB within soil on which sod grown without CMB was transplanted proved the best option for achieving benefits of CMB while reducing nutrient runoff loss compared to sod transplanted from Tifway grown with CMB.

Compost impacts on dissolved organic carbon and available nitrogen and phosphorus in turfgrass soil.

Compost application to turfgrass soils may increase dissolved organic C (DOC) levels which affects nutrient dynamics in soil. The objectives of this study were to investigate the influence of compost source and application rate on soil organic C (SOC), DOC, NO(3), and available P during 29 months after a one-time application to St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] turf. Compost sources had variable composition, yet resulted in few differences in SOC, DOC, and NO(3) after applied to soil. Available NO(3) rapidly decreased after compost application and was unaffected by compost source and application rate. Available P increased after compost application and exhibited cyclical seasonal patterns related to DOC. Compost application decreased soil pH relative to unamended soil, but pH increased during the course of the study due to irrigation with sodic water. Increasing the compost application rate increased SOC by 3 months, and levels remained fairly stable to 29 months. In contrast, DOC continued to increase from 3 to 29 months after application, suggesting that compost mineralization and growth of St. Augustinegrass contributed to seasonal dynamics. Dissolved organic C was 75%, 78%, and 101% greater 29 months after application of 0, 80, and 160 Mg compostha(-1), respectively, than before application. Impacts of composts on soil properties indicated that most significant effects occurred within a few months of application. Seasonal variability of SOC, DOC, and available P was likely related to St. Augustinegrass growth stages as well as precipitation, as declines occurred after precipitation events.

Seasonal dynamics of soil micronutrients in compost-amended bermudagrass turf.

Compost application to turfgrasses can increase plant-available nutrient concentrations in soil and improve growth, but may alter micronutrient dynamics and increase leaching and runoff losses. The objectives of this study were to investigate the influence of compost on the seasonal dynamics of plant-available Mn, Fe, Cu, and Zn in soil after a single application to bermudagrass [Cynodon dactylon (L.) Pers.] turf. Extractable Mn increased from 270 to 670 mg kg(-1) and Cu from 0.36 to 9.89 mg kg(-1) from 0 to 29 months. In contrast, extractable Fe and Zn decreased by 52% and 57% during the same time period. Seasonal trends in extractable Mn and Cu were closely related to dissolved organic C (DOC), and appeared influenced by bermudagrass growth and dormancy patterns and subsequent impacts on DOC. Losses of Mn and Cu from the soil surface occurred after high levels of precipitation during winter dormancy but not during the growing season, while Fe and Zn exhibited an opposite pattern. Thus, seasonal variation of soil micronutrients was likely related to seasonal patterns of bermudagrass growth and dormancy and their effects on DOC, and precipitation events which probably leached DOC and complexed nutrients from surface soil. Composts only influenced the magnitude of changes in micronutrient concentrations, as similar seasonal trends occurred for both compost-amended and unamended soils.