Effects of Subsurface Banding and Broadcast of Poultry Litter and Cover Crop on Soil Microbial Populations.

Agronomic management is aimed at managing the crop environment to maximize crop yield, but soil biology is often ignored. This study aimed to compare the application of poultry litter via broadcast and subsurface banding versus standard inorganic fertilizer to cotton ( L.) and their effects on soil bacterial populations and fecal indicator bacteria. The study comprised a randomized complete block design, with fertilizer and time of application as treatment effects and cover crop as a main effect. Soil cores were collected and analyzed from 2008 to 2014. Fecal indicator bacteria were at detection limits for all treatments, where the integron 1 gene was significantly elevated in litter plots. There were few differences between litter application approaches, but both significantly increased key biogeochemical genes over control plots, whereas a cover crop only increased soil moisture and urease C. Data suggested a positive residual effect of litter application with 16S, phosphatase A, and urease C genes elevated over controls, but similar to standard fertilizer plots. High-throughput 16S ribosomal RNA analysis suggested increased diversity and enrichment indices in litter and standard fertilizer over untreated control plots. Litter and standard fertilizer effects persisted 4 and 2 yr after application, respectively, as evidenced by residual library community structures. This study demonstrated the positive effects of litter application on the soil bacterial community when compared with untreated control plots. Some differences between standard fertilization and litter practices were noted and suggest that there is a positive residual effect on soil microbial populations associated with both practices.

Subsurface Band Application of Poultry Litter and Its Influence on Phosphorus Concentration and Retention after Runoff from Permanent Pastures.

Excessive phosphorus (P) loss from agricultural fields is a major cause of eutrophication to rivers, lakes, and streams. To mitigate P loss after poultry litter (PL) applications, technology is being developed to apply litter below the soil surface. Thus, research was conducted to evaluate the effects of subsurface PL banding on soil P under pasture management. Treatments consisted of surface-broadcasted or subsurface-banded PL (38 cm apart) at 9 Mg ha, surface-broadcasted commercial fertilizer (CF; urea and triple superphosphate blend) at N (330 kg N ha) and P (315 kg N ha) application rates equivalent to PL, and a nonfertilized control. Runoff events lasting 40 min were simulated in bermudagrass ( L.) pastures on common soil types of the Coastal Plain and Piedmont regions. One day later, Mehlich-1 and water-soluble P concentrations in soil were measured at depths of 0 to 5 cm and 5 to 10 cm to determine P distribution and movement. The greatest P concentrations were observed at the shallow depth for all treatments. Phosphorus measurements at the point of application for PL bands were greater than for the surface-applied treatments (PL and CF) and control. Measurements between subsurface PL bands were slightly higher than the control but were statistically similar, suggesting that this application method can abate short-term P movement. Results obtained from this study show that subsurface band applying PL could increase P retention and reduce movement by precluding contact between surface water and litter nutrients.

Nutrient loss in leachate and surface runoff from surface-broadcast and subsurface-banded broiler litter.

Subsurface band application of poultry litter has been shown to reduce the transport of nutrients from fields in surface runoff compared with conventional surface broadcast application. Little research has been conducted to determine the effects of surface broadcast application and subsurface banding of litter on nutrients in leachate. Therefore, a field experiment was conducted to determine the effects of subsurface band application and surface broadcast application of poultry litter on nutrient losses in leachate. Zero-tension pan and passive capillary fiberglass wick lysimeters were installed in situ 50 cm beneath the soil surface of an established tall fescue ( Schreb.) pasture on a sandy loam soil. The treatments were surface broadcast and subsurface-banded poultry litter at 5 Mg ha and an unfertilized control. Results of the rainfall simulations showed that the concentrations of PO-P and total phosphorus (TP) in leachate were reduced by 96 and 37%, respectively, in subsurface-banded litter treatment compared with the surface-applied litter treatment. There was no significant difference in PO-P concentration between control and subsurface-banded litter treatment in leachate. The trend in the loading of nutrients in leachate was similar to the trend in concentration. Concentration and loading of the nutrients (TP, PO-P, NH-N, and NO-N) in runoff from the subsurface-banded treatment were significantly less than for the surface-applied treatment and were similar to those from control plots. These results show that, compared with conventional surface broadcast application of litter, subsurface band application of litter can greatly reduce loss of P in surface runoff and leachate.

Phosphorus runoff losses from subsurface-applied poultry litter on coastal plain soils.

The application of poultry litter to soils is a water quality concern on the Delmarva Peninsula, as runoff contributes P to the eutrophic Chesapeake Bay. This study compared a new subsurface applicator for poultry litter with conventional surface application and tillage incorporation of litter on a Coastal Plain soil under no-till management. Monolith lysimeters (61 cm by 61 cm by 61 cm) were collected immediately after litter application and subjected to rainfall simulation (61 mm h(-1) 1 h) 15 and 42 d later. In the first rainfall event, subsurface application of litter significantly lowered total P losses in runoff (1.90 kg ha(-1)) compared with surface application (4.78 kg ha(-1)). Losses of P with subsurface application were not significantly different from disked litter or an unamended control. By the second event, total P losses did not differ significantly between surface and subsurface litter treatments but were at least twofold greater than losses from the disked and control treatments. A rising water table in the second event likely mobilized dissolved forms of P in subsurface-applied litter to the soil surface, enriching runoff water with P. Across both events, subsurface application of litter did not significantly decrease cumulative losses of P relative to surface-applied litter, whereas disking the litter into the soil did. Results confirm the short-term reduction of runoff P losses with subsurface litter application observed elsewhere but highlight the modifying effect of soil hydrology on this technology's ability to minimize P loss in runoff.