Jasmeet Lamba

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.

Surface Transport of Nutrients from Surface-Broadcast and Subsurface-Banded Broiler Litter

Nutrient buildup, mainly phosphorus (P), and loss from fields fertilized with poultry (broiler) litter contribute to eutrophication of surface waters. In the U.S., broiler litter is typically surface-applied, but recently, to reduce surface transport of P and other nutrients, subsurface-banding of broiler litter has been promoted as a new manure application method. The objective of this study was to evaluate differences in nutrient transport between subsurface-banded and surface-applied broiler litter in a tall fescue pasture. Treatments were surface-applied and subsurface-banded broiler litter at a rate of 5.0 Mg ha-1, and no application of litter (control). Results showed that runoff concentrations and loadings of total P (TP), ortho-P (PO4-P), nitrate-nitrogen (NO3-N), and ammonium-N (NH4-N) were reduced by 83%, 88%, 74%, and 80%, respectively, for the subsurface-banded litter as compared to the surface-applied litter. Concentrations and loadings of all nutrients in surface runoff from the subsurface-banded treatment were similar to those from the control. This study showed that subsurface banding of broiler litter can substantially reduce nutrient losses in surface runoff. However, since less than 10% of the simulated rainfall contributed to surface runoff (more than 90% rainfall infiltrated), subsurface transport of nutrients from surface-applied and subsurface-banded litter needs to be studied in field research.

A Method for Installing Zero-Tension Pan and Wick Lysimeters in Soil

Zero-tension pan lysimeters and passive capillary fiberglass wick lysimeters are useful in determining water quality and volumetric aspects of subsurface water flow. A crucial aspect of installing pan and wick lysimeters beneath undisturbed soil is preventing cave-in of the tunnels in the soil that house the lysimeters. Equipment and a method were developed for installing zero-tension pan lysimeters and wick lysimeters in field plots, and this new method provides substantial structural strength of the tunnels. The dimensions of the upper horizontal surface of the pan lysimeters that were used were 0.280 × 0.430 m, and those of the wick lysimeters were 0.300 × 0.300 m, but the equipment can be modified to accommodate other lysimeter dimensions. The main equipment components are steel boxes which are pushed horizontally from a pit, into soil beneath the field plot, and a guiding frame that pushes the boxes using a hydraulic cylinder powered by a tractor hydraulic system. Following installation of each pair of steel boxes in soil, the soil from within the boxes was excavated, the upper lid of the lysimeter box was removed, and a lysimeter was placed within the box with the upper surface of the lysimeter directly contacting the soil. The equipment and method were used in the sandy loam soil of tall fescue (Fescue arundinacea Schreb.) pasture plots and the equipment and method worked well. The method also helps assure accurate lysimeter depth and levelness. The lysimeters were installed at a depth of 0.500 m beneath the soil surface. Costs and labor requirements for developing the equipment and using the method are presented. There was no evidence that the installation method altered the soil bulk density or the water flow paths above the lysimeters.

Probabilistic assessment of projected climatological drought characteristics over the Southeast USA

The study makes a probabilistic assessment of drought risks due to climate change over the southeast USA based on 15 Global Circulation Model (GCM) simulations and two emission scenarios. The effects of climate change on drought characteristics such as drought intensity, frequency, areal extent, and duration are investigated using the seasonal and continuous standard precipitation index (SPI) and the standard evapotranspiration index (SPEI). The GCM data are divided into four time periods namely Historical (1961–1990), Near (2010–2039), Mid (2040–2069), and Late (2070–2099), and significant differences between historical and future time periods are quantified using the mapping model agreement technique. Further, the kernel density estimation approach is used to derive a novel probability-based severity-area-frequency (PBS) curve for the study domain. Analysis suggests that future increases in temperature and evapotranspiration will outstrip increases in precipitation and significantly affect future droughts over the study domain. Seasonal drought analysis suggest that the summer season will be impacted the most based on SPI and SPEI. Projections based on SPI follow precipitation patterns and fewer GCMs agree on SPI and the direction of change compared to the SPEI. Long-term and extreme drought events are projected to be affected more than short-term and moderate ones. Based on an analysis of PBS curves, especially based on SPEI, droughts are projected to become more severe in the future. The development of PBS curves is a novel feature in this study and will provide policymakers with important tools for analyzing future drought risks, vulnerabilities and help build drought resilience. The PBS curves can be replicated for studies around the world for drought assessment under climate change.

Identifying Sources of Suspended Sediment using Radionuclides in an Agricultural Watershed in South Central Wisconsin

Phosphorus (P) is an essential nutrient for plant and livestock growth. However, P loss in agricultural runoff can increase the frequency of toxic algal blooms and fish kills in receiving waters. Agricultural P loss occurs in both dissolved and particulate (sediment bound) forms. Suspended sediments play an important role in the transport of particulate P from fields to surface waters. Implementing appropriate management practices to control soil erosion and subsequent sediment delivery requires quantification of the relative contribution of sediment sources (e.g. stream bed, stream bank and upland areas under various land uses). Sediment fingerprinting using atmospheric fallout radionuclides can be used to apportion sediment sources, and thus provide valuable guidance for management decisions. Due to their long half-lives, the fallout radionuclides 137Cs and unsupported 210Pb are ideally suited for evaluating sediment transport processes that occur over long time scales. This fingerprinting method is independent of soil and rock type and can be used to differentiate between surficial and channel sources of suspended sediments. The objective of this study was to identify sources of in-stream suspended sediment in an agricultural watershed using the atmospheric fallout radionuclides 137Cs and 210Pb. The study was conducted in the non-glaciated region of southwestern Wisconsin in the Sugar Pecatonica River Basin, which is part of the Upper Mississippi River Basin. The watershed is approximately 5000 ha in size and contains primarily agriculture, forest, and grass land cover. The average watershed slope is about 11% with silt loam soils. Fieldwork included collection of both source materials (upland, streambed, and stream bank) and in-stream suspended sediments. In-stream suspended sediment samples were collected monthly for four months using passive time integrated in-stream tube samplers (Phillips et al., 2000). The samplers consist of a 10.2 cm diameter PVC tube with 0.4 cm diameter inlet and outlet, and collect a sample that is statistically representative of the grain size distribution in small streams. All source material samples were collected from the top 2.5 cm. Upland soil samples were collected from fields that represented various combinations of land use, soil type, and slope within the watershed. Upland samples were collected in a 20 m x 20 m grid with 5 m spacing and composited for analysis. Representative samples were also collected from the top 2.5cm of stream beds and eroding stream banks. All samples collected were stored at 40 °C and analyzed for organic matter content (percent volatile solids) and 137Cs and unsupported 210Pb. Radionuclide analysis was done through low background gamma counters. Over a four month period (mid-April through mid-August, 2010), results indicate that approximately two-thirds of in-stream suspended sediment originated from eroding stream banks and the remainder from upland areas. Within the upland categories (cultivated, pasture, woodland, grassland), cultivated lands followed by woodlands were significant contributors to in-stream sediments.