1a. Objectives (from AD-416)
1. Develop practices to enhance the beneficial use of manure nutrients and reduce offsite losses through management of the environmental fate and transport of organic carbon, nitrogen, and phosphorus derived from poultry, dairy, and beef cattle manures. 2. Develop integrated crop, soil, and dairy/beef/poultry manure management strategies to improve nutrient utilization and minimize leaching and runoff losses.
1b. Approach (from AD-416)
Real-time tools for rapid C, N, and P detection and multi-element analysis of manures, soils, and crops will be evaluated and adapted to develop precision nutrient management practices under changing soil microenvironment and weather conditions. Process knowledge affecting C, N, and P transformations and detection will be gained to establish databases and develop algorithms to assist in the management of bionutrient mineralization and availability in conservation cropping systems.
3. Progress Report
X-ray fluorescence spectroscopy was evaluated to determine phosphorus (P) and other minerals such as potassium in manure-amended field soils. Large field plots and different rates of manure phosphorus were established. Measurements of soil and plant conditions were made periodically during the early stages of corn growth and determine variability across the field and rate treatments. The study will be repeated to obtain year-to-year variations in crop growth, responses to climatic conditions, and differences in x-ray spectral results. In order to reduce soluble phosphorus present in excess in manure and field soils, water treatment residues from the Rockville Drinking Water Treatment facility were evaluated in switch grass field plots. Samples were collected, and analyzed for phosphorus and metal contents. The water treatment residues will be applied in the fall of 2011 and will be left to react with the soil in the various grass plots for the remainder of Year one. Real-time active sensors were compared with manual static sensors in field plots growing continuous corn treated with a range of fertilizer nitrogen (N) rates, or poultry litter applied on a P-based or an N-based management strategy. The comparisons are done at the early-vegetative through early-reproductive stages of development of corn to document total N uptake and grain yield and compare the effectiveness of the two types of sensors for assessing corn N stress. Cover crops have an important role in sequestering or harvesting residual nitrogen. Fertilizer depleted of the labeled nitrogen-15 is being used to directly compare the ability of rye, wheat and native weeds to recover residual labeled N applied to a preceding corn-silage crop. Soil and crop samples were collected in the early winter, early spring, and late spring and analyzed for labeled N to follow changes in soil nitrate-N and the uptake of labeled N by the winter crops. This study will quantify the effectiveness of these crop management strategies for capturing residual nitrate, thus reducing nitrate loss to ground water and the Chesapeake Bay. Carbon (C) can accumulate in soils through the carbon contained in roots and their resistance to breakdown. Preliminary results on the composition and degradability of roots showed large variations between plant species. After six weeks, the decomposition varied from 78% for alfalfa roots and 22% for fescue, and 42% for switchgrass. These differences may indicate the importance of plant species on the contribution of roots to carbon sequestration and turnover in soil. Wood and coal-like materials or biochars were also prepared from a large collection of forages and plant by-products using slow heating at 400, 500 and 600 C. Near- and mid-infrared spectral results and yield data are being compiled and statistically analyzed to prepare manuscripts and non-technical summaries.
1. Managing slurry manure based on its carbon-to-phosphorus composition. Determining the fertilizer value and optimal amount of manure to apply to a crop in phosphorus-based cropping systems requires accurate knowledge of manure composition, the phosphate content, and conversion rate of organic phosphorus forms to the soluble phosphate by microbes under the conditions existing at the site of storage before land application. ARS scientists demonstrated the linkage between organic-mineral phosphorus conversion to the manure carbon-to-phosphorus composition. As the ratio widened, the conversion of insoluble organic phosphorus to soluble phosphate increased and phosphate accumulated in the slurry regardless of how much phosphate is already present, with an upper limit not to exceed the solubility of insoluble minerals such as calcium phosphates. On-farm manure handling and storage conditions should be managed to minimize this conversion to soluble forms that are easily carried away in water, by adjusting the carbon content in slurries, that is, manure solids, to reduce the slurry's carbon-to-phosphorus ratio and lower risks of high levels of mobile and easily lost phosphate to runoff when these manures are land-applied.
2. Small lysimeters were developed to evaluate nitrogen management practices. Lysimeters or columns of minimally disturbed soils extracted from the field are valuable tools for comparing the effects of nitrogen management practices on water quality, which is an important issue in the Chesapeake Bay watershed. ARS researchers at Beltsville, Maryland, improved procedures for excavation, encasement, transportation, and field-testing of tension-drained lysimeters that were derived from large undisturbed soil cores. Field evaluation of eight intact-core lysimeters showed that drainage water commonly moves through soils though rapid-flow channels, such as worm holes of root channels, that by-pass much of the soil pore space. No-tillage lysimeters had higher infiltration rates and hydraulic conductivities than lysimeters receiving annual moldboard-plowing, which was attributed to more inter-connected large pores in no-till. It was concluded that the small intact-core lysimeters can reliably measure movement of soluble nutrients, such as nitrate, out of the crop root zone. The lysimeter data can thus provide comparisons of the effect of nitrogen management practices, like cover crops or tillage or fertilizer timing, on nitrate losses to ground water.
Calderon, F.J., Reeves III, J.B., Collins, H.P., Eldor, P.A. 2011. Chemical differences in soil organic matter fractions determined by diffuse-reflectance mid-infrared spectroscopy. Soil Science Society of America Journal. 75(2)568-579.