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:
Progress was made on both project objectives and their subobjectives addressing Problem Statements 1B and C of National Program 214, Component 1 (management, enhancement and utilization of manure nutrients and resources). Long-term soil and nutrient management practices can have lasting effects on the geographic distribution of soil microorganisms, function, and those of non-mobile nutrients such as phosphorus in large fields. The non-random redistribution may influence the rate of turnover of soil nutrients between their inorganic and organic forms and the efficiency at which crops utilize them. The variability observed in the field is also introduced during land applications of animal manure and composts that are themselves variable in nutrient composition. We conducted a field study of land application of dairy manure in a large field planted to corn and determine the distribution of microbial biomass and those of selected metabolic enzymes present in the soil, based on a grid of precisely known geographic coordinates. A high variability existed, and high microbial mass and enzymatic activities in specific locations reflected a localized high rate of nutrient turnover. They were associated with the differences in the microbial properties involved in the production of organic phosphorus-degrading enzymes. However, conventional soil testing procedures do not adequately measure the accumulation or disappearance of these organic P forms. In addition, the large spatial variability noted above highlights the need to improve current soil testing methods for estimating soil biochemical or microbial properties, and recommendations of crop nutrient requirements that are currently based on measurements of a few representative samples collected from selected locations in the field. Surface applied poultry litter can lose 25-50% of its ammonia nitrogen through volatilization. Analysis of wind tunnel ammonia-trap samples was completed from field studies that compared poultry litter application techniques for conserving ammonia. These data are being statistically summarized and interpreted in preparation for publication in refereed journals. Cover crops have an important role in conserving residual nitrogen. Isotope labeled fertilizer was used to directly compare the ability of rye, wheat, and native weeds to recover residual N applied to a preceding corn-silage crop. Soil and crop samples were collected in the early winter, early spring, and late spring and are being analyzed for labeled N to follow changes in soil nitrate and the uptake of labeled N by the winter crops. This study will quantify the effectiveness of cover crop management strategies for capturing residual nitrate, thus reducing nitrate loss to ground water and the Chesapeake Bay.
1. Large within-season fluctuations in soil phosphorus availability. Seasonal and year-to-year changes in available soil phosphorus have frequently been observed and are a source of uncertainty in making fertilizer recommendations in crop production. This is particularly true when soil phosphorus levels are elevated following repeated applications of animal manure to supply nitrogen to crops. Thus, phosphorus applications are an important factor causing these fluctuations, along with unpredictable weather conditions during the pre-season and the entire growing season. ARS scientists at Beltsville and Bushland found levels of soluble phosphorus, such as forms soluble in rainwater, fluctuated significantly in fertilizer-amended plots during two growing seasons of grain sorghum. Manure amended plots also showed large seasonal variations in soil extractable phosphorus, but there was a delayed release of extractable phosphorus that extended well into the growing season. In contrast, the fluctuations in extractable soil phosphorus in control plots that received no additional phosphorus were not significant except for organic phosphorus forms. A significant dependence of soluble phosphorus on soil acidity and calcium levels suggested that precipitation and dissolution processes contributed to the observed seasonal phosphorus fluctuations. Fluctuations in both inorganic and organic phosphorus forms were two to four times greater than those observed in the crops. These findings highlight the importance of the contributions of the latter organic phosphorus forms in accounting for seasonal soluble phosphorus changes and the offsite discharge risks they present to readjust current mitigation strategies and practices to reduce the loss of phosphorus from agricultural fields.
2. Adapting X-ray fluorescence spectroscopy for managing soil nutrients. Managing declining nutrient use efficiency in crop production has been a global priority to maintain high agricultural productivity with non-renewable nutrient resources such as phosphorus. Rapid testing methods can increase the number of repeated measurements of soil nutrients and improve the accuracy of estimating the rate of phosphorus needed for optimal crop growth and yield. ARS scientists and China Agricultural University researchers observed that soil phosphorus was highly variable along the length of the fields and across the entire area of all seven adjacent fields after a decade of continuous cultivation. A relationship between phosphorus measured by a rapid x-ray fluorescence technique and plant-available phosphorus forms allowed a description of their geographic distribution based on the x-ray fluorescence technique. Distinct management zones were identified for more precise placement of additional phosphorus needed for optimal crop growth. The findings documented the direct element-specific analysis by x-ray fluorescence and its high sample throughput make the technology an important component of a new nutrient sensing approach. The adoption of the technology will allow farmers to sustainably manage phosphorus, and other crop nutrients such as potassium, calcium, or chloride in production fields, based on their location-specific variations in the soil. The precision management approach will reduce adverse effects of unequal nutrient distribution on plant productivity or potential loss of nutrient excesses from a field.
3. Injecting liquid manures reduces ammonia losses, but increases other gaseous N losses. Incorporation of liquid manure is often recommended to reduce ammonia losses, to reduce odor, and to reduce nutrient losses in runoff water. However, incorporation with tillage is not compatible with high-residue conservation practices, such as notill production, and is not possible with pasture or perennial forages. Manure injection technologies allow incorporation with limited disruption of the soil surface or plant residue cover. This critical review and analysis found many publications which show that injection of liquid manures can reduce ammonia N emissions by 40-90%, compared to surface application. However, injection can create anaerobic soil conditions that favor denitrification leading to other gaseous N losses. Research measuring denitrification N losses showed that up to half of the N that is conserved by reducing ammonia emissions can later be lost as N2 gas (a benign gas) or as nitrous oxide (a greenhouse gas). Improved crop utilization of the N conserved by reducing ammonia emissions is the most common observation following injection, but this benefit can be minimal, which is consistent with greater denitrification losses. We conclude that further research is needed to better understand the N dynamics of injected manures. Accruing a better understanding of these N dynamics will provide scientists, nutrient managers, and policy makers with improved estimates of the effects of manure injection on the fate and transport of manure N.
4. Near- and mid-infrared analysis of biochars and biofuel feedstocks. There is increased interest in biochars made from agricultural by-products to store carbon in soil and improve its quality. Near-infrared spectroscopy used to determine the composition of numerous agricultural products is a potential method for determining biochars' composition. However, a high degree of baseline curvature and background noises existed upon detailed examination of biochars made from wheat straw. ARS results obtained with a scanning monochromator were far superior as it collects more spectral data at a lower resolution to improve their interpretation. Mid-infrared spectroscopy has also been used to rapidly determine fiber components and protein in forages and grains at reduced cost and increased speed. The same components are of interest for biofuel production. Practical and technical differences exist between the two sectors’ needs that will dictate how near-infrared and mid-infrared technologies are developed for the biofuel sector. Direct analysis of fiber components and possibly new spectroscopic methods will be needed. These issues will become increasingly important when feedstocks shift away from starch for producing ethanol or plant oil for producing biodiesel to cellulosics.Dao, T.H., Miao, Y., Zhang, F.S. 2011. X-ray fluorescence spectrometry-based approach to precision management of bioavailable phosphorus in soil environments. Journal of Soils and Sediments. 11(4):577-588.