Progress 10/01/00 to 09/30/05
Outputs
The objective of the project were to characterize the leaching losses of organically bound nutrients and carbon from agricultural fields with an emphasis on phosphorus (P), and assess the controls on leachate concentrations. Soil samples were taken spanning sites from low to extremely high available P concentrations in topsoils along a chronosequence of poultry and dairy manure applications. Phosphorus accumulation reached values of 2100 mg /kg by Mehlich-3 extraction and up to 8,000 mg total P /kg soil for long-term and high manure application; such values have not been reported from anywhere in New York State. The ability of the soils to retain additional P was low (adsorption maxima of 51-59 g P /kg) and equilibrium leachate concentrations were high (5.5-7.6 mg MRP /L). The ability to adsorb additional P significantly decreased above 1000-2000 g total soil P/kg soil and leachate P concentrations increased more rapidly above 5000 g /kg. With longer manure
applications, the proportion of organic P decreased from 90 to 2 percent of total dissolved P in leachate, while it decreased in soil only from 44 to 6 percent. Organic P leached more readily than inorganic P in fields with a short-term manure history. This difference disappeared in fields with a long-term history where leaching of inorganic P was more important than that of organic P. Organic P forms in soil extracts determined by P-31 NMR did not change with manure history, but sequential fractionation showed that the proportion of inorganic P pools in soils changed; the proportion of dilute acid-Pi increased from 10 to 62 percent with longer manure additions suggesting the formation of Ca-phosphates as the soil pH increased from 4.1 to 6.0-7.2. The precipitation of P as Ca-phosphates appeared to control P leaching upon high and long-term applications of manure dominated by poultry litter. However, P XANES studies showed only a weak formation of more crystalline and stable
Ca-phosphates. Therefore, P remains highly soluble despite the high pH. With a reduction or elimination of manure amendments to naturally acidic soils, the pH is likely to decrease thereby increasing the solubility of Ca-bonded P. Maintaining a high pH is therefore an important strategy to minimize P losses from such highly amended soils.
Impacts
With a better understanding of the forms of phosphorus which are lost by leaching and its relationship to the ability of the soil to retain phosphorus, we will be able to combat these losses and decrease eutrophication of aquifers. At the same time, we will be able to manage manure applications in a more efficient and economical way. The identified threshold above which accelerated phosphorus leaching can be expected will help in developing regulations for maximum manure application. The evidence for changes in phosphorus forms will inform about strategies to mitigate potentially larger P losses from highly manured soils after applications were to be stopped.
Publications
- Lehmann J, Lan Z, Hyland C, Sato S, Solomon D, and Ketterings Q. 2005. Long-term dynamics of phosphorus forms and retention in manure-amended soils. Environmental Science and Technology 39: 6672-6680.
- Sato S, Solomon D, Hyland C, Ketterings QM and Lehmann J. 2005. Phosphorus speciation in manure and manure-amended soils using XANES spectroscopy. Environmental Science and Technology 39: 7485-7491.
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Progress 01/01/04 to 12/31/04
Outputs
The objective of the project is to characterize the leaching losses of organically bound nutrients and carbon from agricultural fields. The approach includes the analysis of leachate from field experiments and laboratory incubations as well as leaching studies. Soil samples were taken spanning sites from low to extremely high available P concentrations in topsoils. In fact, P accumulation reached values of 2100 mg /kg by Mehlich-3 extraction and over 10,000 mg /kg total P; such values have not been reported from anywhere in New York State. The ability of the soils to retain additional P was low (51-59 g P /kg) and equilibrium leachate concentrations were high (5.5-7.6 mg P /L). The ability to adsorb additional P significantly decreased above 1000-2000 g /kg of total soil P and leachate P concentrations over-proportionally increased above 5000 g /kg. With longer manure applications, the proportion of organic P decreased from 90 percent to 2 percent of total dissolved P
in leachate, while it decreased in soil only from 44 percent to 6 percent. Organic P leached more readily than inorganic P in fields with a short-term manure history. This difference disappeared in fields with a long-term history where leaching of inorganic P was more important than that of organic P. Organic P forms in soil extracts determined by P-31 NMR did not change with manure history, but sequential fractionation showed that the proportion of inorganic P pools in soils changed; the proportion of dilute acid-Pi increased from 10 percent to 62 percent with longer manure additions suggesting the formation of Ca-phosphates as the soil pH increased from 4.1 to 6.0-7.2. The precipitation of P as Ca-phosphates appeared to control P leaching upon high and long-term applications of manure dominated by poultry litter. However, P XANES studies showed no formation of more crystalline and stable Ca-phosphates. Therefore, P remains highly soluble despite the high pH.
Impacts
With a better understanding of the forms of phosphorus which are lost by leaching and its relationship to the ability of the soil to retain phosphorus, we will be able to combat these losses and decrease eutrophication of aquifers. At the same time, we will be able to manage manure applications in a more efficient and economical way.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
The objective of the project is to characterize the leaching losses of organically bound nutrients and carbon from agricultural fields. The approach includes the analysis of leachate from field experiments and laboratory incubations as well as leaching studies. Soil samples were taken spanning sites from low to extremely high available P concentrations in topsoils. In fact, P accumulation reached values of 2100 mg kg-1 by Mehlich-3 extraction and over 10,000 mg kg-1 total P; such values have not been reported from anywhere in New York State. Despite the continuously large manure applications, available P concentrations in soil showing these extremely high P concentrations have not increased over the past 17 years. The potential of the topsoils to sequester added manure P may have been exceeded and excess P may have been leached down in the soil profile. Consequently, soil solution concentrations of total P in saturated soil were high while adsorption was low. The
studied topsoils classified as having high manure loadings apparently do not have the ability to retain appreciable amounts of inorganic P. With higher total P, available and inorganic P increased, while organic P contributed to a lesser extent to the P build-up. The greatest increase was noted for the Ca-bonded P which may control P retention and release. Further studies will highlight the importance of Ca-P forms and how these forms of P interact with other P pools in soil. We will evaluate the use of P-31 NMR and P XANES to study the changes of P in soils that receive such extremely high manure loadings.
Impacts
With a better understanding of the forms of phosphorus which are lost by leaching and its relationship to the ability of the soil to retain phosphorus, we will be able to combat these losses and decrease eutrophication of aquifers. At the same time, we will be able to manage manure applications in a more efficient and economical way.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
The objective of the project is to characterize the leaching losses of organically bound nutrients and carbon from agricultural fields. The approach includes the analysis of leachate from field experiments and laboratory incubations as well as leaching studies. In the reporting period, field sites were identified and water has been collected from tile drainage of corn fields which had previously received manure additions. We are working on experimental sites at Cornell's Willsboro farm investigating the effect of application time and soil type on phosphorus losses by leaching. Preliminary data indicate that P losses in drainage increased dramatically within the first three years of continuous manure applications. Losses were highest in early spring and early fall with almost twice the P concentrations in clayey than sandy soils. Surveys on farms indicated a build-up of available P after a few years of continuous manure applications, which reached values of 2100 mg
kg-1 (Mehlich-3 extraction) after 20 years. These results will be linked to leaching studies from lysimeters and detailed organic analyses to understand the origin and pathways of P leaching from contaminated sites.
Impacts
With a better understanding of the forms of organic nutrients which are lost by leaching, we will be able to combat these losses and decrease eutrophication of aquifers. At the same time, we will be able to manage manure applications more efficiently and economically.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
The objective of the project is to characterize the leaching losses of organically bound nutrients and carbon from agricultural fields. The approach includes the analysis of leachate from field experiments and laboratory incubations as well as leaching studies. In the reporting period, field sites were identified and water has been collected from tile drainage of corn fields which had previously received manure additions. Tile drainages started to yield leachate only in November and water collections are in progress. In a laboratory experiment, manure from cattle which were predominantly fed with corn was incubated with soil for 3 months at 30 and 70 degrees centigrade and 60% water holding capacity. The cattle manure had a delta C-13 signal of -13.1, whereas the soil showed a value of -24.7. We expect to be able to distinguish between the carbon derived from the manure and the soil. Half of the incubated soils were subjected to gamma-irradiation to prevent microbial
activity. In addition to the incubations with the manure, charcoal and inorganic fertilizer applications were included as factors. Batch experiments will be conducted on the incubated materials to quantify the desorption and adsorption of dissolved organic nutrients and carbon as well as inorganic nutrients. These results will be linked to leaching studies from lysimeters and tile drainage. Preliminary results indicate a significant interaction of dissolved organic carbon derived from manure, soil surfaces and retention of inorganic nutrients. Possibly organic amendments may help in retaining nutrients below the depth where the manure was applied and at which dissolved organic carbon is adsorbed.
Impacts
With a better understanding of the forms of organic nutrients which are lost by leaching, we will be able to combat these losses and decrease eutrophication of aquifers. At the same time, we will be able to manage manure applications more efficiently and economically.
Publications
- No publications reported this period
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