Legacy phosphorus in calcareous soils effects of long term poultry litter application on phosphorus distribution in texas blackland vertisol
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Full proceedings available at: http://www.extension.org/72864 Livestock manures, including poultry litter, are often applied to soil as crop fertilizer or as a disposal mechanism near livestock housing. Manures can improve soil quality and fertility; however, over-application can result in negative environmental consequences, such as eutrophication of surface waters following runoff of soluble or particulate-associate phosphorus (P). In soil, P exists in many forms (inorganic/organic, labile/stable) and the fate of manure P is highly dependent upon soil properties, including soil texture and microbial activity. The Houston Black series is a calcareous (~17% calcium carbonate), high-clay soil that occupies roughly 12.6 million acres in east-central Texas. These Blackland vertizols are agronomically important for the production of cotton, corn, hay, and other crops, but their high calcium and clay content could lead to accumulation of P in forms that are not readily available for plant utilization. Accumulated P could serve as a source of legacy P if mineralized or otherwise transformed in situ or transported with soil particles in runoff.
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Legacy phosphorus in calcareous soils effects of long term poultry litter application on phosphorus distribution in texas blackland vertisol
- 2. Background Livestock production in concentrated animal feeding operations (CAFO) = Accumulation of excreted phosphorus (P) near animal housing In United States, ~ 1.03 x 107 Mg of poultry litter produced in 2007 Expensive to transport manure/litter from CAFO to croplands
- 3. Therefore… Manure is often repeatedly applied to a limited land base Increases both total and soluble P in soil and may influence P cycling and availability: worldwide rate of annual STP accumulation = 8 to 40 kg P/ha (Parham et al., 2002) Concern over phytate-loading of soils and issues with accumulated legacy P Creates environmental risk of eutrophication following runoff or leaching
- 4. Surface Water Livestock Manure Or Other Organic Residues Organic P Microbial biomass Organic matter Soluble organic P Sorbed P Clays Al, Fe Oxides Primary P Minerals Apatites Secondary P Minerals Ca, Fe, Al Phosphates Erosion and Runoff (Particulate-associated and Soluble P) Soluble Inorganic P (H2PO4 -, HPO4 2-) Immobilization Mineralization Precipitation-Dissolution Plant Uptake and Crop Removal Leaching Tile Flow to Surface Water Inorganic Fertilizers Plant Residues Inputs Outputs Internal cycling
- 5. Organic P in Soil Organic P (Po) content can vary widely 3 to 90% of total P Usually 10 to 40% Most common forms: % organic P inositol phosphates 10 to 80 phospholipids 0.5 to 7.0 nucleic acids 0.2 to 2.5 unidentified ~50 Require breakdown to inorganic P (Pi) by plant- or microbe-produced phosphohydrolases to be plant- available Associated with solid phase materials similar to Pi
- 6. General Project Overview “Riesel Watersheds”: Established as “Blacklands Experimental Watershed” near Riesel, Texas in 1930s by USDA to evaluate land management effects on soil erosion and floods. 2001: First litter application (turkey or broiler litter annually since then) (Harmel et al., 2004). Management: Native tallgrass prairie, improved pasture, various crops in rotation, grazing cow-calf herd.
- 7. 4-year corn-corn-wheat-fallow with conservation tillage 0, 4.5, 6.7, 9.0, 11.2, or 13.4 Mg ha-1 yr-1 litter (WW); incorporated with tillage 15 to 254 kg ha-1 yr-1 phosphorus Six Cultivated Fields 4.0 to 8.4 hectares
- 8. Native rangeland and improved pasture (grazed or hayed) 0, 6.7, or 13.4 Mg ha-1 yr-1 litter; surface applied 0 to 257 kg ha-1 year-1 phosphorus Four Pasture Fields 1.2 to 8.0 hectares
- 9. Soil Characteristics Houston Black Soil (fine, smectitic, thermic, Udic Haplusterts)…classic Vertisol State soil of Texas: ~ 12.6 million acres Typically 55% clay, 28% silt, 17% sand Highly expansive ~17% CaCO3 pH ~ 7.8
- 10. What we did…… Soil samples from 2002 to 2012 (15 cm, one core/0.4 ha). Sequential fractionation with H2O, NaHCO3, NaOH, and HCl. Extracts diluted and adjusted to pH 5.0 (Waldrip-Dail et al., 2009). Total extracted P (Pt) by ICP-OES, Pi by molybdenum blue method (Dick and Tabatabai, 1977; He and Honeycutt, 2005). Po=Pt – Pi Incubation with acid phosphomonoesterases type IV-S (potato) and type I (wheat germ) and nuclease P1 from Penicillium citrinum to identify forms of Po (He and Honeycutt, 2001). • Monoester-like, Phytate-like, DNA-like • Non-hydrolyzable Po
- 11. Objective Evaluate effects of long-term (10 years) poultry litter application on total extractable soil P, Pi, and Po in watershed-scale cultivated and pasture lands on calcareous, high-clay soil. Do phytate and metal-P complexes accumulate in soils fertilized with poultry litter? What is the effect of litter application rate? How do effects of litter application differ between cropland and pasture?
- 12. H2O 0.5 M NaHCO3 0.1 M NaOH 1.0 M HCl soluble or sorbed on crystalline surfaces associated with Al/Fe oxides or carbonates associated with Ca/Mg Soil Residue Residue Residue Residue NaHCO3-P H2O-P NaOH-P HCl-P Labile-P Incubation with acid phosphatases and nuclease-P1
- 13. H2O Organic C Total N Total P NO3 --N NH4 +-N ----%---- -------------% DM------------- ----------mg kg-1----------- 10-year Average (SD) 26 (12) 43 (8) 3.5 (0.7) 2.4 (1.0) 483 (368) 3772 (1424) Selected Properties of Poultry Litter Litter (manure + bedding) and/or inorganic fertilizer applied to reach a target N rate of 170 kg ha-1 for corn Applied using “real world” practices: desired rate met according to truck speed, gear, and rear gate settings
- 14. 0 500 1000 1500 Totalextractable P(mgkg-1) Control, cultivated 0 500 1000 1500 6.7 Mg ha-1 litter, cultivated 0 500 1000 1500 2002 2004 2006 2008 2010 2012 13.4 Mg ha-1 litter, cultivated 0 500 1000 1500 Control, ungrazed rangeland 0 500 1000 1500 6.7 Mg ha-1 litter, pasture 0 500 1000 1500 2002 2004 2006 2008 2010 2012 H2O NaHCO3 NaOH HCl 13.4 Mg ha-1 litter, pasture Total Extractable Phosphorus 233% 262 mg/kg 640 mg/kg
- 15. 0 500 1000 1500 Totalextractable P(mgkg-1) Control, cultivated 0 500 1000 1500 6.7 Mg ha-1 litter, cultivated 0 500 1000 1500 2002 2004 2006 2008 2010 2012 13.4 Mg ha-1 litter, cultivated 0 500 1000 1500 Control, ungrazed rangeland 0 500 1000 1500 6.7 Mg ha-1 litter, pasture 0 500 1000 1500 2002 2004 2006 2008 2010 2012 H2O NaHCO3 NaOH HCl 13.4 Mg ha-1 litter, pasture Total Extractable Phosphorus
- 16. Changes in Soil Test Phosphorus (2000 to 2012) 0 50 100 150 200 Mehlich-3P(mg/kg) Land use type and litter application rate 2000 2012 -1.0 1.3 4.7 10.9 PastureCultivated 0.3 5.6 11.5 9.9 12.7 13.2 Average annual change (mg kg-1) Mehlich-3 data provided by Daren Harmel, USDA-ARS, Temple, TX. East Texas P threshold
- 17. Organic P Microbial biomass Organic matter Soluble organic P Sorbed P Clays Al, Fe Oxides Primary P Minerals Apatites Secondary P Minerals Ca, Fe, Al Phosphates Soluble Inorganic P (H2PO4 -, HPO4 2-) Phosphorus Forms Extracted with Mehlich-3 Source: Mabry et al., 2012, SSAJ, 177:31
- 18. Extracted P vs. Mehlich-3 STP in 2012 0 600 1200 1800 Phosphorus(mgkg-1) H2O-Pt NaHCO3-Pt NaOH-Pt HCl-Pt M3P
- 19. 0 50 100H2O-P(mgkg-1) Cultivated Pasture 0 250 500 NaHCO3-P(mgkg-1) Litter rate (Mg ha-1) Inorganic Monoester-like DNA-like Phytate-like Non-hydrolyzable organic Cultivated Pasture Composition of Labile Phosphorus in 2012
- 20. 0 100 200NaOH-P(mgkg-1) Cultivated Pasture 0 400 800 1200 HCl-P(mgkg-1) Litter rate (Mg ha-1) Inorganic Monoester-like DNA-like Phytate-like Non-hydrolyzable organic Cultivated Pasture Composition of More Stable Phosphorus in 2012 217% increase
- 21. Control 6.7 Mg ha-1 litter 13.4 Mg ha-1 litter Labile-P ---------------------------P (mg kg-1)----------------------------- Inorganic 42c 152b 272a Monoester 28c 94b 182a DNA 21c 53bc 90ab Phytate 18c 43bc 80ab Non-hydrolyzable 16 ns ns HCl-P Inorganic 16c 28b 33ab Non-hydrolyzable 312c 655b 989a Changes in P Distribution in Cultivated Fields
- 22. Pasture Watersheds Native rangeland Grazed pasture 6.7 Mg ha-1 litter 13.4 Mg ha-1 litter Labile-P ------------------------------P (mg kg-1)------------------------------ Inorganic 124ab 56c 63c 165a Monoester 51b 38c 55b 128a DNA 100a 20c 25c 55bc Phytate 89a 19c 16c 41bc Non-hydrolyzable 3b ns ns 15a HCl-P Inorganic 22cd 19d 18d 39ab Phytate - 0.4b - 14a Non-hydrolyzable 253bc 173c 339b 588a Changes in P Distribution in Pasture
Notas del editor
- Good afternoon I’m happy to be here today. As we all know, animal agriculture can pose a threat to environmental quality when rogue nutrients in manure, such as phosphorus and nitrogen, escape into lakes, streams and oceans, groundwater, the atmosphere, and soil Recently there has been a growing interest in the impact of legacy phosphorus. Legacy phosphorus is that which has accumulated in soil or sediment and has potential to be remobilized or recycled within a watershed over the course of years, decades, or even centuries. Essentially acting as a continual source of P, The tendency for phosphorus to bind to soil minerals means that soils with high clay and calcium contents can hold a good deal of the P that is applied with manure. Which can impact both soil fertility and environmental quality. So, today I’m going to be talking to you about a study we conducted to determine the effects of 10 years of poultry litter application on phosphorus forms in calcareous Black clay soil. I need to acknowledge my co-authors, Paulo Pagliari from the University of Minnesota, Zhongqi He with ARS in New Orleans, Louisiana, Daren Harmel with ARS in Temple, TX, Andy Cole with ARS in Bushland, TX, and Mingchu Zhang with the University of Alaska at Fairbanks
- Production of livestock and livestock product, such as meat, milk and eggs, in concentrated animal feeding operations…aka CAFO leads to a lot of manure that accumulates near barns and other animal housing. In 2007, there was more than 100 million tons of poultry litter produced in the US Poultry litter is recognized as a good source of nutrients and organic matter for crops and forages, but it is often not possible to get the material where it is needed. Litter is heavy, wet, and bulky. It usually it is just not practical or cost-effective to transport manure far from CAFO to crop or pasture land to improve soil fertility.
- So, litter is often over- and repeatedly applied to available land closest to the CAFO. The effects of manure and litter on total and soluble inorganic P in soils have been studied for many, many years. Manure can directly influence P cycling and availability in soil by stimulating microbial growth and activity and altering chemical and physical properties of soil, things like redox status, pH, and concentrations of ions competing for sorption sites. These changes can be related to soil P availability because of their influence on degree of P saturation, sorption potential, and sorption strength. There is a great deal of concern within the community on P accumulation in fertilized fields. Phosphorus can complex with minerals and organic matter to form relatively insoluble phospho-metal compounds. Some forms of phosphorus, such as the inositol phosphates, have many free phosphate groups and may accumulate to a greater extent than other P forms. Phytate is an inositol phosphate that has 6 free P groups which binds with calcium, aluminum and iron. The digestive systems of monogastric animals, such as chickens, turkeys and swine, are lacking in phytase, the enzyme that breaks down phytate. This means that poultry litter is often enriched with excreted, undigested phytate. All of this creates environmental risk of soluble or particulate-associated P being transported in runoff, leachate, or dust. Transport of rouge P can create eutrophic conditions in aqueous systems
- I’d like to quickly go over the soil phosphorus cycle just so that everyone is on the same page. Inputs of P can come from inorganic fertilizers, plant and animal residues, livestock manure, and other organic materials. In soil, the portion of P that is largely available for crop utilization is soluble, inorganic P. But in addition to inorganic P, there is also organic P in microbial biomass, soil organic matter, and in soluble forms. Organic P is converted to inorganic P by mineralization, and soluble inorganic P can be recycled or immobilized as microbial or plant biomass We also have P that is loosely associated with Aluminum and Iron oxides Secondary P minerals are more stable calcium, iron, and aluminum phosphates And lastly we have the primary P minerals, such as apatites, that slowly dissolve into the soluble inorganic P pool. All of these phosphorus pools are in equilibrium to maintain stable concentrations of soluble inorganic P
- While a good deal of work has been conducted on total and STP after manure application, a lot less work has been conducted on organic phosphorus. Soil organic P content can vary widely: reports have found Po contents ranging from 3 to 90% of total P, but it is usually more along the lines of 10 to 40% in the US. Some of the most common forms of phosphorus are the inositol phosphates, phospholipids, and nucleic acids. Around 50% of total organic P may be unidentified.
- The study site was the Riesel Watersheds in east-central Texas. The site was established by USDA in the late 1930s to evaluate land management effects on soil erosion and floods. Comprehensive, long-term data on soil properties and crop yield have been collected for over 70 years and it is currently one of the most comprehensive studies of its type. 2001 the fields saw the first round of poultry litter application. It has been applied annually since then. The litter was from turkey or broiler houses and contained bedding, manure, dropped feed, feathers, and whatever else was there at house clean-out Management
- One thing that is unique about this research site is large “watershed scale” plots of both cropland and pastureland. There were six cultivated fields that were in a four-year corn-corn-wheat-fallow rotation. Towards the end of the study, in 2011, hay and oats were planted. Conservation tillage was used and litter was incorporated with tillage. The litter application rates were 0, none but received inorganic fertilizer, 4.5, 6.7, 9.0, 11.2, and 13.4 Mg litter per ha on a wet-weight or as-applied basis. Manure was tilled in to a depth of 7 cm with a disk or field cultivator. The different treatments provided an average of 15 to 254 kg of phosphorus per hectare per year Slope was 1.1 to 3.2%
- There were four pasture fields, one was native rangeland which was predominantly Little Bluestem, Big Bluestem, Switchgrass, and Indiangrass…….. The rangeland didn’t receive any litter and can be somewhat considered a “control” Improved pasture (Bermudagrass or Kleingrass) which was either grazed by a cow-calf herd (~ 8mo/year) or hayed. Two of the improved pastures had litter surface-applied at 6.7 and 13.4 Mg litter per hectare annually. No supplemental fertilizer Litter provided 0 to 257 kg phosphorus per hectare each year
- Used extensively for production of cotton, sorghum, corn, and forage grasses. Highly expansive with moisture and prone to cracking when dry.
- Soil samples obtained from 2002 to 2012. They were collected to a depth of 15 cm in winter of each year at a frequency of about half a core per hectare. The cores were combined into one composite sample per field. Phosphorus extracted with a modified Hedley fractionation method…will go over that in a bit To characterize organic P the soil extracts (which were diluted and buffered to pH 5.0) were incubated with acid phosphatases and nuclease P1 The specificities of these enzymes are not entirely straightforward….some enzymes can hydrolyze more than one compound. So, we generalized the organic P as monoester-like, phytate-like, or DNA-like based on susceptibility to hydrolysis. Some Organic P was not broken down by the enzymes we used, and I’m going to call that non-hydrolyzable organic P…..considered organic P that is largely protected from mineralization
- Basically, I wanted to see if metal-phosphates accumulated after long-term PL application, what was the effect of litter application rate? How does it differ with land-use type?
- Sequential fractionation has been used to characterize phosphorus since Hedley made the procedure popular in 1982 …… It is a tedious, excruciatingly long process, but its cheap and doesn’t require any fancy equipment. It is often used by those of us who don’t have the money or skill for 31P-NMR Basically, the lability of P in a material is functionally characterized based on solubility in a series of extractants This method has been used to better understand the interactions between manure nutrients and soil and transformation of P following application to soil 1 g soil/25 ml extractant, 1 h for water, 16 h for others Quantify with a molybdate blue method Labile P is that extractable in water and sodium bicarbonate…usually about equivalent to STP NaOH P is considered associated with amorphous aluminum and iron oxides or carbonates HCl P is assumed to be Ca-phosphates All of these fractions contain both inorganic and organic phosphorus. To characterize the organic phosphorus we incubated the soil with an excess of phosphohydrolases
- The poultry litter was obtained from cleanout of turkey and broiler houses near the study site. The litter analyzed prior to application each year. The specific properties varied quite a bit from year to year…The 10 year average was 26% water, and it contained an average of 2.4% total phosphorus on a dry matter basis Management was consistent within each land-use type: included tillage, planting, harvest, application and incorporation of litter, supplemental inorganic N and P when needed, and herbicide and pesticide application
- Now, this is what we found… this figure shows the changes in total extractable phosphorus over time in cultivated and pasture fields and with different rates of poultry litter application. The different colored bars are the different P fractions, the yellow is the HCl P (Ca-associated), the second most prominent fraction the NaHCO3, which is considered labile. Third in line is the Al/Fe-associated NaOH-P, and lastly is the water-extractable P. Key findings: Cultivated fields that got 13.4 Mg/ha litter had 233% more extractable P than control in 2012. This is about 700 mg/kg-1 difference
- Most of the total extractable phosphorus was in the HCl fraction, indicating that it was sparingly soluble and comprised as much as 76% of the total extracted P. Probably caused by sorption to calcite surfaces and subsequent precipitation as a calcium phosphate. Some could have come directly from litter due to Ca and P supplementation in diets to ensure adequate bone structure and energy for metabolism. In previous studies, we have found that around 30 – 50% of the total extractable P in Poultry manure is HCl-P. In short, there was a big accumulation of P not readily available for plant uptake and that could serve as a source of legacy P Little change in NaHCO3 except with high rates of litter (79% greater in 13.4 Mg/ha than control)
- Okay, now this is the change in Mehlich 3-P from the beginning of the study (before fertilizer or litter) and after 10 years of litter. Initial STP concentrations were less than 25 mg/kg and increased to around 170 mg/kg in cultivated and 130 mg/kg in pasture. This corresponded to rates of change of 13 and 11 mg/kg STP for the two different land use-types with the highest rate of litter application. The P threshold for east Texas is currently 200 mg/kg M3P and Mehlich is the recommended extractant
- It is generally thought that the Mehlich 3 extract removes labile, or plant available P. This is a schematic representation of what forms of P are removed with Mehlich….it probably contains some organic P, some desorbed P from clays and Aluminum and iron oxides, and some dissolved metal phosphates 0.2 N acetic acid; 0.25 N NH 4NO 3; 0.015 NH 4F; 0.013 N HNO 3; 0.001 M EDTA Acid soils Similar to Bray on Highly calcareous soils ? Variety and stronger acids than Bray ? More buffered solution
- I was interested in exactly what portion of the total extractable P in soil was encompassed by the Mehlich-3 STP, and here we see that STP does a relatively good job at estimating labile P at low litter application rates, but not so good at higher rates.
- Litter application increased labile P in both pasture and cultivated fields. Note the 10-fold difference in scale on the y-axis between the two fractions. The biggest changes were more inorganic P and Non-hydrolyzable organic P. Similar results were observed in pastures Increase in labile Pi likely due to enhanced microbial activity to hydrolyze organic P and hogging of exchange sites by more complex P forms.
- This figure shows the same information for the more stable, mineral-associated P. Here also note a difference in the scale of the y-axes. Most of the P in the NaOH fraction was inorganic, but there was some monoester, phytate, and DNA-like P. However, its really hard to discern any sort of litter effect here. Now this was the most notable finding of the study. We saw that the fraction of Ca-associated, non-hydrolzable organic P shot up as much as 217% with litter rate. There was very little organic P that was hydrolyzable with our enzymes in that fraction. Indicates saturation of available P binding sites with organic P…implications of which are more free orthophosphate in solution and potential source of legacy P.
- And now for the numbers…. This table shows the changes in soil P forms in cultivated fields from 2002 to 2012. What I want to key you in on are the higher concentrations of inorganic and enzyme-hydrolyzable organic P with litter. Also the huge difference in HCl-extractable non-hydrolyzable organic P.
- This is the same thing in pasture soils, although the numbers are about half that of the cultivated plots. We saw increases in all forms of P in the labile fractions, and significantly more inorganic P and non-hydrolyzable organic P with lots of litter.
- So what does this mean in real life? Basically, STP concentrations were not very well related to total extractable P concentrations. Repeated application of poultry litter to calcareous Texas Black soil increased labile inorganic P concentrations by 7 to 34% Also saw increase in labile organic P that was more pronounced in cultivated fields than pasture The composition of the labile organic P was monoesternucleic acidphytatenon-hydrolyzable organic P About 68% of total extractable P was assumed Ca-associated and unavailable to plants in the short-term Most of that organic P was non-hydrolyzable and this fraction increase 217% with litter