Progress 08/01/04 to 12/31/11
Outputs
OUTPUTS: This project generated one book chapter, five peer-reviewed journal articles, a master's thesis, and 19 presentations given at scientific conferences. This project also generated 11 magazine articles, 37 presentations at landowner forums and field days, an extension bulletin, and two online presentations targeted to private forest owners, farmers, and natural resource management professionals. This project provided information on the implications of fertilization, herbicides, harvesting, and planting practices on ecosystem nutrient cycling and/or forest plantation performance. Research results also led to the addition of eucalyptus to a sulfometuron herbicide label, which will improve productivity and financial performance of eucalyptus plantations in Louisiana and Texas. PARTICIPANTS: Michael Blazier, (PI), Brad Osbon, Kenny Kidd, Lewis Gaston, W. Montgomery Alison, LSU AgCenter; Hal Liechty, Matthew Pelkki, Kenneth Formby, University of Arkansas Monticello; D. Andrew Scott, USDA Forest Service; and John Johnson, MeadWestvaco, LLC TARGET AUDIENCES: Forestry and soil scientists, natural resource management professionals, forest landowners, farmers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
A study of N fertilizer timing relative to mid-rotation thinning in the Western Gulf region, documented the importance of soil texture and timing relative to thinning when fertilizing mid-rotation loblolly pine plantations. Stands respond more to N fertilizer applied post-thinning, but on sandy soils it may be beneficial to postpone fertilization until at least one year after thinning. Phosphorus fertilizers can likely be applied to stands irrespective of the timing relative to thinning. A study of annual straw harvesting and fertilization of a loblolly pine plantation found that equipment traffic from annual straw harvesting compacts soil. Soil compaction and reductions in soil water holding capacity and microbial biomass and activity were greatest when annual straw harvesting was coupled with annual inorganic fertilizer applications. Annual fertilization with poultry litter in tandem with straw harvest did not appreciably alter soil water holding capacity, microbial biomass, and microbial activity. The conventional practice of replenishing soil nutrients lost in straw harvesting with inorganic fertilizer may exacerbate long-term soil nutrient turnover capacity, whereas applying poultry litter to plantations in which pine straw is harvested may better maintain long-term soil physical properties and nutrition. A separate study of poultry litter applied annually for four years to a loblolly pine agroforest found that annual fertilization with up to 10 Mg of litter per hectare per year did not raise phosphorus concentrations above runoff potential thresholds. Nitrogen and phosphorus leaching risks were increased. Although these agroforest systems had a relatively high capacity for nutrient use and retention litter should be applied less frequently than that in this study to reduce environmental risks. A study of seedling stock type, tillage, and planting density practices found that planting 746 containerized seedlings per hectare on a well-drained site had the highest land expectation value. Costs were relatively low while survival and yields of high-value forest products was high. Forest managers have a financially viable alternative for managing loblolly pine plantations on a well-drained soil than the conventional practice of planting approximately 1500 bareroot seedlings per hectare for such soils. Sulfometuron methyl sprayed over the top of eucalyptus trees at 91 mL per hectare controlled competing vegetation without damaging eucalyptus trees as effectively as a directed spray of glyphosate. This discovery prompted updates for sulfometuron labels, and use of this herbicide via aerial application has improved the efficacy and financial performance of eucalyptus plantation management relative to the conventional practice of glyphosate applied via backpack.
Publications
- Felicien, W., Gaston, L.A., Cooper, C., Hotard. S.L., Blazier, M.A. 2006. Effects of pine straw raking and fertilization on runoff water quality. ASA-CSSA-SSSA Annual Meeting Abstracts (CD-ROM). 6-10 November 2005. Salt Lake City, UT. ASA-CSSA-SSSA, Madison, WI.
- Liechty, H.O., Blazier, M.A., Wight, J.P., Gaston, L.A., Richardson, J.D., Ficklin, R.L. 2009. Assessment of repeated application of poultry litter on phosphorus and nitrogen dynamics in loblolly pine: Implications for water quality. Forest Ecology and Management 258:2294-2303.
- Blazier, M.A., Clason, T.R. 2006. Long-term growth responses to diverse chemical site preparation methods and loblolly pine seed type on a well-drained site in north Louisiana. Proceedings of the Southern Weed Science Society Annual Meeting. 24-26 January 2005. Charlotte, NC. 58:173.
- Blazier, M.A. 2007. Improve timber yields on poor soils with better decisions. Forests and People 57(3):34-35.
- Blazier, M.A., Scott, D.A., Coleman, R.A., Beine, R. 2007. Timing of mid-rotation silvicultural operations and soil texture impact soil nitrogen and carbon dynamics. ASA-CSSA-SSSA Annual Meeting Abstracts (CD-ROM). 4-8 November 2007. New Orleans, LA. ASA-CSSA-SSSA, Madison, WI.
- Blazier, M.A., Scott, D.A., Coleman, R.A., Beine, R. 2007. Nitrogen dynamics in response to mid-rotation vegetation suppression across a gradient of soil conditions in Louisiana. Proceedings of the Southern Weed Science Society Annual Meeting. 23-25 January 2006. San Antonio, TX. 59:240.
- Blazier, M.A., Gaston, L.A., Clason, T.R., Farrish, K.W., Oswald, B.P., Evans, H.A. 2008. Nutrient dynamics and tree growth of silvopastoral systems: impact of poultry litter. J. of Environ. Quality 37:1546-1558.
- Blazier, M.A., Hennessey, T.C. 2008. Seasonal soil and foliage nutrient dynamics of a juvenile loblolly pine plantation: impacts of fertilizer formulation and vegetation suppression. Forest Ecology and Management 255:3404-3415.
- Blazier, M.A. 2003. Fertilize to optimize your forests timber production potential. Forests and People. 53(4):14-15.
- Blazier, M.A. 2004. Heres how to optimize timber production through fertilization. Forestry Source 9:11.
- Blazier, M.A. 2005. Define your rotation length to improve forest management profitability. Forests and People 55(2):13.
- Blazier, M.A. 2005. Herbaceous vegetation suppression effects on the soil/plant/microbial system of a young loblolly pine plantation. Proceedings of the Southern Weed Science Society Annual Meeting. 26-28 January 2004. Memphis, TN. 57:168.
- Taylor, E.L., A.G. Holley, and M.A. Blazier. 2006. New planting strategies improve growth on the ground. Tree Farmer. 25(6):4, 34-37.
- Blazier, M.A., Clason, T.R. 2006. Establishment success and growth of southern pine plantations on water- and nutrient-poor soils. Louisiana Agriculture 49(2): 30.
- Blazier, M.A. 2006. Strategy matters: Creating a forest management plan for maximum profitability. Timberlines Winter: 4-6.
- Blazier, M.A., and D.A. Scott. 2006. Nitrogen distribution within the soil-plant-microbial system in response to pre-thinning fertilization treatments in Louisiana. Connor, K.F. (ed.). Proceedings of the 12th biennial southern silvicultural research conference. Memphis, TN, pp. 129-134.
- Blazier, M.A., Scott, D.A. 2006. Soil nitrogen dynamics in intensively managed mid-rotation loblolly pine plantations in Louisiana. ASA-CSSA-SSSA Annual Meeting Abstracts (CD-ROM). 6-10 November 2005. Salt Lake City, UT. ASA-CSSA-SSSA, Madison, WI.
- Blazier, M.A., Patterson, W.B., Hotard, S.L. 2008. Straw harvesting, fertilization, and fertilizer type alter soil microbiological and physical properties in a loblolly pine plantation in the mid-South USA. Biology and Fertility of Soils 45:145-153.
- Blazier, M.A., Dunn, M.A. 2008. Stock type, subsoiling, and density impact productivity and land value of a droughty site. Southern J. Applied Forestry 32(4):154-162.
- Blazier, M.A. 2008. Fertilizing southern pine plantations to improve growth and financial performance. LSU AgCenter Extension Bulletin 3058. 8 pp.
- Liechty, H.O., Blazier, M.A., Tappe, P.A., Pelkki, M.H. 2008. Potential impacts of corn-based ethanol production on coastal ecosystems. Proceedings of the Ecological Society of America Conference on the Ecological Dimensions of Biofuels. 10 March 2008. Washington, D.C. p 47.
- Holley, A.G., Taylor, E.L., Blazier, M.A. 2010. A comparison of woody biomass communition systems in the Western Gulf region. Forestry Source. 15(11): 12-14. Ellum, K.A. 2010. Pine straw raking and fertilizer source impacts on nitrogen mineralization, pine needle gas exchange, and tree water stress in a loblolly pine plantation. M.S. thesis. School of Forest Resources, University of Arkansas Monticello.
- Blazier, M.A., Holley, A.G., Taylor, E.L. 2010. Sell timber now or wait for better prices Forests and People 60(4): 26-27.
- Blazier, M.A., Taylor, E.L., Holley, A.G. 2010. Eucalyptus plantations: An emerging management option in the Southeast. Tree Farmer 29(4): 17-18.
- Blazier, M.A., Dunn, M.A., Clason, T.R. 2011. Pine pushes past poor soils. Interna. Forestry Industries 23:57-59.
- Blazier, M.A., Liechty, H.O., Gaston, L.A., Ellum, K. 2011. Poultry litter fertilization impacts on soil, plant, and water characteristics in loblolly pine (Pinus taeda L.) plantations and silvopastures in the mid-South USA. In: Principles, Application, and Assessment in Soil Science, pp. 44-73.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: This project generated outputs targeted at the scientific community in the form of a master's thesis, and one presentation given at the annual Soil Science Society of America meeting. This project also generated outputs targeted to private forest owners, farmers, and natural resource management professionals in the form of three magazine articles, a presentation at the Wood-based Biofuels Conference, presentations at eight landowner forums, a Forestry and Natural Resources webinar, two agroforestry field days, and a short-rotation woody crop field tour. Research results also led to addition of eucalyptus to a sulfometuron herbicide label, which will improve productivity and financial performance of eucalyptus plantations grown in Louisiana and Texas. PARTICIPANTS: Lewis Gaston, School of Plant, Environmental and Soil Science, LSU AgCenter; Hal Liechty, Keith Ellum, Mathew Pelkki, School of Forest Resources, University of Arkansas Monticello; Eric Taylor, Texas AgriLife, Texas A & M University; Gordon Holley, School of Forestry, Louisiana Tech University TARGET AUDIENCES: Forestry and soil scientists, natural resource management professionals, forest landowners, farmers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In a study of fertilizer source for a loblolly pine plantation in which straw was annually harvested, it was determined that inorganic fertilizer and poultry litter differ markedly in their influences on soil microbial, C, and N dynamics. Inorganic fertilizer reduced microbial biomass and activity and had a nominal effect on soil C and N. Poultry litter sustained microbial biomass and activity to levels comparable to unraked forest soil, increased soil C, and markedly increased soil N mineralization and nitrification. These results suggest that poultry litter is superior to inorganic fertilizer at sustaining microbial function in soil by replenishing C lost in straw harvest, and it increased N more readily than inorganic fertilizer when applied at an equal target N rate. In the same study, investigation of tree water regimes and photosynthetic capacity found that these tree characteristics were unaltered by annual straw raking and fertilization despite reductions in available water holding capacity and increases in soil nitrogen observed in previous studies at this site. In a study of establishing switchgrass under loblolly pine as part of an agroforestry system for producing biofuel, it was found that switchgrass was successfully established in alleys between loblolly pine at a range of pine ages and densities. The loblolly pine overstory apparently provided shading that aided establishment of switchgrass by reducing competing vegetation. Switchgrass biomass by the second year was comparable across all ages and pine densities, which suggests that there may be substantial management flexibility for establishing switchgrass within alleys of loblolly pine. Switchgrass in alleys was associated with greater labile C and microbial activity in soil relative to loblolly pine plantations with intensive suppression of understory, which suggests switchgrass in alleys promoted soil quality and sustainability. Alley cropping may thus be a viable system for growing switchgrass as an energy crop and providing environmental services. In a series of studies in eucalyptus tolerance to broad-spectrum herbicides, it was determined that sulfometuron methyl sprayed over the top of eucalyptus trees at 1.25 oz/acre controlled competing vegetation as effectively as directed spray of glyphosate without damaging eucalyptus trees. This discovery led to label updates for sulfometuron, and use of this herbicide via aerial application has improved the efficacy and financial performance of eucalyptus plantation management relative to the conventional practice of glyphosate applied via backpack.
Publications
- Holley, A.G., Taylor, E.L., Blazier, M.A. 2010. A comparison of woody biomass communition systems in the Western Gulf region. Forestry Source. 15(11): 12-14.
- Ellum, K.A. 2010. Pine straw raking and fertilizer source impacts on nitrogen mineralization, pine needle gas exchange, and tree water stress in a loblolly pine plantation. M.S. thesis. School of Forest Resources, University of Arkansas Monticello.
- Blazier, M.A., Taylor, E.L., Holley, A.G. 2010. Eucalyptus plantations: An emerging management option in the Southeast. Tree Farmer. 29(4): 17-18.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: This project generated outputs targeted at the scientific community in the form of one peer-reviewed scientific publication, two presentations given at the annual Soil Science Society of America meeting, and a presentation at the International Energy Association Task 31 meeting. This project also generated outputs targeted to non-industrial private forest owners and natural resource management professionals in the form of a magazine article, and presentations at the Western Gulf Forest Tree Improvement Cooperative, two research station field days, two forest landowner forums, and an extension agent and forester training workshop. These projects provide information on the implications of loblolly pine planting practices and biofuel harvesting on ecosystem nutrient cycling and/or plantation financial performance. PARTICIPANTS: PARTICIPANTS: Lewis Gaston, School of Plant, Environmental and Soil Science, LSU AgCenter; Hal Liechty, Keith Ellum, School of Forest Resources, University of Arkansas Monticello TARGET AUDIENCES: TARGET AUDIENCES: Forestry and soil scientists, natural resource management professionals, forest landowners PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In several studies conducted in the Western Gulf region, repeated application of broiler litter to loblolly pine forest soil significantly increased soil test P concentrations. When forest and pasture soils received similar rates of litter, the increase in soil test P was greater in forest than in pasture soil. However, soil exchangeable N, mineralizable N, nitrification, and soil water N were lower in forest than in pasture soil under identical litter application rates. These findings suggest that loblolly pine forests can be viable land use alternatives to pastures for broiler litter application, but application rate and frequency as well as inherent differences in P and N cycling are important considerations for environmentally sound nutrient management decisions. In a study of fertilizer source for a loblolly pine plantation in which straw was annually harvested, it was determined that inorganic fertilizer and broiler litter differ markedly in their influences on soil microbial, C, and N dynamics. Inorganic fertilizer reduced microbial biomass and activity and had a nominal effect on soil C and N. Broiler litter sustained microbial biomass and activity to levels comparable to unraked forest soil, increased soil C, and markedly increased soil N mineralization and nitrification. These results suggest that broiler litter is superior to inorganic fertilizer at sustaining microbial function in soil by replenishing C lost in straw harvest, and it increased N more readily than inorganic fertilizer when applied at an equal target N rate. In a study of establishing switchgrass under loblolly pine as part of an agroforestry system for producing biofuel, it was found that initial switchgrass survival and growth was greater under increasing levels of loblolly pine overstory. This finding suggests that loblolly pine shading provided competition control that fostered switchgrass establishment, which may be indicative of a reduced herbicide requirement for switchgrass establishment in an agroforestry system relative to conventional pastoral establishment procedures for switchgrass.
Publications
- Liechty, H.O., Blazier, M.A., Wight, J.P., Gaston, L.A., Richardson, J.D., Ficklin, R.L. 2009. Assessment of repeated application of poultry litter on phosphorus and nitrogen dynamics in loblolly pine: Implications for water quality. Forest Ecology and Management. 258:2294-2303.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: This project generated outputs targeted at the scientific community in the form of four peer-reviewed scientific publications and a presentation given at the Biennial Southern Silvicultural Research Conference. This project also generated outputs targeted to non-industrial private forest owners and natural resource management professionals in the form of a magazine article, an extension bulletin (published in print and online formats), and an online news release. These products provide information on the implications of loblolly pine fertilization and planting practices on ecosystem nutrient cycling and/or plantation financial performance. PARTICIPANTS: Michael Dunn, LSU AgCenter Department of Agricultural Economics and Agribusiness; Lewis Gaston, LSU AgCenter Department of Agronomy and Environmental Management; Steven Hotard, LSU AgCenter Calhoun Research Station; William Patterson, Louisiana Tech University School of Forestry; Kenneth Farrish, Brian Oswald, Stephen F. Austin State University Arthur Temple College of Forestry and Agriculture TARGET AUDIENCES: Forestry and soil scientists, natural resource management professionals, forest landowners PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
When a fertilizer ratio of nitrogen and phosphorus commonly applied to mid-rotation (ages 10-18) loblolly pine plantation was applied to 3- and 4-year-old plantation, foliage phosphorus:nitrogen and potassium:nitrogen ratios fell below optimum levels. These results suggest that juvenile loblolly pine plantations require fertilizer ratios different from commonly used mixtures. Applying less nitrogen per unit of phosphorus would likely better match nutrient demands of a juvenile loblolly pine plantation. In a study of annual straw harvesting and fertilization in a loblolly pine plantation, it was found that equipment traffic from annual straw harvesting compacts soil. It was also determined that soil compaction and reductions in soil water holding capacity and microbial biomass and activity were most pronounced when annual straw harvesting was coupled with annual fertilization with inorganic fertilizer. Annual fertilization with poultry litter when conducted in tandem with annual straw harvest did not appreciably alter soil water holding capacity, microbial biomass, and microbial activity. These findings may indicate that the conventional practice of replenishing soil nutrients lost in straw harvesting with inorganic fertilizer may actually exacerbate long-term soil nutrient turnover capacity, whereas applying poultry litter to plantations in which pine straw is routinely harvested may better maintain long-term soil physical properties and nutrition. In a separate study of poultry litter applied annually for four years to a loblolly pine agroforest, it was found that annual fertilization with up to 10 Mg of litter per hectare per year did not raise soil test phosphorus concentrations above runoff potential thresholds. However, nitrogen and phosphorus leaching risks were likely increased by annual fertilization with up to 10 Mg of litter per hectare per year. Thus, although these agroforest systems had a relatively high capacity for nutrient use and retention at this site, litter should be applied less frequently than in this study to reduce environmental risks. In a study of seedling stock type, tillage, and planting density practices, it was found that planting 746 containerized seedlings per hectare on a well-drained site had the highest land expectation value at highest achievable interest rate for this site of 10%. For landowners to realize a 10% return on their investment, these planting practices should be used because costs were relatively low while survival and yields of high-value forest products were high. These results indicate that forest managers have a financially viable alternative for managing loblolly pine plantations on a well-drained soil than the conventional practice of planting approximately 1500 bareroot seedlings per hectare for such soils.
Publications
- Blazier, M.A., Gaston, L.A., Clason, T.R., Farrish, K.W., Oswald, B.P., Evans, H.A. 2008. Nutrient dynamics and tree growth of silvopastoral systems: impact of poultry litter. Journal of Environmental Quality. 37:1546-1558.
- Blazier, M.A., Hennessey, T.C. 2008. Seasonal soil and foliage nutrient dynamics of a juvenile loblolly pine plantation: impacts of fertilizer formulation and vegetation suppression. Forest Ecology and Management. 255:3404-3415.
- Blazier, M.A., Patterson, W.B., Hotard, S.L. 2008. Straw harvesting, fertilization, and fertilizer type alter soil microbiological and physical properties in a loblolly pine plantation in the mid-South USA. Biology and Fertility of Soils. 45:145-153.
- Blazier, M.A., Dunn, M.A. 2008. Stock type, subsoiling, and density impact productivity and land value of a droughty site. Southern Journal of Applied Forestry. 32(4):154-162.
- Blazier, M.A. 2008. Fertilizing southern pine plantations to improve growth and financial performance. LSU AgCenter Extension Bulletin 3058. 8 p.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: This project resulted in the publication of a Soil Science Society of America conference proceedings paper to share the significance of the results of this study with scientific communities. Results of this project were also integrated into articles in an article for Forests & People magazines and an Ark-La-Tex Forestry Field Tour hosted at a primary research location in order to share this study's results with forest landowners and natural resource management professionals.
PARTICIPANTS: Michael Blazier, PI; Ryan Coleman, graduate student; Andrew Scott, Lewis Gaston, Terry Clason, Brian Oswald, Kenneth Farrish.
TARGET AUDIENCES: Forestry and soils scientific communities, natural resource management professionals, forest landowners.
Impacts
Four annual applications of 5 and 10 Mg poultry litter per hectare per year to a loblolly pine and bahiagrass silvopasture did not result in soil phosphorus concentrations above runoff thresholds and increased pine and bahiagrass growth. However, application of 10 Mg litter per hectare may have increased N and P leaching potential. No increases in leaching potential were observed with the 5 Mg/ha litter rate. Both litter rates increased concentrations of several nutrients in the uppermost soil horizon. Thus, although this silvopasture system had a relatively high capacity for nutrient use and retention at this site, land managers should apply litter less frequently or at lower rates than in this study to reduce environmental risks. Mid-rotation thinning of loblolly pine plantations had a greater impact on plantation N supply and demand in the year following thinning than did fertilization and herbicide treatments on course-textured soils. On such soils, thinning
dramatically increased soil N supply while loblolly pine N demand did not increase as appreciably. Therefore, it would be environmentally and economically beneficial for forest managers to postpone fertilization until at least one year after thinning to improve plantation capture of applied N. However, on a fine-textured soil post-thinning plantation N supply and demand were equivalent. On such soils, forest managers could continue the conventional practice of applying N within one year of thinning. On a well-drained site, planting container seedlings at 746 trees/ha without subsoiling and planting bareroot seedlings with subsoiling improved tree growth relative to the conventional practice of planting 1492 trees/ha without subsoiling. Yield and revenue predictions for these management regimes were similar, but planting 392 container seedlings per hectare without subsoiling had the best land expectation values due to the costs associated with subsoiling and planting 1492 trees/ha.
These results suggest that forest managers can improve growth and financial performance of loblolly pine plantations on droughty sites by planting container seedlings at a lower than conventional density.
Publications
- Blazier, M.A., Scott, D.A., and Coleman, R.A. 2007. Timing of mid-rotation silvicultural operations and soil texture impact soil nitrogen and carbon dynamics. Proc. Soil Sci. Soc. Am. annual meeting
- Blazier, M.A. 2007. Improve timber yields on poor soils with better decisions. Forests and People. 57(3):34-35.
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Progress 01/01/06 to 12/31/06
Outputs
A study on the effects of timing N fertilization and understory control treatments relative to mid-rotation thinning has been established at three loblolly pine plantations with a gradient of soil moisture-holding capacity in north and central Louisiana. Fertilization, before and after thinning, increased soil N mineralization rates, and the effect was more pronounced when herbicide was applied in tandem with fertilization. This finding suggests N fertilization increased organic matter use by soil microbes. With pre-thin fertilization, stand N demand increased in tandem with increases in soil N supplies, indicating good synchronization of fertilization with stand capacity for N use. However, both stand supply and demand were relatively low prior to thinning. Thinning markedly increased soil N supply at the well- and moderately-well drained sites, but soil N of the poorly drained site was relatively unaffected by thinning. Stand N demand was 2 to 8 times greater
post-thin than pre-thin. However, stand N demand did not increase in parallel with increases in soil N supplies at the well- and moderately well-drained sites, suggesting that fertilizing within 6 months of thinning exceeded stand capacity for N use on those sites. The asynchrony between N supply and demand on well-drained sites may have been due to: (1) a droughty summer that reduced the ability of pine crowns to expand and use applied N for growth, or (2) thinning having an overriding impact on soil N supply and demand. A study on timing P fertilization and understory control treatments relative to mid-rotation thinning has been conducted on a well-drained site at the Hill Farm Research Station. Pine growth was comparable between P fertilization treatments applied 1 and 3 years post-thin, but the 1-year post-thin understory control treatment has produced pine growth superior to that of a similar treatment applied 3 years post-thin. These results may indicate that timing relative to
thinning does not impact stand response to P fertilization and that earlier understory control treatments may promote greater stand volume growth in the latter half of plantation rotations. A study on 5 annual applications of poultry litter to a loblolly pine silvopasture on a sandy soil at the Hill Farm Research Station found that loblolly pine and forage growth increased due to litter application while several soil nutrient concentrations increased in only the upper soil horizon. These results suggest that silvopastures buffer against nutrient leaching on a soil with high leaching potential. However, by the third application of litter at 10 Mg/ha, increases in P, Cu, and Ca were found in lower soil horizons, suggesting that this volume of litter exceeded the silvopasture's buffering capacity. Annual litter applications at 5 Mg/ha for 5 years did not increase soil nutrients in lower soil profiles. Loblolly pine growth continues to be higher in response to poultry litter fertilization
relative to an unfertilized control 5 years after the cessation of fertilization. These continued growth responses may bioremediate soil nutrient accumulations created by the 10 Mg/ha treatment.
Impacts
If fertilizing mid-rotation loblolly pine plantations with N fertilizer, it is important to consider soil texture and timing relative to thinning. Stands will likely respond more fully to N fertilizer applied post-thinning. However, on soils with sandy texture it may be beneficial to postpone fertilization until at least one year after thinning. Phosphorus fertilizers can likely be applied to stands irrespective of the timing relative to thinning. When using poultry litter as a substitute for N fertilizer as part of loblolly pine silvopasture management on a sandy soil, repeated applications at rates exceeding 5 Mg/ha is inadvisable due to nutrient leaching potential.
Publications
- Blazier, M.A., R. Coleman, and D.A. Scott. 2006. Soil N dynamics in intensively managed mid-rotation loblolly pine plantations. Proceedings of the Soil Science Society of America Annual Conference. Salt Lake City, UT.
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Progress 01/01/05 to 12/31/05
Outputs
A study on the effects of timing fertilization and understory control treatments relative to mid-rotation thinning has been established at four sites that vary in soil moisture-holding capacity in north and central Louisiana. Fertilization prior to thinning significantly increased soil N and loblolly pine foliage N accumulation relative to an unfertilized control treatment. Pairing fertilization with herbicide applications likewise increased soil N, which was attributable to increased N mineralization and reductions in microbial biomass N. However, loblolly pine foliage N accumulation in response to the combination of fertilizer and herbicide was equivalent to that observed in response to fertilizer applied without herbicide. Herbicide likely did not enhance loblolly pine foliage N accumulation because understory vegetation was a much smaller potential N sink relative to loblolly pine and soil microorganisms in the pre-thinned stands. In the three months following
thinning of the stands, microbial biomass N declined by 20 percent at all sites. This collapse in microbial biomass N may release N available for loblolly pine uptake. This release of microbial N also coincided with common operational fertilization timeframes. A study on high-intensity silvicultural management regimes was established by planting three high-yield half-sib families and two high-yield clonal ideotypes of loblolly pine. Two of the families were from Louisiana, and the clonal ideotypes and one family were from the eastern portion of the natural loblolly pine range. First-year survival of the two clonal ideotypes was comparable to that of the Louisiana families despite a droughty year. However, survival of the eastern family was poorer than that of the Louisiana families. First-year seedling volume of the two clonal ideotypes was 20 to 30 percent greater than that of the Louisiana family, and volume of the eastern family was 15 percent greater than that of the Louisiana
family.
Impacts
If fertilizing loblolly pine stands with N-containing fertilizer prior to a mid-rotation thinning harvest, it may be unnecessary to apply herbicide to promote good pine fertilizer accumulation. If fertilizing loblolly pine stands within three months of thinning, it may be possible to apply N at lower than conventional rates because thinning promotes short-term natural increases in soil N. Planting clonal loblolly pine seedlings of eastern origin may increase loblolly pine plantation productivity because early survival and growth of the clonal seedlings was comparable to that of a high-yield, commonly planted Louisiana family, even in a droughty year.
Publications
- Blazier, M.A., and D.A. Scott. 2006. Nitrogen distribution within the soil-plant-microbial system in response to pre-thinning fertilization treatments in Louisiana. Connor, K.F. (ed.). Proceedings of the 12th biennial southern silvicultural research conference. Memphis, TN.
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Progress 01/01/04 to 12/31/04
Outputs
A study on the effects of timing fertilization and brush control treatments relative to mid-rotation thinning has been established at four sites that vary in soil moisture-holding capacity in north and central Louisiana. First-year results indicate that four sites vary significantly in their capacities to supply N to vegetation, which is likely to impact fertilization responses. Triclopyr brush control treatments significantly reduced the N immobilized by understory vegetation on all four study sites, with the greatest reduction observed on a moderately well-drained site with inherently high understory biomass. Fertilization of the stands one growing season prior to thinning significantly increased the foliar N content of crop trees, which was a function of both increased foliar biomass growth rates and foliar N concentrations. However, these significant increases in foliage N content per acre were observed only when brush control treatments were applied in
conjunction with fertilization. Thus, competition for applied N from understory biomass was high enough at all sites to negate any positive influences of fertilization on crop trees. In anticipation of a study on late-rotation fertilization, final measurements of the effects of mid-rotation fertilization treatments on pine volume and understory development have been collected. To prepare for a study on high-intensity treatments on juvenile loblolly pine stands, a new study site has been planted with five families or clonal lines of loblolly pine because each family or clonal line has been shown in industrial planting trials to demand high nutrition to reach their genetic potential. To get ready for the initiation of a study on the influences of the intensity of fertilization, brush control, and soil organic matter removals on loblolly pine growth and yield and soil nutrient cycling processes, final measurements have been collected in a 46-year-old 6-ha stand currently on the study
site.
Impacts
To effectively fertilize mid-rotation stands before they are thinned, it is necessary to suppress competing hardwoods with herbicide. If a landowner cannot apply herbicide prior to fertilizing such stands, it is best to avoid fertilization until the stand has been thinned.
Publications
- No publications reported this period
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