Browsing by Author "Carl Crozier, Committee Member"

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Effects Of Both Above And Below Ground Biomass On Soil Chemical, Physical And Biological Properties On A Coastal Plain Soil In North Carolina
(2010-03-04) West, Eric; Nancy Creamer, Committee Member; Carl Crozier, Committee Member; Ronnie Heiniger, Committee Chair; Chris Reberg-Horton, Committee Member
The literature has shown the possibility to enhance many of the soil properties that improve production with additions of plant biomass to the soil in conjunction with long-term conservation tillage. Since it has been proven that reduced tillage is extremely beneficial to a soilÃ¢â‚¬â„¢s health, the key question is if the incorporation of deep rooted cover crops and/or large quantities of above ground biomass over a two-year period would result in extensive improvements on a soilÃ¢â‚¬â„¢s natural properties throughout the effective rooting depth, or is this too short of a time period for any beneficial effects to occur to the chemical, physical and biological properties of the soil? While SOC additions to the soil surface through decaying biomass can make measurable improvements to a soil in the humid, tropical southeastern U. S., the dynamics of total carbon (total SOC), total nitrogen (TKN), particulate organic matter (POM), potentially mineralizable nitrogen (PMN), CEC and bulk density (Db) in the 0-5, 5-10, and 10-18 cm depths in a production system that incorporates deep rooted cover crops and/or additions of organic matter from cover crops at rates >6 Mg/ha/yr (3 T/ac) are unknown. The objectives of this research were to determine what effect rye (Scale cereale), barley (Hordeum vulgare), alfalfa (Medicago sativa), wheat (Triticum aestivum), triticale (Triticale hexaploide Lart.), annual white sweetclover (Melilotus officinalis), blue lupine (Lupinus angustifolius), rye/hairy vetch (Scale cereale/Vicia villiosa) and alfalfa/rye (Medicago sativa/Scale cereale) would have on the following parameters: total SOC, POM, TKN, PMN, CEC, and Db after two (2) years of seeding. Significant spatial/temporal interactions and main effects were found in Db, PMN, POM and CEC while significant main effects were found in total C and total N. Significant treatment interactions were found in Db, total C, PMN, POM and CEC. Relative to treatment biomass, significant effects were seen between treatments and treatment*year interaction. Results on Db found spatial variability with depth but not with season and a minimal treatment effect depending on surface texture. Total C and total N decreased with depth but were independent spatially and temporally; however, treatment effect on total C was <5 months. Between Db and total C, the two parameters were inversely correlated. PMN either fluctuated between sampling times or declined with time. Notably, rye and rye/hairy vetch effected PMN in the 0-5 cm depth where other treatments showed no effect. POM declined with time regardless of depth implying a priming effect was occurring; however, rye/hairy vetch appeared to show an early reversal trend. As for CEC, there was no consistent trend. Additionally, CEC exhibited a moderate correlation to POM but not total C. Biomass measurements indicated no treatment consistently exceeded >6 Mg/ha/yr. Rye and rye/hairy vetch more often produced the most biomass and lupine achieved the overall maximum yield. Relationships between biomass and N parameters found a moderate, positive effect from the biomass inputs that appeared to compound with time. Overall, rye and rye/hairy vetch were the best cover crop treatments but two years of biomass inputs were not enough to prevent declines in POM. Conversely, PMN fluxed from applied N, and biomass with low C:N ratios oxidized quickly resulting in less carbon. Total C, total N and Db were not responsive to short term management indicating more effort is needed to define and/or develop a cover crop that will consistently reach the >6 Mg/ha/yr.
Nitrogen Fixation and Mineralization Potential of Winter Annual Legume Cover Crops for Reduced-tillage Organic Corn Production in North Carolina.
(2010-10-20) Parr, Mary; Julie Grossman, Committee Chair; Samuel Reberg-Horton, Committee Member; Carl Crozier, Committee Member
Phosphorus Dynamics from Broiler Breeder Diets in Manure, Soil, and Corn.
(2009-04-27) Casteel, Shaun Nathan; Daniel W. Israel, Committee Co-Chair; John T. Brake, Committee Co-Chair; Carl Crozier, Committee Member; Rory Maguire, Committee Member; Edgar Oviedo, Committee Member
Studies of broiler breeder diet modifications to reduce phosphorus (P) excretion have evaluated bird performance, but no studies have quantified the effects of P in the manure and the impacts to soil and plant availability once soil-applied. Four diets were formulated by factoring two levels, 0.40 and 0.22% available P (NRC, Low, respectively), with or without phytase during the breeder laying phase (wk 22 to 64). Breeders fed phytase produced manures with 15% lower total P concentration, but did not change manure water-soluble P (WSP). However, P in the breeder manures was > 92% orthophosphate. The incubation of the four unique manures in samples of Portsmouth (Typic Umbraquult) and Wagram (Arenic Kandiudult) series generally did not differ in concentrations of Mehlich-3 P, soil WSP, total inorganic P, and total P. Phosphorus-based applications of breeder manures (NRC, Low) and triple superphosphate (TSP, Ca[H2PO4]2 H2O) were applied to a P-deficient, Portsmouth soil in the greenhouse to determine the response of corn (Zea mays). Corn growth was equal among P sources in the initial study, but it tended to be greater in the soils amended with breeder manures in the residual study due to the P applied and the apparent liming effect of the soil. The NRC and Low breeder manures were applied at 39 kg P ha-1 in 2007 at Salisbury (Typic Rhodudult), Lewiston (Aquic Paleudult), and Plymouth (Typic Umbraquult), which ranged in soil P levels. Plymouth included TSP and an untreated control. Corn growth was equal among soils amended with the breeder manures NRC and Low in all site-years and grain P removal was equal five out of six site-years. Grain production, grain P removal, and applied P recovery were equal among P sources in 2007, but the breeder manure treatments were greater than TSP in 2008. Breeder manures should be considered equivalent to TSP in P impacts to the soil and plant availability.
Soil Tests for Winter Wheat Nitrogen Management in the Southeastern USA
(2009-02-06) Wall, David Peter; Ronnie Heiniger, Committee Member; Jeffery G. White, Committee Member; Carl Crozier, Committee Member; Randy Weisz, Committee Chair
ABSTRACT WALL, DAVID PETER. Soil Tests for Winter Wheat Nitrogen Management in the Southeastern USA. (Under the direction of Randy Weisz). Developing a system where soil tests could be used for winter wheat (Triticum aestivum L.) nitrogen (N) management and to determine N-fertilizer requirements in the southeastern USA would have many environmental and economic benefits. The objectives of this study were to: (i) evaluate the effects of sampling time, sampling depth, crop rotation, and N fertilizer application on the amino sugar-N test (ASNT); (ii) determine appropriate and reliable sampling depths for the ASNT and soil mineral N tests; (iii) explore the relationships between these soil N tests and winter wheat N uptake; (iv) calibrate these soil N tests to predict optimum spring N rates (OptN) for winter wheat in North Carolina. Ten study sites were established, to assess changes in ASNT values with sampling depth, crop rotation, and N fertilizer application. A repeated measures experimental design was implemented whereby soil samples were taken from each of the 10 study sites at specific times and depths during the course of a 19-month period. Amino sugar-N (ASN), NO3-N, NH4-N, and soil organic matter (SOM) levels were evaluated at each sampling. At all sites, soil ASN decreased with depth and showed significant variation over time. Soil ASN was influenced by crop rotation and tillage but was not significantly affected by fertilizer applications. When all sites were considered together, soil ASN was well correlated with SOM, however, they were not correlated across time within sites. This suggests that the ASNT is measuring a nitrogenous fraction of SOM that behaves somewhat independently over time. These results indicate that sampling to 30 cm at a specific sampling time will be necessary to capture temporal variability in ASN. Sixty-nine winter wheat N response trials were conducted for three growing seasons over a wide range of soils, drainage and previous crop management practices. A randomized complete block design with five replications and seven growth-stage 30 (GS30) N-fertilizer rates ranging from 0 to 168 kg ha-1 was used. Each February, soil samples were taken over three depths (0-10, 0-20, and 0-30cm) and analyzed for ASN, NO3-N, NH4-N and SOM levels. In the wheat N uptake study, the relationships between these soil N tests and N uptake from the unfertilized check plots (NUPZero) were evaluated. Considering all the experimental locations, the soil tests had poor relationships with NUPZero. When only the well-drained locations (n=58) were considered, the data aggregated into two distinct groups: 1) locations with low residual N, and 2) locations with high residual N and elevated levels of NH4-N and ASN. For locations with low residual N, the ASNT was able to predict NUPZero and grain yield without spring fertilizer applied (YLDZero) and was therefore a good predictor of soil N supply through mineralization. A combination of soil tests (NH4-N, ASNT and SOM) was required to predict NUPZero for all well-drained locations (R2 = 80). In the N fertilizer response study, the ASNT by itself was a poor predictor of OptN for all well-drained locations, however the ASNT was correlated with N uptake at the optimum spring N fertilizer rate (NUPOpt) and N uptake at GS-30 (NUPGS30) for locations with low residual N. The ASNT could not satisfactorily predict OptN for these low residual N locations, but could be used to predict the NUPOpt and wheat yield at the optimum GS-30 N fertilizer rate (YLDOpt) for well-drained fields. A combination of soil tests was required to predict OptN for all locations (i.e., NH4-N and SOM with resultant R2 = 0.59). Soil NO3 tests showed no benefit for winter wheat N management in North Carolina.