Southern pines are typically limited by nitrogen (N) and phosphorus (P) availability in the soil environment. While the absolute quantities of P in forests soils may be large, the concentration of inorganic P in the soil solution is typically very small (< 0.01 mg L²-1). A onetime application of just 56 kg P ha²-1 can substantially increase growth of pine stands over a 20 year rotation (Pritchett and Comerford, 1982; Allen et al., 1990). Phosphorus fertilization of Pinus radiata in New Zealand has also shown long-term effects on labile P pools in the soil which improved stand growth during the subsequent rotations (Ballard, 1978; Gentle et al., 1986). Identifying and quantifying the biologically available P pools in the soil environment will help foresters in making site-specific P fertilizer prescriptions. I examined soil phosphorus pools using the Hedley sequential fractionation procedure and Mehlich-3 soil tests in a long-term loblolly pine (Pinus taeda L.) fertilization trial from four sites in the Atlantic and Gulf Coastal Plains. After 22 years, fertilization effects were limited to the surface depths. Mehlich-3 extractable P was largest in the soil surface (0-10 cm) of the fertilized treatments plots. Hedley labile and moderately labile P pools were also largest in the soil surface and decreased with depth. Results from the Hedley fractionation procedure suggested that the Virginia site has a large pool of organic P in the soil surface. Organic P pools can represent 20-90% of the total P present in most mineral soils increasing with the age of the soil (Condron et al., 2005). This increase in organic P pool suggests that biological cycling becomes more important as the stand develops (Wells and Jorgensen 1975). I used solution 31P nuclear magnetic resonance (NMR) spectroscopy to characterize organic P extracted with NaOH-EDTA in the surface of a Paleaquults from coastal Virginia. Total NaOH-EDTA extractable P was significantly larger in the fertilized treatment. Concentrations ranged from 0.1 mg P L²-1 in the control plots to 5.1 mg P L²-1 in fertilized plots. The surface soils in both treatments were dominated by inorganic orthophosphate. Monoester P compounds were the only organic P compounds detected and were present in very low quantities. The significant increase of NaOH/EDTA extractable P in the soil surface of the VA site suggested there has been a beneficial long-term effect of fertilization similar to the observations from the Mehlich-3 soil test. Results from oxalate loading experiments on ligand exchangeable versus dissolvable P pools in the bulk soil suggested that the long-term effect of P fertilization increased oxalate dissolvable P pools. Plants and microbes have evolved a variety of mechanisms to increase P uptake in low P soil environments. These mechanisms include changes in root morphology and architecture, preferential root growth into high P microsites, the secretion of low-molecular-mass organic acids (LMMOA), and uptake via symbiotic relationships (Fox and Comerford, 1992b; Raghothama, 1999; Hinsinger, 2001; Raghothama, 2005). Results from soil samples taken from the ectomycorrhizal rhizosphere found that loblolly pine mycorrhizal roots modified the soil environment, possibly making recalcitrant P more available. In addition, the long-term effect of fertilization was a 396% increase in biologically available P. Fertilization increased loblolly pine volume growth by 57 m¹3 ha and increased the P content in the litter layer by 118%. After the stand was harvested and replanted, mineralization of the litter layer may also increase soil P pools. Results from this long-term fertilization experiment in the Coastal Plain province of Virginia have demonstrated that there has been a significant increase in soil (33.6 kg P ha²-1) and biologically available P pools (3.0 kg P ha²-1). / Ph. D.

The use of animal manures to replace commercial fertilizer has increased the economic and environmental sustainability of agriculture. However, this practice has resulted in excess P being applied to the soil in some areas. Excess P may run-off into surface water and leach in the ground, causing eutrophication. Decreasing the amount of P fed and improving the utilization of P are two possible nutritional solutions to this problem. Two experiments were conducted to investigate the effects of levels of dietary P, chemical form of P, and phytase supplementation in ruminants. For Exp. 1, 24 steers (average BW = 229 kg) were allotted to two diets containing 0.12 and 0.19% dietary P for a 112-d growth trial. The steers were individually full-fed, weighed every 14 d, and blood samples were collected every 28 d. The steers fed the 0.12% P diet had increased (P<0.02) ADG during the first 28 d, after which there were no differences. They also had higher (P<0.05) feed intake. By d 56 serum P for the 0.12% P group was lower (P<0.01), and this difference continued for the remainder of the trial. For Exp. 2, 18 wether lambs (average BW = 23 kg) were allotted to the following six diets for each of two metabolism trials: 1) a negative control diet deficient in P, 2) control diet supplemented with inorganic P, 3) control diet supplemented with phytic acid, 4) control diet supplemented with phytic acid and phytase, 5) control diet supplemented with cottonseed meal, and 6) control diet supplemented with cottonseed meal and phytase. Each metabolism trial was preceded by a 5 wk depletion phase in which the lambs were fed a low-P diet. The metabolism trials consisted of a 10 d preliminary period followed by a 10-d collection of feces and urine. On the final day ruminal fluid, blood, and saliva were collected. At the end of the second metabolism trial 10th rib bones were collected from each lamb. Absorption of P was lowest (P<0.0001) for the low-P treatment, compared to the other treatments. There was no treatment effect on saliva P. Ruminal fluid P was higher (P<0.05) for lambs receiving P supplementation. Within supplementation treatments, ruminal fluid P was higher (P<0.05) for lambs fed organic P than for those fed inorganic P. Feeding CSM resulted in higher (P<0.001) ruminal fluid P than phytic acid. The addition of phytase to the diets with organic P resulted in more (P<0.04) P in the ruminal fluid. There was a decrease (P<0.003) in serum P associated with the low-P treatment. There was no difference in bone ash or breaking strength. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / Phosphorus (P) is essential for aquatic life; cycling between both inorganic and organic forms to maintain an ecological balance. Its addition into P-scarce freshwaters, either through terrestrial (external) or sedimentary (internal) loading, may disrupt this balance causing blooms of phytoplankton to flourish, often resulting in harmful environmental and anthropogenic consequences. Accordingly, reduction of external P loading has been commonly implemented with a recent focus on sediment-bound legacy P that is mobilized into the water column during dynamic redox conditions. Mobile P species have been identified as both inorganic and organic, with the former representing the most bioavailable fraction, and the latter serving as a source for labile P in freshwaters when in high demand, particularly during blooms. Missisquoi Bay in Lake Champlain, VT experiences harmful cyanobacterial blooms driven by internal P loading and has been the target of numerous geochemical and hydrological studies. This thesis describes a high-resolution investigation of both the organic P and organic matter compositions of the bay with respect to mobility, reactivity, and bioavailability using Fourier Transform-Ion Cyclotron Mass Spectrometry (FT-ICR MS). Sediment from Missisquoi Bay was extracted with a diverse set of reagents, resulting in fractionation of both organic matter and organic P, and illustrating the distribution of various labile and recalcitrant compounds. Many of these molecules are associated with porewater or easily extractable mineral surfaces providing a link to the benthic organic matter and phosphorus fractions available to microorganisms. Additionally, the organic chemistry of the bay was investigated seasonally from May 2017 to January 2018 revealing biological processing from the spring runoff season through the post-bloom summer season. The transition from late summer to under ice conditions in winter was less severe with a higher commonality between both organic matter and organic P compounds, suggesting reduced biological and abiotic degradation. Moreover, short-term anoxic incubations of sediment cores from each season revealed the presence of diverse organic signatures from sorption processes, and a significant contribution of benthic microbial activity to the benthic organic geochemistry.

The tropical savannas cover an area of approximately 1,900 million ha second biome of Brazil. Phosphorus (P) is frequently a major or even the prime limiting factor for plant growth in the subtropical and tropical regions (highly weathered soils). Small-scale farming systems are fairly representative in Brazil, accounting for approximately 84.4% of Brazilian agriculture establishments and the conventional tillage being the common practice in the systems. The objective of this work was to study the dynamics of P in an agronomic experiment located in the Cerrado region, on the efficient use of P in conservation agricultural system: i) assessing soil spatial fertility variability of P, Ca, Mg, K and pH; ii) the C and P stock; and iii) characterizing of species of P by 31P-NMR spectroscopy. The area of study is located at Cerrado biome (Brazilian neotropical savannas) in a clayey Oxisol classified as Haplic Ferralsol. The treatments are characterized by different agricultural practices (conventional tillage - CT; and no-tillage - NT), and the presence or not of cover crops (Brachiaria ruziziensis - a grass specie and Cajanus cajan - a leguminous specie) with maize (Zea mays). In the study of spatial variability the data were analyzed by descriptive statistics and geostatistics. The semivariograms were computed according to the spherical model for pH H2O, pH CaCl2, K, LogK, Ca and Mg. P and LogP were modeled using a nugget effect model. Even ~20 years after deforestation the spatial distribution of pH H2O, pH CaCl2, Ca, Mg and exchangeable K is influenced by the wood windrow burning that took place during deforestation. The spatial distribution of P was not affected by the windrow woods burning. In the study conducted to improve the understanding of the conservation agriculture impact in small-scale farming systems on soil C and P stocks in the 0-40 cm layer due to its importance in agrosystem management. The C stocks (up to 40 cm depth) in NT and MCr treatments were significantly superior. The P stocks varied between 0.63 and 0.91 t ha-1 and were not significantly different among the treatments. No-till treatment and MCr treatments were the only ones that showed gains carbon, where the accumulation was 2.67 and 2.91 t C ha-1 year-1, respectively. The highlight of MCr treatment shows the important role of legumes in carbon sequestering. In the study of soil organic P aiming to determine how the amounts and forms of organic phosphorus vary according to the tillage systems and cover crops used. The Po (PMonoester and PDiester) values determined by NMR were not different among the treatments. The levels of Po were higher than 59% of the total content of POlsen and the main changes in relation to P occurred in the topsoil. The values show that Po does not change (PMonoester and PDiester) among the treatments. The maintenance of the Po levels, no accumulation and loss, suggests that the availability of P is not necessarily linked to accumulation, but to the increase of fluxes between active pools. / As savanas tropicais cobrem uma área de cerca de 1.900 milhões ha sendo o segundo bioma do Brasil. O fósforo (P) é frequentemente um grande ou mesmo o principal fator limitante no crescimento das plantas nas regiões tropicais e subtropicais (solos altamente intemperizados). Os sistemas agrícolas de pequena escala (agricultura familiar) são bastante representativos no Brasil, representando cerca de 85% dos estabelecimentos agropecuários e tendo como principal prática o preparo convencional do solo. O objetivo deste trabalho foi estudar a dinâmica do P em um experimento agronômico localizado na região do Cerrado, sobre o uso eficiente do P em sistema agrícola conservacionista: i) a avaliação da variabilidade espacial da fertilidade do solo de P, Ca, Mg, K e pH ii) o estoque de C e P, e iii) a caracterização das espécies de P por 31P-RMN. A área de estudo está localizada no bioma Cerrado em um Latossolo Vermelho distrófico argiloso. Os tratamentos são caracterizados por diferentes práticas agrícolas (preparo convencional - CT e plantio direto - NT), e a presença ou não de plantas de cobertura (Brachiaria ruziziensis e Cajanus cajan) com milho (Zea mays). No estudo da variabilidade espacial os dados foram analisados por estatística descritiva e geoestatística. Os semivariogramas foram calculados de acordo com o modelo esférico para pH H2O, pH CaCl2, K, logK, Ca e Mg. O P e LogP foram modelados usando um modelo de efeito pepita. Mesmo após ~ 20 anos do desmatamento, a distribuição espacial do pH H2O, pH CaCl2, Ca, Mg e K foi influenciada pela queima de madeira em leiras. A distribuição espacial de P não foi afetada pela queima da madeira em leira. No estudo realizado para melhorar a compreensão do impacto da agricultura conservacionista em sistemas agrícolas de pequena escala sobre os estoques de C e P no solo, na camada de 0-40 cm, os estoques de C nos tratamentos NT e MCr (milho + C. Cajan na linha) foram significativamente superiores. Os estoques de P variou entre 0,63 e 0,91 t ha-1 e não foram significativamente diferentes entre os tratamentos. O plantio e MCr foram os únicos tratamentos que apresentaram ganhos de carbono, onde o acúmulo foi de 2,67 e 2,91 t C ha-1 ano-1, respectivamente. O tratamento MCr mostra o importante papel das leguminosas no sequestro de carbono. No estudo do fósforo orgânico (Po) do solo com o objetivo de determinar como os teores e formas de Po variam de acordo com os sistemas de preparo e plantas de cobertura utilizadas. Os teores de Po (PMonoester e PDiester) determinados por RMN não foram diferentes entre os tratamentos. Os níveis de Po foram superiores a 59% do total do POlsen extraído e as principais alterações em relação ao PoOlsen ocorreu na camada superficial do solo. O Po (PMonoester e PDiester) determinado pela RMN não alterou entre os tratamentos. A manutenção dos níveis de Po sugere que a disponibilidade de P não está necessariamente ligada à sua acumulação, mas ao aumento dos fluxos entre as formas disponíveis (grupos ativos).

The features of upwelled water are cold, salty and nutrient-rich. However, factors such as the air-sea exchanges of heat affect temperature, and freshwater input from rivers, precipitation and evaporation affect salinity. As biologically important elements are mostly in the dissolved inorganic forms in young upwelled waters, and are mostly in the particulate organic forms in old upwelled waters, the aging status of upwelled waters can be expressed as the relative percentages of biologically important elements in the inorganic and organic forms. Further, nutrients may be consumed by biological productivity. For these reasons, we hereby judge upwelling in the Taiwan Strait (TS) between 2000 and 2002 by the Degree of Nutrient Consumption (DNC, DNCC = and DNCX = ¡AX is nitrogen or phosphorus). The value of DNC is low in young upwelled waters but high in old upwelled waters. In summer, autumn and winter, waters at, or east of, a front in the northeastern Taiwan Strait were affected by the Kuroshio off eastern Taiwan. This front divides the Kuroshio water, the South China Sea (SCS) water that flows through the TS and the Coastal China Current water (in winter). The implications are that not all currents in the Taiwan Strait flow in a northerly direction, even in summer. Because the axis of Kuroshio moved away from eastern Taiwan and upwelling weakened in SCS in 2002, salinity east of the front was fresher, and nutrient and DON were lower in 2002 than 2001. On the other hand, upwelling induced higher DON west of the front. In August, 2002, the water in the southern TS was higher in temperature, more salty, but nutrient and DON were lower than in 2001 because of weakened upwelling in the SCS, and water that intruded into the TS had a higher percentage of Kuorshio. The trend of upwelling, DNCC,P,N was along the west Penghu Channel from bottom to surface. Rates of temperature, salinity and DNCC,P,N variation were greater during 2001 than in 2002, reflecting slower rate of upwelling in 2002.

Abstract This research was conducted to understand whether phosphorus limits the phytoplankton production in the South China Sea (SCS). In the nutrient enrichment experiments nitrate and phosphate were supplemented to surface sea water and the enhancement of chlorophyll a concentration during incubation was observed. Seasonal field survey was conducted to measure ambient abundance of phosphorus including phosphate (SRP) and dissolve organic phosphorus (DOP), as well as alkaline phosphatase activity (APA) in the nautral sea water in the contiential shelf and basin of the SCS. Except at the contiential shelf in summer and the mouth of Zhu Jiang River in fall, the nutrient concentration of surface water was low in the SCS. The average¡£NO3+NO2¡¤was 20 nM (fall) - 360 nM (winter ). The average SRP concentration was 16 nM (fall) - 87 nM (winter). The average DOP concentration was 0.08 £gM (summer)- 0.25 £gM (winter). The ¡£NO3+NO2¡¤/ SRP ratio was smaller than the Redfield N/P ratio of 16. The average chlorophyll a concentration (Chl a) was 0.13 £gg l-1 (summer) - 0.48 £gg l-1 (winter). The average concentration of the particlulate organic carbon (POC) was 4.58 £gM (spring) - 8.11 £gM (winter). The average APA was 16 n mol l-1 h-1 (fall) - 87 n mol l-1h-1 (winter). The average of APA/Chl a was 33.94 n mol £gg -1 h-1 (winter) - 97.22 n mol £gg -1 h-1 (spring). The results of the enrichment experiment show that the phosphorus deficiency was observed on the contiential shelf in the summer of 2001 and at the mouth of Zhu Jiang in the fall of 2002. The common characteristics of the phosphorus deficient regions were low salinity (29.90- 30.87 psu ), high¡£NO3+NO2¡¤(1.31 - 3.01 £gM) , and a ¡£NO3+NO2¡¤/ SRP ratio higher than 16. Chl a increased significantly (p<0.05) by the enrichments of phosphorus. In spring and winter when all regions were N-limited, N enrichment significantly (p<0.05) increased Chl a. In fall, all the contiential shelf region except the mouth of Zhu Jiang River, the slope and basin regions were NP co-limited. The Bashi Strait in summer was also NP co-limited. P-limitation that was seen in the contiential shelf SCS and at Zhu Jiang River mouth, was probably caused by the influence of river discharge. N/P, SRP or APA were not effective parameters to assess whether marine phytoplankton growth was limited phosphorus, nitrogen or both. In the SCS, the P-limited water masses were, in general, low in salinity, high in¡£NO3+NO2¡¤,Chl a,¡£NO3+NO2¡¤ / Chl a, APA and a N/P ratio higher than 16. The water masses that were N-limited was high in salinity, and low in¡£NO3+NO2¡¤, Chl a,¡£NO3+NO2¡¤/ Chl a and APA, as well as a N/P ratio smaller than 16. The water masses that were nitrogen and phosphorus co-limited were different from the N-limited ones in that they were low in SRP, SRP/Chl a, and DOP. The SRP and DOP concentration in the NP co-limited region were 11 - 28 nM and 0.09 - 0.23

Much of the phosphorus (P) in grain-based concentrates fed to growing horses is in the form of phytate-P. Little is known about the ability of young horses to degrade phytate-P or whether age affects mineral digestion in horses. The objective of this study was to examine the effect of age on P, calcium (Ca), and magnesium (Mg) digestibility and phytate-P degradation. Four long yearling geldings and 4 mature geldings were fed a diet of alfalfa cubes, timothy cubes and a pelleted concentrate. The diet contained 0.28% total P and 17.4% of that P was in the phytate form. There was a 14-d diet adaptation period followed by a 4-d fecal collection period. There was no difference in apparent P digestibility between the 2 age groups (P > 0.05). Phytate-P disappearance was 94.8% and did not differ between ages (P > 0.05). Apparent Ca digestibility tended to be higher in mature geldings (P = 0.0526), but apparent Mg digestibility did not differ between ages (P > 0.05). Long yearlings have the same ability to digest P and Mg as mature geldings, but more research is needed to determine the effect of age on Ca digestibilities.

This thesis investigates the development of new methodology for the identification and quantification of organic phosphorus compounds in environmental samples. Phosphorus is a vital element for primary production and one of the factors contributing to eutrophication. Eutrophication of aquatic systems leads to algal blooms, changes in ecological balance and deteriorating water quality. Difficulties in studying organic phosphorus stem from the fact that organic phosphorus is present in the environment in a variety of forms and each form may have different degradation and turnover time, having very different effects on eutrophication. New methods for the quantification of phosphorus derived from three groups of organic phosphorus compounds were developed. For the determination of phosphorus derived from DNA and phospholipids selective extraction was combined with digestion and colorimetric determination of the extracted phosphate. For quantification of inositol phosphates high performance liquid chromatography was coupled with tandem mass spectrometry using electrospray ionization.   The methods were applied to studying the distribution of these compounds in a small catchment and in the case of DNA-P and phospholipid-P, the degradation of the fractions in lake sediments. The studies showed that phosphorus bound to DNA, phospholipids and inositol phosphates constitute a sizeable part of the total phosphorus in different environmental samples. The phospholipid-P fraction was the smallest one, accounting for, on average, only a few percent of the total phosphorus in the sample. Inositol phosphates were most prevalent in the soils, with inositol hexakisphosphate accounting for over 10% of the total phosphorus content. The highest content of DNA-P was found in sediments and it was shown that DNA-P degrades more rapidly than phospholipid-P and therefore plays a more critical role in internal loading.

The tropical savannas cover an area of approximately 1,900 million ha second biome of Brazil. Phosphorus (P) is frequently a major or even the prime limiting factor for plant growth in the subtropical and tropical regions (highly weathered soils). Small-scale farming systems are fairly representative in Brazil, accounting for approximately 84.4% of Brazilian agriculture establishments and the conventional tillage being the common practice in the systems. The objective of this work was to study the dynamics of P in an agronomic experiment located in the Cerrado region, on the efficient use of P in conservation agricultural system: i) assessing soil spatial fertility variability of P, Ca, Mg, K and pH; ii) the C and P stock; and iii) characterizing of species of P by 31P-NMR spectroscopy. The area of study is located at Cerrado biome (Brazilian neotropical savannas) in a clayey Oxisol classified as Haplic Ferralsol. The treatments are characterized by different agricultural practices (conventional tillage - CT; and no-tillage - NT), and the presence or not of cover crops (Brachiaria ruziziensis - a grass specie and Cajanus cajan - a leguminous specie) with maize (Zea mays). In the study of spatial variability the data were analyzed by descriptive statistics and geostatistics. The semivariograms were computed according to the spherical model for pH H2O, pH CaCl2, K, LogK, Ca and Mg. P and LogP were modeled using a nugget effect model. Even ~20 years after deforestation the spatial distribution of pH H2O, pH CaCl2, Ca, Mg and exchangeable K is influenced by the wood windrow burning that took place during deforestation. The spatial distribution of P was not affected by the windrow woods burning. In the study conducted to improve the understanding of the conservation agriculture impact in small-scale farming systems on soil C and P stocks in the 0-40 cm layer due to its importance in agrosystem management. The C stocks (up to 40 cm depth) in NT and MCr treatments were significantly superior. The P stocks varied between 0.63 and 0.91 t ha-1 and were not significantly different among the treatments. No-till treatment and MCr treatments were the only ones that showed gains carbon, where the accumulation was 2.67 and 2.91 t C ha-1 year-1, respectively. The highlight of MCr treatment shows the important role of legumes in carbon sequestering. In the study of soil organic P aiming to determine how the amounts and forms of organic phosphorus vary according to the tillage systems and cover crops used. The Po (PMonoester and PDiester) values determined by NMR were not different among the treatments. The levels of Po were higher than 59% of the total content of POlsen and the main changes in relation to P occurred in the topsoil. The values show that Po does not change (PMonoester and PDiester) among the treatments. The maintenance of the Po levels, no accumulation and loss, suggests that the availability of P is not necessarily linked to accumulation, but to the increase of fluxes between active pools. / As savanas tropicais cobrem uma área de cerca de 1.900 milhões ha sendo o segundo bioma do Brasil. O fósforo (P) é frequentemente um grande ou mesmo o principal fator limitante no crescimento das plantas nas regiões tropicais e subtropicais (solos altamente intemperizados). Os sistemas agrícolas de pequena escala (agricultura familiar) são bastante representativos no Brasil, representando cerca de 85% dos estabelecimentos agropecuários e tendo como principal prática o preparo convencional do solo. O objetivo deste trabalho foi estudar a dinâmica do P em um experimento agronômico localizado na região do Cerrado, sobre o uso eficiente do P em sistema agrícola conservacionista: i) a avaliação da variabilidade espacial da fertilidade do solo de P, Ca, Mg, K e pH ii) o estoque de C e P, e iii) a caracterização das espécies de P por 31P-RMN. A área de estudo está localizada no bioma Cerrado em um Latossolo Vermelho distrófico argiloso. Os tratamentos são caracterizados por diferentes práticas agrícolas (preparo convencional - CT e plantio direto - NT), e a presença ou não de plantas de cobertura (Brachiaria ruziziensis e Cajanus cajan) com milho (Zea mays). No estudo da variabilidade espacial os dados foram analisados por estatística descritiva e geoestatística. Os semivariogramas foram calculados de acordo com o modelo esférico para pH H2O, pH CaCl2, K, logK, Ca e Mg. O P e LogP foram modelados usando um modelo de efeito pepita. Mesmo após ~ 20 anos do desmatamento, a distribuição espacial do pH H2O, pH CaCl2, Ca, Mg e K foi influenciada pela queima de madeira em leiras. A distribuição espacial de P não foi afetada pela queima da madeira em leira. No estudo realizado para melhorar a compreensão do impacto da agricultura conservacionista em sistemas agrícolas de pequena escala sobre os estoques de C e P no solo, na camada de 0-40 cm, os estoques de C nos tratamentos NT e MCr (milho + C. Cajan na linha) foram significativamente superiores. Os estoques de P variou entre 0,63 e 0,91 t ha-1 e não foram significativamente diferentes entre os tratamentos. O plantio e MCr foram os únicos tratamentos que apresentaram ganhos de carbono, onde o acúmulo foi de 2,67 e 2,91 t C ha-1 ano-1, respectivamente. O tratamento MCr mostra o importante papel das leguminosas no sequestro de carbono. No estudo do fósforo orgânico (Po) do solo com o objetivo de determinar como os teores e formas de Po variam de acordo com os sistemas de preparo e plantas de cobertura utilizadas. Os teores de Po (PMonoester e PDiester) determinados por RMN não foram diferentes entre os tratamentos. Os níveis de Po foram superiores a 59% do total do POlsen extraído e as principais alterações em relação ao PoOlsen ocorreu na camada superficial do solo. O Po (PMonoester e PDiester) determinado pela RMN não alterou entre os tratamentos. A manutenção dos níveis de Po sugere que a disponibilidade de P não está necessariamente ligada à sua acumulação, mas ao aumento dos fluxos entre as formas disponíveis (grupos ativos).

Made available in DSpace on 2015-03-26T13:53:07Z (GMT). No. of bitstreams: 1 texto completo.pdf: 276223 bytes, checksum: 44aa76a888a6f4ca02c88c5ce85698a1 (MD5) Previous issue date: 2008-09-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The use of organic residues in agriculture as fertilizers or soil amendments has gained importance in Brazil as organic agriculture has expanded and fertilizer prices have increased substantially. However, studies that relate manure rates, especially poultry litter (PL), to maximize crop yield with minimum risk to the environment, are scarce. The present study was carried out under field conditions in an Ultisol to evaluate corn grain yield, the changes in soil chemical characteristics, and the P loss potential as a result of surface application of increasing rates of PL for three consecutive years. The PL rates used were 0, 5, 10, 25, 50 and 100 t ha- 1 (DW basis) and they were annually broadcast for three consecutive years and corn was cultivated. The reported soil chemical characteristics were determined after the third year of corn cultivation, thus reflecting the cumulative effect of PL application. It was found that the application of PL had positive effects on corn grain yield (CGY), which ranged from 4423 in control plots to about 12 000 kg ha-1 in high PL rate treatments. In the third year it was estimated that a maximum physical grain yield (&#375; max) of 12 500 kg ha-1 could be achieved with a PL rate of 74.7 t ha-1. However, a more economical grain yield of 11 207 kg ha-1, assigned as 0.9 &#375; max, could be achieved with a PL rate of 21.7 t ha-1. The application of such a high PL rate (74.7 t ha-1) led to a degree of soil P saturation of 21 % estimated with Mehlich-3 (DPSM-3), and a Mehlich-3 P (PM-3) concentration (131 mg kg-1), below the threshold (critical) value, that most environmental indices warn for a potential risk of P loss. Nevertheless, soil water soluble P (WSP) concentration ranged quite above the environmental threshold level, indicating that DPSM-3 values above which P losses are accentuated are lower than those found for other less weathered soils. This fact demonstrates that soil test results or the DPS taken solely provides limited indication into P loss potential and suggests the need of taking the WSP into account to relate to P loss potential. As such, an environmental threshold that also considers WSP critical level led to a more realistic indication of P loss potential. If such WSP threshold is taken into account, an estimated PL rate of 5.1 t ha-1 would be recommended. The observed changes in soil chemical attributes included increases in soil nutrients concentration (N, P, K, Ca2+, Mg2+ and Zn), Na+, pH and total C, and a decrease in exchangeable Al. Finally, the results indicate the PL rate required to maximize CGY would lead to soil P saturation and a WSP concentrations that are well above the environmental threshold. Hence, when recommending PL rate to corn it is suggested that analysis of WSP should be taken into account other than simply grain yield, PM-3 concentrations and the DPS thresholds. / A utilização de resíduos orgânicos na agricultura como fertilizantes ou condicionadores de solo tem ganho importância no Brasil na medida em que a agricultura orgânica tem expandido e os preços de fertilizantes tem aumentado sobremaneira. Contudo, estudos que relacionem as taxas de aplicação de fertilizantes orgânicos, tais como a cama de frango (PL), com o objetivo de aumentar o rendimento de culturas com mínimo risco ao ambiente tem sido escassos. O presente estudo foi conduzido sob condições de campo em um Argisolo Vermelho-Amarelo objetivando-se avaliar o rendimento de grãos de milho, as alterações em algumas caracteristicas químicas do solo, e o potencial de perdas de fósforo (P) como resultado da aplicação consecutiva de doses crescentes de cama de frango em superfície. As doses de PL utilizadas foram 0, 5, 10, 25, 50 e 100 t ha-1 e estas foram aplicadas superficialmente por três anos consecutivos e milho foi cultivado. As características químicas apresentadas foram determinadas ao final do terceiro ano de aplicação da PL. Foi observado que a aplicação de PL teve efeitos positivos sobre o rendimento de grãos (CGY), o qual variou entre 4443 kg ha- 1 no tratamento controle e 12 000 kg ha-1 nos tratamentos com aplicação de altas doses de PL. No terceiro ano, o rendimento físico máximo (&#375; máx) foi estimado como 12 500 kg ha-1, necessitando, portanto, de uma dose de PL de 74.7 t ha-1. Entretanto, um rendimento mais econômico de 11 207 kg ha-1, representado por 0.9 &#375; máx, foi obtido com uma dose de 21.7 t ha-1. A aplicação da dose mais elevada de PL conduziu a um grau de saturação de P de 21% estimado com o extrator Mehlich-3 (DPSM-3) e uma concentração de P pelo mesmo extrator (PM-3, 131 mg kg-1) considerada mais baixa que o valor limite (crítico) que a maioria dos índices ambientais alertam para o potencial risco de perda de P. Contudo, o valor de P soluvel em água (WSP) variou bastante acima do valor preconizado pelos indicadores ambientais, indicando que valores de DPSM-3 acima dos quais perdas de P são acentuadas estão abaixo daqueles encontrados para solos menos intemperizados. Este fato demonstra que medidas isoladas de valores analíticos, como concentração de P ou o DPSM-3, fornecem indicação limitada do real potencial de perda de P e sugerem, pois, a necessidade de se considerar o WSP como medida auxiliar para uma concepção mais realística do potencial de perda de P. Dessa forma, um nível crítico ambiental que também considera os valores críticos de WSP conduziu a uma indicação mais realística da perda de P. Assim, considerando-se valores de WSP, a dose estimada de PL a ser recomendada seria de 5.1 t ha-1. As alterações observadas nos atributos químicos do solo incluiram aumentos nas concentrações de nutrientes (N, P, K+, Ca2+, Mg2+ e Zn), Na+, pH e Carbono total (CT), e descréscimo em Al3+ trocável. Por fim, os resultados obtidos indicam que a dose de cama de frango requerida para a obtenção de rendimento máximo de grãos conduziriam a valores de saturação de P no solo e concentrações de WSP que estão muito acima dos níveis ambientais. Portanto, com vistas a atender recomendações de PL para cultivo de milho com mínimo risco de perdas de P, estas devem incluir análises de WSP complementares as demais medidas de P das análises de rotina ao invés de somente o rendimento de grãos, as concentrações de PM-3 e os níveis críticos ambientais referidos pelo DPSM-3.