Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / Soil is an important means of supplying water to meet the need for agricultural management systems. It is its physical-water properties that make it capable of regulating the availability of water. This study evaluates how the relief forms and different uses influence some physical-water properties of a Red Latosol on a slope in the Rio Grande do Sul Plateau region, and what the implications of these attributes may be on soil water dynamics. In one part of the experimental area with herbaceous cultivation without agricultural traffic, and in another with the no-tillage system, with crops rotation of wheat, soybean and oat, as well as, the use of machinery on the soil. Ten representative sites of the study area were selected as experimental units. In these experimental units, a trench of 0.9 m depth, 1.5 m length and 1.0 m width was excavated. Three depths 30, 60 and 90 cm were delimited for each experimental unit. At each depth, 5 samples of soil with non-deformed structure were collected, being 15 per experimental unit and 150 throughout the study area. All profiles were morphologically examined to characterize the structure, consistency, color, amount of roots, pore type, horizons and soil spots. Physical analyzes of soil density, total porosity, texture and saturated hydraulic conductivity were performed. Levels contours were generated from a topographic planialtimetric survey. In the computational program, it generated preferential arrows of surface runoff and slope interval. It was characterized, for each experimental unit, the forms of slopes. It was found that, in general, in the study area, the curvature in the profile and plane were convergent concave, respectively. Based on this information, the flow of the area tends to converge to a single region, with flows influenced by declivity ranging from 1.83% to 20% in the area as a whole. In the area under no-tillage system, as a function of the saturated hydraulic conductivity, the vertical movement of the water, when it reached depths of 60 cm, was observed. The clay texture was preponderant to 90 cm depth, indicating distribution of the pore size that leads tortuosity of the preferred water paths for storage. Hydrologically, the Latosol under study contains physical characteristics that imply the generation of sub-superficial lateral flow. The flow pattern is governed up to 30 cm deep by angle variations and position of the slope, controlling the soil's ability to conduct water, infiltrate the profile, and transport sediments. The high percentage of clay is the main factor governing the Dynamics of water in 60 and 90 cm, be attributed to the nature of the soil. / O solo é um importante meio de suprimento de água para atender necessidade em sistemas de manejo agrícola. São suas propriedades físico-hídricas que o tornam capaz de regular a disponibilidade de água. Esse estudo avaliar como as formas de relevo e diferentes usos influenciam algumas propriedades físico-hídricas de um Latossolo Vermelho em uma encosta na região do Planalto do Rio Grande do Sul, e quais podem ser as implicações desses atributos na dinâmica de água no solo. Numa parte da área experimental com cultivo de ervais sem tráfego agrícola, e, em outra, com o sistema plantio direto, com rotação das culturas do trigo, soja e aveia, bem como, o uso de maquinário sobre o solo. Selecionou-se, 10 locais representativos da área de estudo como unidades experimentais. Nestas unidades experimentais, escavou-se uma trincheira de 0,9 m de profundidade, 1,5 m de comprimento e 1,0 m de largura. Delimitou-se três profundidades para cada unidade experimental, sendo estas 30, 60 e 90 cm. Em cada profundidade, coletou-se 5 amostras de solo com estrutura não deformada, sendo então 15 por unidade experimental e 150 em toda a área de estudo. Examinou-se morfologicamente todos os perfis para caracterizar a estrutura, consistência, cor, quantidade de raízes, tipo de poros, horizontes e manchas do solo. Realizaram-se análises físicas da densidade do solo, porosidade total, textura e condutividade hidráulica saturada. Gerou-se curvas de níveis da área, a partir de levantamento topográfico planialtimétrico. Em programa computacional, gerou setas preferenciais de escoamento superficial e intervalo de declividade. Caracterizou-se, para cada unidade experimental quanto as formas de vertentes. Constatou-se que, em geral, na área de estudo, a curvatura no perfil e no plano foram côncavas convergentes, respectivamente. Com base nessa informação, o fluxo da área tende a confluir a uma única região, com fluxos influenciados por declividade que varia de 1,83% a 20% na área como um todo. Na área de solo sob sistema plantio direto, em função da condutividade hidráulica saturada, foi constatado a diminuição do movimento vertical da água, quando esta alcança profundidades de 60 cm. A textura argilosa foi preponderante a 90 cm de profundidade, indicando distribuição do tamanho dos poros que conduzem tortuosidade dos caminhos preferenciais da água para armazenamento. Hidrologicamente, o Latossolo em estudo contém características físicas que implicam na geração de fluxo lateral sub-superficial. O padrão de escoamento é governado até 30 cm de profundidade pelas variações de ângulo e a posição da vertente, controlam a capacidade do solo de conduzir a água, infiltrar no perfil, e transportar sedimentos O elevado percentual de argila é o principal fator que governa a dinâmica de água em 60 e 90 cm, sendo atribuídos a natureza do solo.

This diploma thesis deals with design of soil erosion control measures and flood control measures in the cadastral area of Palkovice. The request for construction came from the village Palkovice. It sits at the foothills of Beskydy with a very sloping terrain. In addition, there are larger soil complexes without any erosion control measures, which leads to degradation and reduction of soil yields. The introduction summarizes desired objectives. Then thesis deals with the description and analysis of the current state of the village and its solution. The solution of technical measures is depicted in the situation and elaborated in more detail. The drawings are enclosed in attachment. The conclusion summarizes the content of the work, achieved goals and benefits.

Zur Umsetzung der Ziele der EU-Wasserrahmenrichtlinie sind in Sachsen bis 2015 für Gewässereinzugsgebiete entsprechende Maßnahmen zur Erreichung bzw. Sicherung eines guten Gewässerzustandes durchzuführen. Für die hierzu erforderliche integrierte Planung und Entscheidungsfindung auf Einzugsgebietsebene stellen Entscheidungshilfesysteme den daran beteiligten Akteuren (Flächennutzer, -besitzer, Fachbehörden usw.) die technische Unterstützung bereit. Am Beispiel des überwiegend landwirtschaftlich genutzten Fließgewässereinzugsgebietes der Jahna (Sächsisches Lösshügelland) wurde ein Entscheidungshilfesystem entwickelt und erprobt. Es umfasst zum einen Werkzeuge zur Analyse der Belastungen der Oberflächengewässer und des Grundwassers durch Nährstoffaustrag (z.B. Modell Stoffbilanz) bzw. durch Wassererosion (Modell EROSION 3D). Zum anderen bietet das Entscheidungshilfesystem verschiedene Modelle und Verfahren an, mit deren Hilfe stoffaustragsmindernde landwirtschaftliche Maßnahmen ausgewählt und hinsichtlich ihrer Wirksamkeit abgeschätzt werden können. Ergänzend dazu wurde ein computergestützter Maßnahmenkatalog zur Unterstützung bei der Auswahl stoffaustragsmindernder Maßnahmen im Bereich Landwirtschaft erstellt. Die Priorisierung der verschiedenen Maßnahmenalternativen unter Berücksichtigung ökologischer und ökonomischer Ziele wurde beispielhaft mit Hilfe der Nutzwertanalyse durchgeführt.

An abundance of waste products from the forestry industry (sawdust and paper pulp) lead to the concept of using them as growing media for high value crops on a field scale. However, management of subsequent weed growth posed a problem as the impact of these novel media on the performance and fate of herbicides was unknown. Three aspects of sawdust and paper pulp waste were examined and compared to two cropping soils, viz. their effect on herbicide behaviour with regard to crop selectivity, weed control efficacy and the environmental fate of selected chemicals. Cropping species such as lettuce and onions were more susceptible to alachlor and chlorpropham in sawdust than in paper pulp. The two cropping soils evaluated (Horotiu sandy loam and Mangateretere silt loam) tended to be intermediate although the former was often close to the sawdust and the latter to the paper pulp in terms of herbicide phytotoxicity to the crop plants. For the less water soluble herbicide pendimethalin, the differences in crop selectivity in the different media were not significant. The effect of the media on the efficacy of weed control was evaluated through plant species with a much lower tolerance to the herbicides evaluated in contrast to the above species. For these plants the efficacy of the herbicides was generally lower in both the sawdust and paper pulp than in the two soils. The effect was more pronounced with the more soluble alachlor, where efficacy was reduced by factors of 5 – 10, compared to pendimethalin where efficacy reduction was by factors of 0 – 3. The two high organic media had contrasting effects on the various environmental behaviour indices evaluated. Herbicide adsorption as quantified by distribution coefficient (Kd) was higher in the two novel media compared to both the Horotiu and Mangateretere soils. However, when the Kd was normalised to organic carbon (Koc), there was less variation amongst the media indicating that organic matter is an important factor in controlling sorption in these media. However, despite the high level of adsorption in the sawdust, herbicides were most prone to leaching in this medium. Conversely the paper pulp tended to be more retentive while the two soils were intermediate. The degradation as quantified by half-lives (t½) of the herbicides was generally slower in the two novel media, probably reflecting the higher sorption in these two media but also due to the lower level of microbial activity in the sawdust and paper pulp. The study shows that herbicide behaviour in these carbon based media differs significantly from that expected from soil organic matter, mainly due to the non-humified nature of the organic matter in the media and its poor biological activity.

Agricultural management practices including tillage and irrigation have a considerable effect on soil physical and hydraulic properties in space and time. Tillage practices initially alter the soil physical and hydraulic properties depending on the type and depth of tillage. These changes are reverted back to original conditions due to reconsolidation during cycles of wetting and drying. Irrigation techniques can manipulate the reversion process dynamically due to different modes of wetting. The combined effects of tillage and irrigation have rarely been investigated. Therefore, two experiments were conducted to investigate the effect of different tillage practices and irrigation techniques on soil physical properties and temporal variations in soil hydraulic properties, one on wheat and second on the following maize crop grown on the same plots. The tillage and irrigation treatments implemented for the wheat crop were repeated for the subsequent maize crop restoring the same treatment layout plan. Intact soil core samples were collected, in the middle of the wheat crop before irrigation and the end of the maize crop season, for the determination of soil physical and hydraulic properties. Field saturated hydraulic conductivity (K_fs) was determined using the Guelph pressure infiltrometer method and volumetric soil water content (θ_v) and potential (ψ_m) was measured in the field using water content sensors and tensiometers, respectively. The wheat crop received rain showers from time to time, while in maize, a heavy spell of monsoon rains following tillage caused most of the soil reconsolidation. So, the greater intensity of rains, rather than the cycles of wetting and drying, became primarily responsible for the differences in soil physical and hydraulic properties between the two crops. Moldboard plow resulted in an increase in yield and improvement of soil hydraulic properties during both crop seasons. Flood irrigation reverted back the effects of tillage on soil hydraulic properties greater than sprinkler irrigation, while it did not affect the yield significantly. The dynamics of volumetric soil water content (θ_v) differed, depending on tillage type, irrigation technique and crop season. Moldboard plow was the wettest after rain or irrigation events but it dried quicker than other tillage treatments. Flood irrigation caused higher wetting than sprinkler irrigation. These wetting effects were greater in wheat as compared to maize crop. Temporal variability calculated as time averaged relative difference in θ_v was greater during wheat as compared to maize, while temporal stability calculated as standard deviation of temporal stability decreased with flood irrigation in both crops. Soil bulk density (ρ_b) and water retention characteristics (θ_v (ψ_m )) measured on the intact soil cores and total porosity (φ), plant available water capacity (θ_PAWC) and pore size distribution calculated from water retention data depended on the time of sampling. During wheat, the ρ_b was lower resulting in a higher φ than after maize. Moldboard plow decreased ρ_b increasing φ, while the effect of flood irrigation was opposite in both crops with greater magnitude in wheat. Similarly, the effects of tillage on θ_v (ψ_m ) were observed in both crops, while those of irrigation were observed in maize only. Cultivator treatment retained higher θ_v at higher ψ_m (−30 and −100 kPa), followed by chisel and moldboard plow. Plant available water capacity (θ_PAWC) was greater in maize as compared to the wheat crop. Cultivator had higher θ_PAWC than chisel and moldboard plow in both crops. Wheat had greater volume of larger pores (> 10 μm, φ_(>10)), whereas extraordinary rains as well as irrigations after tillage caused these larger pores to decrease in maize. Moldboard plow had higher φ_(>10) at 10 cm depth in both crops with greater magnitude in wheat. Field saturated hydraulic conductivity (K_fs) determined before irrigations and at the end of both crop seasons was greater in wheat than in maize especially in the first determination. Moldboard plow exhibited greater K_fs followed by chisel plow and cultivator in both crops and it decreased significantly with time in wheat but not in maize. Flood irrigation was responsible for a reduction in K_fs and the effect was greater in wheat as compared to maize. It was concluded that a greater intensity of water application in the form of rains or irrigations can revert the changes in soil physical and hydraulic properties induced by tillage more effectively than the cycles of wetting and drying. Soil hydraulic properties may be optimized with the combination of suitable tillage and irrigation for efficient utilization of water resources.

The objectives of this research were to develop and evaluate a field method for in situ measurement of soil properties using visible near-infrared reflectance spectroscopy (Vis-NIRS). A probe with an independent light source for acquiring soil reflectance spectra from soil cores was developed around an existing portable field spectrometer (ASD FieldSpecPro, Boulder, CO, USA; 350-2500 nm). Initial experiments tested the ability of the acquired spectra to predict plant root density, an important property in soil carbon dynamics. Reflectance spectra were acquired from soil containing ryegrass roots (Lolium multiflorum) grown in Allophanic and Fluvial Recent soils in a glasshouse pot trial. Differences in root density were created by differential nitrogen and phosphorus fertilization. Partial least squares regression (PLSR) was used to calibrate spectral data (pre-processed by smoothing and transforming spectra to the first derivative) against laboratory-measured root density data (wet-sieve technique). The calibration model successfully predicted root densities (r2 = 0.85, RPD = 2.63, RMSECV = 0.47 mg cm-3) observed in the pots to a moderate level of accuracy. This soil reflectance probe was then tested using a soil coring system to acquire reflectance spectra from two soils under pasture (0-60 mm soil depths) that had contrasting root densities. The PLSR calibration models for predicting root density were more accurate when soil samples from the two soils were separated rather than grouped. A more accurate prediction was found in Allophanic soils (r2 = 0.83, RPD = 2.44, RMSECV = 1.96 mg g-1) than in Fluvial Recent soils (r2 = 0.75, RPD = 1.98, RMSECV = 5.11 mg g-1). The Vis-NIRS technique was then modified slightly to work on a soil corer that could be used to measure root contents from deeper soil profiles (15- 600 mm depth) in arable land (90-day-old maize crop grown in Fluvial Recent soils). PLSR calibration models were constructed to predict the full range of maize root densities (r2 = 0.83, RPD = 2.42, RMSECV = 1.21 mg cm-3) and also soil carbon (C) and nitrogen (N) concentrations that had been determined in the laboratory (LECO FP- 2000 CNS Analyser; Leco Corp., St Joseph, MI, USA). Further studies concentrated on improving the Vis-NIRS technique for prediction of total C and N concentrations in differing soil types within different soil orders in the field. The soil coring method used in the maize studies was evaluated in permanent and recent pastoral soils (Pumice, Allophanic and Tephric Recent in the Taupo-Rotorua Volcanic Zone, North Island) with a wide range of soil organic matter contents resulting from different times (1-5 years) since conversion from forest soils. Without any sample preparation, other than the soil surface left after coring, it was possible to predict soil C and N concentrations with moderate success (C prediction r2 = 0.75, RMSEP = 1.23%, RPD = 1.97; N prediction r2 = 0.80, RMSEP = 0.10%, RPD = 2.15) using a technique of acquiring soil reflectance spectra from the horizontal cross-section of a soil core (H method). The soil probe was then modified to acquire spectra from the curved vertical wall of a soil core (V method), allowing the spectrometer’s field of view to increase to record the reflectance features of the whole soil sample taken for laboratory analysis. Improved predictions of soil C and N concentrations were achieved with the V method of spectral acquisition (C prediction r2 = 0.97, RMSECV = 0.21%, RPD = 5.80; N prediction r2 = 0.96, RMSECV = 0.02%, RPD = 5.17) compared to the H method (C prediction r2 = 0.95, RMSECV = 0.27%, RPD = 4.45; N prediction r2 = 0.94, RMSECV = 0.03%, RPD = 4.25). The V method was tested for temporal robustness by assessing its ability to predict soil C and N concentrations of Fluvial Recent soils under permanent pasture in different seasons. When principal component analysis (PCA) was used to ensure that the spectral dimensions (which were responsive to water content) of the data set used for developing the PLSR calibration model embraced those of the “unknown” soil samples, it was possible to predict soil C and N concentrations in “unknown” samples of widely different water contents (in May and November), with a high level of accuracy (C prediction r2 = 0.97, RMSEP = 0.36%, RPD = 3.43; N prediction r2 = 0.95, RMSEP = 0.03%, RPD = 3.44). This study indicates that Vis-NIRS has considerable potential for rapid in situ assessment of soil C, N and root density. The results demonstrate that field root densities in pastoral and arable soil can be predicted independently from total soil C, which will allow researchers to predict C sequestration from root production. The recommended “V” technique can be used to assess spatial and temporal variability of soil carbon and nitrogen within soil profiles and across the landscape. It can also be used to assess the rate of C sequestration and organic matter synthesis via root density prediction. It reduces the time, labour and cost of conventional soil analysis and root density measurement.

The major land use in New Zealand is pastoral farming of sheep and cattle. In intensively grazed dairy-pasture systems, animals graze on nitrogen (N)-rich legume-based pastures, but do not efficiently utilize the N they ingest. On average only 10.5% of the N in forage-based animal feed is converted into milk and the remainder is excreted in dung and urine. In the pastures, a cow urine patch can typically contain up to 1000 kg N ha-1. Nitrogen input, either in the form of cow urine or fertilizer, often exceeds immediate plant requirements and hence is susceptible to losses as ammonia (NH3) volatilisation and nitrous oxide (N2O) emissions and removal in drainage water through nitrate (NO3-) leaching. This loss of N from grazed pastures causes detrimental environmental impacts in the form of acidification and eutrophication of the soil and water bodies, global warming, destruction of stratospheric ozone, and NO3- toxicity. Various approaches have been attempted to mitigate the economic and environmental impacts of N losses. One such approach is the use of Urease (UIs) and Nitrification (NIs) inhibitors. There have been extensive studies on the value of UIs in arable farming and NIs in grazed pastures. However, only limited work on the impact of UI and NI alone and in combination in influencing the N dynamics, and thus mitigating N gaseous losses from pastures, has been conducted. This thesis examines the impact of UI (Agrotain; N-(n-butyl) thiophosphoric triamide) and NI (Dicyandiamide, commonly known as DCD), when applied alone or in combination to cow urine and urea fertiliser, on N losses through NH3 and N2O emissions and NO3- leaching, and on herbage production under glasshouse conditions and a field-plot study. The degradation rate of DCD, and its effect on nitrification and on N2O emissions from four soils varying in their physical and chemical properties was also examined under laboratory incubations. The results from the field-plot study were then used to predict the effect of DCD on N2O emissions reductions from urine by adapting the process-based NZ-DNDC model. Both NH3 and N2O emissions have common sources in agriculture. Therefore, chambers were adapted to measure their emissions simultaneously using active and passive gas sampling. Active sampling involved continuous air flow and the use of acid (0.05 M H2SO4 and 2% H3BO3) traps for NH3 measurements and passive sampling involved collecting three gas samples over a one-hour period from a static chamber used for N2O emissions. The first glasshouse experiment used UI with urine or urea to assess its effect on NH3 and N2O emissions, changes in soil mineral-N and N uptake by pasture plants. The UI treatments also involved two commercial products, Sustain Yellow (urea coated with Agrotain and elemental S) and Sustain Green (urea coated with Agrotain). The use of UI effectively decreased total NH3 emissions, as well as delaying the time of maximum NH3 emissions from both urea (600 kg N ha-1) and urine (476 kg N ha-1) by 27% and 22%, respectively. The UI-induced decrease in NH3 volatilization ranged from 42-48% when urea was applied @ 100 kg N ha-1. Urease inhibitor was also effective in decreasing N2O emissions significantly from urine and urea applied @ 100 kg N ha-1. The addition of UI increased dry matter yield by 13-19% as compared to the urea-alone treatment. In the second glasshouse study, NI (DCD) was added @ 25 kg ha-1 to urea (@ 25, 50 and 75 kg N ha-1) and urine (@ 144, 290 and 570 kg N ha-1) applied at different rates. Addition of DCD reduced N2O emissions from both urea and urine and NO3- leaching from urine. Dicyandiamide reduced N2O emissions by 34-93% from the added urea and 33-80% from the added urine. However, its use increased the amount of ammonium (NH4+) present in the soil by 3 to 13% both in the urea and urine treatments, and this NH4+ was susceptible to leaching and volatilisation losses. The addition of DCD, however, resulted in a 60-65% reduction in NO3- leaching from urine applied to pasture soil cores. It also caused a significant reduction in NO3- -induced cation leaching. Leaching of K+, Mg+2 and Ca+2 ions was reduced by 36-42%, 33-50% and 72%, respectively, with DCD applied to cattle urine (290 and 570 kg N ha-1). The combined use of UI and NI was more effective in controlling N gaseous losses than using them individually. The combination of UI and NI retarded NH3 emissions by 70% in the urea treatment and by 4% in the urine treatment (field-plot study). It also considerably reduced N2O emissions (50-51%) following the application of urea and urine (field-plot study) to pasture soil. With the combined inhibitors, there was a 14 and 38% increase in herbage yield from added urea and urine (field-plot study), respectively. A laboratory incubation experiment was undertaken to study the effect of soil types and the rate of DCD application on the degradation kinetics of DCD. The rate of degradation of DCD varied among the four soils studied. The degradation was slowest (half-life period of 6 to 11 days) in an allophanic soil with a high concentration of organic matter. The effectiveness of DCD in inhibiting nitrification also varied depending on the nature and amount of soil organic matter and clay content. The maximum inhibition was observed in a soil with low organic matter and high clay content. Finally, 'NZ-DNDC', a process-based model, was adapted and used to simulate the effect of DCD on emissions reduction using DCD inhibition values that vary according to different soil types. This model effectively simulated the effect of DCD on N2O emissions reductions in Tokomaru silt loam following urine application. However, more field data are required from a range of pasture soils with contrasting amount of soil organic matter and clay content under differing climatic conditions to further test this model modification to predict emission-reductions with DCD application in different soil types.

The objectives of this research were to develop and evaluate a field method for in situ measurement of soil properties using visible near-infrared reflectance spectroscopy (Vis-NIRS). A probe with an independent light source for acquiring soil reflectance spectra from soil cores was developed around an existing portable field spectrometer (ASD FieldSpecPro, Boulder, CO, USA; 350-2500 nm). Initial experiments tested the ability of the acquired spectra to predict plant root density, an important property in soil carbon dynamics. Reflectance spectra were acquired from soil containing ryegrass roots (Lolium multiflorum) grown in Allophanic and Fluvial Recent soils in a glasshouse pot trial. Differences in root density were created by differential nitrogen and phosphorus fertilization. Partial least squares regression (PLSR) was used to calibrate spectral data (pre-processed by smoothing and transforming spectra to the first derivative) against laboratory-measured root density data (wet-sieve technique). The calibration model successfully predicted root densities (r2 = 0.85, RPD = 2.63, RMSECV = 0.47 mg cm-3) observed in the pots to a moderate level of accuracy. This soil reflectance probe was then tested using a soil coring system to acquire reflectance spectra from two soils under pasture (0-60 mm soil depths) that had contrasting root densities. The PLSR calibration models for predicting root density were more accurate when soil samples from the two soils were separated rather than grouped. A more accurate prediction was found in Allophanic soils (r2 = 0.83, RPD = 2.44, RMSECV = 1.96 mg g-1) than in Fluvial Recent soils (r2 = 0.75, RPD = 1.98, RMSECV = 5.11 mg g-1). The Vis-NIRS technique was then modified slightly to work on a soil corer that could be used to measure root contents from deeper soil profiles (15- 600 mm depth) in arable land (90-day-old maize crop grown in Fluvial Recent soils). PLSR calibration models were constructed to predict the full range of maize root densities (r2 = 0.83, RPD = 2.42, RMSECV = 1.21 mg cm-3) and also soil carbon (C) and nitrogen (N) concentrations that had been determined in the laboratory (LECO FP- 2000 CNS Analyser; Leco Corp., St Joseph, MI, USA). Further studies concentrated on improving the Vis-NIRS technique for prediction of total C and N concentrations in differing soil types within different soil orders in the field. The soil coring method used in the maize studies was evaluated in permanent and recent pastoral soils (Pumice, Allophanic and Tephric Recent in the Taupo-Rotorua Volcanic Zone, North Island) with a wide range of soil organic matter contents resulting from different times (1-5 years) since conversion from forest soils. Without any sample preparation, other than the soil surface left after coring, it was possible to predict soil C and N concentrations with moderate success (C prediction r2 = 0.75, RMSEP = 1.23%, RPD = 1.97; N prediction r2 = 0.80, RMSEP = 0.10%, RPD = 2.15) using a technique of acquiring soil reflectance spectra from the horizontal cross-section of a soil core (H method). The soil probe was then modified to acquire spectra from the curved vertical wall of a soil core (V method), allowing the spectrometer’s field of view to increase to record the reflectance features of the whole soil sample taken for laboratory analysis. Improved predictions of soil C and N concentrations were achieved with the V method of spectral acquisition (C prediction r2 = 0.97, RMSECV = 0.21%, RPD = 5.80; N prediction r2 = 0.96, RMSECV = 0.02%, RPD = 5.17) compared to the H method (C prediction r2 = 0.95, RMSECV = 0.27%, RPD = 4.45; N prediction r2 = 0.94, RMSECV = 0.03%, RPD = 4.25). The V method was tested for temporal robustness by assessing its ability to predict soil C and N concentrations of Fluvial Recent soils under permanent pasture in different seasons. When principal component analysis (PCA) was used to ensure that the spectral dimensions (which were responsive to water content) of the data set used for developing the PLSR calibration model embraced those of the “unknown” soil samples, it was possible to predict soil C and N concentrations in “unknown” samples of widely different water contents (in May and November), with a high level of accuracy (C prediction r2 = 0.97, RMSEP = 0.36%, RPD = 3.43; N prediction r2 = 0.95, RMSEP = 0.03%, RPD = 3.44). This study indicates that Vis-NIRS has considerable potential for rapid in situ assessment of soil C, N and root density. The results demonstrate that field root densities in pastoral and arable soil can be predicted independently from total soil C, which will allow researchers to predict C sequestration from root production. The recommended “V” technique can be used to assess spatial and temporal variability of soil carbon and nitrogen within soil profiles and across the landscape. It can also be used to assess the rate of C sequestration and organic matter synthesis via root density prediction. It reduces the time, labour and cost of conventional soil analysis and root density measurement.

The objectives of this research were to develop and evaluate a field method for in situ measurement of soil properties using visible near-infrared reflectance spectroscopy (Vis-NIRS). A probe with an independent light source for acquiring soil reflectance spectra from soil cores was developed around an existing portable field spectrometer (ASD FieldSpecPro, Boulder, CO, USA; 350-2500 nm). Initial experiments tested the ability of the acquired spectra to predict plant root density, an important property in soil carbon dynamics. Reflectance spectra were acquired from soil containing ryegrass roots (Lolium multiflorum) grown in Allophanic and Fluvial Recent soils in a glasshouse pot trial. Differences in root density were created by differential nitrogen and phosphorus fertilization. Partial least squares regression (PLSR) was used to calibrate spectral data (pre-processed by smoothing and transforming spectra to the first derivative) against laboratory-measured root density data (wet-sieve technique). The calibration model successfully predicted root densities (r2 = 0.85, RPD = 2.63, RMSECV = 0.47 mg cm-3) observed in the pots to a moderate level of accuracy. This soil reflectance probe was then tested using a soil coring system to acquire reflectance spectra from two soils under pasture (0-60 mm soil depths) that had contrasting root densities. The PLSR calibration models for predicting root density were more accurate when soil samples from the two soils were separated rather than grouped. A more accurate prediction was found in Allophanic soils (r2 = 0.83, RPD = 2.44, RMSECV = 1.96 mg g-1) than in Fluvial Recent soils (r2 = 0.75, RPD = 1.98, RMSECV = 5.11 mg g-1). The Vis-NIRS technique was then modified slightly to work on a soil corer that could be used to measure root contents from deeper soil profiles (15- 600 mm depth) in arable land (90-day-old maize crop grown in Fluvial Recent soils). PLSR calibration models were constructed to predict the full range of maize root densities (r2 = 0.83, RPD = 2.42, RMSECV = 1.21 mg cm-3) and also soil carbon (C) and nitrogen (N) concentrations that had been determined in the laboratory (LECO FP- 2000 CNS Analyser; Leco Corp., St Joseph, MI, USA). Further studies concentrated on improving the Vis-NIRS technique for prediction of total C and N concentrations in differing soil types within different soil orders in the field. The soil coring method used in the maize studies was evaluated in permanent and recent pastoral soils (Pumice, Allophanic and Tephric Recent in the Taupo-Rotorua Volcanic Zone, North Island) with a wide range of soil organic matter contents resulting from different times (1-5 years) since conversion from forest soils. Without any sample preparation, other than the soil surface left after coring, it was possible to predict soil C and N concentrations with moderate success (C prediction r2 = 0.75, RMSEP = 1.23%, RPD = 1.97; N prediction r2 = 0.80, RMSEP = 0.10%, RPD = 2.15) using a technique of acquiring soil reflectance spectra from the horizontal cross-section of a soil core (H method). The soil probe was then modified to acquire spectra from the curved vertical wall of a soil core (V method), allowing the spectrometer’s field of view to increase to record the reflectance features of the whole soil sample taken for laboratory analysis. Improved predictions of soil C and N concentrations were achieved with the V method of spectral acquisition (C prediction r2 = 0.97, RMSECV = 0.21%, RPD = 5.80; N prediction r2 = 0.96, RMSECV = 0.02%, RPD = 5.17) compared to the H method (C prediction r2 = 0.95, RMSECV = 0.27%, RPD = 4.45; N prediction r2 = 0.94, RMSECV = 0.03%, RPD = 4.25). The V method was tested for temporal robustness by assessing its ability to predict soil C and N concentrations of Fluvial Recent soils under permanent pasture in different seasons. When principal component analysis (PCA) was used to ensure that the spectral dimensions (which were responsive to water content) of the data set used for developing the PLSR calibration model embraced those of the “unknown” soil samples, it was possible to predict soil C and N concentrations in “unknown” samples of widely different water contents (in May and November), with a high level of accuracy (C prediction r2 = 0.97, RMSEP = 0.36%, RPD = 3.43; N prediction r2 = 0.95, RMSEP = 0.03%, RPD = 3.44). This study indicates that Vis-NIRS has considerable potential for rapid in situ assessment of soil C, N and root density. The results demonstrate that field root densities in pastoral and arable soil can be predicted independently from total soil C, which will allow researchers to predict C sequestration from root production. The recommended “V” technique can be used to assess spatial and temporal variability of soil carbon and nitrogen within soil profiles and across the landscape. It can also be used to assess the rate of C sequestration and organic matter synthesis via root density prediction. It reduces the time, labour and cost of conventional soil analysis and root density measurement.

The soils used by the East Coast Organic Producers Trust (ECOPT; the grower group that this study is targeted towards) have exceptionally low soil Olsen P concentrations (ca. 6 mg/L). These and other limitations (e.g. poor weed and pest and disease control) result in many ECOPT growers being unable to produce economic yields on anything other than small scale gardens. Fertilisers and manures are seldom used by these growers, which exacerbates the problem. Thus, the object of this research was to provide information to ECOPT on which fertilisers and application strategies would provide the best returns on their phosphorus (P) fertiliser investment. The experimental work was carried out in two parts. A laboratory study tested a range of phosphate rock (PR) based fertilisers and application rates; Ben Guerir reactive phosphate rock (RPR; 67, 133, 267, 533 and 1,333 mg P/kg soil), BioPhos and BioSuper (267 and 1,333 mg P/kg soil) and a no fertiliser Control. Soil fertiliser mixtures were incubated for 155 days and periodic measurements of PR dissolution, soil pH and Bic-P (analogous to Olsen P but expressed in µg/g) were undertaken. The field study used fewer application rates and two application methods; banded and broadcast. Broadcast plots were applied at 678 mg P/kg soil (488 kg P/ha); banded RPR was applied at 236, 678 and 1475 mg P/kg soil (40, 115 and 250 kg P/ha respectively) and banded BioPhos and BioSuper at 678 mg P/kg soil (115 kg P/ha). A Control was also included. Fertilisers were applied in October 2004 and changes in soil pH and Bic-P were measured in the broadcast plots only over a 344 day period. Potato (Solanum tuberosum L. cv. Desiree) was the test crop. Regression analysis was used to generate exponential equations to describe the changes in Bic-P over time (∆Bic-P). Differences between fertilisers in the amount of P dissolved and pH fluxes were used to explain the differences in ∆Bic-P. BioSuper dissolved quicker and generated greater ∆Bic-P than RPR and BioPhos, which were similar. Higher application rates produced greater increases in Bic-P than lower rates but decreased the % of P applied that dissolved. The increase in Bic-P over time from fertiliser application was much slower in the field compared with the laboratory. This was put down to differences in experimental conditions; mainly soil pH and soil aggregate surface area. Potato tuber yield (mean = 35 t/ha) did not respond to any of the fertiliser treatments despite a significant increase in P concentration of the shoots mid-way through the season in all broadcast treatments (shoot P concentration was not analysed in the banded plots). Water and N availability were the main limiting factors in this season as the crop was not irrigated and soil N supply was insufficient to produce a full canopy. Phosphorus response curves generated using the fertiliser response model PARJIB (Reid, 2002), and an economic analysis, indicated that for RPR and BioPhos the optimum economic application rate was 200 kg P/ha and for BioSuper it was 100 kg P/ha (applied every third and second year respectively).