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).

Sulphur is an important nutrient to plants, and reports of its deficiency have been increasing worldwide. Sulphur starvation causes losses in both yield and quality, and it reduces nitrogen use efficiency of plants. As the timing for fertilisation can be decisive for avoiding deleterious effects, improvements in the description of the sulphur balance in fields are a valuable contribution for assisting fertiliser management. Sulphate is the most important inorganic form of sulphur in soils. Being the mobile form, sulphate is readily available for plants, and also prone to be leached. Therefore the description of the movement of sulphate is the key component of the sulphur balance. Leaching of sulphate from the soil can be significantly delayed by its adsorption onto the soil particles. Soil type and pH are the main factors defining the sulphate adsorption capacity; although the presence of other ions in the soil solution can have a considerable effect. It has been reported that in some soils, typically volcanic and tropical soils with variable-charge characteristics, the co-presence of sulphate and calcium can substantially enhance their retention via ion-pair adsorption (IPA). To determine the influence of cations on the movement of sulphate, series of batch and miscible displacement experiments were conducted using two New Zealand soils, of contrasting ion adsorption capacities: the Taupo sandy and Egmont loam soils. These experiments demonstrated the occurrence of cooperative adsorption of sulphate and calcium in the Egmont soil, but not in the Taupo soil. Batch experiments were conducted to examine the IPA adsorption process in the Egmont soil in more detail. Based on the analyses of the results from these two series of experiments, plus the review of published data, three different mathematical approaches for evaluating the amount of solute adsorbed as ion-pairs are proposed. A computer program was built for solving an adsorption model using these three approaches, and was used to compare the model's predictions and the observed adsorption data. An extension of this program, coupling the adsorption model with a solute transport description, was used to simulate the movement of sulphate and calcium. Comparisons between the data from the miscible displacements and the results from this model are used to demonstrate the applicability of the proposed IPA description for modelling the transport of these ions in the soil. Finally, results from a pot trial with Egmont soil are used to examine the relevance of IPA for the movement of sulphate under non-equilibrium conditions, and with active plant growth. Although the results from this experiment regarding IPA were statistically non-significant, some insights could be obtained and are discussed. More studies involving IPA under non-equilibrium experiments are needed for a better understanding of the relevance of IPA in field conditions.

Depuis la seconde moitié du XXème siècle, l'utilisation massive des engrais desynthèse a contribué à l’augmentation des rendements mais aussi à l’accumulation d’élémentsminéraux dans les systèmes agricoles. La limitation de cette accumulation passe par unmeilleur recyclage des éléments minéraux déjà présents dans les systèmes agricoles.L'agriculture biologique, qui interdit le recours aux engrais de synthèse, peut être considéréecomme un prototype d’agriculture à même d’améliorer ce recyclage. L’objectif de cette thèse a été d’identifier les stratégies mises en place par les agriculteurs biologiques pour s’approvisionner en éléments minéraux. Cet objectif a été décliné en sous-objectifs qui ont été(i) d’identifier les pratiques d’approvisionnement en fertilisants et aliments des agriculteursbiologiques, (ii) d’en comprendre les déterminants et (iii) d’évaluer la performance de ces pratiques vis-à-vis du recyclage de l’azote, du phosphore et du potassium. Pour ce faire, 63exploitations biologiques ont été enquêtées afin de recueillir des données concernant la natureet la quantité des matières échangées, ainsi que les fournisseurs et les collecteurs en relation avec ces exploitations. Afin d’étudier l’influence du contexte local, les enquêtes ont été menées dans trois régions agricoles sélectionnées en fonction de leur degré de spécialisation (productions végétales, productions animales et mixte). L’intensité du recyclagelocal a été évaluée grâce à deux indicateurs : l’autonomie, définie comme le ratio entre laquantité d’éléments minéraux provenant d’échanges entre exploitations et la quantité totale d’éléments minéraux entrant dans les exploitations biologiques de la région, et le degré de bouclage des cycles, défini comme la proportion d'éléments minéraux passant au moins deux fois par la même exploitation au sein de la région étudiée. Un premier niveau d’analyse, àl’échelle de l’exploitation, a mis en évidence les déterminants de l’approvisionnement en éléments minéraux des exploitations biologiques. Il a montré que les exploitations biologiques spécialisées dans les productions végétales importaient des quantités importantes defertilisants organiques en provenance de l’agriculture conventionnelle. Un second niveau d’analyse, à l’échelle régionale, a montré que la proximité entre des exploitations agricoles spécialisées dans les productions végétales et d’autres spécialisées dans les productions animales favorisait les échanges entre ces exploitations. Ces échanges permettaient d’améliorer l’autonomie locale même si le degré de bouclage des cycles restait faible. Enfin, une approche par modélisation a permis de quantifier la fraction du phosphore des produits biologiques qui dérive des engrais de synthèse, notamment suite aux échanges entre lesexploitations biologiques et conventionnelles. Plus de deux tiers du phosphore composant les productions biologiques étaient du phosphore initialement issu d’apports d’engrais de synthèse. Les résultats obtenus dans cette thèse ont permis de discuter des forme d’organisation des systèmes agricoles à même d’améliorer le recyclage des éléments minéraux, mais aussi des possibilités de développement de l’agriculture biologique. / From the second half of the 20th century, massive application of artificial fertilisersworldwide has contributed to crop yield increases but also to accumulation of nutrients inagricultural systems. Preventing such accumulation is possible through better nutrientrecycling within agrosystems. Organic farming bans artificial fertilisers and may beconsidered as prototype of agriculture that recycles nutrients efficiently. The objective of thisPhD was to identify the strategies of organic farmers to source nutrients. This objective hasbeen broken down into three tasks: (i) identification of the fertilising materials and feedsinputs of organic farms, (ii) identification of the determinants of these inputs and (iii)assessment of their efficiency in recycling nitrogen, phosphorus and potassium. This workwas based on interviews with 63 organic farmers about their inputs and outputs (nature andamounts of trade products, type of suppliers and collectors). In order to account for theimportance of the local context, the interviews were conducted in three French agriculturaldistricts defined by their farming specialisation: these districts were specialised either in cropproduction or animal production or were kept mixed. Local nutrient recycling has beenassessed through two indicators: the autonomy was defined as the ratio between the amount ofnutrients coming from exchanges among farms and the sum of inputs to the organic farms ofthe district. The cycling index was defined as the proportion of nutrients flowing at least twicethrough the same farm. The analysis was implemented at two different scales. At farm scale,the analysis focused on the nutrient supply of organic farms. Results showed that arableorganic farms imported large amounts of organic fertilising materials from conventionalfarming. At regional scale, results showed that the proximity between arable and animal farmsfostered exchanges among farms. These exchanges increased local autonomy. However, evenfor the mixed district, the cycling index remained low. Finally, a modelling approachquantified the fraction of phosphorus in organic products that derived from artificialfertilisers. Results showed that more than two-thirds of phosphorus composing these productsderived from artificial fertilisers. These results may help to design farming systems thatenhance nutrient recycling and to discuss the possibility of organic farming development.

Phosphorus (P) one of the essential elements to plants and animals, is a non-renewable resource and accuatlly high demanded in agriculture. The World\'s population growth and future estimatives on food demands raises the question about the sustainability of the current agriculture systems, speccially concerns about the low P use efficiency in agroecosystems. Brazilian agriculture requires high P inputs and many researches has been developed to increase the crops yield and, consequently, food production efficiency. However, this development was achieved at the high costs of mineral fertilisers (specially P) and long-term perspectives about the costs of the intensification in the tropical agriculture is accuattly in debate. In this conxtext, in the present thesis chapter two we evaluated the evolution of the Brazilian cropland basis and P demands, quantifying the Brazil P Legacy and, based on scenarios involving the cropland area and yield expansion, we estimated the future (up to 2050) Legacy P and P fertilisers demand. We also estimated the potential aleviation that could be achieved in the mineral fertilizers consumption by utilisation and improvements on manure P recycling. Alternatively, considering the systems intensification and its effects on P availability, we proposed alternative scenarios to promote the Legacy P utilisation in Brazil\'s improved agriculture systems to grant the agriculture expansion without huge increments on the national P fertilisers consumption. A worldwide recognized advance in Brazilian agriculture is the Cerrado, where large cropland areas accually are cultivated twice a year, improving the food and fiber production without any additional disturbance of natural ecossystems. In this context, no-tillage (NT) agriculture has been widely used and, as consequence, soil fertility has been improved, which could be also farorable to the P availability, when rotation with crop species with P mobilization mechanisms are introduced, such as cover crops utilisation. However, the effects of these improved rotated systems on P bioavailability in long-term in tropical soils remains uncert in the literature and was our objective in the chapter three, where is described a study envolving the evaluation of long-term changes on P fractions in tropical Oxisols, from two long-term field trials involving tillage systems (NT and conventional tillage, CT) and cover crops (millet, brachiaria, maize and control, fallow). The long-term cultivation generated large amounts of legacy P in the soil and with the brachiaria introduction as cover crop, more P was recycled in the topsoil and labile P and all the organic P fractions increased. Based on the cover crop effects, we proposed that the bioavailability of the legacy P could be represented by the P extracted by the labile fractions + moderately labile P fractions. In the chapter four, we used other techniques actually widely applied to P speciation, and we applied in tropical soils affected by the native Cerrado conversion into NT and CT agriculture. A multiple approach to identify and quantify the P forms in tropical soils were proposed by the utilisation of Hedley\'s fractionation togheter with P K-edge XANES for P-bindings into inorganic soil matrix and liquid 31P-NMR spectroscopy to complement the organic P species in tropical soils. / Fósforo (P), um dos elementos essenciais às plantas e animais, é um recurso não-renovável e altamente demandado na agricultura atualmente. O crescimento da população mundial e as estimativas futuras da demanda de alimentos aumentam os questionamentos sobre a sustentabilidade dos sistemas agrícolas atuais, especialmente no que se refere a baixa eficiência no uso do P na agricultura. A agricultura brasileira requer altas quantidades de P e muitas pesquisas tem sido desenvolvidas para aumentar a produtividades das culturas e, conseequentemente, a eficiencia da produção de alimentos. Entretanto, este desenvolvimento tem sido alcançado a altos custos com uso de fertilizantes minerais (sobretudo P) e as perspectivas de longo prazo sobre os custos da intensificação da agricultura tropical estão atualmente em debate. Nesse contexto, no capítulo dois da presente tese avaliamos a evolução da área cultivada no Brasil e das demandas de P, quantificando o legado do P no Brasil e, baseado em cenários envolvendo a expansão da área cultivada e da produtividade, estimamos o futuro (até 2050) legado de P e as demandas por fertilizantes fosfatados. Ainda estimamos a potencial redução no consumo de fertilizantes fosfatados que pode ser alcançada pela utilização e melhorias na reciclagem do P oriundo de dejetos. Alternativamente, considerando a intensificação dos sistemas e seus efeitos na disponibilidade de P, propusemos cenários alternativos visando a utilização do \"Legacy P\" em sistemas agrícolas melhorados para garantir a expansão agrícola sem drásticos incrementos no consumo nacional de fertilizantes fosfatados. Um avanço internacionalmente reconhecido na agricultura Brasileira é o Cerrado, onde extensas áreas agrícolas são cultivadas duas vezes ao ano, incrementando assim a produção de alimentos e fibras sem qualquer custo aos ecossistemas naturais. Nesse contexto, a agricultura sob plantio direto (PD) tem sido amplamente difundida e, como consequencia, a fertilidade dos solos tem-se elevado, o que pode também favorecer a disponibilidade de P, quando são introduzidas rotações com espécies de plantas que apresentam mecanismos de mobilização do P, como o uso de plantas de cobertura. Entretanto, os efeitos desses sistemas melhorados de rotação na biodisponibilidade de P em solos tropicais no longo prazo permanecem incertos na literatura e foram objeto de estudo no capítulo três, onde está descrito um estudo envolvendo a avaliação das mudanças de longo-prazo nas frações de P em Latossolos, oriundos de dois experimentos de campo de longa duração no Cerrado, envolvendo a avaliação de sistemas de preparo (PD e preparo convencional, PC) e plantas de cobertura (milheto, braquiária milho e um controle, apenas pousio). O cultivo por longo tempo resultou em grandes quantididades de \"Legacy P\" acumulado no solo e, com o uso de braquiária como cultura de cobertura, maior quantidade de P foi reciclado para as camadas superiores do solo e as frações de P lábil e todas as frações organicas aumentaram. Baseado nos efeitos das plantas de cobertura, sugerimos que a biodisponibilidade do \"Legacy P\" pode ser representada pelo P extraído nas frações lábeis + o P de frações moderadamente lábeis. No capítulo quatro, utilizamos outras técincas atualmente difundidas para a especiação de P, aplicando-as em solos tropicais influenciados pela conversão do Cerrado nativo em agricultura sob PD e PC. Uma abordagem múltipla para identificação e quantificação de formas de P em solos tropicais foi proposta através da utilização do fracionamento de P proposto por Hedley em conjunto com a especiação de P por XANES da borda K do P para identificação de ligação do P a matrix inorgânica do solo, e espectroscopia de ressonância magnética nuclear (NMR) para complementação da identificação de espécies orgânicas de P em solos tropicais.

Phosphorus (P) one of the essential elements to plants and animals, is a non-renewable resource and accuatlly high demanded in agriculture. The World\'s population growth and future estimatives on food demands raises the question about the sustainability of the current agriculture systems, speccially concerns about the low P use efficiency in agroecosystems. Brazilian agriculture requires high P inputs and many researches has been developed to increase the crops yield and, consequently, food production efficiency. However, this development was achieved at the high costs of mineral fertilisers (specially P) and long-term perspectives about the costs of the intensification in the tropical agriculture is accuattly in debate. In this conxtext, in the present thesis chapter two we evaluated the evolution of the Brazilian cropland basis and P demands, quantifying the Brazil P Legacy and, based on scenarios involving the cropland area and yield expansion, we estimated the future (up to 2050) Legacy P and P fertilisers demand. We also estimated the potential aleviation that could be achieved in the mineral fertilizers consumption by utilisation and improvements on manure P recycling. Alternatively, considering the systems intensification and its effects on P availability, we proposed alternative scenarios to promote the Legacy P utilisation in Brazil\'s improved agriculture systems to grant the agriculture expansion without huge increments on the national P fertilisers consumption. A worldwide recognized advance in Brazilian agriculture is the Cerrado, where large cropland areas accually are cultivated twice a year, improving the food and fiber production without any additional disturbance of natural ecossystems. In this context, no-tillage (NT) agriculture has been widely used and, as consequence, soil fertility has been improved, which could be also farorable to the P availability, when rotation with crop species with P mobilization mechanisms are introduced, such as cover crops utilisation. However, the effects of these improved rotated systems on P bioavailability in long-term in tropical soils remains uncert in the literature and was our objective in the chapter three, where is described a study envolving the evaluation of long-term changes on P fractions in tropical Oxisols, from two long-term field trials involving tillage systems (NT and conventional tillage, CT) and cover crops (millet, brachiaria, maize and control, fallow). The long-term cultivation generated large amounts of legacy P in the soil and with the brachiaria introduction as cover crop, more P was recycled in the topsoil and labile P and all the organic P fractions increased. Based on the cover crop effects, we proposed that the bioavailability of the legacy P could be represented by the P extracted by the labile fractions + moderately labile P fractions. In the chapter four, we used other techniques actually widely applied to P speciation, and we applied in tropical soils affected by the native Cerrado conversion into NT and CT agriculture. A multiple approach to identify and quantify the P forms in tropical soils were proposed by the utilisation of Hedley\'s fractionation togheter with P K-edge XANES for P-bindings into inorganic soil matrix and liquid 31P-NMR spectroscopy to complement the organic P species in tropical soils. / Fósforo (P), um dos elementos essenciais às plantas e animais, é um recurso não-renovável e altamente demandado na agricultura atualmente. O crescimento da população mundial e as estimativas futuras da demanda de alimentos aumentam os questionamentos sobre a sustentabilidade dos sistemas agrícolas atuais, especialmente no que se refere a baixa eficiência no uso do P na agricultura. A agricultura brasileira requer altas quantidades de P e muitas pesquisas tem sido desenvolvidas para aumentar a produtividades das culturas e, conseequentemente, a eficiencia da produção de alimentos. Entretanto, este desenvolvimento tem sido alcançado a altos custos com uso de fertilizantes minerais (sobretudo P) e as perspectivas de longo prazo sobre os custos da intensificação da agricultura tropical estão atualmente em debate. Nesse contexto, no capítulo dois da presente tese avaliamos a evolução da área cultivada no Brasil e das demandas de P, quantificando o legado do P no Brasil e, baseado em cenários envolvendo a expansão da área cultivada e da produtividade, estimamos o futuro (até 2050) legado de P e as demandas por fertilizantes fosfatados. Ainda estimamos a potencial redução no consumo de fertilizantes fosfatados que pode ser alcançada pela utilização e melhorias na reciclagem do P oriundo de dejetos. Alternativamente, considerando a intensificação dos sistemas e seus efeitos na disponibilidade de P, propusemos cenários alternativos visando a utilização do \"Legacy P\" em sistemas agrícolas melhorados para garantir a expansão agrícola sem drásticos incrementos no consumo nacional de fertilizantes fosfatados. Um avanço internacionalmente reconhecido na agricultura Brasileira é o Cerrado, onde extensas áreas agrícolas são cultivadas duas vezes ao ano, incrementando assim a produção de alimentos e fibras sem qualquer custo aos ecossistemas naturais. Nesse contexto, a agricultura sob plantio direto (PD) tem sido amplamente difundida e, como consequencia, a fertilidade dos solos tem-se elevado, o que pode também favorecer a disponibilidade de P, quando são introduzidas rotações com espécies de plantas que apresentam mecanismos de mobilização do P, como o uso de plantas de cobertura. Entretanto, os efeitos desses sistemas melhorados de rotação na biodisponibilidade de P em solos tropicais no longo prazo permanecem incertos na literatura e foram objeto de estudo no capítulo três, onde está descrito um estudo envolvendo a avaliação das mudanças de longo-prazo nas frações de P em Latossolos, oriundos de dois experimentos de campo de longa duração no Cerrado, envolvendo a avaliação de sistemas de preparo (PD e preparo convencional, PC) e plantas de cobertura (milheto, braquiária milho e um controle, apenas pousio). O cultivo por longo tempo resultou em grandes quantididades de \"Legacy P\" acumulado no solo e, com o uso de braquiária como cultura de cobertura, maior quantidade de P foi reciclado para as camadas superiores do solo e as frações de P lábil e todas as frações organicas aumentaram. Baseado nos efeitos das plantas de cobertura, sugerimos que a biodisponibilidade do \"Legacy P\" pode ser representada pelo P extraído nas frações lábeis + o P de frações moderadamente lábeis. No capítulo quatro, utilizamos outras técincas atualmente difundidas para a especiação de P, aplicando-as em solos tropicais influenciados pela conversão do Cerrado nativo em agricultura sob PD e PC. Uma abordagem múltipla para identificação e quantificação de formas de P em solos tropicais foi proposta através da utilização do fracionamento de P proposto por Hedley em conjunto com a especiação de P por XANES da borda K do P para identificação de ligação do P a matrix inorgânica do solo, e espectroscopia de ressonância magnética nuclear (NMR) para complementação da identificação de espécies orgânicas de P em solos tropicais.

An injection technique, in which undisturbed soil cores are labelled with ³²P to study dissolution of phosphate fertilisers in the soil, was evaluated in field and glasshouse trials. When ³²P was injected between 0-150 mm depths of the undisturbed soil columns and fertilisers applied at the surface, the amounts of fertiliser P dissolved, as measured by the increases in the exchangeable P pools, were overestimated. Three possible reasons were suggested: (i) the interaction between surface-applied fertiliser, ³²P injected through the whole soil column, and the vertical decline in root density, (ii) the decline of specific activity in the exchangeable P pool due to losses of ³²P to nonexchangeable P pools and continuous addition of P from fertiliser dissolution, and (iii) non-uniform distribution of ³²P vis-a-vis ³¹P phosphate. The injection technique may be employed to assess the effectiveness of phosphate fertilisers by introducing a concept, the fertiliser equivalent (FE). The FE is a measure of the amounts of soil exchangeable P that the fertilisers are equivalent to in supplying P to plants, when applied at the specific location. Soluble single superphosphate (SSP) applied at the surface of undisturbed grassland soil cores (Tekapo fine sandy loam), was much more effective than surface-applied unground North Carolina phosphate rock (NCPR) and 30% acidulated NCPR with phosphoric acid (NCPAPR) within the 56 day period of plant growth. An isotopic dilution method, based on tracer kinetic theory, was developed to study the rates of dissolution (F in) and retention (F out) of phosphate fertilisers in the soil in growth chamber experiments. The estimation of F in and F out required labelling of the soils with carrier-free ³²P and determination of the corresponding values of the specific activities of the exchangeable P pools, SA₁ and SA₂, and the sizes of the exchangeable P pools, Q₁ and Q₂, at times t₁ and t₂. Most of the phosphate in the monocalcium phosphate (MCP) solution entered the exchangeable P pool immediately after addition to the soils (Tekapo fine sandy loam and Craigieburn silt loam), and there was little further phosphate input. With increasing periods of incubation, the phosphate was quickly transformed to less rapidly exchangeable forms. In the soils treated with ground North Carolina phosphate rock (<150 µm, NCPR) or partially acidulated (30%) NCPR with phosphoric acid (NCPAPR), the initial exchangeable P pools were not as large as those in the soils treated with MCP, but were maintained at relatively stable concentrations for extended periods, due to the continuous dissolution of PR materials and to lower rates of pretention. An increase in P-retention caused a slight rise in the rate of PR dissolution, but also a rise in the rate of P-retention by the soil. The rate of dissolution was higher at a lower application rate in relative terms, but smaller in absolute terms. The trends in the changes of plant-available P in the soils, measured by the water extractable P, Bray I P and Olsen P, correspond to those predicted by the F in and F out values. The average rates of dissolution between 1-50 and 50-111 days estimated by the F in, however, were higher than those estimated by extractions with 0.5 M NaOH followed by 1 M HCl, and with 0.5 M BaCl₂/TEA. This is partly because the Fin values reflect a plant growth effect on PR dissolution. The relative agronomic effectiveness of NCPR and NCPAPR with respect to MCP was higher after 50 and 111 days of incubation than after 1 day. The F in values were included in all the two-variable models constructed by stepwise regression to describe the relationship between plant P uptake and soil measurements. The amounts of variation in plant P uptake accounted for by the regression model was significantly improved by including F in in the model. This indicates the importance of fertiliser dissolution rates in affecting soil P supply, when phosphate fertilisers differing in solubility are applied.

*‘Pasja’ (Brassica campestris x napus) and kale (Brassica oleracea var. acephala L.) were grown at Lincoln, Canterbury, New Zealand in 2008 with different levels of phosphorus (P) fertiliser. Banded or broadcast P fertiliser was applied at 0, 20, 40 and 60 kg P/ha at establishment. Total dry matter (DM) production, the proportion of the leaf and stem and leaf area development were measured over time and related to the biophysical environment. For ‘Pasja’, final DM increased with P rate from 3730 kg DM/ha to ~4900 kg DM/ha at 60 kg P/ha. For kale the increase was from 8710 kg DM/ha for the control to ~11000 kg DM/ha for all P treatments. The leaf to stem ratio declined from 22-31 at 17 days after emergence to 10.4 at the final harvest for ‘Pasja’, which meant the crop was effectively made up mainly of leaf (~90%). The ratio for kale declined from 2.7 at 24 days after emergence to 0.64 at the final harvest. The leaf to stem ratio for both species did not respond to either the method of application or rate of P. Seedling DM accumulation increased with applied P over the first 10 to 17 DAE for ‘Pasja’ and kale respectively. The crops went from shoot growth priority to root growth. The phyllochron of both species was unaffected by P application but responded linearly to the temperature above 0°C. For ‘Pasja’ the phyllochron was 60°Cd compared with 109°Cd for kale. As a consequence ‘Pasja’ developed its canopy and reached critical leaf area index (LAIcrit) earlier than kale. Leaf area index (LAI) for the control crops of both species was lower than for P fertiliser treatments with a maximum of 3.6 for ‘Pasja’ and 3.8 for kale. There was no difference in leaf area indices among the P fertiliser treatments for ‘Pasja’, while kale LAI differed with the rate of P application up to 40 kg P/ha. Total accumulated intercepted solar radiation (RIcum) was 8 and 11% greater for ‘Pasja’ and kale crops respectively when P was applied compared with the control. Thus, the difference in total dry matter yield due to P application was attributed to the difference in RIcum. Neither the method of application or rate of P applied affected the radiation use efficiency (RUE) of either crop. For ‘Pasja’ the RUE was 1.1 g DM/MJ PAR and for kale 1.33 g DM/MJ PAR. Based on this research, it was concluded that P application increased RIcum as a result of increased LAI. The difference in total DM yield was attributed to differences in RIcum. It is recommended that farmers growing ‘Pasja’ and kale under similar conditions to this experiment should apply 40 kg P/ha for ‘Pasja’ and band 20 kg P/ha for kale. *‘Pasja’ is considered both as a species and cultivar in this document as it marketed as such in New Zealand. Technically ‘Pasja’ is a leaf turnip.

Deep anthropogenic topsoils – those augmented through long-term additions of mineral bulk among fertilising agents – retain in both their physical and chemical make-up significant indicators for cultural activity. This project researched the geographical distribution and historical context of deep anthropogenic topsoils in Scotland and the Isles, and used this information to investigate the impact of current land cover upon the cultural information they retain. In so doing, the project investigated the potential for conservation of this significant cultural resource. A review of the historical information available on agricultural and manuring practices for Scotland identified several factors likely to affect deep topsoil distribution and frequency. These were: the availability of bulk manures to Scottish farmers, the significance of the seaweed resource in determining fertiliser strategies in coastal areas, and the influence of urban settlement and associated patterns of domestic and industrial waste disposal on the location of deep topsoils. Evidence for widespread deep topsoil development was limited. The primary data source used – the First Statistical Account of Scotland – was manipulated into a spatial database in ArcView GIS, to which geographical data from the Soil Survey of Scotland and national archaeological survey databases were added. This was used to devise a survey programme aiming both to investigate the potential factors affecting soil development listed above, and to locate deep topsoil sites for analysis. Three sites were identified with deep topsoils under different cover types (woodland, arable and pasture). The urban-influenced context of two of these highlighted the significance of urban settlement to the location of Scottish deep topsoils. Analysis of pH, organic matter, and total phosphorus content showed a correlation between raised organic matter and a corresponding increase in phosphorus content in soils under permanent vegetation. By contrast, soils under arable cultivation showed no such rise. This was attributed to the action of cropping in removing modern organic inputs prior to down-profile cycling. The potential for pasture and woodland cover to affect relict soil signatures was therefore observed. Thin section analysis aimed to both provide micromorphological characterisation of the three deep topsoil sites and investigate the effect of modern land cover on micromorphological indicators. Distinctive differences in micromorphological character were observed between the rural and urban deep topsoils, with the latter showing a strong focus on carbonised fuel residues and industrial wastes. All sites showed a highly individual micromorphological character, reflective of localised fertilising systems. There was no correlation between land cover type and survival of material indictors for anthropogenic activity, with soil cultural indicators surviving well, particularly those characteristic of urban-influenced topsoils. Suggestions for preservation strategies for this potentially rare and highly localised cultural resource included the incorporation of deep anthropogenic topsoil conservation into current government policy relating to care of the rural historic environment, and the improvement of data on the resource through ongoing survey and excavation.