No description available.

Maintaining a supply of potable water is a growing concern in the USA, particularly in many southern and western states. One method of sustaining water supply in these areas is the use of greywater for commercial and residential landscape irrigation. Greywater is derived from residential use such as showers, laundering and bathing, and accounts for approximately 65% of residential waste water. I investigated the effects of municipal tap water, harvested rain water, washing machine and bath water (greywater) on the carbon and nutrient dynamics of soil, foliage and leachate and on soil microbial diversity. I also examined the presence or absence of E. coli in source water and leachate. There was a significant difference in leachate chemistry among irrigation treatments. Average leachate pH and conductivity was significantly lower in treatments irrigated with harvested rain water. Fertilization did not affect any of the leachate chemistries with the exception of orthophosphate-P, but significantly reduced carbon in soil without grass (blank) and domestic tap water treatments. E. coli colonies were detected in source water (greywater), but not in leachate suggesting that there was no movement through the soil profile. The results of principal component analysis (PCA) on whole-soil fatty acid methyl ester (FAME) profiles indicated distinct differences in soil microbial community composition due to irrigation with greywater as compared to rainwater, suggesting that water source may affect soil microbial community composition.

Review of the literature suggested possible deficiencies of micronutrients in soils of North Western Zambia. Soil analysis, pot and field experiments were employed to investigate possible deficiencies. The pot experiments investigated how raising soil pH through liming influenced extractable micronutrients and their uptake by plants. Plant Mo and Ca were positively correlated with soil pH, while Mn and Zn were inversely correlated, aggravating the zinc inadequacy on all soils and that for Mn on arenosols. Effects of liming on plant uptakes of micronutrients generally followed the same trends as those on soil extraction. Incubating the soil under grass house conditions was found to influence amounts of extractable micronutrients, increasing most times above their levels before the soil was incubated. Field experiments generally showed that applying micronutrients were beneficial to crop yield only at some sites. Grain yield variables responded variously and were most significantly correlated with overall grain yield. Soil analysis usefully predicted deficiencies of Zn for both maize and soybean. However, predictions for B and Mo were ideal for soybean than maize. Cu also seemed to have been wrongly predicted for soybean. However, plant nutrient concentration was better at predicting nutrient status in relation to grain yield, but the lower limits of the suggested optimal concentration ranges may need to be worked out again. Soybean was found to have more micronutrient latent deficiencies at majority of the sites than maize. One of the characteristics of applied micronutrients was their beneficial residual effects of crop yield. The residual benefit was also noticed on maize when the fertilisers were directly applied to soybeans a season before, suggesting a possibility of crop rotation, thus spreading the costs. Results would suggest changing the current fertiliser recommendations in the region.

No description available.

No description available.

Implementation of Sustainable Management Practices at Two California Central Coast Vineyards and Their Effects on Soil Fertility Dawn Michelle Stimson “Sustainable agriculture” has gained increased popularity in recent years. This study was conducted to determine the effects of sustainable management practices on soil fertility at two California Central Coast vineyards. The effects of cover crops (Erosion Control Mix - blando brome [Bromus hordeaceus], hykon rose clover [Trifolium hirtum All.], and zorro annual fescue [Vulpia mourns]), green waste compost (Forest Blend), and reduced tillage on soil fertility were investigated in San Luis Obispo, California on a clay and sandy loam soil. Between the fall 2007 and spring 2008, which had a low precipitation amount (13.3 & 15.6 inches), there was a significant difference (P <0.001 to 0.007) between vineyards in terms of their mean soil nutrient and ratio concentrations. The range of soil values (soil pH, P, K, exchangeable Ca, Mg, and K, OM, Ca/Mg and C/N ratios) was either completely separate or different between Vineyard One and Two. There was almost no significant difference found between treatments and their effects on soil nutrients, exchangeable cations, and ratios. However, there were some noticeable effects on soil nutrients, exchangeable cations and ratios. Soil P and K concentrations increased in most areas (except cover crop/till where it decreased slightly). Soil P increases ranged from 14 to 143% while potassium increases ranged from 9 to 78%. Soil OM increased in all areas at both vineyards (5 to 55%). Ca/Mg ratios increased in some areas between 8 and 43%. C/N ratios increased in all areas between 5 and 85%. Soil type appears to affect soil nutrients, exchangeable cations, and ratios more than sustainable management practices. Keywords: Sustainable, vineyard, and soil nutrients.

Artificial soils have been employed within the Biomes of the Eden Project since its construction in 2000. Produced from sand, bark, composted green waste and lignite clay, these soils were designed to have their nutrient concentrations controlled through careful fertiliser applications. However, following variable environmental conditions, management practices and planting, the soils across the site are performing variably with regard to nutrient retention and storage. Experiments were conducted to assess the performances of an artificial soil in terms of nutrient cycling. This was carried out in three phases: Firstly, soils from the Humid Tropics and Outdoor biomes were sampled and examined, using a range of analytical techniques, to determine the nutrient characteristics of the established artificial soils from across the Eden Project site. This demonstrated that many of the nutrient concentrations of the artificial soils were consistent with those reported for naturally formed soils within comparable environments. All soil samples were of sandy loam texture (ISO 14688-1), with the sand-sized fraction representing > 50 % of the particle size composition. Statistical analyses suggested that management practices had a greater impact on the nutrient characteristics of artificial soils than environmental conditions. Secondly, an artificial soil was produced, following the Eden Project protocol, to examine its performance under controlled environmental conditions. This was packed into 4 columns (1 m height by 110 mm diameter), maintained at 15 ˚C and subjected to an irrigation regime for 52 weeks. Following 26 weeks of irrigation, 2 of the 4 columns were fertilised. Leachate was analysed for dissolved constituents as were solid samples of the fresh soil and of soil samples collected from the columns following 52 weeks irrigation. Leachate concentrations for all nutrients, excepting phosphate, were observed to decline over the irrigation period. Leached phosphate concentrations increased from weeks 0 to 2, and then remained relatively constant. Low nitrogen concentrations within the leachate from weeks 2 to 38 were caused by nitrogen immobilisation within the soil, whilst subsequent mineralisation resulted in increased concentrations from Week 38. Analyses of solid phase constituents determined little variation with depth. Fertiliser application demonstrated a significant (p < 0.05) increase in leachate concentrations for some dissolved organic nitrogen and nitrate, phosphate, magnesium and calcium and a decrease in pH. Fertiliser application observations showed less prominent differences for the extracted and solid phase constituents. Thirdly, biochar was applied to the artificial soil at three concentrations (10 %, 5 % and 2 %) plus a control (0 %), to determine whether biochar application may improve nutrient characteristics of artificial soils. The biochar amended soils were packed into mesocosms and maintained at 15 ˚C for 6 weeks. In general, leachate analyses demonstrated a decrease in nutrient losses to leaching with increasing biochar concentration, highlighting the potential for improved nutrient retention within the soils.

No description available.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Soilless production of crops relies on the addition of high concentrations of nutrients with the irrigation water. The drained nutrient solution should be re-used to reduce the risk of pollution and to increase the water- and nutrient use efficiency of the system. Besides the risk of pathogen build-up, one of the main impediments of a wider application of this method is the frequent analysis required to maintain optimum nutrient concentrations and ratios in the rootzone. Yield reductions may be caused by an unbalanced nutrient solution. Alternatively the addition level of nutrients can be calculated through the use of nutrient uptake models that simulate the change in the re-circulated nutrient solution. To simulate crop water and nutrient demand necessary for model based regulation it was necessary to quantify the key factors affecting nutrient uptake by plants. The nutrient solution concentration and ratios between the macro-nutrients affected the uptake of water and nutrients. The total nutrient uptake per root dry weight increased and more specifically the nitrate (NO3 -), phosphate (H2PO4 -), potassium (K+) and sulphate (SO4 2-) uptake increased with an increase in nutrient solution electrical conductivity (EC) from 0.8 to 4.0 mS cm-1 while water uptake decreased. Except for Ca2+ uptake there was no correlation between nutrient and water uptake. Nutrient uptake can thus not be calculated based on water uptake. Instead a mechanistic high-affinity Michaelis-Menten based model can be used to estimate macro-nutrient uptake (Un, mg m-2 hr-1). Water and nutrient uptake was also affected by the solar radiation levels. Since nutrient uptake is related to the growth rate, solar radiation levels can be expected to influence nutrient uptake. The uptake of all ions increased with an increase in the solar radiation levels and for NO3 -, K+ and H2PO4 - the uptake rate was higher at higher nutrient solution concentrations. The Michaelis-Menten based model was adjusted to incorporate the effect of solar radiation levels on nutrient uptake. Water uptake (Wu, L m-2 day-1) was simulated as a function of crop transpiration and crop leaf area using a linear regression model, but since leaf area development was affected by solar radiation levels this was additionally incorporated into the estimation of the leaf area index (LAI). The composition of the nutrient solution also affected the biomass allocation of the crop which can again affect nutrient use as well as the fruit yield. There was also a direct effect of nutrient solution composition on fruit yield and quality with higher EC’s resulting in smaller fruit but an increase in fruit dry matter %, total soluble solids (TSS), titratable acidity (TA) and lycopene content. The results in this thesis make a valuable contribution to our understanding of the effect of nutrient availability (concentration and ratios) and nutrient requirement for growth (solar radiation levels) on nutrient uptake. Incorporating these into nutrient uptake models resulted in the development of a handy tool to simulate changes in composition of re-circulating nutrient solutions ultimately resulting in an improvement of the water and nutrient use efficiency of soilless systems. / AFRIKAANSE OPSOMMING: Die grondlose verbouing van gewasse is afhanklik van toediening van voedingselemente teen hoë peile in die besproeiingswater. Die voedingsoplossing wat dreineer moet hergebruik word om die risiko van besoedeling te verminder en ook om die water en nutriënt verbruik doeltreffendheid van die sisteem te verbeter. ʼn Ongebalanseerde voedingsoplossing kan ʼn verlaging in opbrengste veroorsaak. Benewens die risiko van patogene wat opbou, is die gereelde analises nodig word vir die handhawing van optimale nutriënt konsentrasies en verhouding tussen elemente in die wortelsone een van die hoof faktore wat ʼn meer algemene gebruik van die metode verhoed. Alternatiewelik kan die nutriënt toedieningspeile bereken word deur voedingstof opname modelle en simulasie van die verandering in water en nutriente wat dreineer. Om ʼn model gebaseerde reguleringsmetode daar te stel was dit nodig om die belangrikste faktore wat nutriënt opname beïnvloed te kwantifiseer. Beide die konsentrasie van die voedingsoplossing en die verhouding tussen elemente het ‘n effek gehad op die opname van water en nutriënte. Die totale nutriënt opname per wortel droë massa het toegeneem. Terwyl water opname afgeneem het met ‘n toename in die elektriese geleding (EG) van die voedingsoplossing vanaf 0.8 tot 4.0 mS cm-1 het die nitraat (NO3 -), fosfaat (H2PO4 -), kalium (K+) en sulfaat (SO4 2-) opname verhoog. Behalwe vir Ca2+ opname was daar geen korrelasie tussen water en nutriënt opname nie. Nutriënt opname kan dus nie bepaal word gebaseer op wateropname nie. Alternatiewelik is die gebruik van ʼn meganistiese hoë-affiniteit Michaelis-Menten-gebaseerde model voorgestel om die opname van makro-nutriente (Un, mg m-2 hr-1) te bepaal. Water- en voedingstofopname is beinvloed deur die ligintensiteit vlakke. Voedingsopname word bepaal deur die groei van die plant, daarom is dit verwag dat ligintensiteit vlakke die opname van voedingstowwe sal beïnvloed. Die opname van al die ione het toegeneem met 'n toename in die ligintensiteit vlakke en die tempo van NO3 -, K+ en H2PO4 - opname was hoër by 'n hoër voedingsoplossing konsentrasie. Die Michaelis-Menten gebaseerde model is aangepas om die effek van ligintensiteit vlakke op nutriënt opname te inkorporeer. Opname van water (Wu, L m-2 dag-1) is gesimuleer as 'n funksie van transpirasie en blaaroppervlakte met behulp van 'n lineêre regressiemodel en aangesien die blaaroppervlak ontwikkeling ook deur ligintensiteit vlakke beïnvloed word, is dit opgeneem in die skatting van die blaaroppervlakte-indeks (LAI). Die samestelling van die voedingsoplossing het die biomassa verspreiding beïnvloed. Dit kan nutriënt gebruik en vrug opbrengs beïnvloed. Die voedingsoplossing samestelling het vrug opbrengs en - kwaliteit beinvloed met kleiner vrugte, maar 'n toename in droëmateriaal %, totale oplosbare vastestowwe (TOVS), titreerbare suur (TA) en likopeen inhoud by ʼn hoër EG. Die resultate in hierdie tesis lewer 'n waardevolle bydrae tot ons begrip van die effek van nutriënt beskikbaarheid (konsentrasie en verhoudings) en voedingstof behoefte vir groei (ligintensiteit vlakke) op voedingsopname. Deur die inligting te inkorporeer in voedingsopname modelle het gelei tot die ontwikkeling van 'n handige instrument om die veranderinge in die samestelling van hersirkulerende voedingsoplossings te simuleer. Dit lei gevolglik tot die verbetering van die water en voedingstof gebruik doeltreffendheid van grondlose stelsels.

In order to predict how terrestrial ecosystems will respond to global change, there is growing recognition that we need to better understand linkages between plant and soil processes. Previously the factors and processes with potential to influence the terrestrial carbon (C) cycle have been investigated in isolation from each other. This study investigated the interactions of nutrient availability and warming in controlling the soil carbon dynamics, with regards to the fate of already sequestered carbon in soil, under conditions of increasing atmospheric temperatures. The project objectives were addressed by three independent experiments designed to explain specific components of the carbon-nutrient cycle interactions, and the findings brought together to describe the implications for future soil carbon storage. The main measurements collected throughout this project included soil carbon dioxide (CO2) fluxes, partitioned into autotrophic and heterotrophic components, net ecosystem exchange and respiration fluxes, and background soil moisture and temperature data, backed by gas, soil and biomass analyses. In the two field experiments, these measurements were taken from plots with or without any inorganic nutrient additions or in the presence or absence of legumes providing biological nitrogen addition to the ecosystem. In the laboratory, temperature and nutrient availability were manipulated within the ecosystem. The reduction in decomposition rates, without reduction of productivity as a result of inorganic nutrient additions, indicated the potential for increasing C storage. There was also evidence that nutrient availability controls the strength of the link between plant and soil processes in semi-natural grasslands. The yields, decomposition rates and soil C fluxes recorded in the presence and absence of legumes provided some evidence of N2 fixation, improving ecosystem productivity and soil properties while reducing soil C effluxes, in a managed grassland. In the laboratory, the warming of soils from lysimeters with and without plants, receiving or not receiving fertiliser, supported the findings from field experiments regarding the importance of the soil-plant link in controlling C fluxes. However, C stocks and δ13C analyses showed that over a year’s worth of warming and nutrient manipulations made little difference to the amount of C stored in the soil, indicating that edaphic factors have greater control over the response of C dynamics to increased temperatures.