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    Nitrate enrichment does not affect enteropathogenic Escherichia coli in aquatic microcosms but may affect other strains present in aquatic habitats
    (PeerJ, Inc, 2022-09-27) Davis MT; Canning AD; Midwinter AC; Death RG; Oehlmann J
    Eutrophication of the planet's aquatic systems is increasing at an unprecedented rate. In freshwater systems, nitrate-one of the nutrients responsible for eutrophication-is linked to biodiversity losses and ecosystem degradation. One of the main sources of freshwater nitrate pollution in New Zealand is agriculture. New Zealand's pastoral farming system relies heavily on the application of chemical fertilisers. These fertilisers in combination with animal urine, also high in nitrogen, result in high rates of nitrogen leaching into adjacent aquatic systems. In addition to nitrogen, livestock waste commonly carries human and animal enteropathogenic bacteria, many of which can survive in freshwater environments. Two strains of enteropathogenic bacteria found in New Zealand cattle, are K99 and Shiga-toxin producing Escherichia coli (STEC). To better understand the effects of ambient nitrate concentrations in the water column on environmental enteropathogenic bacteria survival, a microcosm experiment with three nitrate-nitrogen concentrations (0, 1, and 3 mg NO3-N /L), two enteropathogenic bacterial strains (STEC O26-human, and K99-animal), and two water types (sterile and containing natural microbiota) was run. Both STEC O26 and K99 reached 500 CFU/10 ml in both water types at all three nitrate concentrations within 24 hours and remained at those levels for the full 91 days of the experiment. Although enteropathogenic strains showed no response to water column nitrate concentrations, the survival of background Escherichia coli, imported as part of the in-stream microbiota did, surviving longer in 1 and 3 mg NO3-N/Lconcentrations (P < 0.001). While further work is needed to fully understand how nitrate enrichment and in-stream microbiota may affect the viability of human and animal pathogens in freshwater systems, it is clear that these two New Zealand strains of STEC O26 and K99 can persist in river water for extended periods alongside some natural microbiota.
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    Design and fabrication of a climate-controlled lysimeter and testing of new controlled-release fertilisers : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PHD) in Agricultural Engineering and Environmental Sciences at Massey University, Palmerston North, New Zealand
    (Massey University, 2021) Gunaratnam, Abhiram
    Pastoral agriculture is the backbone of the New Zealand (NZ) economy and nearly 9 million hectares of land (33% of the total land area in NZ) is under pastoral farming. The higher and continuous applications of readily available N fertilisers to pastoral land use increase nitrogen (N) losses, which degrade the water and air quality. Controlled-release fertilisers (CRFs) have been shown to be an effective strategy to mitigate N losses in many parts of the world. This study was undertaken to develop different CRF formulations and test their effect on ryegrass under a simulated climate condition. A new controlled-environment lysimeter system was designed and fabricated, since lysimeter designs available in the literature are not suitable to conduct a controlled-environment study. The lysimeter was permanently capped to provide a confined space for controlling the microclimate of ryegrass, and equipped with sensors to monitor the environmental variables. An environmental controlling unit (ECU) was designed to emulate a climate model and control the environmental variables in the lysimeter. Taranaki region’s (spring season of the year 2013) climate model was selected to emulate in this design. The ECU modifies the ambient air according to the climate model and circulates it through 40 lysimeters using air conduits and distributors. The ryegrass was grown for three months under simulated climate conditions, and DM yield was measured. In addition, microclimate temperature, relative humidity (RH), evapotranspiration and drainage of each lysimeter during the experimental period were recorded. The performance of the ECU was tested by comparing the observed temperature and RH values of the plant proximity with setpoints of the climate model. In addition, the performance of the lysimeter system on recreating the climate model was tested by comparing the observed drainage, evapotranspiration, and DM yield values with the estimated values derived from the climate model. The root-mean-square error (RMSE) of temperature was 1.96 °C day⁻¹, which was marginally higher than the targeted temperature variation range of 1 °C day⁻¹. However, the RMSE of RH was 4.45% day⁻¹, which was within the targeted fluctuation range of 5% day⁻¹. These observations showed that the ECU satisfactorily controlled the environmental variables as per the climate model. The observed drainage, evapotranspiration and total DM yield were within the estimated values; 525 mm, 104 mm and 2167 kg-DM ha⁻¹, respectively. These results revealed that the selected Taranaki climate model was successfully emulated in the newly developed lysimeter system design. A low-cost, simple lysimeter soil retriever (LSR) design was fabricated to retrieve the soil, and its performance was examined. The soil moisture influenced the retrieval process, where lower disturbances for soil block structure and roots were observed for soil with high moisture (28%) than low moisture (13%). The linear actuator used in this design was powerful enough to perform soil retrieval and showed consistent performance after 80 soil columns were retrieved. Force given by the linear actuator did not damage the lysimeter body, but was sufficient to push the soil column out of the lysimeter. Therefore, this design is suitable to retrieve soil blocks from mini (<100 kg) and small (100-1000 kg) lysimeters. Different forms of CRFs were developed by coating urea with epoxy-lignite (Epox) or polyester-lignite (Poly) polymer composites. Each composite was coated three or five times, and therefore four CRFs were formulated depending on the type of composite and coating thickness; Epox3, Epox5, Poly3, and Poly5. The complete release of urea took place at 144, 408, 120 and 175 hours for Epox3, Epox5, Poly3 and Poly5, respectively, in water. Increasing the coating thickness prolonged the duration of urea release for both composites. Although no cracks were identified in all the CRF coatings, micropores were seen under high magnification in the scanning electron microscopy (SEM) images. The interactions between lignite and polymer were demonstrated using Fourier Transform Infrared Spectroscopy (FTIR) analysis. The lignite dominated in all coatings compared to the polymer, and lignite compositions were 2.1 to 5.3-fold higher than polymers in CRFs. The Epox5 showed overall better performance than other formulations. The CRF formulations which showed more controlled-release characteristics in water; Epox5 and Poly5, were selected to study their performance on ryegrass against urea and diammonium phosphate (DAP) in the climate-controlled lysimeter system. The total DM yield, root DM distribution, herbage N recovery and nitrogen utilisation efficiencies (NUE) were not significantly different between N treatments. Although N₂O emission and nitrate leaching losses were not significantly different between N treatments, the values were very low in comparison to the values obtained in similar studies reported in the literature. An investigation was carried out to find out the reason for these observed low N₂O and nitrate levels with different hypotheses. The only hypothesis tested that showed a significant relationship with these observed results; the high iron content of sand could have decreased the nitrate in leachate and N₂O emission. In this study, a 2 x 4 factorial design was used with two types of sand (low and high iron sand) and four N levels (0, 50, 100 and 200 kg-N ha⁻¹). It was found that high iron sand significantly lowered (P<0.05) the nitrate leaching at all N levels compared to low iron sand, except for the 0 kg-N ha⁻¹ treatment. The N2O emission was significantly lower (P<0.05) for high iron sand than low iron sand, only at the 200 kg-N ha⁻¹ application level. These observations support the hypothesis, that iron is involved in nitrate reduction and the possible mechanism was dissimilatory nitrate reduction (DNR) pathway. A new controlled-release fertiliser (Ver-1) was developed by Verum Group Ltd using lignite and urea. In this study, the effectiveness of two different types of CRFs (Epox5 and Ver-1) and two levels of iron application (239 and 478 kg-FeSO4 ha-1) on controlling N losses were tested in lysimeters where ryegrass was grown. The Epox5 and Ver-1 significantly (P<0.05) reduced N leaching losses by 37% and 47%, respectively, whereas only Epox5 significantly (P<0.05) increased N₂O emission compared to the urea treatment. Iron treatments were not effective in controlling N losses, which suggests that the expected DNR pathway was not prominent in this study. The DM yield and NUE were not significantly increased by CRFs and iron applications compared to the urea treatment. The hierarchical clustering analysis revealed that Ver-1 was the best treatment for controlling N leaching losses. Future research is recommended to investigate (a) the mechanism which underlies the reduction of nitrate in high iron content sand, (b) the effectiveness of iron application on N leaching losses on different soils, and (c) the performance of new CRFs formulations (Epox5 and Ver-1) at the field level.
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    Development of sustainable nutrient management strategies for taro growers on Taveuni Island, Fiji : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science, Massey University, Palmerston North, New Zealand
    (Massey University, 2021) Lal, Rohit
    Taro (Colocasia esculenta) is a major component of the socio-cultural, dietary and economic livelihood of Pacific Island countries, including Fiji. However, Fiji’s total taro exports have substantially declined over the last decade, mainly due to a reduction in production from Taveuni Island. A trend of decreasing taro yields has been further exasperated by recent extreme climate events, which have reduced the availability and affordability of planting material. The combination of lower yields and increased costs, have reduced farmers’ returns on existing farm land, which has contributed to further deforestation of forest reserves. The overall aim of this study was to develop improved nutrient management practices on existing farm land, to help growers to achieve sustainable taro yields and financial returns. This study included a survey of 73 taro farmers, which involved a quantitative analysis of taro yields and soil fertility. Fresh taro corm yields were very low, being an average of 6.9 t/ha. About 75% of the farms surveyed had low soil Olsen phosphorus (P) levels of < 10 mg/kg and 65% had low soil exchangeable potassium (K) levels of < 0.4 me/100g. Fertiliser nutrient inputs were also low, with semi-commercial farmers using an average of 31 kg nitrogen (N), 17 kg P and 27 kg K/ha, and commercial growers using an average of 41 kg N, 26 kg P and 40 kg K/ha per crop. The survey also identified that fertiliser placement and application timing practices may also reduce nutrient use efficiency by the crop. Two successive field experiments were repeated over three sites, on Taveuni Island, to evaluate a range of nutrient management strategies to improve soil fertility and taro productivity. When no N and P fertiliser was applied, average fresh taro corm yields were very low (6.2 t/ha), irrespective of K and sulphur (S) fertiliser inputs. The addition of up to 200 kg N/ha and 120 kg P/ha, resulted in a substantial average yield increase to 14.9 t/ha. Taro yields were also responsive to K fertiliser use, with significant increases in yield up to 200 kg K/ha, the highest rate of K assessed. There was a strong linear relationship between N fertiliser use and taro sucker population up to 300 kg N/ha. In the second experiment, sucker numbers increased with increasing N fertiliser rate up to 280 kg N/ha. Further increasing N rates up to 360 kg N/ha did no further increase sucker production. When no fertiliser was applied, average taro sucker population across the three sites was about 20,500 suckers/ha, which increased to about 122,500/ha at 280 kg N/ha. The response of sucker numbers to N was not influenced by P fertiliser use, but there was a small effect with increasing K fertiliser rate, from 100 to 200 kg K/ha. Following natural disasters, when sucker numbers are limited, the use of N fertiliser may be an effective short-term strategy to help re-establish the taro industry and minimise inflated sucker prices. The use of the legume mucuna, as a green manure crop intercropped with taro, reduced N fertiliser requirements. Mucuna provided a benefit, for both corm yield and sucker numbers, equivalent to N fertiliser applied at a rate of approximately 80-100 kg N/ha. Some of the benefit may also be due to improved weed suppression and a mulching effect from mucuna. Mixing P fertiliser in the planting hole increased corm yields by 38%, compared to the when P fertiliser was placed at the bottom of the hole. Despite the high rates of P fertiliser used in the first experiment there were no significant P carry-over effects on taro yields in the second experiment. This was due to the higher soil P status from P fertiliser application being confined in close proximity to the planting holes. The Soil Plant Analysis Development (SPAD) chlorophyll meter was evaluated as being effective at predicting N status of taro crops and yield potential, when other major nutrients were non-limiting. When SPAD readings were greater than 65, at 8 and 12 weeks after planting (WAP), then the taro yields were mostly high (i.e. > 12 t/ha). SPAD readings less than 40, at 8 and 12 WAP, would indicate that plant N status is likely to limit taro yield and that a review of N fertiliser use is required. The recommended nutrient management strategy for taro farmers with farms with degraded soil fertility, involves the use of inter-cropping taro with a mucuna green manure crop in combination with fertiliser at the following nutrient rates; 120 kg N, 120 kg, 200 kg K/ha and 80 kg S/ha. At current taro corm and sucker prices, this recommended strategy is expected to provide a net income of NZ$35,835, which is 247% higher than for the average grower practice. The recommended practice also produces 74% more taro suckers than the current grower practice. Increasing sucker production is an important strategy to enable taro growers to increase production quickly following a natural disaster, helping farmers be more resilient to the effects of Climate Change.
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    Effects of soil & foliar nutrient application strategies for improving fruit quality for 'Zesy002' kiwifruit : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Sciences at Massey University, Palmerston North, New Zealand
    (Massey University, 2021) Hashmatt, Marya
    Nutrient management research work has been conducted in established kiwifruit varieties such as ‘Hayward’ and ‘Hort16A’. But less is known about such research on the newly commercialised ‘Zesy002’ kiwifruit cultivar. A goal is to optimise sustainable production of quality fruits with high fruit dry matter percentage (FDM, a quality predictor at-harvest), without driving excessive vine vigour. The project is aimed to (i) increase calcium (Ca) nutrition and to (ii) optimise potassium (K) fertilisation to produce high quality ‘Zesy002’ kiwifruit at-harvest. The fundamental knowledge of the role of Ca and K nutrients and their interactions was used to increase the photosynthetic performance and improve at-harvest fruit quality. The study was based on the hypothesis that the competitive effect of high K supply on the uptake of Ca may be reduced at soil level by using (i) spatial and (ii) temporal separation of soil-applied Ca and K fertilisers, and (iii) foliar Ca applications after fruit set through to fruit maturity during the growing season. The study also tested the hypothesis that K application at different rates and growth stages through (i) soil-applied and (ii) foliar-applied fertilisation may better meet the nutrient demand of kiwifruit vines and developing fruit and therefore, may improve the potential of the fruit to compete for dry matter import. The results showed that both spatial and temporal separation of soil-applied Ca and K fertilisers reduced the competitive effect of high K input on the availability and uptake of Ca and therefore significantly increased leaf and fruit Ca concentration in ‘Zesy002’ vines compared to true control, not spatial and not temporal strategies and grower practice in each orchard. Likewise, foliar Ca significantly increased Ca concentration in leaf and fruit tissues in ‘Zesy002’ vines and significantly improved photosynthetic performance, nutrient uptake (vine physiology) and at-harvest fruit quality (fruit size and firmness). Both soil and foliar-applied nutrient strategies, which were used mainly to increase Ca nutrition, showed promising improvements in fruit quality; larger and firmer fruit with high soluble solids (SSC) and fruit dry matter concentration (FDM) at-harvest and after thirty-day storage. The results also showed that three split applications of soil K fertilisers (each 100 Kg K ha⁻¹) from bud-break (BB) through to 90 days after full bloom (DAFB) compared to one application either at BB, FB or 90 DAFB, improved at-harvest fruit quality in commercial orchards at Bay of Plenty and Hawke’s Bay, New Zealand. Foliar application of K fertilisers from fruit set through to harvest also improved vine physiology and at-harvest fruit quality. The optimisation of K by using both soil and foliar fertilisation strategies improved fruit growth rate during the growing season, at-harvest fruit weight, SSC and FDM compared to true control. The soil and foliar-applied nutrient (Ca and K) fertilisation strategies employed here were specifically targeted using ‘the right time’, ‘right amount’ and ‘right plant organ’ principles and successfully, delivered larger fruit with higher SSC and FDM at-harvest. For growers, this translates to a lower fruit count per tray (size class) and a higher taste Zespri grade, triggering increased premium payments and orchard gate returns. The fertiliser input used in foliar strategies was 3-8 Kg. ha⁻¹ and only a fraction of soil-applied fertilisation 50-300 Kg. ha⁻¹. Therefore, the foliar nutrient fertiliser application strategies employed in this study were inherently more sustainable approach compared to the soil-applied fertilisation. These research findings have significant implications in horticultural fruit crops to increase leaf chlorophyll, net photosynthesis and stomatal conductance, and increase leaf and fruit Ca and K concentration to deliver high quality fruit at-harvest. The research strategies used in this study can be very easily adapted to the existing fertilisation programs and applied in the commercial orchards. For example, fertiliser spreaders can be modified to side dress K to the weed-strip or broadcast K to alternate rows and broadcast Ca over the whole orchard floor to implement spatial separation of Ca and K fertilisers. Temporal separation of Ca and K can be very easily implemented by applying soil Ca fertiliser at BB and by delaying application of soil K fertiliser until closer to FB. Foliar Ca and K applications can also be easily included in the early season spray programs. For future research, there is a true potential to further maximise fruit quality gains by supplementing soil-applied fertilisation strategies with specific timely foliar applications.
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    Hyperspectral imaging of hill country farms : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy of Agriculture and Horticulture at Massey University, Manawatu, New Zealand
    (Massey University, 2019) Cushnahan, Thomas Anthony
    This thesis uses hyperspectral aerial imagery, processed and classified using a Support Vector Machine (SVM) approach applied to categorise the New Zealand hill farming environment. The analysis of hyperspectral imagery presented in this thesis provides information on land use and land cover that can assist land management decision-making for hill country farming. The ability of the approach to provide a mechanism to examine complex and inaccessible environments and capture information in fine detail makes it relevant to the management of other heterogeneous environments and marginal farming systems worldwide. Precision farming techniques, used regularly in other farming sectors, hold the promise to better understand the hill farming landscape and therefore improve strategic management decisions. Pasture is the primary resource on the farm but due to the heterogenous nature of the hill farm landscape, the pasture area is currently only estimated. Aerially applied fertiliser applications represent the largest single input for these farms and are also a major source of nutrient contamination in waterways so finding ways to reduce costs and environmental damage are important. The definition of the area and various pasture groups is critical information needed to improve fertiliser efficiency via use of Variable Rate Application Technology systems. This research was able to classify pasture area to 99.59% (Kappa 0.991). Accurate base landscape information can improve management decisions, the accuracy of valuations, income expectations from lending organisations and the overall prosperity of the hill farming sector. Currently farmers and external groups must make major financial and strategic decisions with local expert opinion which is difficult to validate or question. Therefore, information derived from the hyperspectral classification is also shown to have benefits for strategic farm management decision-making and the wider farming community. This research was able to classify a number of economically valuable resources to high accuracies including;water bodies (99.97%), Thistle (98.51%), Pine (99.44%), Kanuka (89.03%) and Manuka (97.71%). By applying SVM to hyperspectral imagery the classification of pasture could be enhanced by the use of plant functional groups. The classes of High Fertility Responsive (HFR) represented sown rye varieties and had a classification accuracy of 89.06%. Low Fertility Tolerant (LFT) represented mixed swards dominated by browntop with a classification accuracy of 89.81%. The highest accuracy achieved for the legume class was 99.81%. The findings from this study represent a notable advance in our understanding of hill country farm and remote sensing research relevant to hill country farming. This is the first study to classify several key landscape components that are economically or environmentally important to the hill country farming community and this study created the most detailed map of hill farm pasture quality using plant functional groups so far. The ability to use a single hyperspectral aerial survey, to provide such a wide variety of information, useful to many industry actors, improves the potential return on investment and viability of the survey operation.
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    A study of the cause of germination injury following contact placement of dried blood fertilizer with seeds : a thesis presented in partial fulfilment of the reqiuirements for the degree of Master of Agricultural Science (Horticulture) at Massey University, New Zealand
    (Massey University, 1958) Baigent, Nancy Lynn
    The use of organic fertilizers has suffered a decline since the initiation of large scale production of soluble inorganic salts. Nevertheless, a demand for natural organic forms of nit­rogen persists, especially in regions of high rainfall and sandy soils, and in connection with the production of crops of high acre value. In recent years knowledge of the principles and practice of fertilizer application also has expanded rapidly. Localized or contact placement of fertilizer has been found to favour rapid early growth, and to lessen "fixation'' of fertilizer nutrients by the soil. Difficulties in the forms of impaired germination and damage to young seedlings have arisen from contact placement of organic fertilizers. Many mechanisms have been put forth to explain the basis of fertilizer toxicity; viz. plasmolysis of root tissues by the high solute concentrations, production of excessive local acidity or alkalinity from fertilizer materials, direct toxic effects on the young plant by free ammonia or cyan­ide formed by chemical or microbial breakdown of fertilizer materials. Accordingly, it was decided to evaluate the hypothesis that germination injury to seeds results from the production of in­jurious quantities of free ammmonia during mineralization of dried blood fertilizer placed in contact with the seeds. [From Introduction]
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    The effects of high conductivity liquid feeds on the yield and quality of outdoor grown tomatoes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science in Vegetable Production at Massey University, Palmerston North, New Zealand
    (Massey University, 1993) Fadallan, Edgardo F
    Studies were conducted to evaluate the effects of high conductivity liquid feeds applied using drip irrigation on the yield and quality of outdoor grown tomatoes. Seed of the tomato cv. Extase were propagated in cell trays. During propagation the seedlings were fed using a stock solution containing 100 ppm nitrogen, 34 ppm phosphorous and 100 ppm potassium. The transplants were planted out on 3 December 1991 in the Karapoti Sandy Loam soil at the Plant Growth Unit, Massey University. The spacing used was 150 cm between the rows and 60 cm 2 in the row. A base maintenance dressing of Nitrophoska (12-16-10) fertilizer was applied at a rate of 500 kg per hectare banded 20 cm on either side of the row prior to planting. There were 3 conductivity treatments of 2, 4, and 6 mS cm-1 and a control treatment. A randomized complete block design was used with 4 blocks and 12 plants per plot. The 3 conductivity treatments were based on a standard greenhouse liquid feed, while the control plant received water only. Irrigation requirements were calculated based on a crop factor, area per plant and potential evapotranspiration. Conductivity treatments oommenced at the stage were 50% of the plants had commenced flowering on the first truss. Conductivity treatments were applied every 2 days for 2 hours regardless of rain, while control plants were irrigated with tap water when soil moisture deficits exceeded 28 mm day-1 except when rainfall immediately followed the scheduled irrigation. Plants were trained to 2 stems. The second stem was produced from the leaf axil immediately below the first inflorescence. The Otaki system of training and supporting tomato plants was used with the first support attached 25 days after planting and thereafter every 30 cm. Plants were delateraled regularly and stopped by removing the terminal buds at 2 metres high. Leaf analysis was carried out on 2 occasions, 30 and 55 days after planting, while the conductivity of the soil solution was determined at final harvest. Yield data was collected for each truss on a per stem basis per plant. Fruit were weighed individually and also size graded to the accepted commercial standard. From these data the number and weight of marketable and reject fruits were determined. Fruit samples were taken for 6 consecutive weekly harvests for compositional analysis. Firmness, total solids, titratable acidity and total soluble solids were measured from sample fruits from each treatment. Increasing the conductivity of the liquid feed increased the concentration of nitrogen and potassium in the leaves 30 days after planting, while phosphorous and magnesium were not affected by the treatments. Calcium fell with each increase in conductivity. At the reproductive stage (55 days after planting) the nitrogen, phosphorous and potassium content fell with increasing conductivity over the range of control to 4 mS cm-1• Calcium and magnesium content also fell with increasing conductivity of the liquid feed. The conductivity of the soil solution increased as the conductivity of the liquid feed increased. As the distance from the dripper increased the conductivity of soil solution decreased. Tomato plants in this study supported an average of 13 trusses. There were 18 harvests where fruits were harvested at a commercial acceptable stage of maturity and a 19th harvest was used to remove all the remaining fruit on the plant. The main stem carried approximately 65% of the fruit load. Conductivity treatments had no effect on the number and weight of fruit of individual trusses on the main stem except for the 4 mS cm-1 treatment which had a higher number and yield of fruit in the third truss. No explanation can be offered for this effect. There were no differences between treatments in the number or yield of fruit per truss on the lateral stem. Neither the number or yield of marketable fruit or the total number or total yield of fruit at final harvest were affected by the conductivity treatments. There was however a trend for yield to decrease with the 6 mS cm-1 treatment. It is possible that if the experiment had been continued for a longer period a treatment effect on the number and yield of fruit may have been obtained. It was suggested that the heavy rain experienced during the experiment may have delayed the occurrence of a yield reduction. Although there was no significant effect of conductivity on fruit size, the number of fruit in the two largest size grades tended to be highest for the control plants, while the 6 mS cm-1 treatment had the smallest number of fruit in these size grades. This is further evidence that the conductivity treatments tended to have an effect on fruit size and thus yield. The main cause for fruits to be rejected was due to fruit cracking, which usually occurred when harvesting preceded heavy rainfall. The occurrence of blossom end rot was low since both rainfall and the regular application of liquid feeds did not place the plants under a fluctuating moisture stress. Overall there were very few rejects. The conductivity treatments increased titratable acidity above that of control plants, but there were no difference between the conductivity treatments. Over time titratable acidity of the fruit declined and this may have been associated with either a seasonal effect or the position of the fruit on the stem. Total solids was increased as the concentration of the liquid feeds increased. The percentage of total solids allocated to structural material fell as the concentration of the liquid feed increased. This suggests that the increase in the total solids was due to an increase in the soluble solid component. There was no effect of conductivity on fruit firmness, however firmness fell from an initial value at harvest 1. Total soluble solids of the fruit increased with each increase in conductivity. Over time the trend was for soluble solids to fall slightly up to harvest 5 with a marked decline occurring at harvest 6. As improvements in fruit flavour are associated with increases in titratable acidity, total solids and total soluble solids the conductivity treatments used in this experiment were successful in improving this aspect of fruit quality. This was achieved without any decrease in yield. As suggested however, a trade off between quality and yield may have occurred if the experiment had been continued for a longer period of time. This research suggests that the use of trickle irrigation to supply high conductivity liquid feeds to field grown tomatoes has the potential to significantly improve fruit flavour.
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    A study of the effect of periodic irregularities of fertiliser distribution along the row on the establishment, growth, development and yield of barley : a thesis presented at Massey College in part fulfilment of the requirements of the degree of Master of Agricultural Science in the Victoria University of Wellington
    (Victoria University, 1962) Webb, B. H.
    A considerable volume of evidence derived from field trials throughout New Zealand points to the application of artificial fertilizers (especially superphosphate) to pastures and crops as a primary factor in increased yields: The efficiency of the fertilizer is dependant on the care taken to ensure maximum recovery of the applied nutrient by the crop. This means a consideration of factors such as, time of application, quantity applied, form of fertilizer and also correct placement and efficient distribution. [From Introduction]
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    Influences of climate and fertiliser application history on various measures of soil fertility and productivity in Wairarapa hill country : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Soil Science at Massey University, New Zealand
    (Massey University, 1994) Moir, James Laing
    During the agricultural downturn of the mid 1980's, it became uneconomic for many Wairarapa farmers to apply fertiliser. Those farmers who could afford to apply maintenance fertiliser, often chose to apply diammonium phosphate (DAP). The increasing popularity and apparent effectiveness of fertilisers such as DAP, which has a nitrogen component, prompted further questions of whether traditional P and S fertiliser application (as single superphosphate), applied to stimulate pasture legume growth and biological nitrogen fixation, was the most cost effective fertiliser strategy. A review of literature revealed that soil fertility and pasture production data for different rainfall regimes in the Wairarapa was scarce. No published data was available on how effective single superphosphate (SSP) applications to Wairarapa hill country farms had been in increasing annual N fixation rates and plant­ available soil N, and hence increasing pasture production. It was concluded that it was necessary to conduct a series of pasture field trials on sites varying in soil type, fertiliser history and climate (annual rainfall) in order to provide data applicable to the Wairarapa region. Sites falling within three rainfall regimes were selected, those being Mauriceville (high rainfall), Gladstone (summer dry) and Whareama (low rainfall) sites. Using total soil phosphorus, sulphur and nitrogen analyses, a total of 14 sites were selected for study, with sites ranging in fertility status within each climate zone. The objective has been to characterise the soil types, soil nutrient status, climate and current pasture production of Wairarapa hill country farms, with a view to completing further studies examining in more detail the complex interactions of soil, climate and pasture. Soil chemical analyses revealed a wide range of soil fertility status across all sites. Soil total phosphorus (P) contents ranged from 430 µgP/g soil (site 4) to 1470 µgP/g (site 1), while total soil sulphur (S) showed less variation, ranging from 345 µgS/g (site 11) to 860 µgS/g (site 9). Soil total nitrogen (N) contents followed a similar pattern to that seen for total S, and ranged from 4280 µgN/g (site 11) to 7950 µgN/g (site 9). Fertiliser history had a large influence on the accumulation of P, S and N in these hill country soils, where higher rates of accumulation were associated with greater levels of fertiliser input. However, P accumulated at a far greater rate than S and Nin these soils, which is possibly the result of high S and N leaching losses. Measurements of plant-available nutrient levels followed a similar trend to that seen for soil total elemental analyses, where higher levels of nutrient were correlated with higher fertiliser inputs. Estimates of the efficiency of past fertiliser applications were made for these sites, using the results of various soil analyses. Traditional P and S fertiliser applications and pasture management on Wairarapa hill country appear to have been particularly inefficient in causing soil N to accumulate. The calculations used to derive these estimates have limitations, but do indicate that either product N and leaching losses are high or N fixation rates are low (or both) in these soils. July 1993 to March 1994 was an average growing season, and total herbage yields harvested from August 1993 to March 1994 ranged from 4 tDM/ha (site 4) to 15.5 tDM/ha (site 1). Soil fertility status (and hence historical SSP applications) was the main factor influencing total herbage yield, where high yields were recorded at high fertility sites, and the reverse for low fertility sites. Climate (soil moisture levels) also influenced total yield but to a lesser extent than soil fertility status. Pasture growth at Gladstone and Whareama sites stopped when soil volumetric water content in the top 7.5 cm fell below 0.2. At the wetter Mauriceville sites, soil moisture was not limiting until mid-February 1994. Legume growth was particularly sensitive to soil moisture stress. By converting pasture production to stock units, gross margin analyses were performed. The most profitable options in all three rainfall regimes were sites which had received frequent fertiliser applications. This suggests that historical fertiliser applications are economically effective, which is an important factor in sustainable agricultural enterprises. Herbage N and P uptake results supported this finding, and showed that pasture N uptake varied widely between high and low fertility sites. Pasture N uptake ranged from 70 kgN/ha at low fertility site 4, to 250 kgN/ha at high fertility site 1 for the period of early August 1993 to early January 1994. This implies that historical superphosphate applications have been effective in providing large increases in annual amounts of plant-available soil N at high fertility sites when compared to unfertilised sites, despite the fact that soil N accumulation was less than expected. Acetylene reduction activity (ARA) measured at each harvest showed that annual N fixation levels are limited by extended summer dry periods which stop legume growth. The wetter Mauriceville sites fixed more N on an annual basis than Gladstone and Whareama sites. ARA was linearly related to yield. Variations in the data indicated that species and other short-term soil condition changes have a large effect on the relationship between ARA and N fixation rates. Although soil N accumulation is slow in these pasture systems, annual pasture N uptake is dramatically increased where fertiliser inputs have been high. The results indicate that rapid cycling of soil/plant N is occurring, and that annual leaching and product losses of N may nearly equal N fixation rates. This was exemplified in a simple budget of the nitrogen cycle, taking account of N losses and gains in a low fertility and high fertility system. There was insufficient information to conclude why soil N is not accumulating in these grazing systems. Further research is required to fully explain this N cycle, including the relative quantities of N inputs and losses from the system.
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    An analysis of the regional impact of the Kapuni ammonia / urea plant : a research report constituting two 14.499 Research Reports, in partial fulfilment of the requirements for the degree of Master of Agricultural Business and Administration, Massey University
    (Massey University, 1982) Lusk, Simon Stewart
    Successive post war governments in New Zealand have emphasised industrial development as the basis of economic growth. During this period national-level planning has become institutionalised. Central to the choice of planning policy for industrial development is the balance of payments problem. This has tended to mask other considerations which can be identified as pertinent to national and regional level decision making by private and public organisations . A major difficulty for the researcher is establishing which questions are relevant in a New Zealand context. This research exercise pursues the perspectives and questions which might be brought to bear on specific national development projects. The research focuses on the Kapuni Amronia/urea plant and analyses the regional impact of that project.