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    A study of the relationships between leaf area index, chlorophyll content per unit of ground area and rate of dry matter increase in a perennial ryegrass sward : a thesis presented at Massey College in part fulfillment of the requirements for the degree of Master of Agricultural Science in Victoria University of Wellington, New Zealand
    (Massey University, 1962) Hunt, L. A.
    Many recent attempts to obtain a more detailed understanding of pasture growth have involved an intensive study of relationships between the rate of dry matter increase and various characteristics of the photosynthetic system. Leaf area has been widely used as a measure of the size of the photosynthetic system despite the fact that many photosynthetically active cells occur in the stalks, sheaths and petioles. Chlorophyll is essential for photosynthesis and Brougham (1960) found that there was better correlation between maximum rate of dry matter increase and the chlorophyll content per unit of ground area above the level at which 95% of the noon light was intercepted than between maximum rate of dry matter increase and leaf area index above a similar measurement level. As a logical extension of such work this thesis involves a study of the relationships between rate of dry matter increase, leaf area index and chlorophyll content per unit of ground area during the growth of a pasture.---From Introduction
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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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    The effects of defoliation and rootpruning on cocksfoot and perennial ryegrass and the influence of soil moisture on root initiation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Field Husbandry, University of New Zealand
    (Massey University, 1949) Edmond, D. B.
    The world is short of food (1). The population of the world is unequally distributed in relation to the productive ability of the land. Countries, where an extension of the farmed area is possible, are handicapped by a lack of available labour. In general these are the countries where production has not, as yet, reached a maximum level. As labour hinders extension an endeavour must be made to utilise present farm areas in the most efficient manner possible, In this way surpluses of food may be accumulated in these countries, e.g. New Zealand, for despatch to needy areas where the consumption of food is at a low level. New Zealand produces animal products in quantity. To increase this quantity better use must be made of our chief stock food - grass. By more efficient use of our grasslands the production of our existing herds and flocks will be increased. while an increase in our animal population will be inevitable. [From Introduction]
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    An investigation into the effect of seasonal root replacement upon plant longevity in perennial ryegrass (Lolium Perenne), Italian ryegrass (L. multiflorum), tall fescue (Festuca arundinacea) and annual meadow grass (Poa annua) : a thesis presented at Massey Agricultural College in part fulfillment of the requirements for the degree of Master of Agricultural Science in the University of New Zealand
    (Massey University, 1955) Schwass, R. H.
    Any reader of the American news magazine, "Time", will know that the editors occasionally publish a "grass roots report" dealing with some current question of public interest. It takes the form of a survey of the fundamental issues involved, and attempts to assess their significance, in-so-far as those issues are known. It is a tacit recognition by a non-scientific body of opinion of the importance of the underground organs to the well-being of a plant, and that these organs are more essential, despite their hidden and inaccessible habitat, than is commonly recognized. [From Introduction]
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    A study of root aphid Aploneura lentisci Pass. biology and root aphid-host interactions with perennial ryegrass/endophyte associations in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Entomology at Massey University, Manawatū, New Zealand
    (Massey University, 2019) Müller, Jana Leonie
    The root aphid Aploneura lentisci Pass. is an underestimated, under-researched pasture pest likely to become more problematic in New Zealand if the environmental temperature and the frequency of water deficit stress increase, as predicted. The research presented here aimed at gaining first insights into its biology and interaction with plants and endophytes to promote future pest management research. For this purpose, root aphids were observed in model systems (in climate chambers, glasshouse or insectary; in empty microcentrifuge tubes or on diploid perennial ryegrass Lolium perenne L. plants grown on nutrient-enriched agar, with or without endophy Epichloë festucae var. lolii [Latch, M.J. Chr. & Samuels] C.W. Bacon & Schard of the AR1, AR37 or common-toxic CT strains). Apterous neonate offspring, the presumed main dispersal stage of A. lentisci, survived up to four weeks without food (median survival: 8 days). On endophyte-free, mature ryegrass kept at 17 to 21 °C, neonates developed to adults within three to four weeks and lived about two months, feeding mainly on young roots of first and second branching order. Taking into account lower outdoor temperatures, root aphids are thus likely to complete six to nine generations per year in the field. Adults produced 39 to 70 offspring over their lifetime. Presuming a similar nymphal mortality in the field as in the experiments, outdoor root aphid populations could theoretically multiply 23- to 45-fold at each generation. Root aphids raised on endophyte-infected, mature plants were shorter-lived than peers raised on endophyte-free plants. Most aphids on AR37-infected plants did not even reach reproductive maturity. The response to CT-infection was dependent on the plant genotype. Why AR1-infected plants frequently support larger root aphid populations than endophyte-free plants in the field could not be explained by the data collected, however. Root aphid feeding affected the root biomass but not the shoot biomass of perennial ryegrass in the experimental environment. This finding differed from previous reports. Furthermore, colour analyses suggested root aphid feeding could modify some leaf properties. More research will be required to confirm these findings and assess whether irrigation or fertilisation could mitigate root aphid yield losses in the field.
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    Examining perennial ryegrass (Lolium perenne L.) persistence through identifying genetic shifts within two cultivars after nine years in the field : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Breeding at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) O'Connor, Jessica Richelle
    Perennial ryegrass (Lolium perenne L.) is a commercially important forage species in New Zealand agriculture. Ryegrass persistence is important for farmers as it substantially decreases the costs associated with reseeding pastures. Breeding for ryegrass persistence is difficult because of the complex interaction between genotype and environment; and the short time of field trial assessment compared to the expected longevity of pasture. A nine year old cultivar comparison trial at Poukawa, Hawkes Bay, New Zealand was identified and plants surviving in the cultivar plots of ‘Grasslands Samson’ and ‘Commando’ were retrieved. These populations that had survived were termed Persistent. A sample of commercially sourced seed of these cultivars were also grown to represent the ‘Original’ genetic pool of the cultivars sown in the field. Persistent populations were compared to Original cultivar seed to characterise morphology and underlying genetics associated with persistence. Results were interpreted to determine if a genetic shift had occurred in Persistent populations due to advantageous phenotypes surviving. Three methodologies were used to compare populations: 1) In a glasshouse, eight morphological traits were measured after 10 weeks growth for Original and Persistent populations of ‘Grasslands Samson’; 2) Half-sibling families were generated from Persistent and Original populations for both cultivars and were assessed for additive genetic variation of seven traits as one metre rows in the field over 13 months; 3) Simple sequence repeat (SSR) markers were used to explore the genetic composition of Original and Persistent populations of each cultivar. Analysis and interpretation of data showed genetic shifts were cultivar specific. The greatest differences were identified between populations of ‘Grasslands Samson’. Compared to the Samson Original population, Samson Persistent plants had significantly greater means for four traits in the glasshouse and half-sibling families showed evidence of shifting population means of traits associated with animal grazing avoidance. SSR marker results were confounded by late detection of contamination in samples. Analysis of a reduced sample size showed no significant differences between any of the four populations using F statistics and genetic structure analysis. These results suggest future studies could reduce risk of contamination by collecting single tillers from the field of Persistent populations. Further investigation of the genetics of persistence should focus on the role of lamina sheath lengths in tiller production, and using the half-sibling families identified in this study for germplasm development and quantification of genotype-by-environment interactions.
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    A preliminary investigation into the root systems of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) using a prescribed sampling method for the study
    (Massey University, 1939) Hopewell, H G
    The roots of' plants are the least known, least understood and least appreciated part of the plant." Weaver end Bruner. The fundamental importance of an extensive, well developed and healthy root system cannot be over emphasised. It must hold the plant firmly in the ground, provide a large effective absorptive area through which ample nutrients will become available for growth, and, by penetrating deeply, or by building up reserves, it must protect plant against the exigencies of a dry season. The study of the roots then, important as they are, would appear to have been unduly neglected when one considers the amount of research carried out using as a basis some above ground feature of the plant. In this connection W.F. Loehwing ( 1) may be quoted - "As one surveys the monumental literature dealing with crop production, the small fraction thereof devoted to roots and the absorption processes seems entirely out of prorortion to their importance. [From Introduction]
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    A study of the reaction of several variables of top growth of a perennial ryegrass/white clover pasture to different defoliation treatments and measurements on soil moisture status : a thesis presented at Massey Agricultural College in part fulfilment of the requirements for the degree of Master of Agricultural Science in the University of New Zealand
    (Massey Agricultural College, 1959) Kerr, James Patterson
    The agricultural research worker must on occasion adopt a broad view of farming purely as the management of plants and animals to produce human food. He has the task of outlining many of the principles to be used in farming practice, to increase world food production, in order to meet the challenge of a growing world population. He needs to consider the biological efficiency of the living processes and systems involved in food production; in much the same way as a businessman or farmer must consider the business efficiency of his factory or farm operations. Food production may be increased either by bringing more land under cultivation or by intensifying agriculture on the existing areas of cultivation, thereby increasing production per acre. Watson (1958) described the problem as fundamentally one of increasing the total annual photosynthesis per unit area of crop, for it is the net product of photosynthesis which the farmer harvests. Photosynthesis requires light, moisture and nutrients, and as light is the only one of these factors which can not be readily supplied artificially, Donald and Black (1958) have suggested that the ultimate measure of agricultural efficiency could well be expressed in terms of the proportion of light energy utilised by the crops or pastures. The size and activity of the photosynthetic system then becomes one of the determinants of crop yield. The potential rate of photosynthetic activity is controlled by the genetic make-up of the plant. The same is true to a certain degree of the size of the photosynthetic system, but the farmer too, through various cultural and management methods, exerts considerable control over the size of the system. [FROM INTRODUCTION]
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    Variations in lipid composition of perennial ryegrass (Lolium perenne) and barley (Herdeum vulgare) with special reference to galactolipids : a thesis ... M. Agr. Sc.
    (Massey University, 1965) Gray, Ian Keith
    In New Zealand, dairy cows are fed mainly on pasture in situ. This is in contrast to feeding practices in other countries where lactating cows are normally fed diets containing appreciable proportions of food products, other than fresh pasture. Although lipids form only 4-6% of the dry weight of leaf tissue (Hilditch and Williams, 1965) it has been estimated that a cow by eating 9 kg. of dry matter of grass per day may consume up to 700 g. of lipid (Hawke, 1963). The nature of dietary lipid and its modification in the rumen (Reiser and Reddy, 1956) is of particular interest as it may influence the composition of the depot and milk fats of ruminants. Only a few investigators have studied possible relationships between the composition of the milk fat and dietary lipids when ruminants are fed entirely on pasture species. (McDowall and McGillivray, 1963; Hawke, 1963).The latter worker demonstrated that young succulent short rotation ryegrass (Lolium multiflorum x Lolium perenne) contained a higher content of lipid (β of dry wt.) than mature grass which contained appreciable stalk material. Furthermore the lipid from the new growth contained higher proportions of linolenic acid and lower proportions of linoleic and palmitic acids. When pairs of monozygous twin cows were grazed on these two types of pasture, the cows feed on the young grass had higher levels of unsaturated fatty acids in the milk fat. This was thought to be related to higher levels of unsaturated fatty acids in the young grass and to the degree of hydrogenation of the unsaturated fatty acid components of the dietary lipid in the rumen. A large proportion of the dietary lipid of ruminants fed on pasture would consist of galactosyl glycerides since these components are the major lipids of photosynthetic tissue (Weenink, 1961 ; Sastry and Kates, 1964). Consequently the comparative levels of galactosyl glycerides and changes in their fatty acid composition in L. perenne leaf tissue of varying age has been investigated. The present investigation also includes a study of the effect of the light environment on the levels and composition of lipid, especially the galactolipids, and on the biosynthesis of fatty acids. [From Introduction]
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    Some aspects of leaf death during the regrowth of a perennial ryegrass (Lolium perenne L.) white clover (Trifolium repens L.) sward : a thesis presented in partial fulfilment of the requirements for the degree Master of Agricultural Science at Massey University
    (Massey University, 1968) Hunt, Warren Ferguson
    In order to achieve high animal production from grass-legume pastures such as are used in New Zealand, it is necessary to meet three basic requirements. (a) large amounts of high quality feed must be grown, the seasonal distribution of which must approximate the seasonal curve of animal requirements. (Conservation practices can be used to rectify minor discrepancies.) (b) A large proportion of this feed must be harvested by the animal. (c) Efficiency of conversion within the animal must be at a high level. (McMeekan 1956) Agronomists are concerned primarily with the first of these factors, but as maximum production for a system is approached, the second factor assumes major importance. These aspects must be studied against the background of a wide range of management techniques that may be employed in defoliating pastures. In the past, the importance of both leaf area grass tiller density and organic reserve materials have been studied as they are influenced by defoliation management, and their role has to some extent been determined. (Milthorpe and Davidson 1965). The emphasis in such investigations has been on the initial stages of regrowth from defoliation and there remains a number of aspects of primary productivity at medium and high Leaf Area Index values (L.A.I. i.e. the area of leaf per unit area of ground) requiring investigation (Brougham 1962, Alberda 1965a, Brown and Blaser 1968). One of these aspects, leaf death, is the subject of the investigation reported below and has been selected because of its significance to both productivity and utilisation. [From Introduction]