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Item An evaluation of greenhouse gas emissions reduction potential of plantain (Plantago lanceolata L.) in pastoral dairy production systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agriculture Systems Management at Massey University, Manawatu, New Zealand(Massey University, 2025-05-16) Sivanandarajah, KomahanThere is increasing interest in the ability of plantain (PL) to reduce nitrogen (N) leaching losses and mitigate nitrous oxide (N₂O) emissions, while maintaining milk and pasture production. While PL’s role in lowering urinary N concentration is well established, the results regarding the effect of PL on N₂O emissions have been inconsistent. Furthermore, evidence has shown that cows fed pure PL produce less methane (CH₄) emissions compared to those fed ryegrass. However, whether this CH₄ reduction can be achieved with PL in mixed pasture, along with a clear understanding of the mechanism(s) behind those reductions, are still to be determined. This thesis evaluates PL’s potential to mitigate CH₄ and N₂O emissions through a series of in vitro and a field experiment, focusing on mixed pastures with moderate PL levels. When pastures, either a conventional ryegrass-white clover (RWC) or an RWC mix containing ~40% of PL (PLM), were collected during different seasons and tested in an in vitro rumen batch culture system, differences in their chemical composition led to significant differences in CH₄ and rumen ammonia (NH₃) production. Compared to RWC, PLM had lower fibre (neutral detergent fibre and acid detergent fibre), higher lignin, more fermentable carbohydrates (non-structural carbohydrates), and plant secondary metabolites (PSM, acteoside and aucubin) detected only in PLM, while maintaining similar digestibility and crude protein (CP) levels. Consequently, PLM produced up to 27% less net NH₃ in spring, up to 19% less CH₄ in summer, and 17% less net NH₃ in autumn compared to RWC (p<0.05) in vitro. Plant secondary metabolites found in PL, have been associated with reducing N losses from grazed pastures. However, their influence on enteric CH₄ emissions remains unexplored. Additionally, the dose-response relationship between CH₄ and NH₃ production at different concentrations of PSM needs to be established. To address this, purified compounds (>99% purity) of acteoside and aucubin were incubated with perennial ryegrass (RG) as a basal substrate, and gas and CH₄ production were measured in vitro. The addition of acteoside to RG increased gas production (GP) by up to 12%, with a similar quantity of CH₄ production, but a 5–15% lower proportion of CH₄ in gas (%CH₄), compared to the control. Aucubin addition resulted in a longer lag phase for GP and CH₄ production. On addition of aucubin, it took up to 15% more time to reach the halftime (T1/2) GP and up to 20% longer to reach the T1/2 CH₄ production. The combined treatments of acteoside and aucubin produced up to 13% greater GP with similar CH₄ production and reduced %CH₄ by around 9%. These reductions are attributed to the modification of the hydrogen utilisation pathway (less hydrogen to produce CH₄) affected by acteoside. Aucubin reduced rumen net NH₃ production by up to 46%, with a similar reduction observed when acteoside was combined with aucubin. These reductions are attributed to the possible antimicrobial activity of aucubin. These results suggest that PL influences rumen fermentation in vitro, resulting in lower CH₄ and NH₃ production. Since higher rumen NH₃ correlates with greater urinary N excretion into the environment, reducing NH₃ levels in the rumen is advantageous. Previous studies have shown that N₂O emissions from PL pastures may be reduced due to smaller N concentrations in urine and/or biological nitrification inhibition (BNI) activity. In this study, urine collected from cows fed diets containing 0% PL, ~20% PL, and diluted urine from PL-fed cows, was applied to pastures containing 0% PL, 30% PL, and 40% PL during spring. The N₂O emissions were measured over 55 days. Results indicated a trend toward lower N₂O emissions as assessed using the emission factor (EF₃) metric, with increasing PL content (p<0.09), with an average reduction of around 28% for pastures containing 30–40% PL compared to RWC pastures (p=0.03). This reduction in N₂O emissions from PL pastures was attributed to BNI activity rather than differences in urine-N concentrations per se. These results enhance our understanding of PL’s role in mitigating environmental impacts from grazing ruminants in temperate systems. This thesis concludes that medium PL pastures (30–40% PL) exhibit significant environmental benefits compared to RWC pastures in vitro, with reductions in CH₄ and rumen NH₃ influenced by PSM in PL and the seasonal variability in chemical composition. Moreover, under conditions conducive to higher N₂O emissions (in spring), maintaining 30–40% PL in the pasture could reduce N₂O emissions more effectively than excluding PL.Item Investigation of tropical pasture species to improve dairying in the tropics : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Manawatū, New Zealand(Massey University, 2023) Jayasinghe Mudiyanselage, Priyanath JayasingheDespite the ever-increasing demand for dairy products, dairy production in tropical regions is often lower than in temperate regions, due to a range of factors including the lower nutritive value of pastures. The availability of high-quality tropical pastures is a key requirement to increase the productivity of dairy cows as well as manage enteric methane emissions. Warm-season perennial grasses are the dominant forages in tropical and subtropical regions, and thus exploring their nutritive characteristics and evaluating their likely performance in existing dairy production systems, is imperative in the effort to improve dairy productivity. This thesis was undertaken to investigate tropical pasture species for improving dairying in the tropics via a modelling and simulation approach. A dearth of data comparing the nutritive values of tropical pastures grown across different environments limits the selection of forages for livestock in the tropics. A database was constructed containing a total of 4750 records, with 1277 measurements of nutritive values representing 56 tropical pasture species and hybrid cultivars grown in 26 different locations in 16 countries, in order to compare the nutritive values and greenhouse gas production across different forage species, climatic zones, and defoliation management regimes. The average edaphoclimatic (with minimum and maximum values) conditions within this data set were characterized as 22.5°C temperature (range 17.5–29.30°C), 1253.9 mm rainfall (range 104.5–3390.0 mm), 582.6 m elevation (range 15–2393 m), and a soil pH of 5.6 (range 4.6–7.0). The data revealed spatial variability in nutritive metrics across bioclimatic zones and between and within species. The ranges of these nutrients were as follows: neutral detergent fibre (NDF) 50.9–79.8%, acid detergent fibre (ADF) 24.7–57.4%, crude protein (CP) 2.1–21.1%, dry matter (DM) digestibility 30.2–70.1%, metabolisable energy (ME) 3.4–9.7 MJ kg⁻¹ DM, with methane (CH₄) production at 132.9–133.3 g animal⁻¹ day⁻¹. The arid/dry zone recorded the highest DM yield, with decreased CP and high fibre components and minerals. Furthermore, the data revealed that climate, defoliation frequency and intensity, in addition to their interactions, have a significant effect on tropical pasture nutritive values and CH₄ production. Overall, hybrid and newer tropical cultivars performed well across different climates, with small variations in herbage nutritive value. Results revealed that greater pasture nutritive values and lower CH₄ production can be potentially achieved through the selection of improved pastures and subsequent management. Subsequently, the suitability of three improved tropical perennial pastures: Chloris gayana ‘Rhodes grass cv. Reclaimer’ (RR), Megathyrsus maximus ‘Gatton Panic’ (GP), and Brachiaria ruziziensis x B. decumbens x B. brizantha ‘Brachiaria Mulato II’ (BM) for tropical dairy production was evaluated using their carbon assimilation, canopy structure, herbage plant-part accumulation and nutritive value parameters under irrigated conditions. A field experiment was conducted at Gatton Research Dairy (27° 54′ S, 152°33′ E, 89 m asl) Queensland, Australia, which has a predominantly subtropical climate. Photosynthesis biochemistry, canopy structure, herbage accumulation, plant-part composition, and nutritive value were evaluated. Photosynthesis biochemistry differed between pasture species. The efficiency of CO₂ assimilation was highest for GP and quantum efficiency was highest for BM. Pasture canopy structure was significantly affected by an interaction between pasture species and harvest. Forage biomass accumulation was highest in GP, while BM produced more leaves and less stem compared to both GP and RR. A greater leafy stratum and lower stemmy stratum depth were observed in the vertical sward structure of BM. Brachiaria Mulato II showed greater carbon partitioning to leaves, leaf: stem ratio, canopy, and leaf bulk density. The BM also demonstrated greater nutritive value (Total digestible nutrients (TDN), ADF, NDF, neutral detergent insoluble protein (NDICP), starch, non-fibre carbohydrates (NFC), ME, mineral profile (Mg, P, K, Fe, Zn) and dietary cation-anion difference (DCAD)) for leaf, stem, and the whole plant. Overall, the observed greater quantum efficiency, leaf accumulation, and nutritive value of BM suggested that BM is an attractive forage option for dairying in pasture-based systems in tropical and subtropical climates. The DairyMod-SGS, a mechanistic biophysical pasture model was parametrised and robustly validated for the prediction of the growth of the three tropical pastures (BM, GP, and RR), aiming to use the model as an effective tool to explore the likely performances of newer species under different edaphoclimatic and agronomic management practices. The model was calibrated using measurements of biomass components, canopy structure, and carbon assimilation collected from the field experiment at the Gatton Research Dairy Farm. Subsequently, the model was tested extensively using the published and unpublished data (16 data sets, 32 experiments, 14 different locations across South America, North America, Australia and Africa) to ensure that the parameterised model performed well and was reliable across a diverse set of environments and management practices. In the model parameterisation stage, the model predicted the above-ground biomass with good agreement for all tropical pastures with a high R² of 0.92, 0.98, 0.74 and low RMSE of 341, 583, 848 kg DM ha⁻¹ for BM, GP, and RR, respectively. The model agreement was good for the validation data with R² of 0.86, 0.80, 0.87 and RMSE of 954.5, 790.5, and 633.2 kg DM ha⁻¹ for BM, GP, and RR, respectively. The predicted leaf and stem partitioning was relatively poor, and the model also struggled to simulate realistic pasture growth in Mediterranean and desert environments (R² < 0.50). The present study has improved the robustness and accuracy of DairyMod-SGS in relation to tropical pastures and indicated that the model can be successfully used for investigating the likely performance of improved tropical pastures under a broad range of conditions. The validated DairyMod-SGS pasture model was applied to simulate the long-term pasture production of three improved pastures (BM, GP, and RR) in major dairying regions of Sri Lanka under three management scenarios: 1) rainfed pasture production system under the industry average nitrogen (N) fertiliser rate (Yₜᵂᴺ = yield over time under water and N limitation); 2) rainfed pasture production system under non-limiting N fertilisation (Yₜᵂ = yield over time with no N limitation but water limitation); and 3) potential pasture production system under non-limiting N and irrigation (Yₜ = yield over time with no N and water limitations). Simulations were carried out for 16 sites across Sri Lanka (8 sites in the dry zone (DZ), 5 sites in the intermediate zone (IZ), and 3 sites in the wet zone (WZ)) over a 30-years period (1980–2010). The model simulated that the long-term pasture production greatly varied between climate zones, pasture species and management scenarios. Overall, the Yₜᵂᴺ scenario showed a seasonal cycle following the rainfall pattern, with a reduction in growth rates in dry seasons (May to September). Growth rate and herbage accumulation were greater in GP at Yₜᵂᴺ, and BM at Yₜᵂ and Yₜ, while RR always showed the lowest growth rate. The variability of pasture growth between climate zones was highest in DZ (May to September) whereas the variability between species was lowest in RR. Pasture accumulation of both BM and GP outperformed their standard cultivars currently grown in Sri Lanka. In general, the pasture accumulation under Yₜᵂ increased (doubled) the growth rate, while the Yₜ scenario substantially increased (nearly tripled) the growth rate. Overall, the finding of this thesis suggested that all three pasture cultivars tested (BM, GP, and RR) are suitable for growing across major dairying regions in Sri Lanka, and that appropriate fertiliser and irrigation management can greatly intensify the herbage accumulation. In particular, BM appeared to be promising in terms of nutritive value, and agronomic and physiological traits. However, regional edaphic conditions, and the management ability of the farmers with respect to inputs and defoliation management, will ultimately determine the performance of improved cultivars such as those used in this thesis. There is a need for extension activities to support farmers in the management required to achieve best performance (yield, nutritive value and persistence) from these species. Future research is recommended to: 1) validate the model under Sri Lankan conditions, using both unimproved and improved cultivars, to determine its suitability in estimating tropical pasture yield; and 2) use additional models to evaluate the performance of improved tropical pastures in the context of the whole farm system, to identify the likely impact on dairy production and economic return.Item Impact of plantain (Plantago lanceolata) based pasture on milk production of dairy cows and nitrate leaching from pastoral systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatu, New Zealand(Massey University, 2023) Nguyen, Truong ThiIn temperate dairy systems, the traditional perennial ryegrass (Lolium perenne)-white clover (Trifolium repens) (RGWC) pasture often has excessive nitrogen (N) content relative to the N requirement of animals, posing a risk of nitrate (NO₃⁻) leaching into the environment. Recently, incorporating plantain (Plantago lanceolata) with RGWC pasture has been increasingly used to improve economic and environmental benefits for dairy farms. However, the impact of plantain incorporation on farm productivity and NO₃⁻ leaching at the farm level has not been fully understood. The objectives of this thesis were to quantify the effect of incorporating increasing rates of plantain in grazing swards on pasture production, milk yield and composition of dairy cows, and NO₃⁻ leaching from pastoral dairy systems. To address the objectives of the thesis, a grazing trial was implemented at a research dairy farm between September 2019 and December 2021. Pasture treatments were RGWC (perennial ryegrass cv. ONE⁵⁰ and white clover cv. Tribute), RGWC + low plantain (cv. Agritonic) rate (PLL), RGWC + medium plantain rate (PLM), and RGWC + high plantain rate (PLH). Pastures were established with 20 experimental plots and four adaptation areas in April 2019 and were rotationally grazed by dairy cows over 22 grazing events during the experimental period. In each grazing, 60 or 80 cows were assigned to graze for 6 days in their adaptation areas and 1.5–3 days in the experimental plots. The experimental cows were managed under a typical practice, milking twice daily, offering grazing pasture and approximately 25% supplementary dietary feeds. Measurements were conducted to quantify the yield, botanical composition and nutritive value of the pasture, milk yield, milk composition and N excretion of dairy cows, and NO₃⁻ leaching from the pastoral system. The results showed that, over the first two lactation years after sowing, plantain-based pastures have a similar dry matter yield and contain higher water content, non-structural carbohydrates, minerals, and bioactive compounds than the RGWC pasture. The average plantain proportion in the swards over the first two years after sowing was 32% in PLL, 44% in PLM, and 48% in PLH, which increased in the first 15 months and declined to 20% in PLL and 30% in PLM and PLH at day 705 after sowing. Cows grazing the plantain-based pastures had a similar milk yield, composition and yield of solids, protein, fat, and lactose as those grazing the RGWC pasture. Furthermore, when 25% plantain was included in the diet of cows in late lactation, it resulted in a 44% increase in urine volume and a 29% reduction in urine N concentration by 29%. By incorporating an average of 30% and 50% plantain with RGWC pasture, NO₃⁻ leaching was reduced by 32 and 52%, respectively, over two drainage years after establishment, with a greater reduction in the first year than in the second year. Among sowing rates, PLM resulted in the greatest decrease in NO₃⁻ leaching, with 64% in the first year and 41% in the second year. The decreased NO₃⁻ leaching was associated with increased plantain content, enhanced herbage N uptake, reduced UN excretion of dairy cows and a lower N load in urine patches. In conclusion, in a typical practice, as in the present study, incorporating 30–50% plantain with RGWC pasture decreases NO₃⁻ leaching from pastoral systems without adversely impacting farm productivity for at least two years from sowing. However, the reduction of plantain content in the second year suggests further measurements to determine the effectiveness of plantain-based pasture in the longer term. In the conditions and time scale of the present study, the medium plantain rate treatment (PLM) is suggested to achieve a high effectiveness of plantain incorporation in reducing NO₃⁻ leaching.Item Pursuing pasture tolerance and resilience through species with different functional traits and soil-plant-water interactions : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Manawatu, New Zealand(Massey University, 2020) Ordóñez Vásquez, Iván PabloHigher stability, persistence and yield can be achieved through increasing the biodiversity of pasture plants. The combination of species with different functional traits confers niche differentiation (e.g. different root depth). Otherwise species compete for the same resources in the same location and time. In diverse pasture, agricultural needs should overlap between species, enhancing species survival during critical periods. Productive ecosystems with low complexity (low plant functional diversity) show more the negative impacts of climate change, being less stable through the stress periods. Bromus valdivianus Phil. is regarded as having high potential for grazing systems, due to its high yield and good nutritive quality. It also has high tolerance to periods of soil water restriction, maintaining a higher growth rate during summer in comparison to Lolium perenne L. Alongside L. perenne, B. valdivianus co-dominates permanent perennial pastures in the South of Chile, indicating that it is a good competitor in mixed cool-temperate pastures. However, key parameters associated with recovery from defoliation, such as watersoluble carbohydrate (WSC) reserves, growth rate, tiller number and persistence, are unknown for B. valdivianus. Therefore, the first step in this thesis was to determine these defoliation criteria in relation to similar defoliation criteria of other highly productive species, L. perenne and Plantago lanceolata, to determine if and when any overlap occurred. This thesis consisted of three main experiments, which cover the physiological, morphological and competitive traits of B. valdivianus. The first experiment was designed to determine a theoretical optimum defoliation interval for B. valdivianus, and it was concluded that defoliation at leaf stage 4 (LS-4) was the optimum defoliation in terms of highest shoot and root growth rates, and accumulation of WSC. The second experiment was designed to determine the resilience and tolerance between monocultures and mixtures of B. valdivianus, L. perenne and P. lanceolata. All three species were defoliated when B. valdivianus reached LS-4, which coincided with approximately 3.5 regrowth leaves/tiller for L. perenne, and over 6 leaves/plant for P. lanceolata. Measurements included biomass production across critical periods, botanical composition, physiological response against water stress (waterlogging and soil water restriction) and water uptake at different depths, and it was concluded that a more diverse pasture (B. valdivianus + L. perenne + P. lanceolata) maintained higher biomass under soil water restriction and also had a more effective water uptake from the soil profile. The third experiment was designed to determine the tiller population dynamics, photosynthetic carbon fixation capacity (PCFC) and competitive ability of B. valdivianus in relation to L. perenne. It was concluded that L. perenne was a better competitor than B. valdivianus, however, B. valdivianus was able to recover its tiller population during a period of soil water restriction and reached a full recovery at the end of the experimental period. Also, a B. valdivianus + L. perenne mixed pasture had the highest values for PCFC during the waterlogging and soil water restriction periods. Pasture plants such as B. valdivianus and P. lanceolata can access water from deeper in the soil than L. perenne, having a direct effect on their physiological traits. Water accessibility (root depth) plays a key role in maintaining their photosynthesis, production, and improving their survival, during periods of soil water restriction, relative to L. perenne. On the other hand, L. perenne tolerate waterlogging and maintain a relatively high growth rates during winter. Pasture establishment and performance, in a climate with dry and wet seasons and in soils with a high percentage of silt and/or clay (low gas permeability), is related to species tolerance to drought and waterlogging conditions. Thus, increasing species diversity is a good strategy that confers stability to the pastoral ecosystem, especially when global warming has enhanced droughts and unpredictable rain events. Mixtures of L. perenne + T. repens + P. lanceolata or L. perenne + T. repens + B. valdivianus can reach higher growth rates during water restriction periods, in comparison to L. perenne + T. repens pastures, along with relatively high growth rates during winter. Therefore, combining species with the aim of complementary resources uptake, and depending on the contribution of each species within the pasture, will change the seasonal herbage growth rate under the stress periods. However, to keep a great contribution of the desirables pasture species it is essential to use a defoliation criterion that allow them to replenish its water soluble carbohydrates, only then, the persistence, survival and yield of the pasture and the desirables species within it will be maximized.Item Unveiling the potential of proximal hyperspectral sensing for measuring herbage nutritive value in a pasture-based dairy farm system : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agriculture and Horticulture at Massey University, Manawatū, New Zealand(Massey University, 2020) Duranovich, Federico NicolásThe aim of this thesis was to unveil the potential of proximal hyperspectral sensing for measuring herbage nutritive value in a pasture based-dairy farm system. Hyperspectral canopy reflectance and herbage cuts as well as data on herbage and supplement allocation, and milk production were collected regularly from Dairy 1 farm at Massey University during the 2016-17 and 2017-18 production seasons. Milk, fat and protein yields and body condition score of cows were measured at monthly herd tests while live weights were recorded daily. Calibration equations determining herbage the nutritive value traits digestible organic matter in dry matter, metabolisable energy (ME), crude protein, neutral detergent fibre and acid detergent fibre from hyperspectral canopy reflectance data were developed and validated using partial least squares regression. Canopy reflectance calibration models were able to determine the various herbage nutritive value traits with R2 values ranging from 0.57 to 0.78. Variation of herbage nutritive value traits were mostly explained by month within production season (42.7% of variance among traits) followed by random error (33.4%), production season (13.1%) and paddock (10.7%). The relative importance of herbage nutritive value and other herbage quantity and climate-related variables in driving performance per cow in the herd was determined using multiple linear regression. Herbage metabolizable energy explained 20% to 30% of milk, fat and protein production per cow while herbage quantity and climate- related factors were relatively less important (below 15%). Random regression models were used to model lactation curves of milk, fat, protein and live weight to estimate daily ME requirements of individual cows. The daily ME estimated requirements was nearly a fifth above or below the daily mean ME supplied. The deviation of the daily ME estimated requirements of a cow from the actual ME supplied per cow in the herd was mostly explained by the observations made within a cow rather than between cows or breeds. Variation in herbage nutritive value in addition to the within and between cow variation of ME estimated requirements were high enough to justify the use of proximal hyperspectral sensing as measurement tool to assist with feed allocation decision-making. However, the potential of this technology could be further enhanced using more precise technologies to allocate herbage to individual cows or groups of cows. The potential benefits of more precise feed allocation will result in more efficient grazing management and thus improved utilisation of herbage and hence milk production.Item A study of the yields of various species of pasture plants, and some of their strains, when growing in a soil brought to various levels of hydrogen-ion concentration : thesis submitted for M. Agr. Sc. degree / by "548" [A.J. McNeur](Massey University, 1948) McNeur, Archibald JamesDuring the past few decades, our country, along with other important primary producers, has come to realise with increasing force the real importance of pasture production to mankind. In New Zealand over nine tenths of the value of our exports comes directly or indirectly from grasslands. This realisation has been reflected in the marked extension in research, not only towards the improvement of pasture species and strains, but also in an attempt to learn more of the conditions in the soil that are most ideal for maximum production. As a plant can produce only as much as its inherent potential and its external environment will allow, it becomes all workers to consider both sides of the question of maximum production. As a result of work done by the Grasslands Division of the Plant Research Bureau since its inception, strains of new pasture species have been developed which will produce very highly under conditions favourable to their growth. Thus if these strains are used in agriculture and maximum production is not obtained, managemental and environmental factors must be the limiting ones. Of the environmental factors, five claim pride of place where pasture production is concerned:- (a) Soil moisture (b) Soil and air temperature (c) Light intensity (d) Soil fertility (e) Soil acidity. In practice the first three factors are mainly dependent on climatic conditions, though by suitably controlled irrigation and drainage both soil moisture and soil temperature can be influenced and plant growth markedly increased. [From Introduction]Item Investigation on the effect of biochar addition and the use of pasture species with different rooting systems on soil fertility and carbon storage : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy (MPhil) in Soil Science at the Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand(Massey University, 2015) Wisnubroto, Erwin IsmuThere is a potential to increase soil carbon (C) sequestration in New Zealand pastoral soils, especially in the subsoils where the soil C stocks have been reported to have a greater C saturation deficit than the topsoils. Selecting pasture species with deeper root systems will enhance soil formation at depth and mineral weathering, thus enhancing the potential for soils to stabilize organic matter (OM). Moreover, the addition of biochar may increase the stable C pool of soils and provide other additional benefits. Up to the present time few studies have investigated the potential of biochar to promote root growth and allocation of plant C to the subsoil. A glasshouse study was carried out to examine the effect of adding a nutrient-rich biochar at various dose (0, 1.5, 5 and 10 Mg ha–1 without nitrogen (N) fertiliser; 0, 1.5, 10 and 20 Mg ha–1 with N fertiliser at a dose of 113 kg N ha–1) to a sandy soil on plant growth (aboveand below-ground). The results indicated that, in the absence of N limiting conditions, biosolids-derived biochar could improve plant biomass yield as a result of the addition of available P and K. This amendment also caused an increase in plant root length. Subsequently, a 2-year lysimeter trial was set up to compare changes in C stocks of soils under deep- or shallow-growing pastures as well as to investigate whether biochar addition below the top 10 cm could promote root growth at depth. For this: i) soil ploughing at cultivation for pasture establishment was simulated in two different soils (a silt loam soil and a sandy soil) by inverting the 0–10 and 10–20 cm depth soil layers, and biochar was mixed at a rate of 10 Mg ha–1 in the buried soil layer, where appropriate; and ii) three pasture types with contrasting root systems were grown. Distinctive biochars were selected for these two soils so that soilspecific plant growth limitations could be overcome. In the silt loam, soil inversion resulted in a net loss of native organic C in the buried horizon under shallow-rooted species, but not under deep-rooted species. The addition of a C-rich pine biochar (equivalent to 7.6 Mg C ha–1) to this soil resulted in a net C gain (6–16% over the non-biochar treatment, calculated up to 30 cm; P < 0.05) in the buried soil layer under all pasture treatments; this overcame the net loss of native organic C in this horizon under shallow-rooted pastures. In the sandy soil all pasture species were able to maintain soil C stocks at 10–20 cm depth over time. In this soil, the exposure of a skeletal and nutrient-depleted soil layer at the surface may have fostered root growth at depth. The addition of a nutrient-rich biosolids biochar (equivalent to 3.6 Mg C ha–1) to this soil had no apparent effect on total C stocks. In this 2-year study, none of the biochar amendments affected either pasture yield or root growth. More research is needed to understand the mechanisms through which soil C stocks at depth are preserved.Item Chicory (Cichorium intybus) and plantain (Plantago lanceolata); physiological and morphological responses to water stress, defoliation, and grazing preference with implications for the management of the Herb and Legume Mix : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, Massey University, Te Kunenga ki Pūrehuroa, New Zealand(Massey University, 2014) Cranston, Lydia MargaretHerb and legume sward mixes containing chicory (Cichorium intybus), plantain (Plantago lanceolata), red clover (Trifolium pratense) and white clover (T. repens) are being increasingly used by farmers to improve animal performance compared to perennial ryegrass and white clover swards. However, little is known about the agronomic properties of this Herb and Legume Mix. The objectives of this research were to examine key factors likely to affect the success of the Herb and Legume Mix as a perennial sward mix. This thesis included a series of glasshouse experiments, a grazing experiment (examining plant parameters and animal grazing preference) and a mowing experiment. The glasshouse experiments indicated that chicory and plantain have different strategies for coping with moisture stress. The results suggest plantain may be more productive under moderate drought due to its greater shoot mass fraction, whereas chicory may be more productive and persistent under severe drought due to its greater root mass and taproot diameter. The Herb and Legume Mix accumulated greater annual dry matter when removed under Hard grazing (post-grazing residual of 4cm) compared to Lax grazing (post-grazing residual of 8cm). Hard grazing favoured plantain growth and persistence, while Lax grazing favoured red clover growth and resulted in chicory with a larger taproot diameter. It was concluded that grazing management decisions should be determined by ensuring optimal management of chicory. Ewe lambs displayed grazing preference for species within the Herb and Legume Mix; however this varied between seasons and was affected by the species availability, vertical access and palatability. The Herb and Legume Mix had a greater herbage nutritive value than the ryegrass and white clover sward and had a more stable composition over time than pure swards of chicory and plantain under a wide range of defoliation regimes. The results suggest the Herb and Legume Mix might be a more flexible perennial forage option than pure swards of chicory and plantain. Overall the results of this thesis indicated that the Herb and Legume Mix can be successfully utilised in most New Zealand grazing systems as a perennial forage sward.Item Nutrient efficiency of some grasses and legumes in relation to environmental stress : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agronomy at Massey University(Massey University, 1975) Scott, Robin StewartThis thesis provides a definition of relative nutrient efficiency (RNE) by which species and strains of pasture plants can be differentiated in a quantifiable manner according to the shape of their response surface to applied nutrients. Attention is drawn to the fact that RNE is under genetic control and to the probability that no single casual mechanism controls RNE because of the interdependence of plant physiological processes. Experiments are reported investigating the RNE of strains of Yorkshire fog (Holcus lanatus L.), perennial ryegrass (Lolium perenne L.), Lotus pendunculatus Cav. (Syn L. uliginosis Schkuhr., L. major Sm.) and white clover (Trifolium repens L. ). Initial experiments examined a number of strains of each species for their RNE in response to N for the grasses and P for the legumes. Subsequent experiments compared strains of both grass species in response to N and legume species in response to P together with the effects of climate. Measurements were made of dry matter yields, shoot:root ratios, N absorption and utilization, and in addition for legumes their N fixing activity and P absorption and utilization. A final experiment examined climatic paramaters affecting RNE of two strains of white clover in response to P and their relative abilities to remobolize and re-utilize N and P in younger compared to older tissue. Results of all experiments showed differences in RNE among strains of each species. They also showed that RNE is dependent upon climate, with high RNE generally being expressed under conditions most favourable for maximum growth. A bred strain of Yorkshire fog - Massey Basyn, was found to provide high yields relative to others at low levels of N. This was attributed to its greater ability to absorb and utilize N. Among perennial ryegrasses Mangere strain possessed low RNE under a 15/10°C day/night temperature and 200 Wm2 light intensity due to its inability to absorb N through restricted root development. Comparison of the most efficient strains of Yorkshire fog and perennial ryegrass showed that they did not differ in RNE and it is concluded that the 'low fertility' classification of Yorkshire fog is unwarranted. The initial experiment with Lotus identified strains differing in RNE but this finding was not confirmed in the subsequent experiment. A strain of white clover from the Netherlands (Tamar) was found in two experiments to have high RNE through providing high yields at medium to high levels of P. In the final experiment where Tamar was compared with Huia white clover, its greater RNE was due to a greater ability to absorb and utilize N and P, to remobolize N and P from older to younger tissue and to mobolize soluble sugars from shoots to roots. Comparison of the most efficient strains of white clover and Lotus showed that the former responded better to high levels of P. It is concluded from this series of experiments that genetic variability exists among the species studied and that their differing RNE could be exploited to bring about economies in the use of fertilizers.Item A study of the combined effects of irrigation frequency and phosphorus fertility on summer pasture production : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Soil Science, Institute of Natural Resources, Massey University, Palmerston North, New Zealand(Massey University, 2003) Hewana Arachchige SumanasenaDuring the last five years, there has been an increase in both the area of irrigated pasture in New Zealand and the intensity of this irrigation. Research has failed to keep pace with this change: the benefits of irrigation to pasture production have not been studied in a sustained manner since the 1980s. Since then a number of factors have changed including; a change in the type of irrigation system commonly employed, the productive potential of new pasture cultivars, an appreciation of the importance of relationships between water and nutrient uptakes by plants, and a heightened awareness of the environmental implication of irrigation. It is claimed that the ability of irrigation systems such as centre pivot and long lateral systems to increase irrigation frequency affords a major advantage to pasture production. As yet, these claims are largely unsubstantiated in New Zealand. In addition, there has been no research of the mechanisms or processes that might account for this phenomenon. The study described here set out to quantify the benefits of more frequent irrigation (in the readily available water range) to ryegrass and white clover production, including the relationship with increased nutrient status, and to elucidate the mechanism(s) that might explain this response. The responses of ryegrass and white clover to irrigation frequency (within the readily available water range) and nutrient addition, particularly phosphorus (P) were investigated with a pot experiment using Ramiha silt loam. The rate of fertiliser addition to the pots had a significant and consistent effect on a number of indicators of ryegrass and clover performance including total yield. In contrast, irrigation frequency did not significantly or consistently affect total pasture production. It was concluded that when soil, nutrients and plants roots constitute a relatively homogenous mix (i.e. the pot environment), more frequent watering is not significantly advantageous to plant growth and, therefore, all of the readily available water is equally available. Although there was no response in pasture production to irrigation frequency in the pot experiment, it was hypothesised that irrigation frequency (in the readily available range) in the field, where P values vary with depth in the soil profile, would affect pasture production. The response of swards of ryegrass and white clover growing in Manawatu fine sandy loam to irrigation frequency and P status was measured in a field experiment during the summer of 2000/01. Three irrigation frequencies within the readily available water range (irrigation triggered at soil water deficits of 20 mm (I-20), 40 mm (I-40) or 60 mm (I-60)) were combined with two P fertility treatments (no P fertiliser added or 40 kg P ha-1 applied). For comparative purposes, there were also 4 non-irrigated, non-P fertilised plots outside the main trial block. Plant production, nutrient content of plant material, soil moisture content, soil N and P contents, and nitrate-N, ammonium-N and phosphorus concentrations of soil water samples were measured. The herbage on the plots was cut and removed i.e. there was no grazing. In the field, irrigation frequency had a significant effect on ryegrass and clover production. Irrigation of ryegrass and white clover at I-20, over the summer period resulted in the greatest pasture production and was associated with the most efficient water use (defined as k with units kg DM ha-1) of the irrigated treatments, I-60 gave the smallest production and water use efficiency. Application of the recommended quantity of P fertiliser (40 kg ha-1) significantly enhanced total pasture production and hence water use efficiency. Soil P and N was most concentrated in the surface soil. The results of the field trial support the hypothesis that ryegrass and white clover production is greatest when the plant is taking most of the water it requires from the surface soil where nutrients are most concentrated i.e. the frequent (I-20) irrigation case. Production is smaller when the plant is extracting large quantities of water from depth where nutrient concentrations are smaller i.e. the less frequent irrigation (I-60) case. The effects of irrigation frequency and P fertility on root re-growth activity of ryegrass and white clover swards were evaluated using a modified refilled core method. Root growth of both species decreased with depth. Fertiliser P application significantly increased root growth of both species in two of the three sampling depths at the December and February harvests. In only one root harvest did irrigation frequency significantly affect root activity. At the April harvest, the greatest root growth in the surface soil was observed for I-60, P-0 plots. It is suggested that in addition to encouraging more moisture uptake from nutrient-rich surface soil, an additional benefit of frequent irrigation is that in soils that are consistently moist, plants need to produce fewer roots. A simple water balance model was developed to simulate volumetric soil water contents in the three depths of the Manawatu fine sandy loam that are most closely related to the three irrigation frequencies i.e. 0-150 mm, 0-300 mm, and 0-450 mm. The model illustrates how initially the plants extract most of their water requirement from the surface soil and then as the profile dries they remove more water from lower depths. Accordingly, it highlighted differences in soil water contents between the irrigation frequencies particularly in the surface soil (0 - 150 mm). Soil water sampling was conducted using ceramic suction cups. Estimated total nitrate-N losses until 31 July, 2001 indicated that irrigation frequency of ryegrass during the previous summer did not have a major effect on the overall nitrate-N leaching losses during the late autumn/early winter period but nitrate-N losses under clover tended to be lower under less frequent irrigation. P and ammonium-N leaching losses were negligible. Using the understanding developed in the pot and field trials, a model was constructed to predict ryegrass and clover production on Manawatu fine sandy loam under the different irrigation frequency and P fertility regimes. The model relates pasture production (G) to evaporation from a series of soil water deficit ranges (Ei) according to G = k1E1 + k2E2 +...+ knEn (where kiEi is the pasture production when soil water is in the ith soil water deficit range, and ki is the water use efficiency when soil water is in the ith soil moisture deficit). The ki values were derived using the production data from the field trial. The model was used to simulate the effect of irrigation frequency and P fertility on seasonal (1 November to 30 April) pasture production for a range of climate conditions using the past 26 years weather data. The simulation illustrates how pasture production under irrigation varies markedly with climate, irrigation frequency, P fertility status and the ryegrass:clover composition of the sward. Increasing irrigation frequency from I-60 to I-20 increased pasture production, on average, by 1473 kg DM ha-1 (23%) and 1105 kg DM ha-1 (19%) for P-0 and P-40, respectively. For the farmer contemplating the adoption of irrigation, the purchase of a system that allows more frequent irrigation is as significant a consideration as the decision to adopt irrigation itself. On a cautionary note, the model suggests that I-20 irrigation typically increases drainage losses by about 40 mm (42%) compared to I-60 irrigation.