Introducing effective irrigation management in arid and semi-arid regions, like most areas of South Africa, is an indispensable way of maximising crop yield and enhancing productivity of scarce freshwater resources. Holistic improvements in agricultural water management could be realised through integrating the knowledge of crop-specific water requirements. In order to develop effective irrigation schedules for rose-scented geranium (Pelargonium capitatum x P. radens), greenhouse and field experiments were conducted at the Hatfield Experimental Farm of the University of Pretoria, Pretoria, South Africa, from 28 October 2004 to 2006. Results from 20, 40, 60 and 80% maximum allowable depletion (MAD) levels of the plant available soil water (ASW) indicated that plant roots extracted most of the soil water from the top 40 cm soil layer, independent of the treatment. Both essential oil yield and fresh herbage mass responded positively to high soil water content. Increasing the MAD level to 60% and higher resulted in a significant reduction in herbage mass and essential oil yields. An increase in the degree of water stress apparently increased the essential oil concentration (percentage oil on fresh herbage mass basis), but its contribution to total essential oil yield (kg/ha oil) was limited. There was no significant relationship between MAD level and essential oil composition. For water saving without a significant reduction in essential oil yield of rose-scented geranium, a MAD of 40% of ASW is proposed. Response of rose-scented geranium to a one-month irrigation withholding period in the second or third month of regrowth cycles showed that herbage mass and oil yield were positively related. Herbage yield was significantly reduced when the water stress period was imposed during the third or fourth month of regrowth. A remarkable essential oil yield loss was observed only when the plants were stressed during the fourth month of regrowth. Essential oil content (% oil on fresh herbage mass basis) was higher in stressed plants, especially when stressed late, but oil yield dropped due to lower herbage mass. The relationship between essential oil composition and irrigation treatments was not consistent. Water-use efficiency was not significantly affected by withholding irrigation in the second or in the third month of regrowth. With a marginal oil yield loss, about 330 to 460 m3 of water per hectare per regrowth cycle could be saved by withholding irrigation during the third month of regrowth. The overall results highlighted that in water-scarce regions withholding irrigation during either the second or the third month of regrowth in rose-scented geranium could save water that could be used by other sectors of society. In greenhouse pot experiments, rose-scented geranium was grown under different irrigation frequencies, in two growth media. Irrigation was withheld on 50% of the plants (in each plot) for the week prior to harvesting. Herbage and essential oil yields were better in the sandy clay soil than in silica sand. Essential oil content (% oil on fresh herbage mass basis) apparently increased with a decrease in irrigation frequency. Both herbage and total essential oil yields positively responded to frequent irrigation. A one-week stress period prior to harvesting significantly increased essential oil content and total essential oil yield. Hence, the highest essential oil yield was obtained from a combination of high irrigation frequency and a one-week irrigation-withholding period. In the irrigation frequency treatments, citronellol and citronellyl formate contents tended to increase with an increase in the stress level, but the reverse was true for geraniol and geranyl formate. Leaf physiological data were recorded during the terminal one-week water stress in the glasshouse pot trial. Upon rewatering, stomatal conductance (Gs) and transpiration rate (Rt) were significantly lower in the less often irrigated than in the more often irrigated treatments, while leaf water potential (yw) and relative water content (RWC) were the same for all plants, indicating that water stress had an after-effect on Gs and Rt. At the end of the stress period, Gs, Rt, yw and RWC were lower in the plants from the more often irrigated than from the less often irrigated treatments. Irrespective of irrigation treatment, one type of non-glandular and two types (different in shape and size) of glandular trichomes were observed. In water stressed-conditions, stomata and trichome densities increased, while the total number of stomata and trichomes per leaf appeared to remain more or less the same. Water stress conditions resulted in stomatal closure. / Thesis (PhD)--University of Pretoria, 2009. / Plant Production and Soil Science / unrestricted

La biodiversité favorise un grand nombre de fonctions et services écosystémiques des écosystèmes forestiers tels que la production de bois ou la résistance aux attaques d’insectes et aux maladies. Cependant l’impact de la diversité sur l’acquisition et l’utilisation de l’eau et du carbone reste largement méconnu dans ces écosystèmes. De plus, dans le contexte actuel de changement climatique, l’influence de la diversité sur la réponse des écosystèmes forestiers à des événements climatiques extrêmes tels que la sécheresse reste à étudier. L’objectif de ce travail est donc de déterminer l’impact de la diversité en espèces d’arbre sur d’importantes fonctions du cycle de l’eau et du carbone telles que la transpiration, la composition isotopique du carbone ou la profondeur d’extraction de l’eau à l’échelle de l’arbre et de l’écosystème sous des conditions contrastées dedisponibilité en eau du sol. Ce travail a été réalisé dans le cadre du projet FunDivEUROPE sur un réseau de parcelles forestières ainsi que dans des plantations expérimentales le long d’un gradient Nord-Sud en Europe afin de couvrir une importante gamme de conditions climatiques. Nos travaux ont montré une importante variabilité de la réponse à la diversité à l’échelle de l’arbre et de l’écosystème en termes de relations hydriques et carbonées à travers l’Europe. La diversité en espèces ne semble pas influencer les relations hydriques et carbonées des espèces et des écosystèmes forestiers dans des conditions non limitantes de disponibilité en eau. Cependant, un fort effet de la diversité a été observé en conditions de sécheresse pour certains types forestiers. A partir de ces résultats, je discute des mécanismes d’interaction entre espèces qui peuvent expliquer les effets observés. Nos données ont montré que l’influence de la diversité en espèces est fortement dépendante du contexte et peut êtremodifiée par les conditions environnementales locales et les conditions climatiques. En terme de gestion forestière, je suggère que pour certaines régions en Europe, promouvoir la diversité en espèces ainsi que contrôler la densité des parcelles doit être recommandé afin d’adapter les écosystèmes forestiers aux futures conditions climatiques / Biodiversity is known to support and boost a wide range of forest ecosystem functions and services like productivity and resistance against insect pests and diseases. However, whether tree species diversity also promotes water and carbon acquisition and use in forest ecosystems is still unclear. Furthermore, in the current context of global warming, information on how tree species diversity can influence the response of forest ecosystems to extreme climatic events such as drought are urgently needed. In this framework, the objective of my PhD thesis was to determine how tree species diversity influences important functions of the water and carbon cycle including transpiration, carbon isotope composition and water extraction depth at the tree- and ecosystem-Scale under contrasting soil water conditions. My work was conducted within the FunDivEUROPE project in a network of permanent forest stands and tree plantations across a North-South gradient in Europecovering a wide range of climatic conditions. I found considerable variability among species or forest types in the response of transpiration and carbon isotope composition at the tree- and ecosystem-Scale across Europe. Species diversity did not affect the water and carbon relations of tree species and forest ecosystems under non-Limiting soil water conditions. However, a strong effect of species diversity was observed under drought conditions in some forest types. Based on these data, I discuss the potential mechanisms of species interactions that may explain the observed patterns. I also point out that the influence of species diversity is highly context-Dependent, and changes with local environmental and climatic conditions. In terms of forest management applications, I suggest that, at least in some regions, controlling for tree species diversity along with stand density and total basal area could be recommended to help forests adapt to drier conditions

As average global temperatures rise, cool-season C3 turfgrasses, such as the most commonly grown Kentucky bluegrass (Poa pratensis L.; KBG), struggle to tolerate extreme summer heat and increase their water consumption. Hybrid Bermudagrass (Cynodon dactylon [L.] Pers. × Cynodon transvaalensis Burtt Davy; HBG) is a warm-season C4 grass that may be increasingly suited for northern ecosystems traditionally classified as transition or cool-season climate zones. Glasshouse and field studies were conducted to compare HBG and KBG water use. The objective of the glasshouse study was to evaluate plant health and growth for two HBG cultivars (‘DT-1’ and ‘NorthBridge’) compared to a blend of KBG cultivars in all combinations of deficit, moderate, and high irrigation at optimum or short mowing height. The study was conducted in a glasshouse at Provo, UT, USA from 2020-2021. Grass was grown in pots arranged in a randomized complete block, full factorial design, with four replications of each treatment. The moderate KBG was also significantly different from both high and deficit for verdure and for the last half of NDVI. The objective of the field study was to evaluate two HBG cultivars (‘Tahoma 31’ and ‘Latitude 36’) compared to a blend of KBG cultivars for water loss and canopy health, temperature, and growth when subjected to deficit, moderate, and high irrigation. The study was arranged in a randomized complete block, full factorial design with three replications per treatment, and was conducted at Provo, UT, USA throughout the summer of 2021. In both the glasshouse and field trials, the deficit irrigated KBG consistently scored lower for NDVI and visual turf quality than all other treatments, including moderate and high KBG. This same trend was seen in the field study for percent cover. Although not observed in the glasshouse trial, it was observed in the field trial that the different irrigation levels of HBG resulted in no significant differences for any measurements but the HBG regularly scored better than KBG. The canopy temperatures of deficit irrigated KBG were also higher than all other treatments on most dates. The shoot mass, thatch mass, and total biomass of KBG were significantly less than either HBG cultivar. In the glasshouse trial it was observed that all deficit grasses were significantly lower than the other irrigation treatments and HBG had significantly deeper roots than KBG, although these results were not seen in the field trial. The data suggest that irrigation needs will be less for HBG than KBG and that HBG could provide a water-saving turfgrass alternative to KBG in semi-arid, cool-season regions with increasing water scarcity.

MSCAGR (Soil Science) / Department of Soil Science / The application of organic manures as alternatives to reduce the use of mineral fertilizers is considered a good agricultural practice for smallholder farmers. However, the effect of organic manure on soil properties and crop yield depends upon its application rate and chemical composition. Climatic seasonal variability within the study area could adversely affect crop production. The amount of rainfall and temperature are among the most important factors that determines crop production. This field experiment was carried out during the 2013/2014 and 2014/2015 cropping seasons at the University of Venda experimental farm which is located about 2 km west of Thohoyandou town in the Vhembe District, Limpopo Province. The main objective of this study was to determine the effect of three types of organic manure (cattle, poultry and their combination (1:1)) on yield and water use efficiency of sunflower (Helianthus annuus L.) and selected soil physical and chemical properties under rainfed conditions. The experiment was a randomized complete block design (RCBD) with four treatments and four replications (control (C0), cattle manure (CM), poultry manure (PM) and their combination (CM + PM)). All organic manures were applied 21 days before planting at a rate equivalent to 20 t ha-1. The manures were incorporated in the soil using a hoe to an approximate depth of 10 cm. Crop water use (WU) and water use efficiency (WUE) were determined using the water balance equation. Rainfall was measured using three standard rain gauges installed on the experimental site. Change in soil moisture storage was determined by monitoring soil moisture content weekly using a neutron water meter (NWM), calibrated on the experimental site. Data on sunflower dry matter and leaf area index (LAI) was collected at flower bud stage, flowering stage and at grain maturity stage. Plant height and stem girth were also determined at the same developmental stages. Grain yield was measured at physiological maturity. xv Analysis of variance (ANOVA) was carried out using SPSS software. Due to seasonal variability encountered during the two cropping seasons, particularly in terms of rainfall, further analysis of two factors (viz. cropping season and organic manure) and their interaction were performed. The differences between treatment means were separated using the least significant differences (LSD) procedure. The results showed that organic manure application had no significant effect on soil physical properties. Poultry manure application resulted in lowest bulk density (BD) with a decrease of 32% in the top layer (0 – 20 cm) compared to control. Cattle manure + PM and CM application decreased BD in the top layer by 14% and 9% compared to control, respectively. Poultry manure and CM recorded almost the highest similar stable aggregate fractions at all soil depths. Poultry manure recorded the highest final infiltration rate and cumulative infiltration followed by CM and CM + PM. The control treatment retained the highest mean water content compared to other treatments at both field capacity (FC) and wilting point (WP). Cattle manure + PM and PM recorded the least mean water content among others at FC and WP respectively. This could be as a result of increased micropores by organic manure application on a clayey soil which allowed an ease movement of water that control treatment which had no manure application. Total N, Ca, and Zn were significantly different between treatments in the first cropping season while K, Na, CEC and Zn were significantly different in second cropping season. pH recorded no significant difference in all treatments in both cropping seasons. CM + PM recorded the highest OC at top layer (0 – 20 cm) in both cropping seasons compared to other treatments. Dry matter yield and LAI at flower bud, flowering and maturity stages increased with the application of different manures compared to the C0. Organic manure application showed a significant (p<0.05) effect on dry matter at all growth stages in the second cropping season. Organic manure had a significant effect on LAI only at flower bud stage of the first cropping season, with PM and CM + PM recording the highest similar value of 1.31. The manure xvi application also showed a significant (P<0.05) effect on plant height and stem girth at all growing stages in the second cropping season, whereas in the first cropping season the significant effect was only in the flower bud stage for both parameters. Grain yield was significantly affected by the manure application in the second cropping season. Manure application in the second cropping season resulted in an increase in the grain yield compared to the first cropping season, except for PM where the grain yield decreased significantly by 167.92% from the first cropping season. Then high grain yield in the second cropping season could be as a result of high WUE reported. The manure application had a significant effect (p<0.05) on water use efficiency (WUE) in the second cropping season. The WUE recorded the highest values under CM and CM + PM treatments in second cropping season than in first cropping season, while PM recorded the highest WUE value in the first cropping season. Generally, organic manures used obtained higher grain yield and WUE compared to control. Keywords: Organic manure, smallholder farmers, sunflower and water use efficiency

MSCAGR ( Soil Science) / Department of Soil Science / See the attached abstract below

<p>This thesis is a collection of three research articles to quantify carbon fluxes and isotopic signature changes across global terrestrial ecosystems. Chapter 2, the first article of this thesis, focuses on the importance of an under-estimated methane soil sink for contemporary and future methane budgets in the pan-Arctic region. Methane emissions from organic-rich soils in the Arctic have been extensively studied due to their potential to increase the atmospheric methane burden as permafrost thaws. However, this methane source might have been overestimated without considering high affinity methanotrophs (HAM, methane oxidizing bacteria) recently identified in Arctic mineral soils. From this study, we find that HAM dynamics double the upland methane sink (~5.5 TgCH₄yr^-1) north of 50°N in simulations from 2000 to 2016 by integrating the dynamics of HAM and methanogens into a biogeochemistry model that includes permafrost soil organic carbon (SOC) dynamics. The increase is equivalent to at least half of the difference in net methane emissions estimated between process-based models and observation-based inversions, and the revised estimates better match site-level and regional observations. The new model projects double wetland methane emissions between 2017-2100 due to more accessible permafrost carbon. However, most of the increase in wetland emissions is offset by a concordant increase in the upland sink, leading to only an 18% increase in net methane emission (from 29 to 35 TgCH₄yr^-1). The projected net methane emissions may decrease further due to different physiological responses between HAM and methanogens in response to increasing temperature. This article was published in <i>Nature Climate Change</i> in March 2020.</p> <p>In Chapter 3, the second article of this thesis, I develop and validate the first biogeochemistry model to simulate carbon isotopic signatures (δ¹³C) of methane emitted from global wetlands, and examined the importance of the wetland carbon isotope map for studying the global methane cycle. I incorporated a carbon isotope-enabled module into an extant biogeochemistry model to mechanistically simulate the spatial and temporal variability of global wetland δ¹³C-CH₄. The new model explicitly considers isotopic fractionation during methane production, oxidation, and transport processes. I estimate a mean global wetland δ¹³C-CH₄ of -60.78‰ with its seasonal and inter-annual variability. I find that the new model matches field chamber observations 35% better in terms of root mean square estimates compared to an empirical static wetland δ¹³C-CH₄ map. The model also reasonably reproduces the regional heterogeneity of wetland δ¹³C-CH₄ in Alaska, consistent with vertical profiles of δ¹³C-CH₄ from NOAA aircraft measurements. Furthermore, I show that the latitudinal gradient of atmospheric δ¹³C-CH₄ simulated by a chemical transport model using the new wetland δ¹³C-CH₄ map reproduces the observed latitudinal gradient based on NOAA/INSTAAR global flask-air measurements. I believe this study is the first process-based biogeochemistry model to map the global distribution of wetland δ¹³C-CH₄, which will significantly help atmospheric chemistry transport models partition global methane emissions. This article is in preparation for submission to <i>Nature Geoscience</i>.</p> <p>Chapter 4 of this thesis, the third article, investigates the importance of leaf carbon allocation for seasonal leaf carbon isotopic signature changes and water use efficiency in temperate forests. Temperate deciduous trees remobilize stored carbon early in the growing season to produce new leaves and xylem vessels. The use of remobilized carbon for building leaf tissue dampens the link between environmental stomatal response and inferred intrinsic water use efficiency (iWUE) using leaf carbon isotopic signatures (δ¹³C). So far, few studies consider carbon allocation processes in interpreting leaf δ¹³C signals. To understand effects of carbon allocation on δ¹³C and iWUE estimates, we analyzed and modeled the seasonal leaf δ¹³C of four temperate deciduous species (<i>Acer saccharum, Liriodendron tulipifera, Sassafras albidum, </i>and <i>Quercus alba</i>) and compared the iWUE estimates from different methods, species, and drought conditions. At the start of the growing season, leaf δ¹³C values were more enriched, due to remobilized carbon during leaf-out. The bias towards enriched leaf δ¹³C values explains the higher iWUE from leaf isotopic methods compared with iWUE from leaf gas exchange measurements. I further showed that the discrepancy of iWUE estimates between methods may be species-specific and drought sensitive. The use of δ¹³C of plant tissues as a proxy for stomatal response to environmental processes, through iWUE, is complicated due to carbon allocation and care must be taken when interpreting estimates to avoid proxy bias. This article is in review for publication in <i>New Phytologist</i>.</p> <p> </p>

No description available.

Reducing disease and increasing fruit quality in vigorous vineyards with dense canopies is demanding of time and resources; unfortunately, vineyards of this nature are common in humid environments. This study investigated the effectiveness with which vine capacity and water status could be regulated as well as if they related to fruit quality and wine sensory perception. The treatments regulating vine size and water status were under-trellis groundcover, root manipulation, rootstocks, and irrigation. Treatments were arranged in a strip-split-split plot design before the introduction of the irrigation treatment resulted in incomplete replication in each block. Treatment levels were under-trellis cover crop (CC) compared to under-trellis herbicide (Herb); root restriction bags (RBG) compared to no root manipulation (NRM); three compared rootstocks (101-14, 420-A, riparia Gloire); low water stress (LOW) compared to high water stress (HIGH). Vines grown with RBG and CC regulated vegetative growth more so than conventional treatments, resulting in 56% and 23% greater cluster exposure flux availability (CEFA). High water stress (HIGH) and RBG reduced stem water potential and discriminated less against 13C. Vines grown with RBG and CC consistently reduced harvest berry weight by 17 and 6% compared to conventional treatments. Estimated phenolics were consistently increased by RBG and were correlated with berry weight, vine capacity and CEFA. Sensory attributes were significantly distinguishable between wines produced from vines that differed in both vine capacity and water status, amongst other responses. Treatments have been identified that can alter the sensory perception of wines, with the potential to improve wine quality. / Master of Science

Cette thèse visait à développer nos connaissances quant au contrôle génétique et environnemental et la structuration géographique de la variabilité phénotypique pour des caractères fonctionnels chez le peuplier noir (Populus nigra L.). Trois caractères fonctionnels ont été étudiés : la phénologie de croissance, WUE et la résistance à la cavitation. La variabilité phénotypique exprimée pour la phénologie de croissance et WUE a été évaluée au sein d’une collection européenne de peuplier noir regroupant 1085 génotypes échantillonnés dans 13 métapopulations et installés en test clonal en pépinière dans deux sites expérimentaux. Nos résultats ont révélé une importante variabilité génétique ainsi qu’une importante plasticité phénotypique des caractères phénologiques et de WUE au sein des métapopulations. Une différenciation génétique modérée à forte des métapopulations a été observée pour la phénologie de croissance et WUE. Les différences entre métapopulations se structuraient selon des patrons plus ou moins complexes, qui semblaient refléter, pour la phénologie de croissance, une adaptation locale des métapopulations aux conditions de photopériode et de température. Tenant compte des capacités de phénotypage limitées pour la résistance à la cavitation, la variabilité génétique exprimée pour ce caractère a été évaluée au sein d’une population naturelle de peuplier noir regroupant 33 génotypes et installée en test clonal en pépinière dans un site expérimental. Nous avons détecté une variation significative du niveau de résistance à la cavitation entre génotypes. De manière générale, aucune relation phénotypique significative n’a été détectée entre la phénologie de croissance, WUE et la résistance à la cavitation au niveau intra-population, suggérant le maintien d’une diversité de combinaisons fonctionnelles. Le développement d’une puce à 10 331 marqueurs SNPs distribués à l’échelle du génome de P. nigra, notamment dans des régions candidates pour la phénologie de croissance, devrait permettre, à court terme, de confirmer l’adaptation locale des populations de peuplier noir et d’explorer ses bases génétiques. / This work aimed at improving our understanding of the genetic and environmental control as well as the geographic structure of phenotypic variation for functional traits in black poplar (Populus nigra L.). Three functional traits were studied: bud phenology, water-use efficiency (WUE) and xylem resistance to drought-induced cavitation. The phenotypic variation expressed for bud phenology and WUE was evaluated in a European P. nigra collection composed of 1085 cloned individuals sampled in 13 natural metapopulations and established in clonal test in nursery at two experimental sites. Substantial genetic variation and substantial phenotypic plasticity for bud phenology and WUE were observed within all metapopulations. Moderate to strong genetic differentiation of metapopulations was evidenced for phenological traits and WUE. Patterns of genetic differentiation were more or less complex depending on traits and seemed to reflect, for phenological traits, local adaptation of metapopulations to photoperiod and temperature. Taking into account the limited phenotyping capacity for xylem resistance to cavitation, genetic variation expressed for this trait was evaluated within one single natural population of black poplar composed of 33 genotypes which were established in clonal test in nursery at one experimental site. Significant variations were observed between genotypes for the degree of cavitation resistance. Overall, no significant relationship was detected between bud phenology, WUE and cavitation resistance at the within-population level, indicating the maintenance of a diversity of functional combinations. The development of an array covering 10 331 SNPs distributed across the P. nigra genome, notably in candidate regions for bud phenology, will enable in the short-term to confirm local adaptation of P. nigra populations and to identify its genetic basis.

The annual and seasonal water use efficiency of six pasture combinations were calculated from the ‘MaxClover’ Grazing Experiment at Lincoln University. Pastures have been established for six years and are grazed by best management practices for each combination. Measurements for this study are from individual plots of four replicates of ryegrass (RG)/white clover (Wc), cocksfoot (CF)/Wc; CF/balansa (Bal) clover; CF/Caucasian (Cc) clover; CF/subterranean (Sub) clover or lucerne. Water extraction measurements showed soils for all dryland pastures had a similar plant available water content of 280±19.8 mm. Dry matter measurements of yield, botanical composition and herbage quality were assessed from 1 July 2008 until 30 June 2009. Lucerne had the highest annual yield of 14260 kg DM/ha/y followed by the CF/Sub at 9390 kg DM/ha/y and the other grass based pastures at ≤ 6900 kg DM/ha/y. All pastures used about 670±24.4 mm/y of water for growth. Lucerne had the highest annual water use efficiency (WUE) of 21 kg DM/ha/mm/y of water used (total yield/total WU). The WUE of CF/Sub was the second highest at 15 kg DM/ha/mm/y, and the lowest was CF/Wc at 9 kg DM/ha/mm/y. The CF/Sub pastures had the highest total legume content of all grass based pastures at 21% and as a consequence had the highest annual nitrogen yield of 190 kg N/ha. This was lower than the monoculture of lucerne (470 kg N/ha). Ryegrass/white clover had the highest total weed component in all pastures of 61%. For dryland farmers spring is vital for animal production when soil temperatures are rising and moisture levels are high. The water use efficiency at this time is important to maximize pasture production. In spring lucerne produced 8730 kg DM/ha, which was the highest dry matter yield of all pastures. The CF/Sub produced the second highest yield of 6100 kg/DM/ha. When calculated against thermal time, CF/Sub grew 5.9 kg DM/ºCd compared with lucerne at 4.9 kg DM/ºCd. The higher DM yield from lucerne was from an extra 400 ºCd of growth. The highest seasonal WUE of all pastures occurred in the spring growing period. Linear regressions forced through the origin, showed lucerne (1/7/08-4/12/08) had a WUE of 30 kg DM/ha/mm (R2=0.98). Of the grass based pastures, CF/Sub produced 18 kg DM/ha/mm (R2=0.98) from 1/7 to 10/11/08 from 270 mm of water used. The lowest spring WUE was 13.5 kg DM/ha/mm by CF/Bal pastures which was comparable to the 14.3±1.42 kg DM/ha/mm WUE of CF/Wc, CF/Cc and RG/Wc pastures. During the spring, CF/Sub clover had the highest spring legume component of the grass based pastures at 42% and produced 120 kg N/ha. This was lower than the 288 kg N/ha from the monoculture of lucerne. Sub clover was the most successful clover which persisted with the cocksfoot. Based on the results from this study dryland farmers should be encouraged to maximize the potential of lucerne on farm, use cocksfoot as the main grass species for persistence, rather than perennial ryegrass, and use subterranean clover as the main legume species in cocksfoot based pastures. By increasing the proportion of legume grown the water use efficiency of a pasture can be improved. When pastures are nitrogen deficient the use of inorganic nitrogen may also improve pasture yields particularly in spring.