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Item Measurement and modelling of salt and nutrient dynamics under Salicornia irrigated with saline groundwater, desalination reject-brine, and aquabrine : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Soil and Environmental Sciences, School of Agriculture and Environment, Massey University, Palmerston North, New Zealand(Massey University, 2024-07-27) Al Tamimi, MansoorEnvironment Agency-Abu Dhabi (EAD) has implemented several scientific research projects with Plant and Food Research (PFR) New Zealand and OnlyFromNZ Limited (OFNZ) to determine the irrigation requirements for date palms, arid forestry, and field crops, for Law 5 which states that groundwater in the Emirate is the property of the Government which has the responsibility for management, organization and licensing the activities related to groundwater. The Government entity is EAD-Environment Agency of Abu Dhabi). can be implemented using sound scientific bases to protect the interests of all. This is a cooperation with external partners, plus both governmental and non-governmental agencies. These projects aimed to determine the irrigation requirements for date palms, forests, and field crops. While these projects have determined irrigation requirements, they have not, to date, addressed the environmental impacts of farming on groundwater quantity and quality. This Ph.D. research explored the trade-offs between improved technologies for the use of alternative water supplies, such as desalination brines, and the environmental consequences of brine re-use. The results will form part of the future solutions at the nexus among food, energy, and water in Abu Dhabi. This doctoral research builds on nearly a decade of scientific knowledge developed in collaboration with the New Zealand teams. It identifies the opportunities for reject brine from desalination units in aquaculture and halophytic agriculture, as well as the environmental consequences of the fate of this salt and nutrients. Measurements are critical to understand groundwater impacts and the benefits of using saline groundwater and brines from desalination plants to irrigate halophytes in hyper-arid environments. In 2020, a pilot trial was set up using irrigation with highly saline waters. However, two difficulties were encountered, and the pilot trial was a failure. The first part of the thesis describes how the practical challenges of the measurement technologies used in this saline environment were overcome. Further, experiments were then carried out to quantify the efficiency and impact of salt leaching in removing salt from the rootzone. Two years of field experimentation were undertaken to determine the economic productivity and environmental impact on groundwater of irrigating the halophyte Salicornia bigelovii with three types of saline waters in the hyper-arid United Arab Emirates. In the first year, the irrigation waters employed were groundwater (GW) at 25 dS m⁻¹, reverse-osmosis brine (RO) from a desalination unit at 40 dS m⁻¹, and Aquabrine (AQ) effluent from land-based aquaculture in tanks filled with RO brine, also at 40 dS m⁻¹. Bubblers (BUB), pressure-compensated drippers (PCD), or subsurface irrigation tape (SUB) were used to apply the three waters Salicornia fresh tip, harvest forage, and seed yields were highest for AQ applied through BUB, reaching 650 g m⁻². The dry forage yield with AQ through BUB was found to be 2-2.6 kg m⁻², compared to 1-2.3 kg m⁻² for the other irrigation waters and emitter devices. The highest water productivity WPI (kg m⁻³) across all three crop outputs resulted from Aquabrine applied by pressure-compensated drippers. Gross economic water productivity (GEWP₁, $ m⁻³) was assessed based solely on gross revenue. The highest GEWP₁, at US$5.8-6.2, was achieved with AQ applied through PCD and SUB, primarily due to revenue from fresh tips. Notably, the GEWP₁ significantly exceeded the cost of desalination at $1.5 m⁻³. Drainage and leaching were measured using fluxmeters. The greatest salt load into the groundwater, at 135-195 kg m⁻², was observed with BUB irrigation. For PCD and SUB, the salt load ranged between 14-36 kg m⁻². Simple mass-balance calculations of these salt loadings were then employed to predict the impact on the saline quality of aquifers. An exemplar loading of 75 kg m⁻² was used, resulting in a projected annual salinity rise of 2.6 dS m⁻¹ y⁻¹ for an aquifer with a saturated depth of 100 m. This significant increase in groundwater salinity would represent a continual decline in the resource's utility. This simple mass-balance arithmetic highlighted the need for modelling. New data from the following year’s experiments highlighted the economic value of using nitrogen-rich saline waters, either from groundwater or reject brines from desalination units, to irrigate the halophytic crop Salicornia bigelovii for food, fodder, and fuel in a hyper-arid environment. The greatest benefit was, again, achieved using pressure compensated drippers. Field measurements of drainage and leaching under the crop showed that, in sum, all of the salt, as well as the nitrogen drawn up from the groundwater were returned back to the aquifer as leachate. The only loss of water to the system was through crop evapotranspiration ET𝒸. A simple heuristic model of groundwater quantity and quality was developed to infer the environmental impacts of irrigating crops with saline and high-nitrate groundwater in a hyper-arid environment. The time-rise in solute concentration in groundwater is found to be a hyperbola. The parameters needed for this simple model are the fraction of the land above the aquifer that is irrigated, the initial depth of the saturated thickness of the aquifer, the saturated water content of the aquifer, and the annual rate of crop evapotranspiration. An indicator of the rate-of-rise in solute concentration, akin to a half-life, is the numbers of years to double the solute concentration in groundwater. This can be found as Ө hₒ /2 ET𝒸, where Ө is the saturated water content, hₒ is the original thickness of the saturated layer, and ET𝒸 is the annual rate of crop evapotranspiration. The general model is simple and straightforward to parameterise. It is easily understood and useful for assessing the impacts and trade-offs of policy and regulatory options. The knowledge gained from these experiments and the predictions resulting from the heuristic modelling have been used to highlight future needs to be addressed for the critical issues at the food-water-energy nexus in hyper-arid regions.Item Estimating grapevine water status using hyperspectral and multispectral remote sensing and machine learning algorithms : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Agriculture and Horticulture at Massey University, Manawatū, New Zealand(Massey University, 2023) Wei, Hsiang-EnModerate water deficit is desirable for achieving the optimal grape composition which determines the values of wine, especially for red cultivars. To attain consistency in grape quality in vineyards, it is critical to manage grapevine water status (GWS) to the target range, but to avoid severe dehydration, between fruit set and veraison. Together with the foreseeable climate changes and stricter environmental regulations, there is a need for viticulture to estimate GWS variability across fields along growing seasons before irrigating to eliminate the uncertainty of controlling hydration status and to produce consistent grapes with premium quality. Precision viticulture (PV) recognizes that not all areas within a vineyard are uniform in terms of their soil, climate, and other environmental conditions. Therefore, it tailors viticultural management to the unique needs of different vineyard zones by focusing on applying site-specific or time-specific management practices. PV aims to enhance grape quality and yield while minimizing resource usage and environmental impacts. As the final product (wine) for viticulture has the potential of high additional values, it is worth considering the application of PV in decision-making according to the information on spatio-temporal variability across the fields. The advancement and availability of remotely sensed spectral information, geospatial technologies, and machine learning models have opened a new chapter for spatio-temporal GWS monitoring. However, there are technical shortcomings that need to be addressed before extensive application and adoption of these techniques in viticulture. These include a lack of understanding of GWS-related spectral data analysis methods, a lack of data interoperability for GWS estimation between data sourced from various devices with different formats, and a lack of availability of high-coverage images with high spatial and temporal resolution. Therefore, this study tackled the technical bottlenecks, related to the application of proximal sensing and remote sensing (RS) in GWS estimation, from three perspectives: (i) the exploration of relevant spectral regions over the electromagnetic spectrum, (ii) the complementation from differently sourced datasets other than RS information, (iii) the provision of large-scale GWS prediction. This study was undertaken in two Pinot Noir vineyards trained with vertical shoot positioning for two growing seasons in Martinborough, New Zealand. The investigation window, corresponding to the critical periods of GWS management, between fruit set and veraison in each growing season, includes November, December, January, and February. Stem water potential (Ψstem), serving as a proxy for GWS, is measured on 85 and 63 canopies in the first and second growing seasons. Each sampled grapevine is recorded for its location with a global navigation satellite system with real-time kinematic correction. Five times field data collection, including measuring hyperspectral point data using ASD FieldSpec 4 Spectroradiometer (proximal sensing data) and taking multispectral images using DJI Phantom 4 UAV (remote sensing data), were carried out in each growing season. An electromagnetic induction survey was implemented by using EM38-MK2 to acquire apparent electrical conductivity (ECa) maps (complementary data). Several satellite images collected by PlanetScope (remote sensing data) during the study periods and the LiDAR-based digital elevation model (complementary data) were downloaded and added to the analysis datasets. An on-site weather station continuously records and provides meteorological information, including air temperature (°C), relative humidity (%), rainfall (mm), wind speed (km/h), and irradiance (W/m2) (complementary data). The identification of the relationships between spectral information and Ψstem is an essential step for the robust application. By analyzing hyperspectral spectra, it shows that the statistically relevant wavelengths disperse across visible, near-infrared, and shortwave infrared (SWIR) spectral bands. They are specifically located around blue, red, and red edge bands, two weak water absorption bands at 970 and 1200 nm, two strong absorption bands at 1400 and 1940 nm, and some dry matter-related bands. When analyzing multispectral images taken by UAV, it shows Transformed Chlorophyll Absorption Reflectance Index and Excess Green Index are the multispectral indices mostly correlated (R2 = 0.35 and 0.3, respectively) with the changes in Ψstem. It implies that the variation in leaf pigments, especially chlorophylls, is better for describing the Ψstem variation of Pinot Noir than the alteration in canopy structure. When applying the Ψstem-sensitive spectral bands through airborne or spaceborne platforms, the missing SWIR for most commercial multispectral sensors and the presence of vapor in the air obstruct the usefulness of the Ψstem-sensitive spectral bands. Therefore, this study assesses the complementary effects provided by other environmental aspects, including soil/ terrain, vegetation, temporal, and weather variables, to improve the GWS estimating capabilities of aerial multispectral sensors. The results prove the complementary effects by displaying that the detection accuracy is improved from RMSE of 213 to 146 kPa and RMSE of 221 kPa to 138 kPa. To monitor the fields at a large-scale using multispectral satellites, it is common to encounter several technical issues: coarse resolution pixels that contain background information, weather dependence, and delay in the image delivery. This study addresses the limitation of coarse spatial resolution using two-stage calibration to scale information provided by ground measurement up to satellite images, along with removing interference from the inter-row components. It demonstrates that satellite images can approximate the collected Ψstem with high accuracy (RMSE = 59 kPa). To deal with the contamination by weather and delivering delay of image products, a prediction model is established based on the calibrated satellite images and various environmental variables (day of the year, rainfall, potential evapotranspiration, irrigation, fertigation, plucking, trimming, normalized difference vegetation index, ECa, elevation, and slope). The developed model is able to predict Ψstem trend in an independent growing season with high consistency when compared with the reference (r = 0.89 and 0.87 for the two vineyards, respectively).Item Modelling the long-term impact of modernized irrigation systems on soil water and salt balances, and crop water productivity in semi-arid areas under current and potential climate change conditions : integration of agrohydrological model, geographical information system, remote sensing, and climate change model : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2022) Khan, Muhammad HamedIrrigated agriculture plays a key role in ensuring food security and rural livelihoods across semi-arid and arid regions, like in the Indus basin of Pakistan. However, the Indus basin irrigation system of Pakistan is facing serious threats of low crop yields and increasing water scarcity, waterlogging, soil salinity, and overexploitation of groundwater. Considering the irrigation water-management issues, water managers and policymakers in Pakistan are looking into the modernization of the irrigation practices by introducing sprinkler and drip irrigation systems with the intent to save water and enhance crop water productivity. However, such intervention if adopted at a larger scale could seriously affect regional soil water and salt balances, solute leaching, and recharge to groundwaters in semi-arid and arid regions. Therefore, a robust assessment of the long-term potential impacts of modernised irrigation systems, particularly under the potential climate change scenarios, is essential for improving productivity and sustainable irrigated agriculture in semi-arid and arid regions. Field experiments are practically difficult to quantify the long-term impacts of modernised irrigation practices on soil water and salt balances and crop growths, especially under projected climate change conditions. This thesis developed a modelling framework using local field experiments, and geographical and remote sensing information, combined with a spatially distributed agrohydrological model and climate change projections to analyse the potential impacts of different irrigation application scenarios at the field and canal command scales. This methodology is applied to evaluate the potential impacts of current and proposed modernized irrigation systems on soil water and salt balances, soil salinity build-up, percolation to groundwaters, crop yield and crop water productivity of irrigated crops under long-term contemporary climate (1987-2017) and potential climate change (2070-2099) scenarios. The main irrigated crops of wheat, rice, and cotton were studied in the Hakra branch canal command as a case study. The Hakra branch canal (HBC) command, located in the Indus basin irrigation system of Pakistan, covers 0.21 million ha and is characterised by the typical problems of canal water scarcity, poor groundwater quality, waterlogging and soil salinity, and less-than-optimal crop production. The information collected from local field-scale experiments during the years 2016-2017, GIS, remote-sensing techniques and global climate models are integrated to parametrise, calibrate, and validate the agrohydrological Soil-Water-Atmosphere-Plant (SWAP) model application at both field- and canal command- scales. The SWAP model simulated soil water and salt balances, percolation to groundwaters, and water- and salt-limited crop yields and crop water productivity values of main irrigated crops of wheat, rice, and cotton from field- to canal command- scales in the study area. The modelling assessment of current irrigation practices revealed significant variation in canal water supplies and over-exploitation of groundwater, resulting in high spatial variability in soil water percolation and salt build-up in the soil at the spatial scale of the head, middle and tail reaches of the canal command. The canal water-inflow is about 19% and 42% higher at the head reaches than at the middle and tail reaches, respectively. The significant seepage from the canal network and the cultivation of high water-consuming crops such as rice are the potential cause of waterlogging at the head reaches. Whereas limited canal inflow and use of poor-quality groundwater (> 3 dS m⁻¹) appear to be potential causes of soil salinity at the tail reaches of the HBC command. The detrimental effects of limited canal inflow and the use of marginal to poor groundwater causes considerable spatial variation in simulated water and salt-limited crop yields. The simulated water and salt-limited crop water productivity values are not only different for the different crops of wheat, rice and cotton, but also for the same crop across the study area. The field- and canal-command scale modelling was applied to simulate and assess the potential impacts of the proposed modernized irrigation scenarios, such as • sprinkler irrigation is defined as a high-efficiency irrigation system with leaching fraction (HEIS_LF) and without leaching fraction (HEIS_noLF), and • precision surface irrigation system (PSIS) for cotton-wheat cultivation under contemporary climate (1987-2017) and potential climate change (2070-2099) scenarios RCP 2.6 (low emission) and RCP 8.5 (high emission or business-as-usual). The long-term simulation results suggest a saving of about 40% in irrigation water under the HEIS_noLF scenario. However, this irrigation water-saving under the HEIS_noLF scenario resulted in the risk of an increase in soil salinity due to reduction in soil percolation and its associated salt build-up in the soil profile. Under the HEIS_noLF scenario for cotton-wheat cultivation, the soil salinity is simulated to increase from 2.6 to 8.0 dS m⁻¹ at the field-scale, and from 2 to >12 dS m⁻¹ at the canal command scale, affecting crop yields due to salt stress. The high salt build-up is simulated to reduce crop yields by 38% for cotton, and 48% for wheat under the contemporary climate (1987-2017) at the canal command scale. The soil salinity is simulated to get even worse in poor-quality groundwater areas, resulting in wheat failure of < 1 ton/ha with HEIS_noLF under the RCP 8.5 scenario of potential climate change (2070-2099) conditions. The modelling analysis suggests a significant leaching fraction is required to maintain acceptable soil salt balance for successful crop production. This leaching fraction could be achieved by a pre-sowing irrigation of 60 mm depth at the start of the season, followed by an additional 10 mm depth with each irrigation interval using a high-efficiency irrigation application, simulated as HEIS_LF. The HEIS_LF scenario resulted in 50 to 65% higher average water- and salt-limited crop water productivity values (kg/m³ ET) of 0.5 for cotton, and 1.87 for wheat. This is compared to the HEIS_noLF scenario of 0.25 for cotton, and 0.65 for wheat under potential climate change (2070-2099) conditions. However, the PSIS irrigation scenario resulted in similarly favourable soil water and salt balances, water and salt-limited crop yields and crop water productivity values for the cotton - wheat cultivation. Under the PSIS irrigation scenario, the average water-and salt-limited crop water productivity values (kg/m³ ET) are simulated as 0.50 for cotton and 2.79 for wheat under the contemporary climate (1987-2017), and 0.50 for cotton and 1.92 for wheat in potential climate change (2070-2099) conditions. The modelling analysis simulated the average soil percolation rate as 10 to 20% higher, resulting in the leaching of 20 to 30% more salts from the soil profile under the PSIS scenario than the HEIS_LF under potential climate change conditions. The key findings of this modelling assessment suggest that modernisation of irrigation systems as higher-efficiency (HEIS) irrigation applications, with no appropriate leaching fraction, would compromise salt build-up in the soil profile. This would potentially reduce crop yields and crop water productivity in the long-term, especially under potential climate change (2070-2099) conditions. There appears very limited scope for real irrigation water savings using a high-efficiency irrigation system for long-term sustainable crop production in areas making conjunctive use of limited canal water supplies and marginal- to poor-quality groundwaters. Hence, proposed initiatives for implementing high-efficiency irrigation systems should be carefully evaluated in terms of their long-term potential impacts on regional soil water and salt balances, crop yields and crop water productivity values in areas such as the Indus basin irrigation system in Pakistan, particularly under potential climate-change conditions.Item Water stress and apple fruit quality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science at Massey University(Massey University, 1992) Moremong, MapasekaRegulated Deficit Initiation (RDI) has been used successfully in dry climates to control vegetative growth of fruit trees during the early part of the growing season without seriously disadvantaging fruit growth or quality. This project was undertaken as part of a study to investigate the feasibility and practicality of using the RDI concept in a humid fruit growing environment using Royal Gala apple trees. Treatments consisted of a lucerne cover crop, black polyethylene undertree covers and a within-row herbicide strip which is the normal commercial practice in New Zealand orchards. A full irrigation treatment (FI) was used on half the experimental trees and an RDI treatment was used on the other half of the trees. The RDI treatment consisted of withholding water until 105 days after full bloom, then using a full irrigation for the remainder of the season. Integration with depth of the soil moisture content (θ) (measured with a neutron probe) at the commencement of the experiment revealed 230 mm of water was stored in the top 900 mm of soil. Full irrigation resulted in θ increasing, with storage of about 250 mm 83 days after bloom and remaining at this level for the remainder of the season. The storage in the RDI treatments decreased in a linear manner until 58 days after bloom, after which it remained constant until initiation was started 105 days after bloom. The lucerne RDI (LRDI) treatment had a lower storage (105 mm) during this constant period than plastic RDI (PRDI), or herbicide (HRDI) treatments which both had a storage of 130 mm. The amount of water in the soil at this time for LRDI and for PRDI/HRDI was 42% and 52% of the total available capacity. Immediately after irrigation commenced on the RDI treatments, profile water storage returned to the values of the FI treatments remaining at these values for the rest of the season. Removal of water from the soil profile was not uniform. It appeared that lucerne removed moisture from the upper horizons first, before extracting it from the zone below 500 mm. Leaf water potentials (ψₑ) were lower in RDI treatments, when measured at midday (but not pre-dawn), than in FI treatments. Leaves from LRDI trees had lower ψₑ values than did leaves from PRDI and HRDI trees. Rate of fruit growth was reduced in all RDI treatments during the early part of the season, but returned to the same value as FI fruit once irrigation was resumed, except for LRDI fruit which did not attain the same growth rate of FI fruit. There were less large fruit and more small fruit from LRDI treatments than from other treatments where no significant effects on fruit size were measured. Fruit from RDI treatments were firmer, less mature and contained more soluble solids at harvest than FI fruit; some of these differences were maintained through 12 weeks storage at 4°C. There was no consistent effect of irrigation or cover treatment on fruit colour, mineral content or disease incidence at harvest or after storage. Vegetative growth, measured as pruning weights and the increment in trunk diameter, was significantly reduced by RDI treatments with LRDI causing the greatest reduction in pruning weight and PRDI inducing the smallest trunk diameter increase. The combined lucerne cover crop and RDI treatment was the most successful method found for reducing soil moisture in a humid climate. It also resulted in the greatest amount of stress being induced in these trees, reducing both vegetative growth - a desirable effect, but also fruit growth, a commercially undesirable effect. It is suggested that different methods of managing lucerne, or the use of less successful water extracting plants will need to be evaluated before recommending a successful, yet practical method of using the RDI concept in apple orchards growing in humid environments.Item Coupled effects of irrigation management and water salinity on date palm cultivars in the hyper-arid environment of the United Arab Emirates : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Soil and Environment Sciences, School of Agriculture and Environment, Massey University, Palmerston North, New Zealand(Massey University, 2019) Al Muaini, Ahmed HassanDates, and the farming of date palms (Phoenix dactylifera L.), are culturally, aesthetically and economically important in the United Arab Emirates. In this hyper-arid region, dates require irrigation, as rainfall is virtually non-existent. Groundwater is relied upon as the source of this irrigation water. Yet, the groundwater reserves in the Emirates are expected to run-out in about 55 years. Furthermore they are becoming more saline. In the Emirate of Abu Dhabi, Law 5 has been passed and that will limit the amount of water that can be withdrawn for agriculture, or any other purposes. Thus there are imperatives to minimise the amount of water being used for the irrigation of date palms, and to limit the amount of salt leaching from the rootzone of the date palms. These critical issues provide the underpinning reasons for the research described in this thesis. Environment Agency – Abu Dhabi (EAD) has invested in two research projects to determine the minimum amount of irrigation water, as a function of salinity that needs to be applied to date palms to ensure economic returns from date production. These two projects underpin my doctoral research. Using the Compensation Heat Pulse Method (CHPM) of monitoring sapflow has enabled quantification of palm-tree water use, ETc. This was carried out on three cultivars of differing salt tolerances: the salt-tolerant ‘Lulu, the moderately tolerant ‘Khalas’, and the salt-intolerant ‘Shahlah’. Two salinities of groundwater were considered: 5 dS m⁻¹ and 15 dS m⁻¹. The sustainable daily rate of irrigation was considered to be 1.5 ETc, which accounts for a 25% factor-of-safety, and a 25% salt-leaching fraction. This represents considerable savings over current practices. As well, both proximal and remote sensing were used to extrapolate these findings onto commercial date farms. Finally, an assessment of the green, blue and grey water footprints of date production was made. The grey-water footprint from salt leaching was found to be the largest. A benefit-cost assessment was made of the option of using desalinated water to augment and dilute the brackish groundwater used for irrigation. To dilute 15 dS m⁻¹ groundwater to 5 dS m⁻¹ irrigation water was shown to have a benefit-cost ratio of 1.4. However, the environmental impact of the reject brine will need to be considered.Item New sensing methods for scheduling variable rate irrigation to improve water use efficiency and reduce the environmental footprint : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2020) El-Naggar, AhmedIrrigation is the largest user of allocated freshwater, so conservation of water use should begin with improving the efficiency of crop irrigation. Improved irrigation management is necessary for humid areas such as New Zealand in order to produce greater yields, overcome excessive irrigation and eliminate nitrogen losses due to accelerated leaching and/or denitrification. The impact of two different climatic regimes (Hawkes Bay, Manawatū) and soils (free and imperfect drainage) on irrigated pea (Pisum sativum., cv. ‘Ashton’) and barley (Hordeum vulgare., cv. ‘Carfields CKS1’) production was investigated. These experiments were conducted to determine whether variable-rate irrigation (VRI) was warranted. The results showed that both weather conditions and within-field soil variability had a significant effect on the irrigated pea and barley crops (pea yield - 4.15 and 1.75 t/ha; barley yield - 4.0 and 10.3 t/ha for freely and imperfectly drained soils, respectively). Given these results, soil spatial variability was characterised at precision scales using proximal sensor survey systems: to inform precision irrigation practice. Apparent soil electrical conductivity (ECa) data were collected by a Dualem-421S electromagnetic (EM) survey, and the data were kriged into a map and modelled to predict ECa to depth. The ECa depth models were related to soil moisture (θv), and the intrinsic soil differences. The method was used to guide the placement of soil moisture sensors. After quantifying precision irrigation management zones using EM technology, dynamic irrigation scheduling for a VRI system was used to efficiently irrigate a pea crop (Pisum sativum., cv. ‘Massey’) and a French bean crop (Phaseolus vulgaris., cv. ‘Contender’) over one season at the Manawatū site. The effects of two VRI scheduling methods using (i) a soil water balance model and (ii) sensors, were compared. The sensor-based technique irrigated 23–45% less water because the model-based approach overestimated drainage for the slower draining soil. There were no significant crop growth and yield differences between the two approaches, and water use efficiency (WUE) was higher under the scheduling regime based on sensors. ii To further investigate the use of sensor-based scheduling, a new method was developed to assess crop height and biomass for pea, bean and barley crops at high field resolution (0.01 m) using ground-based LiDAR (Light Detection and Ranging) data. The LiDAR multi-temporal, crop height maps can usefully improve crop coefficient estimates in soil water balance models. The results were validated against manually measured plant parameters. A critical component of soil water balance models, and of major importance for irrigation scheduling, is the estimation of crop evapotranspiration (ETc) which traditionally relies on regional climate data and default crop factors based on the day of planting. Therefore, the potential of a simpler, site-specific method for estimation of ETc using in-field crop sensors was investigated. Crop indices (NDVI, and canopy surface temperature, Tc) together with site-specific climate data were used to estimate daily crop water use at the Manawatū and Hawkes Bay sites (2017-2019). These site-specific estimates of daily crop water use were then used to evaluate a calibrated FAO-56 Penman-Monteith algorithm to estimate ETc from barley, pea and bean crops. The modified ETc–model showed a high linear correlation between measured and modelled daily ETc for barley, pea, and bean crops. This indicates the potential value of in-field crop sensing for estimating site-specific values of ETc. A model-based, decision support software system (VRI–DSS) that automates irrigation scheduling to variable soils and multiple crops was then tested at both the Manawatū and Hawkes Bay farm sites. The results showed that the virtual climate forecast models used for this study provided an adequate prediction of evapotranspiration but over predicted rainfall. However, when local data was used with the VRI–DSS system to simulate results, the soil moisture deficit showed good agreement with weekly neutron probe readings. The use of model system-based irrigation scheduling allowed two-thirds of the irrigation water to be saved for the high available water content (AWC) soil. During the season 2018 – 2019, the VRI–DSS was again used to evaluate the level of available soil water (threshold) at which irrigation should be applied to increase WUE and crop water productivity (WP) for spring wheat (Triticum aestivum L., cv. ‘Sensas’) on the sandy loam and silt loam soil zones at the Manawatū site. Two irrigation thresholds (40% and 60% AWC), were investigated in each soil zone along with a rainfed control. Soil water uptake pattern was affected mainly by the soil type rather than irrigation. The soil iii water uptake decreased with soil depth for the sandy loam whereas water was taken up uniformly from all depths of the silt loam. The 60% AWC treatments had greater irrigation water use efficiency (IWUE) than the 40% AWC treatments, indicating that irrigation scheduling using a 60% AWC trigger could be recommended for this soil-crop scenario. Overall, in this study, we have developed new sensor-based methods that can support improved spatial irrigation water management. The findings from this study led to a more beneficial use of agricultural water.Item Maintaining the hyper-arid forests of Abu Dhabi by sustainable irrigation using treated sewage effluent in conjunction with groundwater : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Soil and Environmental Sciences, School of Agriculture and Environment, Massey University, Palmerston North, New Zealand(2019) Al Yamani, WafaThe late H.H Sheikh Zayed bin Sultan Al Nahyan, the founding President of the United Arab Emirates sought to ‘green the desert’ through planting of trees. These forests in the hyperarid desert of Abu Dhabi depend on irrigation with groundwater (GW). A wide range of valuable ecosystem services are delivered by the forests. In the 2017 State of the Environment Report, Environment Agency – Abu Dhabi (EAD) noted that “… considerable water resources are required to maintain these forests”. Over-consumption of GW, and the increasing salinity of the aquifers means that the GW of Abu Dhabi is under threat. To manage sustainably the GW resources, in 2016 the government of Abu Dhabi passed Law 5 on GW management and identified the requirement for limits to be placed on GW allocation for vegetation. The means to realise reductions in GW use are: minimised irrigation schedules for GW; and the replacement of GW with treated sewage effluent (TSE). To achieve this, a Government-to-Government partnership was established between EAD and the New Zealand Government. The NZ partners are Maven International and Plant & Food Research. This doctoral research was carried out under this larger partnership. The actual water uses, ETc, of the 3 major forest species of Al Ghaf, Al Sidr and Al Samr were measured by heat-pulse sapflow methods in trees irrigated with either GW or TSE. The impacts on ETc and tree health of the lower salinity TSE are detailed. The complex links between tree water-use, the reference ETo, and trees’ phenology are described. Relationships between the crop factor, Kc (=ETc/ETo), and tree canopy characteristics were inferred using a light-stick to measure the percentage light intercepted by the trees’ canopy. From this research, guidelines have been proposed for Law 5 for the water-allocation limits for these 3 species. These guideline values for GW are based on 1.5 ETc to account for a 25% factor-of-safety, and a 25% salt-leaching fraction. For TSE, there is no need for salt leaching. These recommendations will lead to GW savings of 35-70% compared to current practice. Eventually TSE should replace GW to sustain the forests.Item Root growth and crop yield of two varieties of wheat grown under differing irrigation regimes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University(Massey University, 1974) Piggot, Graeme JamesRoot growth and crop yield of Gamenya, a standard height variety, and Karamu, a semi-dwarf, spring wheat were compared under 3 irrigation regimes: daily watering; infrequent (fortnightly) watering; and sub-irrigation, where water was introduced into the soil profile at 40cm, the plots being protected from rainfall. Root growth and development were similar between varieties apart from an indication that the Karamu root system was more extensive at depth. The three irrigation treatments grew distinctly different root systems which was probably due partly to soil compaction differences between the treatments rather than the spatial distribution of the soil water supply. Karamu outyielded Gamenya because of a higher grain weight per ear due to higher floret viability and greater grain weight. Yield differences between irrigation treatments, where the infrequently irrigated treatment was superior, was due to ear population differences related to the differing root systems. With daily irrigation Gamenya used more water, due possibly to the lower leaf water potentials developed in the crop. An inverted water potential difference between the ear and the flag leaf was observed during the middle of the day.Item Evaluation of small irrigation projects in the Philippines : the case of small water impounding projects : a thesis submitted in partial fulfilment of the requirements for the degree of Masters in Agricultural Economics(Massey University, 1995) Salguero, Sonia MAn economic evaluation of the proposed Camagsingalan Small Water Impounding Project was conducted using the benefit-cost analysis framework to determine its economic desirability to the society. The project will be located in Sual Pangasinan and envisioned to provide irrigation water to about 55 hectares which will give the upland farmers an oportunity to shift from dryland to irrigated farming systems. The recommended cropping pattern for the project area is a crop of rice followed by a crop of mungbean or garlic. Moreover, about 20 hectares each of mango and cashew will be planted in the surrounding portion of the watershed area. Based on the twenty period economic analyis, the Camagsingalan Small Water Impouding Project would generate a substantial gain to the province and to the nation in general. At discount rate of 15 per cent, the project will result in a Net Presnt Value of P 536,194.00 using the Cropping Pattern 1 and an Internal Rate of Return (IRR) of 39 percent. On the other hand Cropping Pattern 2 will result in a Net Present Value of P 5,911,844.00 and an Internal Rate of Return of 41 per cent. In summary, the project based on quantifiable costs and benefits is economically desirable and worthwhile undertaking. However, a number of enviromental problems have not been dealt with in the economic analysis. These include the possible environmental and socio-economic problems that will result due to the construction of the SWIM project. Though the scale of the project is small, the extent of effect is however not yet established. Water pricing is not also dealt with in the analyis.Item The effects of temperature and irrigation on the establishment and growth of lucerne (Medicago sativa L.) on Manawatu sand country : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University(Massey University, 1973) Brown, Noel SamuelThis research was undertaken to study the establishment of lucerne on one of the drier soils of the Manawatu sand country. Lucerne has often been difficult to establish on these soils, yet once established grows well, possibly due to the large supply of water that is to be found in the water table a metre or so below the surface. Difficulty in establishing lucerne has often been attributed to shifting of the unconsolidated cultivated sand surface by wind, and also to the low moisture holding capacity of the soil. Lucerne stands are usually sown in the spring, but the available soil moisture may be quickly evaporated by the strong prevailing westerly wind at this time and wind erosion may occur, often burying plants with sand and leaving other young plants with their root systems exposed. Another possible reason for poor establishment of lucerne could be the high surface temperatures often experienced on the bare surface. The aim of the field study was to examine the effects of soil temperature, soil moisture and wind erosion on lucerne establishment. Subsequently, glasshouse experiments were conducted to investigate the effects of temperature variations in the soil and on the surface on the growth and survival of lucerne seedlings. [From Introduction]