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    Nutrient solution management for greenhouse tomatoes : a multiple-case study : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science at Massey University
    (Massey University, 2006) Xu, Minhua
    Nutrient solution released from hydroponic greenhouse operations has been considered as a potential pollution source by New Zealand regional authorities. The Management of Nutrient Solutions Released from Greenhouses: A Code of Practice (COP) is designed to assist New Zealand greenhouse growers in managing nutrient solution release in hydroponic systems to comply with The Resource Management Act 1991 (RMA) and regional resource plans prepared by regional authorities to ensure that their constituents act appropriately. A multiple-case study was designed to investigate the nutrient solution management and disposal practices of New Zealand hydroponic greenhouse tomato growers and, further, to investigate whether or not these practices meet the guidelines set out in The Management of Nutrient Solutions Released from Greenhouses: A Code of Practice. Three hydroponic greenhouse properties that represent the current New Zealand greenhouse tomato industry were selected as case studies. How the greenhouse growers manage nutrient solution in these greenhouses was investigated by interviewing the growers. The results show that none of the case study growers fully met the guidelines given in the COP. However, recirculating growers manage nutrient solution better than do the run-to-waste grower in terms of reducing nutrient solution discharge frequency. They release less volume of nitrogen into the environment per 1000 kg of tomato produced in their recirculating growing systems. The research results indicate that high-technology recirculating grower could better satisfy the requirements set out in the COP. Low-technology run-to-waste growers are unlikely to meet those requirements due to their system design. Therefore, adopting a recirculating growing system is considered as a trend of the industries in the future.
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    An evaluation of the economic benefits of active cooling and carbon dioxide enrichment of greenhouse cucumbers (Cucumis sativus L.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science at Massey University
    (Massey University, 1996) Van Heijst, Marcus Johannes Aart Everardus
    Cooling a greenhouse with a refrigeration system rather than conventional ventilation makes it possible to maximise the fractional enrichment time for carbon dioxide, and more importantly enrich during periods of high photosynthetically active radiation. Using conventional climate control methods, enrichment is limited to periods when the greenhouse is not being ventilated, thus reducing the potential enrichment time of the crop. The objective of this study was to develop a simulation model of a greenhouse crop growing with a closed cycle climate control system, using a heat pump, with a reversible (dual) cycle, for heating and cooling. A computer implemented mathematical model developed by Wells (1992) was modified to simulate cucumber crop growth in a greenhouse of commercial size and allowing certain parameters to be set. These parameters included: two types of control system, four levels of enrichment, three crop periods, and at two locations, Auckland and Christchurch. The three crop periods chosen were 26 Jan to 26 April, 25 May to 23 August, and 20 September to 19 December. The two types of control involved conventional fan ventialtion and electric heating, and closed cycle climate control using a reverse cycle heat pump. Greenhouse carbon dioxide enrichment levels used were 350, 600, 900, 1200 μ1.1-1 . The two locations chosen were Auckland and Christchurch. An economic analysis of the results was carried out calculating Annual Marginal Return (AMR) and Internal Rate of Return (IRR) for treatments compared to control. It was concluded that carbon dioxide enrichment combined with conventional control is a worthwhile investment in Christchurch but less so in Auckland. Due to the high capital cost, carbon dioxide enrichment combined with closed cycle climate control is a less attractive investment. However, as considerable energy savings are possible with closed cycle climate control, it is worthwhile investigating other less expensive forms of closed cycle climate control. The economic feasibility of the application of this technology to other, higher value, crops is worthwhile investigating.
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    Planning and control of IPM for greenhouse tomato growers : processes used by expert consultants : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Agricultural Systems & Management at Massey University
    (Massey University, 1999) Singgih, Shinta Milasari
    Given the clean, green image used to promote New Zealand produce, greenhouse tomato growers are under pressure to shift from conventional pest control to more environmentally-friendly methods such as IPM. However, growers often lack the specific knowledge required to tailor IPM strategies to their properties. Greenhouse consultants with expertise in IPM may provide a valuable source of assistance in terms of IPM adoption. However, little is known about how expert greenhouse consultants conduct this task. This study investigated the processes used by expert greenhouse consultants to assist greenhouse tomato growers with the planning and control of IPM strategies. A Multiple case study research method was selected as the most appropriate method for meeting the study objectives. Following the review of the literature, two expert greenhouse consultants were selected, and the data were collected using semi-structured interviews, field observations, and relevant documentation. Qualitative data analysis techniques were used to analyse the data. The two consultants were found to use similar IPM consultancy processes which, for the purpose of this study, have been separated into the physical activities, and planning and control processes. Both consultants perform similar physical activities (telephone calls and visits) to those used by farm management consultants. However, the two consultants studied distinguish between planning and control purpose telephone calls and visits, which the farm management consultants do not. In addition, both consultants use additional communication tools during the control stage. Throughout the consultancy processes, rapport is considered important to enable a trusting relationship to be built between the client and the consultant. The study highlights the presence of three phases during the consultancy processes, which were not mentioned in other farm management consultancy literature. The "screening" phase is used to ensure the development of the client's favourable attitudes toward IPM in the planning process. The "provision of information" phase, which occurs throughout the processes, is critical due to the complex nature of IPM. The "validation" phase is used to confirm the existence of the problems in the control process. During the planning and control processes, the client and the consultant share several roles and responsibilities. As the clients own the problem, they are responsible for making the decisions, implementing the plans, and undertaking monitoring. In order to do this, the clients act as the information providers and receivers for the consultant. The consultant is responsible for understanding the clients' system, providing the information required by the clients and designing the preventative IPM strategies during the planning stage. At this stage, the consultant also provides a monitoring strategy and contingency plans to be used by the clients. During control, the consultant is responsible for validating and diagnosing existence of the problems, providing information about the causal effect of the problems and designing the curative IPM strategies to solve the problems. During the design phase, the consultant uses decision rules to modify his IPM template, according to the need of each client. Factors such as type of crop, greenhouse age, crop age, whitefly population levels, the ability to heat, season, stud height, and persistence period are mentally structured to come up with various Encarsia introduction rates. In contrast, the IPM manual suggests a single Encarsia rate is used for all situations. The Encarsia introduction rates comprise the initial and maintenance rates. Case Study One starts with low rates of Encarsia for 2-4 weeks, followed by increasing the rates. Case Study Two starts with high rates of Encarsia for 6-10 weeks, followed by reducing the rates. Introduction is discontinued when the sustainable level of whitefly parasitism has been achieved. A more detailed IPM manual which allows for the specific circumstances in greenhouse tomato growers' properties is required to assist growers in the adoption of IPM strategies Key words: consultancy, planning, control, IPM, greenhouse tomatoes, Encarsia formosa, multiple case studies.
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    Modelling the greenhouse environment and the growth of cucumbers (Cucumis sativus L.) : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agricultural Engineering at Massey University
    (Massey University, 1992) Wells, Colin Mark
    Mathematical models which describe the greenhouse environment, and the growth of a crop of cucumbers, in that environment, have be en developed and tested. The models have been used to predict: the response of the greenhouse to varying weather conditions, the growth of the crop leaf canopy, and the weight and number of fruit harvested The greenhouse environment has been modelled using a system of non-linear differential equations, derived from a consideration of the energy and mass balances of the glazing, internal structure, crop canopy, root media, fl oor, deep soil layers, and the greenhouse air space. The equations have been solved for five minute time steps, using measured values of outside weather conditions and control inputs as boundary values. Entry of solar radiation into the greenhouse, and absorption by various surfaces, has been determined using transmission tables generated using a "ray-tracing" light transmission model. The light transmission model has been calibrated in a separate experiment. The incoming solar radiation has been partitioned between diffuse, direct, photosynthetically active and near infra-red radiation, for use in the crop model. Validation experiments have been performed to test the greenhouse environment simulation model. The results of the validation exercise showed that the model was capable of predicting the temperatures in the greenhouse, within a few degrees. The mean errors were smaller for the crop canopy, root medium, and floor, than for the glazing or air temperature. Prediction errors for relative humidity and carbon dioxide concentration were more variable. An existing model of cucumber development rate, and leaf expansion, has been modified and validated. This gave good results when adequate account was taken of leaf senescense, and initiation of lateral growths. Sub-models for photosynthesis, respiration, and assimilate partitioning have been develope d , and c ombined with the greenhouse environment and leaf expansion models. The combined model has been used to predict the course of growth of a cucumber crop over one growing season, and the number and weight of fruit harvested. The predictions have been compared to results from a test crop. This revealed that while the total number of fruit harvested was accurately predicted, the total weight of harvested fruit was not. The models are intended to be used in the s tudy of optimal control of the greenhouse environment.
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    Automated wireless greenhouse management system : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Electronics and Computer Systems
    (Massey University, 2011) Vu, Quan Minh
    Increases in greenhouse sizes have forced the growers to increase measurement points for tracking changes in the environment, thus enabling energy saving and more accurate adjustments. However, increases in measurement points mean increases in installation and maintenance cost. Not to mention, once the measurement points have been built and installed, they can be tedious to relocate in the future. Therefore, the purpose of this Masters thesis is to present a novel project called “Automated Wireless Greenhouse Climate Management System” which is capable of intelligently monitoring and controlling the greenhouse climate conditions in a preprogrammed manner. The proposed system consists of three stations: Sensor Station, Coordinator Station, and Central Station. To allow for better monitoring of the climate condition in the greenhouse, the sensor station is equipped with several sensor elements such as CO2, Temperature, humidity, light, soil moisture and soil temperature. The communication between the sensor station and the coordinator station is achieved via ZigBee wireless modules and the communication between coordinator station and the central station is achieved via long range RF modems. An important aspect of designing a wireless network is the reliability of data transmission. Therefore, it is important to ensure that the developed system will not lose packets during transmission. An experiment was carried out in one of the greenhouses at Plant and Food Research Ltd, New Zealand in order to determine the functionality and reliability of the designed wireless sensor network using ZigBee wireless technology. The Experiment result indicates that ZigBee modules can be used as one solution to lower the installation cost, increase flexibility and reliability and create a greenhouse management system that is only based on wireless nodes. The overall system architecture shows advantages in cost, size, power, flexibility and distributed intelligent. It is believed that the outcomes of the project will provide the opportunity for further research and development of a low cost automated wireless greenhouse management system for commercial use.