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    Fruit water relations, growth, yield, and quality of 'Braeburn' apple in response to deficit irrigation and to crop load : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Physiology at Massey University
    (Massey University, 2001) Mpelasoka, Bussakorn Sriprasert
    Allocation of water for agriculture has decreased due to increased demand as a result of population growth, industrial development, and water pollution. Irrigation management aiming at efficient use of water has become a high priority. Deficit irrigation (DI), if applied judiciously, saves water, decreases vegetative growth and pruning costs, reduces leaching of agrichemicals into ground water, and may improve fruit quality. In apple, there is less beneficial effect of DI on shoot growth reduction because fruit set and cell division phases occur at the same time as predominant shoot growth and so DI applied during this period will reduce fruit size. However, there appear to be potential of DI in apple fruit quality improvement but research findings on this aspect have been inconclusive. To promote the adoption of DI in apple production, there is need to confirm and expand the effects of DI on fruit quality and to minimise DI effects on fruit size reduction. This study was to confirm DI effects on fruit quality by addressing relationship between fruit size and quality and to investigate DI effects on under-researched aspects of fruit quality such as physiological disorders, maturation and ripening, aroma volatiles, and storage potential. The possibility of integrating light crop load with DI to increase fruit size was also explored by investigating interactions of DI and crop load on tree water use, fruit size regulation, yield, and quality. The study involves three experiments. Irrigation treatments include control irrigation (CI), early deficit irrigation (EDI) applied from 63 to 118 days after full bloom (DAFB), late deficit irrigation (LDI) applied from approximately 118 DAFB until final harvest, and whole-season deficit irrigation (WDI) applied from 12 DAFB until final harvest. Crop load treatments, which were included in two experiments, were commercial crop load (CCL) and light crop load (LCL) equivalent to 60-67% of CCL. 'Braeburn' apple (Malus domestica Borkh.) was used in all experiments. Deficit irrigation applied at any time during the growing season reduced fruit growth and size. Fruit size reduction by DI was counteracted by a lighter crop load. The interactions of DI and crop load on photosynthetic rate, fruit water potential, and fruit turgor potential (which were generally similar between CCL and LCL under CI but were lower in CCL under DI) are possible mechanisms for this counteraction. Tree water use (TWU) was reduced in DI and in LCL. The difference in TWU between CI and DI were greater at CCL than at LCL and that between CCL and LCL were greater under CI than under DI. Among the quality attributes studied, only firmness and dry matter concentration (DMC) were affected by fruit size with their values being higher in smaller fruit. The DI fruit were firmer and had higher DMC than CI fruit when comparing fruit of similar size. Total soluble solids (TSS) and total sugar concentration (TSC) were higher in DI fruit than in CI fruit in all experiments. In general, DI did not affect titratable acidity (TA) except for one experiment where TA at harvest was higher in EDI fruit than in CI fruit. Fruit ripened more quickly in LDI and WDI than in EDI which was similar in this respect to CI. The advancement in ripening of DI fruit appeared to be responsible for the enhanced production of aroma volatiles. This enhancement was observed on some occasions during ripening and after cold storage. Deficit irrigation may increase storage potential of the fruit as DI did not affect incidence of physiological disorders but decreased the weight loss during storage. The DI fruit were also firmer than CI fruit for at least 10 weeks of cold storage but this advantage was loss after longer storage due to the advanced ripening of the DI fruit. Apart from the enhancement on individual quality attributes, DI also improved overall fruit quality when many quality attributes were considered collectively using multivariate analysis. This was true both at harvest and after storage. There was no interaction between irrigation and crop load on any quality attributes under investigation. Light crop load improved fruit quality at harvest in terms of increased firmness, TSS, TSC and fruit density but increased weight loss during storage and incidence of bitter pit after storage. This research programme showed that deficit irrigation has a great potential as a strategy to save water and to improve fruit quality in apple production. 'Braeburn' is a large-fruited variety. Although fruit size was reduced under DI, DI fruit still met standard export requirements. In situations where price favours large size fruit, light crop load may be integrated with DI to increase fruit size but light crop load may adversely affect fruit quality after storage.
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    Participatory irrigation management and the factors that influence the success of farmer water use communities : a case study in Cambodia : a dissertation presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Environmental Management at Massey University, New Zealand
    (Massey University, 2010) Ros, Bandeth
    The Participatory Irrigation Management approach was introduced into Cambodia in 2000, which was called the Participatory Irrigation Management and Development (PIMD). The goal of PIMD is to establish Farmer Water User Communities (FWUCs) to take over the management of irrigation schemes in their district in order to improve the performance of irrigation schemes and farmers’ livelihoods. The implementation of FWUCs has resulted in both failure and success. Several studies have identified factors that influence the failure of FWUCs, but little research has focused on their success. By employing a single embedded case study approach, this research selected the most successful scheme in Cambodia to identify factors that influenced the success of the FWUC in irrigation management. The findings of this research could provide concrete assistance to the government, donors, and non-governmental organisations in improving the performance of less successful FWUCs in Cambodia. The result of this research showed that the success of the O-treing FWUC was influenced by five internal and two external factors. The internal factors were: 1) the level of local participation, 2) the governance and management of the scheme, 3) the value of the benefits that flow from the irrigation scheme, 4) the quality of the irrigation infrastructure, and 5) the characteristics of the farmer members within the scheme. The external factors were: 1) the level of external support provided to the scheme, and 2) market access. The success of the FWUC required farmer participation and this participation was enhanced when farmers obtained benefits from it. This research also found that access to markets was critical to make the benefits that flowed from the irrigation scheme more profitable to farmers, leading to farmer participation. Similarly, it was also important to make sure that the irrigation infrastructure was of a high quality to ensure the delivery of an adequate and timely supply of water to farmers so that they could grow crops that provided them with the benefits. This required external support from the Ministry of Water Resources and Meteorology, NGOs, and local authorities to help rehabilitate the scheme. External support was also critical for enhancing the governance and management of the scheme through assistance with the formation process, provision of financial resources, capacity building, rule enforcement, and conflict resolution. The governance and management of the scheme, in particular the leadership capacity of the FWUC was another critical factor because it ensured the maintenance and development of the irrigation infrastructure, the timely and adequate supply of water to farmers, farmers’ trust and respect for leaders, and farmer participation. Finally, the success of the FWUC could not be viewed independently from farmer characteristics within the scheme. Farmers tended to participate in irrigation management when they had a history of self-organisation, when they were relatively homogenous, and when they were dependent upon farming for their livelihoods. This research suggests that the successful implementation of FWUCs requires a focus on the seven factors and the interactions that occur between these factors. Irrigation stakeholders such as the Ministry of Water Resources and Meteorology, donors, NGOs, local authorities, local leaders, and farmers should work together to enhance these factors in order to ensure the success of FWUCs.