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close this section of the library Nisha, Sofina

View the PDF document Examining the chemical fertility of soils in Taveuni, Fiji : the problem of soil health and food security
Author:Nisha, Sofina
Institution: University of the South Pacific.
Award: M.Sc.
Subject: Soil fertility -- Fiji -- Taveuni, Soil productivity -- Fiji -- Taveuni, Soils -- Quality -- Fiji -- Taveuni, Soils and nutrition -- Fiji -- Taveuni, Food security -- Fiji -- Taveuni
Date: 2014
Call No.: pac S 596 .7 .N572 2014
BRN: 1195014
Copyright:Over 80% of this thesis may be copied without the authors written permission

Abstract: Studies have shown that the soil health in Taveuni, Fiji is deteriorating over time due to continuous plantation and indiscriminate and imbalanced fertiliser use. The declining trend in soil fertility on the island of Taveuni, Fiji has threatened taro producers. There are visible impacts of deteriorating soil health such as stagnating/plateauing crop yields and slow agricultural growth. This situation has resulted in high rates of deforestation on the island as farmers are forced to search for new fertile soil. Despite the crucial role of agriculture in Fiji’s economy and the increasingly serious issue of soil degradation in Taveuni, Fiji, a perusal of literature reveals that no chemical analysis of the soils in the taro growing areas of Taveuni has been carried out. This project was therefore undertaken to study the problem of soil health affecting food security by examining the chemical fertility of soils in Taveuni, Fiji. Four farms were selected as the study sites. Soil samples were collected four times during the cultivation period of taro: before planting of mucuna beans, before planting of taro, three months after planting of taro and at the time of harvest. The soil samples were analyzed for macronutrients (Ca, Mg, K, P and NO3 --N), micronutrients (Cu, Fe, Mn and Zn), soil organic matter (SOM) and soil pH. Structured questionnaire survey was also conducted on 50 farmers from areas near the sampling sites to get a feedback on the trend of their crop production over the years, fertiliser usage and some of the constraints the farmers faced in following proper soil fertility management practices. The adequacy of applied methodology for soil nutrient analysis was confirmed by measures of accuracy, reproducibility and recovery. Calibration was performed by the method of standard additions and quality control. Inter-laboratory comparison of results was carried out to confirm the accuracy of the method used. The detection limit for the essential nutrients in the soil matrix was also determined as a quality control measure. Measurements of each sample were carried out in three replicates. Mean, standard iv deviation and relative standard deviation were calculated for interpretation and comparison of data. At the time of harvest, Matei site showed low levels of SOM, NO3 --N, available P, exchangeable Ca and extractable Zn. The site however, had ideal levels of exchangeable Mg and K, as well as extractable soil Cu, Fe and Mn. During the same period of time, Mua site showed low levels of SOM, NO3 --N, available P and extractable Zn. Extractable soil Cu, Fe and Mn were at ideal levels while exchangeable Ca, Mg and K were at critical levels. For Vione site, SOM and extractable Cu, Fe and Mn were at sufficient levels, while NO3 --N, available P and extractable Zn were at low levels. The site also showed Ca, Mg and K deficiency. Similarly, Delaivuna site had low levels of exchangeable Ca, Mg and K as well as SOM, NO3 --N and extractable Mn and Zn. There was however sufficient levels of available P and extractable Cu and Fe. Statistical analysis of the soil test data confirmed the declining trend of the soil fertility on the island of Taveuni, Fiji. Crop output obtained through questionnaire survey also revealed the declining trend of taro production over the years. There was significant reduction (ρ < 0.05) in the soil macronutrients, micronutrients and SOM in all the four study sites and showed below critical levels, critical to medium levels of these nutrients in the soil at the end of the cultivation period of taro.
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