Soil erosion and the subsequent loss of soil fertility is a major cause of soil degradation in the Pacific, causing crop yields to fall and poverty levels to rise. In many cases, the landowners and local communities are ignorant of the causes because the symptoms appear gradually over several years and are not linked to inappropriate land use systems.
The CROPPRO project drew upon knowledge available within the Environmental Sciences Group on the measurement of rainfall, discharge, moisture content, plant characteristics and soil characteristics. The data collected was input into the LISEM erosion model. We collaborated closely with an international multidisciplinary team.
The overall objective of the CROPPRO project is to develop integrated farming approaches for sustainable crop production in environmentally constrained systems in the South Pacific region. The aim is to increase crop productivity and reduce land degradation.
The project areas in the various countries differ considerably. The study area in Fiji lies outside the capital Suva, where crops are grown under a mixture of land use systems: intensive commercial farming of taro, cassava, ginger and vegetables; extensive subsistence and semi-commercial farming; and mahogany plantation forestry. In Samoa the project area is near the capital Apia. It consists largely of sloping land where farmers practice extensive agroforestry with some cropping under coconuts, and bush fallow. The project area in Tonga is located on the main island of Tongatapu, which has no rivers or streams and is mostly flat with little or no sloping land. Here the project focuses on farming systems for growing pumpkins as a cash crop. The research investigates the movement of fertiliser and pesticide residues in the soil, and the risks of these leaching into the groundwater lens and lagoon, which supplies the public water system.
The project objectives are addressed in seven work packages, which consist of an interrelated series of data collection activities, farming system analysis, model application and simulation, definition and evaluation of alternative farm technology packages, and the development and promotion of guidelines for sustainable crop production in the Pacific region, and ultimately their adoption by end users.
Each project area proved to be unique and required a special approach to obtain the best results. In Fiji and Samoa we identified land suffering from excessive soil loss, most of which is intensively farmed, and linked this to ongoing land use patterns. The outcomes of model calculations were explained to the local communities, which initiated discussions about land use alternatives. The model was thus used as a tool in the negotiation process with stakeholders, leading to the promotion of sustainable farming systems that significantly reduce soil erosion. In each country, project partners have worked closely with farmers, young people and communities to heighten awareness of soil erosion, and have launched initiatives to develop and apply sustainable farming methods.
The project area in Tonga consists mainly of flat land and the farmers are often experienced and knowledgeable. Besides the risks posed to the freshwater lenses and lagoon by fertilisers, pesticide use is also a significant concern as growers try to prevent powdery mildew disease. Experiments and modelling results showed that fertiliser should be applied later and in split applications to meet the crop’s demand and reduce pollution.
A number of reports have been produced on the CROPPRO project, including a number of MSc theses. The project has also resulted in a valuable dataset for an area where no measurements at this scale had been performed, and in the further development of the LISEM model.