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

Abstract

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.