Tools and Strategies for Sustainable Nitrogen Fertilisation of Vegetable Crops

Abstract

In intensive vegetable production, N fertiliser applications often contribute to a supply of N that appreciably exceeds crop N requirements resulting in the loss of N to the environment which can result in NO3 contamination of water bodies. There is a range of tools and strategies that can assist vegetable growers to improve N management. These include various methods based on soil analysis or estimation of the soil N supply, N balance calculations, methods based on plant analysis, methods based on monitoring crops with optical sensors, and the use of computerised decision support systems based on simulation models or data bases. Use of these tools has been demonstrated to appreciably reduce fertiliser N application and N losses while maintaining production. The selection of tools to be used by a grower will be influenced by factors such as availability, the grower’s technical level, and economic considerations. For fertigation systems with high frequency N application, a combination of a planning method such as a decision support system with a monitoring method is recommended. Additional tools that can assist in demonstrating to stakeholders the benefit of improved N management are simulation models that provide scenario analysis. Fundamental strategies for improving N fertiliser management are to consider all N sources such as root zone soil mineral N and N mineralised from organic materials, and to partition N application so that it coincides with crop N demand.