Optimisation of fertiliser dissolution under differential pressure tank during fertigation

Fertiliser dissolution is usually carried out in a differential pressure tank. Fertiliser concentration at tank outlet is essential information for the correct control of optimum fertilisation. To enable optimisation, a fertiliser concentration equation was derived from the continuity equation with a source term. The source term described fertiliser dissolution using the initial dissolution rate and a decay rate of dissolution. An analytical equation was obtained from the fertiliser concentration equation for a traditional fertilisation process. The analytical equation fitted experimental data well, providing significantly good quantitative predictions. The equation reduces to the standard exponential form when the source term disappears. The influence of the fertiliser dissolution and outflow on concentration variation is discussed. An optimum fertilisation method considering dissolution is further proposed to provide constant fertigation flux and optimum fertiliser concentration based on the fertiliser concentration equation. The optimum fertilisation method controls a flux division of the fertigation system. Fertiliser dissolution is analysed for its influences on the flux division and fertiliser concentration at tank outlet under optimum conditions. Fertiliser dissolution increases the optimum fertilisation time, and leads to reduced inlet flux compared with the optimum fertilisation case without fertiliser dissolution. Environmental impact assessment is discussed by comparing optimum fertilisation to traditional fertilisation. The optimum fertilisation method could offer positive to fertiliser management and environmental protection by avoiding the excessive nitrogen and phosphorus losses found in traditional fertilisation. (c) 2021 IAgrE. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study investigates the impact of fertilizer dissolution on optimal fertilization, proposing a method considering dissolution. It is found that fertilizer dissolution increases optimal fertilization time and leads to reduced inlet flux compared to the case without dissolution. Implications of environmental impact assessment and benefits of optimal fertilization over traditional methods are also discussed.