Effect of manifold layout and fertilizer solution concentration on fertilization and flushing times and uniformity of drip irrigation systems

Applying fertilizer through drip irrigation system is a very important method to save fertilizer and labour. Three manifold layouts (water supply in one end for transversal drip tapes (M1), water supply in both ends for transversal drip tapes (M2) and water supply in one end for longitudinal drip tapes (M3)) and four different fertilizer solution concentrations (50.00 g L−1 (C1), 66.67 g L−1 (C2), 100 g L−1 (C3) and 200 g L−1 (C4)) were selected to investigated the effect of the manifold and concentration on water fertigation uniformity. Results showed that the emitter at the extreme end of the manifold needed more time to clean the rudimental fertilizer in the drip tapes. The minimal flushing time increased from 8 to 13, 4 to 7 and 7 to 12 min with increasing the fertilizer concentration from C1 to C4 for M1, M2 and M3, respectively. The drip irrigation system needed more time for flushing to reduce the risk of emitter clogging when a higher fertilizer solution concentration was applied. In order of performance, M2 had the highest water and fertilizer uniformity, followed by M3 and lastly by M1. The fertilizer solution concentration had no significant effect on water distribution. However, it had a significant effect on fertilizer distribution. The mass of the applied fertilizer for the drip tapes close to the inlet increased with increasing fertilizer solution concentration from C1 to C4, which indicated that higher fertilizer solution concentration can result in lower fertilizer distribution uniformity. There was a significant effect of the manifold layout on water uniformity. The fertilizer concentration and the interaction between manifold layout and concentration had no significant effect on the water uniformity. Similarly, both the manifold layout and concentration had a significant effect on fertilizer uniformity. The interaction between manifold layout and concentration had a significant effect on the Christiansen's uniformity (CU) and distribution uniformity (DU) for fertilizer, whilst, a significant effect on emission uniformity (EU) was not found. The manifold layout and fertilizer solution concentration should therefore be considered in the design and operation of fertigation system.