Deep placement of fertilizer solution in puddled soils. Part 2 : Rice growth and yield

To investigate the influence of depth and manner of placement of fertilizer solution on transplanted rice, a field experiment was conducted using a pressurized injecting device prototype. Fertilizer was injected 30 days before panicle initiation at different depths in points and in band to assess effects on plant growth and yield. Results indicated similar trends in the levels of leaf and total plant N, tillering, and dry matter production. No significant differences were observed between deep placement and split broadcast except at the onset of panicle initiation when deep placement started to affect the plants with deeper injection, i.e., at 15 cm performing better for plant growth. Grain yields of fertilized plots were not significantly different and ranged from 6.1 to 7.1 t/ha although deeper placement yielded higher. Results showed that high N rate, machine performance, and the presence of water during injection affected plants’ response to deep placement. There is an indication, however, that to maximize yield, deeper placement may be necessary when N is injected before panicle initiation since plant roots are already well-developed for efficient N uptake. Deep placement has potential in reducing the frequency of N application without affecting plant growth and yield but there is still a need to improve the management of factors that affect the performance of deep placement of fertilizer, particularly when using a machine.