H.G. de Boer for the 7th Annual Conference of the BSTA, 1989

At the 4th Annual BSTA Conference, a graph was published (de Boer, 1986) based on work by Chase (1969-1981) which clearly indicated an optimum level of N application of somewhere between 115 and 140 lbs N per acre – less for plantcane, more for ratoons. This optimum level will vary with the cost of fertilizer, with receipts for cane sold and with the cost of harvest.

The Agronomy Research Unit (ARU) of Barbados Sugar Industry Ltd (BSIL) decided in 1983 to carry out some experiments to test the common perception among farmers that higher levels of fertilizer would be worth their while. It was also felt that maybe the figures produced by Chase were not directly applicable to current farming practice since his trials were carried out entirely by hand labour. It was considered possible that the cane would respond to higher levels of fertilizer under farming conditions where fertilizer is applied mechanically and the cane cut by combine harvester.

Excerpts from the conclusion

Not only did the cane in the trials reported on here not respond any better to extra fertilizer than in the MAFF trials by Chase (1969-1981), it did not respond at all to extra fertilizer – except in the presence of compost. The reason(s) for this need investigation and this paper indicates a number of possible lines of action.
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In the meantime, farmers need to be advised that ap plying excess fertilizer is most likely to be a waste of scarce resources. The fact that the cane may look healthier and/or greener after heavy doses of fertilizer is no guarantee of extra yield. The data presented in this paper are accurate reflections of exactly what happens under commonly used farming practices and must therefore be taken seriously

More fertilizer more yield? pdf