Care has to be taken with flood fallowing, bed conversion in sugar industry

Dear Editor,

I note with some concern that flood fallowing has been quoted by several sources as a panacea for the ills which plague our sugar cane fields. This erroneous assumption can probably lead us into deeper waters in our sugar industry, if indeed there are waters which are deeper than that which we find ourselves struggling in today.

Trials conducted in the 1930’s yielded the following results:

“The mean yield of sugar per acre over four crops (plants and three ratoons) in a series of trials to investigate flood fallowing in the 1930s were:-

 

Duration of flood-fallowing    Yields (ts/a/crop)           % Control

No flooding (control)                                  4.22                   100

4 months                                                     4.95                   117

6 months                                                     5.27                   125

12 months                                                   5.54                   131

 

To sum up the table above, if one was to flood fallow for 4 months one would get a total of 2.92 tons of sugar more, over a four year period – plants and three ratoons  i.e. 17% more per crop.

If one were to flood fallow for 6 months the results would be an increased yield of 4.2 tons of sugar over 4 years i.e. 5.27 – 4.22 x 4 years, an improvement of 25%.

Flooding for one year yielded 5.28 tons of sugar more over the four-year period, an improvement of only 31%.

These figures now have to be studied within our new ethos and we have to decide on what period we will flood our fields for.

Clearly flooding for 6 months is the most economical period since we get a return of 25% per crop over 4 years compared to a 31% improvement if we flooded for an entire year. So flooding 200 acres for 6 months will result in an improvement of 50% more sugar over 4 years [i.e. 25% from each 100 acres] when compared to a total of only 31% for flooding 100 acres for one full year.

There are also benefits to flooding for 4 months which should not be overlooked. i.e. flooding for 4 months returned an improvement of 17% over 4 years i.e. 4.25% per month of flooding  whilst flooding for 6 months returned an improvement of 25% i.e. 4.16% per month of flooding!

So Mr. Chand is better advised to focus on a four-six month period of flood fallow rather than a one year period.

In some of the reports we have seen, we observe that to mechanise the sugar industry in Guyana GuySuCo has ill-advisedly embarked on a massive conversion from cambered bed field layout to a flat land layout to facilitate this mechanisation. Nearly half of its total lands in 5-6 years!

This operation is riddled with danger, and entails pushing off all of the fertile top soil into where the old drains were located to create a flat field thereby exposing the infertile top soil at the top of the bed and inevitably supressing overall growth. I am not sure that introducing flood fallow will supply the full answer to the resulting infertile fields that this massive amount of conversion with concomitant drops in yield that it has caused.

First of all the subsoil thus exposed will be acid since we are using Sulphate of Ammonia as a fertilizer and when the ammonia is used by the plants to supply it with nitrogen we are left with sulphuric acid. Now since we are usually ploughing to a depth of 12 to 18 inches in the cane fields and we can only legitimately expect leaching to that depth the subsoil may be very acid indeed, so the usual industry practice of applying one ton of Limestone or aragonite per acre must be modified to applying more like 5 tons in the first instance to offset this high acidity in the cane fields which results from the conversion for mechanisation. This can be done immediately and have a quicker effect on the whole than doing a 5% per annum flood fallow which could take 20 years to treat all of the affected soils.

Additionally we are not positive what layout we have ended up with in our cane fields across the industry as a result of this conversion to flat lands i.e. will it have the shape to allow for the high rainfall runoff necessary to prevent water lodging on top of the beds, and will it be conducive to allowing the cane fields to drain to a depth of at least one foot to allow for the proliferation of a proper root system to allow for better yields. A poor root system will not yield a heavy growth of canes above ground. Estate by estate will have to tell us how much conversions they have done, how they have converted it and what the yield of the plant cane cycle was after conversion when compared to before the conversion.

Also we know that some of the benefits of flood fallowing is to give structure and tilth to the soil aggregates, and to flush out the acids, but under no circumstances is it the full answer, it is only part of it and so we must be cautious in how we address this problem and not underestimate the complexity of the mess this massive conversion has left us in. Also it is inevitable that the quality of land preparation must improve, fertilizer and weedicides etc must be applied on time to allow for proper growth. i.e. a complete turnaround by implementing proper field husbandry practices. And now that we have flat lands, have we embarked on a mechanised system of applying fertiliser? doing inter row tillage between ratoons to mould up the canes and improve drainage, to do root stubble shaving to guarantee better regrowth after harvesting etc?  These will be necessary to return us to having cane in the fields instead of Mr.  Paul Bhim’s famous cry there are “no canes in the fields!”

We cannot depend on trials done in the 1930’s to give us the answer to the problems of today since their genesis is so different, one from overworking the soil over centuries and one from exposing a significant amount of unfertile subsoil in the effort to convert the cambered fields to flatlands for mechanisation, so trials should be conducted with the necessary chemical and physical analysis of the soils before and after 6 months of flood fallowing to give us answers. Also we need to know what level of limestone we need to apply to make the soils less acid and we have to be sure that the layout we have converted to is workable, and drains well enough to support a good level of growth and therefore yields. In Guyana fallowing with legumes was not the preferred method of “resting” the land since flood fallowing is so much cheaper and certainly yields far more benefits, so for the time being I would not in fact consider it a proper alternative to flooding. And Mr. Chand must understand that since this is a national problem, anyone found blowing a flood fallow field before 6 months will be guilty of a felony and imprisoned. A lot of our estates gave up the practice of flood fallowing since the workers themselves living in the villages surrounding the estates would deliberately blow the flooded fields at three or four months to catch the fish growing in them.

Finally I see in the newspaper that there is first harvesting and then ratoon harvesting, I have never heard of this, we reap plants and we reap ratoons and since our replant programme is 20% of the total cultivation, our system visualises the reaping of plant canes and 4 ratoons as dictated by policy, I don’t know where this first harvest comes from!!  After the 4th ratoon we then abandon the fields plough them and start over again with plant fields.

Yours faithfully,
Tony Vieira      

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