Effect of Soil Micro-Relief of a Louisiana Bank System of Field Drainage After Conversion from the Cambered Bed System on Sugar Cane

In the Caribbean, sugar cane (Saccharum officinarum L.) fields are being converted from Cambered Beds to Louisiana Banks to facilitate mechanization. After conversion the fields often subside particularly in the areas where former drains were located. This subsidence influences field drainage, soil water relations, and sugar yields. The effect of soil micro-relief on sugar cane growing in the field on Louisiana Banks after conversion from Cambered Beds was studied during the wet season in Trinidad. Three types of topographies depression, elevated, and sloping areas occurring within a field of the soil type aquic eutropepts, were selected for study. Areas of soil depression caused mainly by soil subsidence after conversion were found to have significantly higher soil moisture than areas of elevations and were also observed to have ponding water for continual periods during the course of the experiment. The nutrient and moisture levels of the top visible dewlap leaf of 21-week-old sugar cane, stalk growth, juice quality, and final yields of sugar cane and sugar measured on plots on the three topographies were used as indices of sugar cane performance. These parameters were found to be significantly affected by areas of soil depressions in the field. Only juice quality was favorably affected during the wet season by the areas of soil depression, as flooding caused premature ripening of canes. This better juice quality was not maintained as the soil dried out and there was no significant difference in juice quality at harvest. Losses in sugar cane and sugar yields from areas of soil depression compared with elevated and sloping areas varied between 41 and 47%. It is therefore recommended that allowances be made for soil subsidence and that more precise grading and land smoothing operations be carried out when fields are converted from Cambered Beds to Louisiana Banks.