| || || Ram, Ashween Nischal.|
| || || A study of soil loss and sugar content in sugracane (Saccharum officinarum cv. Naidiri) on a sloping farm in Fiji|
Author:Ram, Ashween Nischal.
Institution: University of the South Pacific.
Call No.: Pac SB 229 .F5 R35 2006
Copyright:Under 10% of this thesis may be copied without the authors written permission
Abstract: The growing of sugarcane on sloping land receiving high intensity rainfall causes extensive soil erosion in Fiji. This soil loss and accompanying declining cane yields on undulating terrain are of major concern to the Fijian sugar industry. In recent years the growers have not only abandoned best management practices to conserve soil but they have also uprooted the border crop vetiver grass thatwas planted at the time of expansion of the cane belt. This to a large extent has accelerated the loss of top soil and thus soil degradation causing, with the burning of trash, the yield to decline even more rapidly. As quantitative data on erosion from field plots are scanty in Fiji, an experiment was initiated on a sloping cane farm (8o slope) to determine soil loss under different management practices and impact on the cane yield of the plant cane and of ratoon crops. Significant (P<0.05) responses in cane and sugar yields of the plant cane crop were found but this was probably due to the increased length of planting within a treatment-plot rather than best management practices used. In ratoons, no significant response to the best management practices adopted was found. However, in plots in which trash wasconserved and cane planted across the slope produced higher (>80 tcha-1) cane yield compared to other three treatments with no trash (T 1-cane planted across slope, T 2-cane planted uphill and downhill, T 3-cane planted across slope with vetiver hedgerow) . The retention of trash and cane planted across the slope would earn the grower an additional F$150-$400 and F$700-$1000 in the first and second ratoon crop respectively. Soil loss was largely affected by the different planting strategies associated with the conservation practices. Trash acted as buffer under high intensity rain with the result that only 153 and 221 kg soil ha-1yr-1 were eroded in the first and second ratoon crops, respectively. Where the sugar cane was planted uphill and downhill soil losses were 16 376, 259 and 2274 kgha-1yr-1, in plant cane and in the two succeeding ratoon crops, respectively. The very low soil loss in the first ratoon crop could be attributed to the drought conditions prevailing that year. The annual rainfall for study period (2001-2004) was 2140, 1007 and 2351 mm for plant cane crop and ratoon crops being 92, 43 and 102 % of the 117 years long-term mean. The top soil properties including pH, organic matter (OM), available P and exchangeable bases monitored after harvest of successive crops indicated that changes could generally be related to a change in organic matter (decrease) and associated ion exchange properties with increasing period of cultivation. Treatments 1, 2 and 3 were affected more than the trash retained plot. Such was the case that organic matter decreased by 33 % where cane was planted uphill and downhill from the time of initial sampling to final harvest. As observed during the study trash mulch reduced weed infestation, increased water retention in the root zone for healthy plant growth and provided better anchorage in regards to cane lodging compared to other plots. In view of the above, growers will realize the benefit in terms of zero tillage, spot spraying compared to broad application of herbicides, harvesting of green cane, improved soil fertility and sustained production level.Planting sugar cane across slope and conserving trash mulch therefore reduces soil erosion and with increasing period of cultivation will sustain cane production to provide stable economic return to the farmers. This practice is environmentally friendly and cost effective.