Effects of sugar cane production practices on soil quality in Mauritius
| MSI07P4281 | |
| Ng Cheong, L. R. | |
| Department of Soil, Crop and Climate Sciences, Faculty of Natural and Agricultural Sciences, University of Free State, Bloemfontein, South Africa | |
| Effects of sugar cane production practices on soil quality in Mauritius | |
| Thesis, PhD | |
| thesis | |
| 2007 | |
| 193 p.: 68 figs, 8 tbls, 3 appen. | |
| en | |
| En | |
| Sugar cane is the most important crop on the Indian Ocean island of Mauritius, covering some 85 per cent of its cultivated area. In spite of the progress in agronomic practices and development of better sugar cane varieties, no apparent gain has been observed in sugar cane productivity over the last twenty years. This situation has raised the question as to whether the soils of Mauritius were not subject to a decline in quality, a phenomenon observed elsewhere on account of sugar cane monocropping. In this context, a study was done to establish whether or not sugar cane production, and the adoption of mechanized practices, were impacting negatively on soil quality, with special attention being devoted to any temporal effect. This study was conducted between 2002 and 2006 on five sugar estates representing the five major soil groups of Mauritius, namely the P, L, H, B and F groups. To assess the effects of sugar cane cropping on soil quality, pristine soils were compared with sugar cane soils not subjected to derocking and/or land grading. The latter were then compared to sugar cane soils where such land preparation practices had been implemented to assess the effects of adopting mechanized practices. For temporal effects, older cane soils (> 50 years) were compared to younger cane soils (< 25 years) in the P and L groups, and early mechanized soils (> 10 years) were compared to recently mechanized soils (< 3 years) in the P group only. The soil quality parameters that were determined were biological - organic matter and microbial biomass; chemical - pH, cation exchange capacity and exchangeable bases; and physical - particle size distribution, aggregate size distribution and stability to water, bulk density, plant available water, and stabilized water infiltration rate. Sugar cane cropping had both positive and negative effects on soil quality. These effects were associated with cultural practices, mainly tillage, organic amendments, fertilization, and trash management. Some of these differed according to climate, and therefore led to contrasting results. Topsoil organic matter generally decreased with cropping, probably because of exposure to accelerated decomposition following tillage. Subsoil organic matter increased since tillage also produced mixing of topsoil with subsoil. Topsoil microbial biomass decreased with sugar cane cropping for less material was available for decomposition. The higher subsoil organic matter content had a positive effect on aggregate stability. Addition of organic amendments to the soil generally improved pH, exchangeable bases and base saturation. Acidification also occurred in one instance, probably because of nitrogenous fertilizers. Fertilization increased yields and this led to a higher return of organic matter to the soil. Trash management at harvest played an important role in soil quality. Pre-harvest trash burning lowered the return of carbonaceous material to the soil, whereas trash conservation under green cane harvesting had an enhancing effect. The adoption of mechanized practices did not affect soil chemical quality. Soil organic matter content decreased following mechanization in the dry zones as a result of increased soil disturbance. The most important effects of the adoption of mechanized practices were on soil physical quality with compaction occurring in the topsoil as a result of mechanized harvesting. Water infiltration rate declined because of reduced topsoil macro-porosity, while plant available water increased. Soil quality was not systematically aggraded or degraded under long-term cropping in the sub-humid soils of Mauritius, and changes were mainly small and variable. However, soil quality declined with time after the adoption of mechanized practices as large amounts of amendments were initially added to the soil and subsequently allowed to be depleted. The impact of adopting mechanized practices on soil physical quality was observed right from the onset and did not evolve with time. Soil quality can be enhanced by rebuilding topsoil organic matter levels through trash retention, addition of large amounts of organic wastes and green manuring. The best strategy to combat compaction is prevention, via the use of low-pressure tyres, combined field operations and controlled traffic paths. | |
| sugarcane soils soil quality organic matter mechanization compaction microbial biomass pH cation exchange capacity soil physical properties trash management | |
| Mauritius | |
| Sugarcane: Soils and plant nutrition | |
| Soils | |
| 2007-08-24 | |
| en | |
| LIB | |
| CAT | |
| 1 | |
| IRRIG |