G. Platford & R.S. Bond

Transcription

1 G. Platford & R.S. Bond ENVRONMENTAL MANAGEMENT PLAN FOR THE SOUTH AFRCAN SUGAR rnustry G. Platford & R.S. Bond South African Sugar Association, Expt. Station, Mount Edgecombe ABSTRACT Damage to the sugarcane environment is caused by uncontrolled surface runoff from field areas, budg of sugarcane prior to harvest, cultivation of some wetlands, stream bank degradation, alien plants, cane spillage and factory effluents. This can be aggravated by poor soils, steep topography and heavy rainfall. Movement of water through the soil and sudace runoff were investigated, and the programs are outlined. An industrial plan to reduce the damage was prepared, and these recommendations to protect the industry's natural resources became the Environment Management Plan (EMP). The EMP and its application are described. Local environment committees were formed to enable the effective implementation of the EMP. Keywords: Sugarcane, environmental management, South Africa. NTRODUCTON Conditions in most of the South African' sugarcane industry are not suited to maximum sugar production. Soils are often shallow and on steep slopes. Tlie average annual rainfall (1000 mm) is highly variable in intensity and distribution with periodic floods and prolonged droughts. Ambient temperatures and humidity levels are well below those that what would give the highest crop yields. n the northern areas where temperatures are more suitable for maximum economic growth, rainfall is low and water requirements must be provided by irrigation. PROBLEMS AND SSUES Erodible soils Over half the soils of the SA sugar ndustry can be termed highly erodible. As much of the cane is grown on relatively steep slopes, high-intensity rainfall can lead to large amounts of soil being carried away in the &off water. The advent of chemical cane killers makes it possible to avoid cultivating the soil before replanting and is especially important on slopes and soil types where it is hazardous to use a plow. Burning the cane before harvest is a practice that also aids soil erosion by removing a large part of the crop mulch. f the cane tops are left scattered in the field after burning, soil losses are reduced., Burning or trashing at harvest and air pollution The problems associated with burning can be grouped into five categories. m Reduced production. n some cases reduced yields occur following the increase in runoff and therefore a lower efficiency in effective use of rainfall. W Possible health risk from cane smoke. Results of studies in the USA have shown no correlation between respiratory diseases in field workers and cane burning (Jenkins 1994). n SA a survey undertaken by Terblanche (1993) showed that there was an increase in levels of atmospheric particulate matter during the cane harvest season and a link with cane burning was inferred. 8 Disruptions of power supplies. Burning cane under the power lines can cause interruptions in the power supply, affecting both domestic and industrial users. 8 Nuisance of ash fallout. Several public campaigns to stop cane burning have been mounted by urban residents close to cane farms. 8 Traffic safety. Where the smoke from cane fires obstructs visibility on public roads, there is a hazard to traffic. During the harvesting season daily weather forecasts from the weather bureau are relayed to growers it1 sensitive areas to enable them to pilaxi burning so as to minimize inconvenience. Wetlands Cane has frequently been planted 011 bottom lands, ignoring their function in terms of flood abatement or filtration of stream water. Despite the high costs of drainage and die risk of periodic flooding, cu1ti;ation continues. Tlie South

2 Plenary Session: Environmental and Sustainability African Sugar Association (SASA) is committed to preserving and improving existing wetlands through sound management of all the catchment resources, control of runoff, stabilization of the drainage lines, and protection of stream banks and fivers. QUANTFYNG THE CHALLENGES The perennial nature of the cane crop and the production of large amounts of surface mulch cover protect the soil from most of the very heavy rain storms, which can occur in the cane-growing area. This makes the crop well adapted to the steep areas along the Natal coast where annual crops cannot be grown. Before high-powered equipment was available to till the ground, little damage was done to the soil as only small areas were replanted annually. As equipment became more powerful, larger areas were replanted and fields grew in size. At that time very little was known about the way to protect those new blocks, which were mostly on steep land. "Contour" banks, which had been used quite effectively for annual crops on flatland, were used. Very good meteorological data were available, but there was very little erosion or water-quality data prior to t was essential to acquire these figures so that recommendations for protection could be made. A research program was started in 1977 (Platford 1979) to measure soil and water losses. Research program Runoff plots and research catchments. The Universal Soil Loss Equation (USLE, Wischmeier & Smith 1978) was the basis for research projects in soil conservation. Five paired runoff plots were constructed and results from these showed that the major contribution to soil loss was when the crop was replanted (Table 1). A catchment project at La Mercy (Platford & Thomas 1982) was started to gather data from four small catchments of between 3-6 ha each. These were equipped with HL flumes to measure soil and water losses. nitially, the catchments were kept as cultivated bare fallows, but in 1984 they were planted to sugarcane. Different planting and crop management systems were used (Maher 1990). A summary of the results is given in Table 2. Rainfall simulation A rainfall simulator program was started in 1980 and soil losses determined (Haywood 1982). The expected high erodibility of coarse grained coastal sands, as calculated by a nomograph (Wischmeier et a1 1971), was not substantiated. After the initial work, trial work concentrated on establishing crop factors for reduced or minimum tillage. Soil loss modeling. Results from the research catchment work showed that accurate predictions of soil loss could be made using imported and locally developed soil loss models. Results from this research program has enabled the SASA Experiment Station to set the technical standards and recommendations for protecting resources in sugar areas. The Government's Dept. of Agriculture has accepted these guidelines. Development of the SASEX nomograph. Given the wide range of soil types and slope in the sugar industry, a set of recommendations was needed that could take account these differences. Recommendations for spacing of banks, designed by the Dept. of Agricultural Development for annual crops, were modified, and a nomograph (Fig. 1) was developed to allow for the variables of soil, slope, crop and management factors (Platford 1987). Soil conservation specifications obtained with the nomograph are designed to keep annual soil losses <20 t/ha/annum. The nomograph provides a means of integrating all the factors (i.e., tillage method, slope, soil erodibility index and whether the cane will be burned or trashed) that need to be considered when designing conservation plans for cane fields. Using the nomograph, the grower can select options that meet the requirements of the Conservation of Agricultural Resources Act (1983). Drainage lines and streams. The guidelines for the protection of stream banks and drainage lines have now been completed and approved in consultation with the Dept. of Agricultural Development and the Direetorate of Resource Conservation. For natural drainage lines, the limit line for cultivation is the bank height plus 3 m. Once the limit line has been set, the bank must be stabilized. f shaping is necessary, a 1: 1 gradient is established before planting with creeping grasses or suitable trees. Very often planting of suitable rhizomatous grasses is all that is needed to form a well-stabilized channel.

3 G. Platford & R.S. Bond TLLAGE 1 SOL LOSS Design - 20 l/ ha / onnum lor 1 20 yeor storm 1 APPLY TO SLOPES LESS PERCENT STRP PLANT OR NO STRP PLANT d,, 1 2 l r s s l ' VER~C~L NT'~R:A'N'~E?RE~S 1 8 i :? 1 7 l ~ l ~ l ~ l > ~ ~ ~ l 9 VERTCAL NTERVAL N METRES -TRASHED 1 i & s O it ~ k i 6 i i VERTCAL NTERVAL N MElRES SCATTEREO \\ 4 struc lops-- TURES NO STRP PLANT TERRACES REQURED Figure 1. Monograph developed from research data to determine field panel widths.

4 Table 1. Summary of annual water runoff and sediment losses from five sets of plots. Year Mt Edgecornbe CFS La Mercy Sbakaskraal Mtunzini Rain R.off Sed Rain R.off Sed Rain R.off Sed Rain R.off Sed Rain R.off Seed mm mm t/ha mm mm t/ha mm mm t/ha mm mm tlha mm mm tiha Table 2. Average losses from La Mercy catchments. Rainfall (mm) Runoff (mm) Avg soil loss (tlha) l Drought. Cyclones Demoina and inboia. Sept. floods.

5 ~ protection G. Platford & R. S. Bond The SASA Environment Management Plan After an extremely severe series of rain storms in 1987, industry leaders demanded adequate internal control of, environment issues affecting cane cultivation. Although initiated by the need to control stream bank and river line erosion, environment protection committees were formed in each of the sugar mill areas. These moves were approved by Government and ratified by the SASA Council. SASA drew up an Environment Management Plan (EMP) with i the stated mission to use its best endeavors to set an example of sound environment resource management and the of the sugar industry's natural resources. The plan saw a need to coordnmte all environmental efforts within tlie industry and win respect for the correct use of natural resources. Key issues defined were die need to conserve catchments within the industry, including all rivers, i stream banks and wetlands, asdwell as alien plant control, cane spillage and the need to minimize pollution caused by cane burning, factory emissions and pesticides. The EMP also saw the need to educate internal and external stakeholders about environmental issues that affect the ndustry and to monitor threats and opportunities arising from the industry's activities. mplementation of the EMP is primarily through the ndustry Environment Committees, whose activities are coordinated by SASA. However, every farmer, miller arid SASA staff member is encouraged to participate in the plan, aid SASA continues to develop strong contacts with environmentally active groups.,,,(~: 8, f DSCUSSON The uicr~asing conceni for all enviro~~~nent matters, not only soil and water conservation, requires a new approach to enviro~ment protection. Resource economics can play an important role in determining the responsibilities for envko~metit cotiservatio~l and how the process sliould be managed. Foresters, agriculturists, environmentalists and the life scientists can enumerate the benefits which emanate from the land; but a resource economist can assign values to diese and assess the costs-benefits. ~esourceconomics bridges the gap between life scientists and decision-makers by ascribing values to possible conservation options. Tlie land resource includes the soil, water, air, plants and animals. Tlie labor resource consists of mnanpower, entrepreneursllip and expertise. The finance resource is the capital required to run tlie system. Equity is required when slmrhig products froni tlie lmtural resources among all members of the comnmunity, aid it must consider both tlie present and future generations. Resources sliould be utilized, but regeneration encouraged. For everyone to slme in tllis h~lited supply of natural resources, it is essential that the e~iviro~me~ital protectloll plan be strictly implemented. This is the aun of SASA's EMP. REFERENCES Haywood, R.H. (1988). A comparison of soil aid water losses from conventional and minimum tillage replanting methods using a rainfall simulator. Proc S. Afr. Sug. Technol. Ass. 62: Jenkins, B.M. (1994). Atmospheric pollutant emission factors from open bun~ig of sugarcane by witid tunnel simulation. Report to the HSPA, Aiea, Hawaii. Maher, G.W. (1990). Phase two of die small catchment project at La Mercy. Proc S. Afr. Sug. Technol. Ass. 64: Platford, G.G. (1979). Research into soil and water losses from sugarcane fields. S. Aft. Sug. Technol. Ass. 53: Platford, G.G. (1987). A new approach to designing widths of panels in sugarcane fields. Proc S. Afr. Sug. Teclmol. ASS.:^^ Platford, G.G. & Thomas, C.T. (1982). The small catchent project at La Mercy. Proc S. Afr. Sug. Technol. Ass. 59: , Terblanche, P. (1993). Total suspended particulate levels ui tlie Canelands Valley. Report to SANACHEM, Canelands, Verulam, Natal. Wischmeier, W.H. & Smith, D.D. (1978). Predicting rainfall erosion losses - a guide to conservation planning. USDA, Agricultural Handbook 537, Wash. DC. Wischmeier, W.H., Johnson, C.B. & cross, B.V. (1971). A soil erodibility nomograph for farmland and construction sites. J. Soil Wat. Conserv. 26: '