In terms of global production, sugar cane (Saccharum officinarum L.) is the world’s primary sugar crop. Current production stands at 1450 million tons of cane from 22 million hectares worldwide. Brazil and India are the world's major sugar cane producing countries, accounting for nearly 60% of the global production.
In addition to its presence within the food industry, this crop is gaining enormous significance in the biofuel industry. Brazil, for example, uses 48% of its sugar cane production to produce ethanol, while the remainder is used for sugar production. In Asia, countries such as India, China, Thailand, Philippines and Pakistan have already drawn up ambitious plans to use sugar cane as a biofuel crop for ethanol production. Such a production will meet fuel mixture requirements such as E10 - where 10% of the fuel is ethanol and 90% is gasoline, among other fuel requirements (E5, E7, etc.).
Sugar cane is grown in more than a hundred countries under temperate, subtropical and tropical conditions. The sugar cane is basically a crop of tropical climates, with yields affected significantly by temperature, relative humidity and solar radiation. The optimum mean daily temperature range is 14 to 35°C. Likewise, relative humidity ranging between 55 – 85% at grand growth period favors stalk development. The optimal solar radiation requirement is 18 – 36 MJ/m2 (Total annual: 6350 MJ/m2). Stalk growth increases when daylight is in the range of 10 – 14 hours. Sugar cane can be grouped into three varieties: early, mid-late and late. Varieties resistant to several pests and diseases have also been developed in major sugar cane growing regions across the subtropical and tropical world.
Sugar cane requires a well-drained, well-aerated, porous soil with pH of 6.5. Compacted soils (> 1.6 to 1.7 g/cm3) affect root penetration, water and nutrient uptake. The crop is moderately sensitive to soil salinity. The planting pattern is dual or paired row and spacing adopted (1.4m + 0.4m) is 0.15m under drip irrigated conditions, while sowing depth is generally 10cm. The crop is grown by vegetative propagation and requires 40,000 two-bud1 or 30,000 three-bud setts2 per hectare in order to maintain a desired millable stalk population target of 130,000/ha.
The implementation of drip irrigation and fertigation in sugar cane has proved to be technically feasible and economically viable. In many diverse agro-ecological situations, drip irrigation registered higher yields (50 to 90 tons/ha), conservation of water (30 to 45%) and fertilizers (25 to 30%). Furthermore, drip irrigation accounts for the improvement in sucrose content compared to conventional furrow, overhead, dragline and center pivot sprinkler irrigation methods.
In Africa, under Swaziland conditions, subsurface drip irrigated sugar cane grown on 6715 ha for nine years (plant crop + 8 ratoon3 seasons), registered an average cane yield of 107 to 126 tons/ha and pol4 of 15.6 to 18.2 tons/ha. While the sucrose increase was 1.6 tons/ha/year, the accompanying results, in comparison to a dragline sprinkler system, were as follows: power conservation 4.6 kVA/ha/year, operations & maintenance conservation 140 USD/ha/year, water conservation 150mm/ha/year and an internal rate of return (IRR) of 29%.
For high yields, the seasonal crop water requirements for sugar cane crop were estimated at between 1100 to 1500 mm/ha under a range of climatic conditions and varying lengths of growing seasons (12 – 14 months), with a daily evapotranspiration rate of 4 to 7 mm/day. Using tensiometers in irrigation scheduling (25 – 60 centibars at different crop developmental stages) enables the efficient use of water, fertilizers and energy inputs.
Sugar cane is a heavy feeder of nutrients. Its root system is shallow and fibrous, therefore, fertigation is recommended for higher nutrient availability and use efficiency. The aim of the fertigation program is to bridge the gap between crop demand and supply. The nutrient requirements of drip irrigated sugar cane are relatively high: 250 to 300 kg/ha N, 80 to 100 kg/ha P2O5, 125 to 250 kg K2O per ha. The amounts of nutrients removed by sugar cane plants per ton of cane yield are as follows: 0.7 – 1.2 kg N, 0.4 – 0.8 kg P2O5, 1.8 – 2.5 kg K2O. Best management practices include earthing up, detrashing, propping, protection of crop from pests and diseases, need based weed management, crop logging, harvesting and post harvesting operations to minimize sugar losses.
- A bud is a developing part of a plant that will grow into a flower, new leaf or stem.
- A sett is a piece of cane stalk that contains roots and buds. When roots develop, they anchor the sett and provide food for the germination of the buds from which the cane stalk grows. In this way the stool is created and new roots develop.
- A ratoon is the cane that grows from buds remaining in the stubble left in the ground after a crop has been harvested. One plant usually grows three to four ratoon crops.
- A pol (polarisation) is a measure of the sucrose content of sugar. Sugar with 98 pol (or 98 degrees pol) contains about 98% sucrose.