Sugarcane, Saccharum officinarum L., is grown under diverse agro-climatic conditions around the world. It is a renewable and natural agricultural resource that provides sugar, besides biofuel, fibre and fertilizer. Out of the total white crystal sugar production, approximately 70% comes from sugarcane and 30% from sugar beet. According to FAO, 2011 report, worldwide sugarcane occupies an area of 25.44 million ha with a total production of 1794 million metric tons. Out of 121 sugarcane producing countries, Brazil, India, China, Thailand, Pakistan, Mexico, Cuba, Columbia, Australia, USA, Philippines,

 

South Africa, Argentina, Myanmar and Bangladesh collectively represent 86% of the area and 87% of production. Brazil has the highest area (9.601 million ha), while Australia has the highest productivity (81.7 tons/ha).

 

India, the second largest sugarcane producing country after Brazil, cultivated sugarcane in 5.09 million ha area, which is much less compared to area under cereals, pulses and oilseeds, with a production of 357.67 Million Tones in the year 2011 to 2012. Sugarcane is grown mainly in the states of Maharashtra, Karnataka, Gujarat, Tamil Nadu, Uttar Pradesh, Punjab, Haryana and Bihar. Among these, Uttar Pradesh alone occupies about 43% of the total area under sugarcane cultivation dominating in production but in terms of productivity, Tamil Nadu leads with 104 tons/ha followed by Karnataka (90 tons/ha) and Maharashtra (83 tons/ha) which is higher than the national average productivity of 68.6 tons/ha. In the state of Uttarakhand it is grown mainly in its Tarai region (foot hills) where its production has gone down to 5.05 million tonnes in year 2010 compared to 7.34 million tonnes in year 2001. Highest sugarcane production of 7.68 million tonnes was registered during the year 2008.

 

It has been observed that the productivity of sugarcane, national average, is stagnating around 65-70 tons/ha for the last about 2 decades. Non implementation of package of practices and shortage of agricultural labour to undertake various cultural practices in time including poor weed management are some of the reasons responsible for low sugarcane yield. Therefore, there is a need to focus on other means including proper weed management for improving the production and productivity. It is reported that the yield loss caused by weeds may range from 15 to 75%  depending upon its nature and intensity (Olaoye and Adekanye, 2006; Hasanuzzaman et al., 2009). The initial 90 to 120 days period of crop growth is considered as most critical period of weed competition and therefore weed-free field condition during these days must be ensured for higher yield.

 

Manual weeding, which is a common practice including in Tarai region of Uttarakhand, provides almost a clean weed free field but is highly labour demanding operation. The labour requirement for weeding/ interculture operation alone ranges between 400 to 600 man-h/ha (Tajuddin, 1996; Singh and Panghal, 2012) which is the highest when compared to wheat and rice (Table 1). Also it is a slow, arduous and time consuming process leading to higher cost of production. Scarcity of agricultural labourers during the peak season makes this task more difficult. Because of this reason as well as concern over environmental degradation and a growing demand for organically produced food, mechanical method of weed control is gaining popularity over manual and chemical methods. It is very effective, eliminates drudgery involved in manual weeding, kills the weeds and also keeps the soil surface loose ensuring better soil aeration and water intake capacity. Most of the tractors owning farmers, in Tarai region of Uttarakhand state, are using cultivator and rotavator, by manipulating the tynes/blades spacing, to cope up with the shortage of labour for weeding operation in sugarcane. Also there has been an increasing interest in the use of rotary tillers (mechanical intra-row weeders) due to their availability in the area during the recent years for weeding operation in sugarcane crop. However, systematic data is not available in respect of these equipment for weeding operation in sugarcane. The present study was, therefore, undertaken to compare the field performance of a rotary tiller, cultivator and rotavator for weeding operation in sugarcane crop along with traditional method including their economics.

 

 

 

Description of equipment used

 

Three types of equipment namely self propelled rotary tiller (3.5 kW petrol engine operated), tractor drawn cultivator and rotavator were used for this study. The rotary tiller has a working width of 50 cm and only one row was covered during its operation. The second equipment was a tractor mounted type spring loaded 11 tine cultivator with overall width of 230 cm. Out of 11 tines, 5 tines were removed to adjust the cultivator within the row spacing of sugarcane. Three rows of sugarcane were covered at a time during single pass of this implement. The third equipment was a tractor mounted type rotavator having a work width of 200 cm. It had 8 flanges arranged on a rotor shaft with four L-shaped blades on each flange. Out of 8 flanges, 5 flanges were removed to adjust the rotavator to operate in between the rows of sugarcane. Three rows of sugarcane were covered at a time during single pass of this rotavator. Table 2 shows the technical details of the equipment used for the experiment. Manual method of weeding, a very common practice, was used as control for this experiment. The common tool used for manual weeding is Kassi which is a long handled spade with 20 cm wide blade. It is commonly used in upright posture by the labourers. Figure 1 shows the different equipment in weeding operation.

 

 

 

 

 

 

Weeding efficiency

 

The weeding efficiency was determined by considering the weight of weeds before and after weeding operation. The weeding efficiency for single pass and double pass of rotary tiller was found highest followed by treatment T₃ and T₂ (Table 3). Weeding efficiency for double pass of rotary tiller was found higher by 5% than its single pass. The higher soil cutting ability of rotary tiller and rotavator contributed to higher weeding efficiency where as the reversible shovel does not provide better soil cutting leading to lower weeding efficiency. Weeding efficiency of manual weeding method (T₄) was observed highest among all the treatments which may be due to the fact that more precisely intra row area could be covered in manual method of weeding. Statistical analysis (Table 4) indicated that the weeding efficiency for different weeding methods varied significantly at 5% level of significance except treatments T_1S and T₃.

 

 

 

Plant damage

 

The plant damage for single pass and double pass of rotary tiller was found 1.11 and 1.83% (Table 3). The plant damage for treatment T_1D (double pass of rotary tiller) was found to increase by about 0.72% compared to treatment T_1S (single pass of rotary tiller). This may be due to the increase in depth of operation causing more uprooting of the plants. The plant damage, on an average, for other weeding methods viz manual weeding, rotavator and cultivator was found 0.56, 2.63 and 3.67% respectively. The lowest plant damage was observed in case of manual weeding that may be because of shallow depth of operation and care taken during the weeding operation. Among the mechanical methods of weeding, single pass of rotary tiller showed minimum plant damage. The plant damage was found statistically significant for all the weeding methods (Table 4).

 

Field capacity and field efficiency

 

Actual field capacity for different weeding methods was determined which showed higher field capacity for treatment T₂ followed by treatments T₃ and T₁ (Table 3). The higher field capacity for treatment T2 was due to more width of operation of cultivator. The field capacity of rotary tiller in double pass (T_1D) was found 35% higher when compared with its single pass which may be due to higher speed of operation. The field capacity for different weeding methods was found statistically significant (Table 4). The field efficiency (Table 3) for single pass of rotary tiller was found to vary in between 96.69 to 97.18% with an average of 96.93% which was found slightly less (94.1%) for double pass of the tiller. The average field efficiency of weeding by rotavator and cultivator was 87.08 and 80.92% respectively.

 

Fuel consumption

 

The fuel consumption for single pass of rotary tiller (T_1S) was found 0.58 l/h and little less, 0.53 l/h, for its double pass operation (T_1D). The fuel consumption for other treatment T₂ and T₃ (weeding by cultivator and rotavator) was found as 3.19 and 2.87 l/h respectively (Table 5). The statistical result indicated that the fuel consumption for different weeding methods varied significantly at 5% level of significance (Table 4). 

 

 

Clod size and bulk density

 

The clod mean weight diameter for single and double pass of rotary tiller was found as 7.67 mm and 4.01 mm respectively (Table 5). The reduction in clod size, in case of double pass, was about 47.7% which may be due to similarly clod size in treatment T₂ and T₄ was also comparable. However, statistical analysis showed that clod size varied significantly, at 5%, for all the weeding methods (Table 4).

 

The average bulk density (Table 5) for treatment T_1S and T_1D was found as 1.27 and 1.26 g/cc. The reduction in bulk density values, in rotary tiller, was observed nearly same. The average bulk density for treatments T₂, T₃ and T₄ was found as 1.29, 1.23 and 1.24 g/cc respectively. The decrease in bulk density was observed higher (8.05%) in case of treatment T₃ and the same was observed less (3.88%) in case of weeding by cultivator (T₂) when compared with other treatments. The bulk density value for treatment T₂ was found significantly higher than other treatments. The change in bulk density values for all other treatments except T₂ was found insignificant (Table 4).

 

Moisture content

 

Soil moisture content was determined for each test plot and the results have been presented in Table 5. The average initial soil moisture content of the experimental plots was observed as 16.68%. The final soil moisture content was observed to reduce for all the treatments as compared to initial value, however, the moisture loss was observed more in treatments T_1D and T₄ followed by T₂, T₃ and T_1S. In treatments T₂ and T₄ the moisture loss was observed to be almost similar that may be due to bigger size of clods providing more surface area for moisture evaporation.

 

Cost analysis

 

Cost of weeding operation for different treatments was determined using the data presented in Table 6. The detailed analysis is presented in Table 7 which showed least expenditure (INR 374.37 per ha) for treatment T₂ followed by T₃ (INR 507.27 per ha), T₁ (INR 1186.18 per ha). Highest expenditure of INR 13194.55 per ha was found incase of T₄ that is, manual method of weeding. The minimum cost of weeding in T₂ is due to the higher field capacity of cultivator as compared to weeding by other methods. Manual weeding was found to be expensive which is due to very less field coverage per unit of time. Similarly the cost reduction over the conventional method was found highest (97.16%) in T₂ followed by T₃ (96.16%) and T₁ (91.01%).

 

 

 

Among the mechanical methods, treatment T_1D and T_1S (weeding by rotary tiller - one and two pass) was found more effective compared to treatments T₂ (weeding by cultivator) and T₃ (weeding by rotavator) based on higher weeding efficiency and minimum plant damage. Treatment T_1S and T₃ was found equally effective as far as weeding efficiency is concern. The cost of weeding, when compared  with  conventional  method,  reduced  in T2, T3 and T1 by 97.16, 96.16 and 91.01% respectively. The conventional method of weeding was found expensive compared to mechanical methods. The use of rotary tiller, among the mechanical methods, can be recommended to the farmers for efficient weed management even though the cost of operation is high. The advantage is that as it covers single row of the crop it can be used even at a later stage when plant grows tall enough. The use of cultivator and rotavator is not feasible at later stage (beyond 120 days of crop) as it covers more than one row and the plant will get damage when the height of the plant is more than the toolbar height.

The authors have not declared any conflict of interest.