AN ECONOMIC CULTIVATION SYSTEM FOR LARGE SCALE -CANE PRODUCTION

Transcription

1 Agricultural Engineering AN ECONOMIC CULTIVATION SYSTEM FOR LARGE SCALE -CANE PRODUCTION S.W.D. Baxter Massey-Ferguson (Australia) Ltd. Cane Equipment Division, Bundaberg, Queensland, Australia ABSTRACT Cultivation of cane fields is necessary with mechanical cultivation, to aerate the soil and shape the land to enable harvesters to work efficiently. Much cultivation is done with tractors that could handle larger implements that are attached to them. Suitable implements, and the economics of various tractor power ratings and implement widths, are discussed. INTRODUCTION As the use of mechanical harvesters becomes more widespread, so does mechanical cultivation of cane fields - often in situations where cultivation has not previously bee11 practiced after initial establishment of the crop. Much of this cultivation is still done with single row implements, but attached to tractors of 60 kw and higher, that could handle bigger implements capable of covering a larger area per hour. Furthermore, even larger tractors are now available presenting even greater opportunities for economies of scale. In view of the world-wide drift of labour from rural areas and the ever increasing cost of labour, these larger tractors must come into increasing use to enable producers to grow more sugar with fewer people. Table I shows the theoretical cost of cultivating with tractors of increasing power allowing 40 hp (29.8 kw) to cultivate one row at 1.5 metre spacing at 5.5 kph, using tractors, implements and operators at costs shown in Table 11. All quotations are in US$. A power rating of 40 hp per row is generous and is suitable for heavy cultivation such as subsoiling. In practice, different operations have different power requirements and an 80 hp tractor that will subsoil 2 rows will comfortably interow cultivate and fertilise 3 rows in the same soil. A tractor of 80 hp will also handle a-5 row trash rake in most firm soil conditions. While Table I shows a cost disadvantage to the very high powered tractors in the cultivation tasks listed, it must be appreciated that they would, in practice, travel faster than a lower powered tractor in a particular soil with the same width implement, thus reducing their per ha cost. Furthermore, the high power units show real cost benefits in heavy work such as primary cultivation. B ' (%+

2 AGRICULTURAL ENGINEERING

3 S.W.D. BAXTER 2049 It should be noted that 2 and 4 row complete cultivation (cultivating both sides of each row) requires special row crop tractors with wide rear axles. One, 3 and 5 complete rows can be cultivated by standard 4 wheeled tractors, as can 1 complete and 2 halves, or 3 complete and 2 halves. Five row cultivation requires fields to be thoroughly levelled and row spacing to be precisely maintained. Three row cultivation is not quite so demanding and suits the hp tractors that are in common use on cane plantations. In consequence this paper discusses a group of implements suited to this power, and to pre harvest and/or post harvest burning of cane trash. TABLE 11. Hourly operating cost of tractors and implements. US$. Capital cost1' Cost per o~er- ating hour2' Tractors 200hp 4 56, representative Australian prices IY mid ' for detail see Table 3. Implements Trash rake - implement per row of 1.5 m 0.14 Subsoiler n II II II 0.24 Cultivator !I n!!!! 0.38 Cost per oper- ating hour per row 2. Operator Cost $5.00 per hour plus 40% fringe cost

4 AGRICULTURAL ENGINEERING TABLE 111. Tractor running cost calculations. Based on total life of 10,500 hours in 7 years ie 1,500 hrs per annum. Tractor hp Capital cost US$ 6,000 14,000 24,000 35,000 56,000 Fixed costs per annum Depreciation 857 2,057 3,428 Interest at 10% on 50% capital ,200 Insurance, registration and housing at 1.5% capital Total fixed costs 1,247 2,993 Running costs per annum Parts, service and maintenance at 100% capital 857 2,057 3,428 5,028 8,000 Fuel (litres per hr) at 10 cents per litre (9)1,350 (14)2,100 (23)3,450 (3114,650 (40)6,000 Oil (litres per annuml at 75 cents per litre (90167 (135)101 (180)135 (225)168 (270)202 Total running costs 2,264 4,258 7,013 9,846 14,202 Total annual cost 3,511 7,251 12,001, 17,162 25,842 Cost per hour

5 S.W.D., BAXTER TABLE 111. (contd). Implement running cost calculations. Based on total life of 5,000 hours in 5 years ie 1,000 hrs per annum. Implement No Capital cost - per row of 1.5 m Fixed costs Depreciation Interest at 10% on 50% capital Insurance and housing at 1.5% capital Total fixed costs Running cost Parts, service and maintenance at 100% capital 6 o Total annual cost cost per hour - per row DISCUSSION To be most economic a system should include the least possible number of operations. Ricaudl found no significant difference in yield under Louisiana conditions in plant and ratoon cane, in fields that. received a broadcast application of long term residual herbicide, and and 6 cultivations, so long as heavy infestation of johnson grass was not present.,, King2 reported that, under Australian conditions, too frequent cultivation of the soil may be harmful to soil structure. The minimum appears to be: A. In the plant crop 1. two or three passes of a cultiva$ng/fertilizing implement to-fill in the furrows. - J'

6 2052 AGRICULTURAL ENGINEERING 2. form a ridge along the cane rows. 3, destroy weeds in the interow space. 4. level the interow space and ridge tops to establish correct conditions for the harvester. 5. apply fertiliser to the root zone. 6, apply a pre emergent herbicidc at final cultivation to control weed growth until the crop canopies. It appears possible to fill the plant cane furrow and form a 10 cm high ridge for dry land culture in 2 passes. A higher, 15 to 20 cm ridge for flood irrigation culture can generally be formed in 3 passes. Fertilizer should be placed about 10 cm deep in the soil and close to the root zone for rapid availability. If applied when cane leaves have reached about 60 cm in height, it is safest to apply at 5 to 8 cm only and about 45 cm from the row centre, to avoid root damage. Herbicide spray equipment can be attached to- cultivation implements, or special units may be used for this purpose only. The latter method has the advantage of requiring fewer operators with the necessary, specialised knowledge and fewer supply vehicles - a decided advantage in large scale operations. B. In the ratoon crop 1. a trash raking operation immediately after harvest to gather the trash residue into windrows, in which it may be burned. This clears the land for subsequent cultivation. 2. one pass of a subsoiling implement in each interow space to aerate the soil, aid water penetration and combat the possible compacting effect of cultivation tractor, harvester, and transport wheels. 3. one or 2 passes of a cultivating/fertilising implement to cultivate and level the interow space. 4. reform ridges to suit the harvester at next harvest. 5. apply fertilizer in the soil close to the root zone. 6. off bar wide stools if necessary in later ratoons. 7. apply pre-emergent herbicide to control weed growth until the crop canopies. One or two such cultivations should reshape the land for the subsequent harvest so long as herbicides are used to control weed growth. ' To carry out these operations, 3 implements are necessary.

7 S.W.D. BAXTER The trash rake for operation B 1. This is a light duty, high speed operation and 5 rows can generally be covered by an hp tractor. In 1.5 m row spacing, the implement would require to be 7.80 m wide. This would give 15 cm overlap in the interow space between 2nd and 3rd rows out from the tractor to ensure that the interow is thoroughly cleaned of trash. (See Fig. 1.) FIGURE 1. Implement No. 1. The implement is based on a suitable toolbar. Two rows of tines at 7.6 cm spacing give cleanest raking. Tines are free to lift a minimum of 5 cm and adjustable bars that limit this are set to allow those that run on the ridge sides and tops to lift considerably more. A quick lift hitch makes the rake dump its load of trash quickly when the linkage arms of the tractor are lifted. The finger wheel type hay rake can also be used for this purpose and is possibly faster than the trash rake. Implement 2 I The subsoiler for operation B 2. This must be a heavy duty tool and, since it is used immediately after harvest, when soil may be dry, and it is necessary to cultivate to approximately 30 cm depth, 2 rows is the maximum that an hp tractor can be expected to handle. It may handle 3 in light, loam soils. Tractors hauling cultivation implements tend to compact the interow centre. Tractors and in-field tfailers tend to compact a zone close to the ridges, as they are driven olf-centre of<,the ridges to position themselves,"?,

8 2054 AGRICULTURAL ENGINEERING correctly under harvester elevators. Harvester wheels operate close to ridges and sometimes further contribute to compaction of this zone. Thus, when mechanical harvesters are used, it is not uncommon to find a compaction profile as shown in Fig. 2. FIGURE 2. Compaction profile sometimes found in mechanised fields In consideration of this the author believes that the most thorough soil aeration and decompacting effect will be obtained with 2 tines per interow spaced as per Fig. 3. This arrangement attends to the 2 interow areas that have carried the most traffic. FIGURE 3. Implement No. 2.

9 S.W.D. BAXTER 2055 Agronomists should establish the subsoiling depth to be achieved. However, work by Maclean3 suggests that this should be to around 30 cm - at least in the soils in the Goondi district of Queensland. The implement may be based on a heavy x 10.6 cm toolbar 2.20 m long. The 4 tines may be 7.6 x 3.7 cm curved type or 15.0 x 3.2 cm straight type. Impiement 3 The cultivating/fertilizing tool for operations A 1. to 6. and B 3. to 7. This can cover 3 cane rows, with 2 complete interows and 2 half interows as shown in Fig. 4. It would be based on a suitable toolbar 4.5 m long. It would be fitted with 5 coil tines per interow plus 3 at each outer end to cultivate the 2 half interows, the total being 16 coil tines 3.2 x 3.2 cm. Those adjacent to ridges would be fitted with 6.2 cm wide reversible points. All others would be fitted with 15 cm points. They would be fitted in a staggered pattern. For plant cane furrow filling and ratoon cane ridge reforming a pair of 45 cm diameter discs are fitted to each row making a total of 6. Turned to throw outwards, the same discs can be used to off bar old stools in ratoon cane. The disc attaching brackets may remain on the toolbar, the discs being fitted into them when necessary. FIGURE 4. Implement No. 3.

10 2056 AGRICULTURAL ENGINEERING Hoppers for granulated fertilizer may be fitted to the toolbar or to the tractor above the rear axle. In either case the fertilizer is introduced to the soil through rubber or plastic hoses that feed into steel tubes attached to the rear of the tines adjacent to cane rows. If these implements are fitted to a 3 row toolbar the linkage lift capability of the tractor may require to be in excess of 2,000 kg. If liquid fertilizer is used, the tanks are normally arranged on the tractor, and a pump directs the fertilizer to injectors attached to the tines adjacent to cane rows. A minimum cultivation system would indicate a once only application of fertilizer. Bieske4 found no difference in yield of cane resulting from one or two applications of nitrogen in southern Queensland soils. It is also generally accepted in Queensland that, except in the lightest sand soils, one application of fertilizer as soon as possible after harvest gives results equal to those of multiple applications. Once fitted, fertilizer hoppers may remain on the jmplempnt. In large scale operations it should be possible to program district work to make full use of implement 3 with and without the granulated fertilizer hopper. Implement 3 may be fitted with multiple discs instead of coil tines. However, the author prefers the latter for preparing fields to be mechanically barvested because: a) with implements fitted with gangs of multiple discs, it is virtually impossible to avoid building ridges higher than desirable, with the resultant danger of rapid drying out in dry weather and possible effect on yield. b) it is very difficult to achieve the ideal flat topped, sloping sided, narrow ridge and flat interow as shown in Fig. 2. Multiple disc gangs tend to form banks and furrows, rather than ridges and flat interows. c) while the author cannot refer to studies that evaluate the relative costs, it is generally held by practical farmers that the cost of tine points and their retaining bolts, plus some allowance for tine breakage, is cheaper than that for discs, bearings and lubricant on comparable disc implements. Arched toolbars are not discussed. Traditionally used for late cultivation and fertilizing they have no place in a minimum cultivation program so long as the last cultivation is carried out before the crop reaches a height that would cause the straight toolbar to damage the cane. This is when leaf height exceeds about 60 cm, which is generally as late as desirable if damage to the root zone is to be avoided. An important point on implements in general is that everything possible should be welded, to reduce maintenance.

11 S.W.D. BAXTER 2057 ' REFERENCES 1. Ricaud, R. (1973). Effects of Varying Numbers of Cultivation on Sugarcane Production in Louisiana. ISSCT, King, N.J., Mungomery, R.W. and Hughes, C.G. Manual of Cane Growing (revised edition, 1965) Angus & Robertson Ltd. Sydney. 375 p. 3. Maclean, N.R. Long Term Effects on Sugar Cane Production of some Physical and Chemical Properties of Soils in the Goondi Mill Area. QSSCT Bieske, G.C. Split Applications of Nitrogen Fertilizers on Ratoon Crops. QSSCT UN SISTEMA DE CULTIVO ECONOMIC0 PARA PRODUCCION DE CANA EN LARGA ESCALA S.W.D. Baxter RESUMEN El cultivo de campos de cafia con cultivadoras mecanicas es necesario, para aerear el suelo, ajustar la tierra y permitir un trabajo eficiente de las cosechadoras. Se efectua mucho cultivo con tractores que pueden manipular implementos grandes acoplados. Se discute sobre 10s implementos apropiados y sobre la economia de varios grados de fuerza de tractor y ancho de 10s implementos.