PERFORMANCE OF CHOPPER HARVESTERS AND THEIR EFFECTS ON SOIL AND CROP AT BEAU CHAMP SUGAR ESTATE. V Rivière, C Marot, R Ng Cheong and E Jacquin

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1 PERFORMANCE OF CHOPPER HARVESTERS AND THEIR EFFECTS ON SOIL AND CROP AT BEAU CHAMP SUGAR ESTATE V Rivière, C Marot, R Ng Cheong and E Jacquin Mauritius Sugar Industry Research Institute ABSTRACT Beau Champ estate was affected by agricultural labour shortage at the end of the 1980 s. Two chopper ers were purchased and are presently ing about tonnes annually. Their performance are reviewed and discussed. Results of a trial set up to assess the effect of mechanized ing on soil and crop at Beau Champ are also discussed. Keywords: sugarcane, mechanisation,, chopper ers, yields, soil physical properties, compaction, dry bulk density, software INTRODUCTION After a first attempt in the mid 1970's, mechanical ing of sugar cane was once more introduced at Beau Champ Sugar in the early 1990's. Like many other estates at that period, Beau Champ was faced with an increase in the wages of agricultural labour and a shortage of seasonal labour normally hired for cane cutting. After having tried the two types of machines (whole-stalk and chopper er) belonging to a contractor, the choice was made to purchase a chopper er in Figure 1 Trend in chopper ing at Beau Champ Area ha Weight k tons Year 0 Land preparation to allow mechanization was carried out (mainly derocking and levelling) and the area suitable for mechanized ing was such that in 1995, a second chopper er was acquired. The amount of cane ed mechanically by chopper ers has increased regularly across the years to reach tonnes (24.3 % of the estate's total cane production) in 1998(Figure 1). The two main cane varieties ed mechanically are R 570 (34 %) and M 695/69 (33 %). This paper highlights the performance of the chopper er at Beau Champ and its effect on cane yield and soil physical properties. 39

2 HARVESTER PERFORMANCE As mechanical ing had just been introduced in the island, information on ing sites and parameters affecting er performance had to be gathered. Computer software, MECABASE, was devised by the Biometry Department of the Mauritius Sugar Industry Research Institute (MSIRI) in Beau Champ was one of the three estates utilizing the software which requires the presence of one full-time employee daily on the ing site to note down the following parameters: area and weight ed, hours of operation, various downtimes namely mechanical breakdown, field downtime (changing of base cutter and chopper blades) and er waiting time due to lack of transport units and soil moisture. The data collected are then fed into the software to generate er performance on a daily basis. Weekly and monthly summaries are also available from the software. Data on er performance on the three main sections where mechanized ing is practiced at Beau Champ, extracted from MECABASE between 1991 and 1994, are given in Tables 1 and 2. Table 1 Harvester performance at Beau Champ Unit Area ha Weight t Field hours h Overall output t ha Field breakdown % Mech breakdown % Waiting time % Effective output t ha Overall er output refers to the cutting rate taking into account both productive and unproductive times (downtimes) of the er. On the other hand, effective er output refers to the cutting rate with downtimes being excluded. Table 2 Harvester performance at Beau Champ Unit Area ha Weight t Field hours h Overall output t ha Field breakdown % Mech breakdown % Waiting time % Effective output t ha Generally an increase in the overall er output is observed over time, except for 1994 where cane yield was affected by a severe cyclone. Several factors are responsible for this increase. Over the years er operators have acquired experience and knowledge of the ing sites of the estate so that they are able to operate the machine at higher speeds thereby increasing the amount of cane cut per unit 40

3 time of operation. In addition, ing efficiency has increased due to longer cane rows having been planted, as recommended (MSIRI 1991). The same trend is observed for effective er output. The percentage downtimes from 1991 to 1994 have been reduced from 28.4 % to 22.9 % with a more significant reduction in 1993 (19.9 %). Different trends are shown after partitioning of these downtimes (Tables 1 and 2). Field downtime due to change of base cutter and chopper has decreased showing that the continuing practice of stone and rock removal from fields was a judicious decision. However, mechanical breakdown has increased steadily over the years as ers become more prone to breakdown with time. A strict maintenance schedule is kept at Beau Champ S.E. Every morning a thorough check up is performed before the er starts operating in order to minimise the risk of important breakdowns. Harvester waiting time has been reduced over the years. This is due to a significant investment policy on transport units from the field edge to the mill. In 1991and 1992 there were only six tractor-drawn rear tipper trailers (12 tonnes capacity) operating on the estate. In case of mill breakdowns or traffic jams in the mill yard, these trailers did not return in time to the ing site causing stoppages. As from 1993, rear tipper trailers with greater payloads (between 18 and 20 tonnes), drawn either by lorries or fast tractors, were introduced gradually to replace the smaller units so as to decrease er-waiting time. In 1998 eleven such trailers were used during the ing season. The 12- tonne units are used as spares whenever there is a need on the ing site. The software was not designed to distinguish between lack of transport units and soil conditions. The proportion of downtime due to soil conditions is more significant than lack of transport units especially in the wet winter months of July to September. Harvester efficiency has increased still further since 1995, e.g. in 1997, one machine ed 714 tonnes of cane in twelve hours. MECABASE has allowed the estate personnel to identify the various causes of er downtime and fields where the daily output was low (slope, field and road not at same level). Remedial actions have been taken so that when a second er was purchased in 1995, there was no longer need for the same type of follow up which, as stated earlier, requires one full time employee. EFFECTS OF CHOPPER HARVESTING ON CANE YIELD AND SOIL PHYSICAL PROPERTIES From the onset of mechanized ing, cane growers have expressed concern about compaction and associated effects (decrease in porosity and lowering of infiltration rates) caused by chopper ers and in-field transport. Traffic-induced compaction has been found either to reduce yields (Swinford and Boevey 1984) or to have no effect (De Beer et al. 1993). As sugar cane is ratooned for at least 7 years, there may be a long-term cumulative effect of traffic-induced compaction in the interrows. In this context, in 1993 a trial was initiated at Beau Champ in plant cane (variety R 570, burnt) to assess whether cane yields and soil properties were affected with the traffic of chopper er in fields. The experimental site was situated at section at an altitude of 114 m with a mean annual rainfall of 2400 mm. The soil belongs to the Humic Latosol group (Parish and Feillafé 1965). The treatments applied were manual ing followed by mechanical in field loading and mechanized ing with a chopper er accompanied by infield loaders. The trial design was a randomised block with 8 replicates. Dry bulk density was considered the most appropriate parameter for assessing compaction. The gamma-neutron probe (MC-S-24 model) was chosen for reliability of results with little soil disturbance (Soane et al 1981). This equipment, which has been calibrated under local conditions, records soil volumetric moisture content and wet bulk density. Dry bulk density is computed by difference. Readings were taken at 10, 20 and 30 cm depths on a monthly basis both in these cane rows and interrows. 41

4 Effect on cane yield Table 3 presents cane yields from the two treatments from 1994 (1 st ratoon) to 1997 (5 th ratoon). As from the 3 rd ratoon, the amount of extraneous matter was also determined and the clean cane yield calculated. Table 3 Cane yield at t ha -1 Total cane yield Clean cane yield Year Manual Mechanized L.S.D p = 0.05 Manual Mechanized L.S.D p = Mean Total cane yields in the mechanized treatment were higher in all years, except 1994, which was a cyclonic year. Significant differences were observed in 1995 and 1996 but when extraneous matter was excluded, both treatments were comparable. It is to be noted that unavoidable losses, namely through the fan extractors of the er have not been considered. Previous studies have shown that 1-2 tonnes of cane per hectare may be lost through the cleaning device of the er. The above data indicate that chopper ing does not affect adversely cane yield. Effect on soil physical properties Dry bulk density results are presented in Figures 2and 3 for the cane rows and interrows respectively from the 2 nd to the 4 th ratoon. For each the graphs show the bulk density status before, immediately after and just before the next. An increase in dry bulk density was observed in both the cane rows and interrows. The increase was more obvious in second and third ratoons. In the second ratoon, bulk density in the cane rows increased to a similar extent in both treatments. However in the third ratoon, a larger increase was observed in the mechanized plots. For the interrows, increase in bulk density was equally important for both treatments especially in the second and third ratoons. This indicates that cane rows and interrows are compacted by both the er and the mechanical loader confirming the cane yield results above. The most noticeable change in bulk density was observed at 10 cm depth with little change at 30 cm. Similarly Torres et al (1990) observed that compaction was mostly confined to the shallower part of the soil profile. Bulk density decreased with time and this change was most obvious at 10 cm. The compaction effect at shallow depths is therefore not permanent. Since no decompaction measures were taken, this phenomenon may be the result of natural processes occuring in the soil namely microorganism activity, root development as well as wetting and drying. The soil structure is modified by these processes with formation of new pores and enlargement of existing ones causing the bulk density to decrease between each 42

5 Figure 2 Dry bulk density in cane rows g cm -3 2 nd ratoon Dry bulk density g cm -3 3 rd ratoon 4th ratoon Depth cm Before Immediately after after 12 months 43

6 Figure 3 Dry bulk density in cane interrows g cm -3 2 nd ratoon Dry bulk density g cm -3 3 rd ratoon 4 th ratoon Depth Cm Before Immediately after after 12 months Future development The area under mechanized ing at Beau Champ S.E has followed an increasing trend since 1991 with a field planning and layout programme. Table 4 summarizes the extent of the area under mechanized ing for the different sections in 1991 and 1998 and the target aimed by the year It is observed that in 1998 more than 90 % of the areas targeted have been reached at, and. Ferney section is being developed at a fast rate. This has been possible since Ferney, as well as, and, have a relatively rock-free soil. Further developments will depend on the availability of funds and on the acreage being prepared to allow mechanization. 44

7 Sections Table 4 Trend in the area ed mechanically Area under Area under mechanical ing ha cane ha % achieved in Ferney La Lucie CONCLUSIONS MECABASE has proved to be a very useful tool in the improvement of mechanical ing sites and er performance. Mechanical ing under experimental conditions does not affect cane yield. Change in soil physical properties resulting from the passage of chopper ers and accompanying in-field transport does not affect yield. Chopper ers are a successful substitute to manual cane cutting at Beau Champ. ACKNOWLEDGEMENTS The authors wish to thank the Director of the Mauritius Sugar Industry Research Institute for his permission to publish this work. Grateful thanks are also due to the staff of Beau Champ S.E for their help. REFERENCES DE BEER G, HUDSON JC, MEYER E and TORRES JS Cost effective mechanization. Sugar Cane (4) : MSIRI see under MAURITIUS SUGAR INDUSTRY RESEARCH INSTITUTE MAURITIUS SUGAR INDUSTRY RESEARCH INSTITUTE Mauritius Sugar Industry Resaerch Institue, Annual Report 1990, pp PARISH D and FEILLAFÉ SM Notes on the 1: Soil Map of Mauritius. MSIRI Occasional Paper 22, 43 pp. SOANE BD, BLACKWELL PS, DICKSON JW and PAINTER DJ Compaction by agricultural vehicles: A review. I. Soil and wheel characteristics. Soil and Tillage Research (1) : SWINFORD JM and BOEVEY TCM The effects of soil compaction due to infield transport on ratoon cane yields and soil physical properties. Proc. S. Afr. Sug. Tech. Ass. : TORRES JS, YANG SJ and VILLEGAS F Soil compaction and cane stool damage by semimechanized ing systems in the wet season. Sugar cane (5):