BSuphanburi Field Crops Research Centre, U-thong, Suphanburi 72160, Thailand.

Land preparation and stool removal for sugarcane cultivation can be a major contributor to the overall production costs. Braunack et al. (1999), gives estimates of the number of tillage operations for conventional land preparation being between eight to 10, whilst McMahon and Teske (1989) report up to 18 times. De Beer et al. (1993) estimates that mechanization can contribute as much as 50% of the total production costs. Hence, by determining techniques which can reduce the need for the number of soil cultivations whilst still maintaining or improving yields is a practical way for farmers to reduce their costs and increase their net profit. Much of the research in recent years using minimum or no-tillage techniques combined with trash management has shown beneficial results both for improving cane yields as well as reducing detrimental environmental impacts (Wood, 1991 and De Beer et al., 1993). However, in Thailand such improved techniques are infrequently adopted, due mainly to the lack of information regarding their implementation and effectiveness.

This paper reports upon the third cycle of a long-term sugarcane trial being conducted in the Central Region of Thailand. The main objective of the trial is to assess the cost effectiveness of conventional tillage, minimum tillage and no-tillage techniques of land preparation and stool removal and cane cultivation.

The trial was conducted at Suphan Buri Field Crops Research Centre in central Thailand on a Typic Haplustalf soil. The climate is tropical wet and dry with a mean annual temperature of 28^oC and mean annual rainfall of 1116 mm. The experimental design was that of the split plot, with the main plots representing the tillage system (Table 1). The sugarcane variety used was U-Thong 2.

In the plant and first ratoon crops of tillage treatments T1 to T4, yields are often significantly larger than the yields of the no-tillage treatment, T5 (Table 2). The highest overall cane yield occurs in the minimum tillage (T2) treatment. There are no significant differences in yield for all treatments in the second and third ratoon crops.

The fuel and labour cost analyses of each tillage operation were assessed using data from Prammanee et al. (2000) and Chinawong and Cheosamutr (2000) for 1 hectare of land. Actual average yield data (Table 2), for each of the tillage treatments, were used to calculate net profit. The minimum tillage treatment (T2), gave the best return, followed by T3, T4, T1 and T5 with net profits of $US 1041.6, 946.0, 931.9, 775.9 and 747.3, respectively (Table 3).

In terms of cost analysis of fuel and labour, large savings in land preparation costs were made for the minimum tillage (T2 to T4) and no-tillage (T5) treatments (Table 3). However, much of this was offset by the high costs of herbicide application (including labour) and manual planting. Despite this, the higher yields that were associated with the minimum tillage treatments, particularly T2, resulted in better net profits. Minimum tillage treatment T2 was about 34.2 and 39.4% more profitable than the conventional and no-tillage treatments, respectively.

The minimum tillage treatments (T2 to T4) are recommended under the existing conditions of irrigation availability and associated high ground water table, together with availability of machinery. The minimum tillage without subsoiling (T2) was particularly good with the best economic returns.

Despite the substantial cost savings from the absence of mechanisation, labour costs are likely to offset a large part of the savings. Because of this and due of the time required for manually cultivating the crop, there will be limitations of scale with a cut off point when field size becomes too large to be economically and practically feasible. However, such a system will work on a small scale, where ownership and access to machinery is limited and low input –low returns are acceptable. Such farms are common in Thailand, with for example the average size of the holding in the Central Region of Thailand being only about 4 ha.