Abstract

Media summary

Key Words

Crop diversity, land and water management, no-tillage, vegetables.

Introduction

Unreliable water supplied from the erratic low rainfall, plus poor management, often restrict agricultural production in rice-based (Oryza sativa) cropping systems on rainfed Vertisols in the semi-arid tropics of Southern Lombok (Ma`shum et al. 2003). The region is influenced by monsoonal rainfall with a short wet season from November/December to March/April, and 7 to 8 dry months from April/May to October.

With the unreliable rainfall in Southern Lombok, the conventional system of gogorancah, with intensive tillage on flat land, is no longer suitable due to low water use efficiency (Ma`shum et al. 2003) and the high cost of labour required for land preparation and weed control (Meindertsma 1997). Secondary crops, usually soybean (Glycine max) or tobacco (Nicotiana tabacum), are most successful when sufficient water is stored in the soil, plus water is supplied from that harvested in dams (embungs) during the wet season. Therefore, new systems with higher water use efficiency that better match crop growth to water supply should be developed for Vertisols in the region

Permanent raised beds have been widely reported elsewhere to increase diversity of crop production, alleviate waterlogging in soils, improve soil structure (Van Cooten and Borrell 1999), and enable rice to be rotated with other crops (Garside et al. 1992). In Western Australia, raised beds also significantly increased yield of pasture, even in seasons that were drier than average (Hamilton et al. 2003). Information on improving production and economic revenue of secondary crops under raised beds in the semi-arid tropics is still limited. This paper compares the yield and revenue from the secondary intercropped tomato-mungbean (Lycopersicon esculentum-Vigna radiata) on permanent raised beds, and from chilli (Capsicum frurescens) on wavy raised beds with the yield and revenue from soybean grown under gogorancah on Vertisols in Southern Lombok..

Materials and methods

Field experiments were established at two sites in Southern Lombok, Indonesia, in the dry season of 2001. The experiments were: Site 1 - Wakan (District East Lombok, Sub-district Keruak; 8^o 44’S, 116^o 30’ E; 90 m above sea level, with 700 to 1300 mm average rainfall), and Site 2 - Kawo (District Central Lombok, Sub-district Pujut; 8^o 45’ S, 116^o 20’ E; 180 m above sea level, with 1000 to 1400 mm average rainfall). The Vertisols (USDA 1998) at each site were dominated by montmorillonite (Krisdayanti 1996), and contained 668 g clay /kg soil (Site 1) and 624 g clay/kg soil (Site 2).

Each experiment was a randomized block with 3 replicates (Table 1). Plots (each 10 m long and 6 m wide) were separated by border bunds (0.2 m high, 0.5 m wide), with an outer furrow 0.8 m wide. Before the secondary crop was sown, each plot was mulched with residue from the primary crop. Treatments with permanent or wavy raised beds consisted of 4 raised beds, each 1.2 m wide and 0.2 m high, and were irrigated from the embung with water harvested from each treatment during the wet season. Secondary crops were sown after the primary crops were harvested (Table 1). Pests were controlled by applying appropriate insecticides in each treatment.

Table 1. Treatments used in experiments on Vertisols at Site 1 (Wakan) and Site 2 (Kawo).

^aFlat Beds 0.2 m higher than base of furrows
^bSuperphosphate banded at depth of 5 cm
^cComposted dung and plant residue was also applied at 5 t/ha.
^dCentre of beds 0.4 m higher and edges of beds 0.2 m higher than base of furrows
^eIntercropped after intercropped maize-soybean. In 2002, intercrops planted at the same time; in 2003, tomato transplanted one week before mungbean sown
^fOne row of tomato (intra-row spacing of 40 cm) between two rows of mungbean (spacing 20 x 20 cm) ^gGogorancah, as used by local farmers

At harvest, yield was determined on samples from two quadrants (each 1 x 1.5 m) from a) the two middle beds of each treatment on permanent, or wavy, raised beds, and b) in the middle of each treatment on flat land. Data were analysed using Analysis of Variance for the yield in treatments with soybean and lsd was calculated to compare means.

Results and discussion

Soybean yield did not differ significantly (P<0.05, data not shown for each treatment) treatments S1, S2, S4 or S6 at either site in 2002 and 2003 (Table 1; Table 2). At each site, the yield of chilli (S3), and of intercropped tomato-mungbean (S5), were higher than the average yield from local farms in that area (Table 2). The yield of tomato was higher in 2003 (tomato transplanted early, and well established before mungbean sown) than that in 2002.

Table 2. Yield of secondary crops (t/ha) at Site 1 (Wakan) and at Site 2 (Kawo), and average yields

on local farms.

^aMean yield of all treatments with soybean as secondary crop (S1, S2, S4, S6 - Table 1)
^bIntercropped
^cNot applicable

The lower yield of chilli at (Site 2) compared to at Site 1 in both 2002 and 2003 (Table 2) was due to a viral disease during early growth, reflecting the higher rainfall recorded at this site. Chilli, a crop that requires small amounts of water, performed better in the drier than wetter climate. In 2003, the maximum yield of chilli (Harvest 6) was higher at Site 1 than that at Site 2 (Figure 1).

The maximum yield of tomato at the drier site (Site 1) was reached at an earlier harvest, and the growing season was shorter, than those at Site 2 (Figure 2).

Of all treatments, chilli grown on permanent raised beds produced the highest revenue, followed by intercropped mungbean-tomato on wavy raised beds (Figure 3). Also the canopy of the secondary crops on the permanent raised beds and the wavy raised beds , suppressed weeds in both the current crop, and also the next wet season (data not shown), resulting in reduced labour costs for for weeding. Furthermore, chilli from Southern Lombok is sold about one month before that sold from other regions on Lombok, resulting in a price advantage of up to Rp. 4000/kg.

Figure 3. Revenue of secondary crops in 2003 (Table 1) at

Site 1 (Wakan) and at Site 2 (Kawo). (LSD (P < 0.01) Site 1 = 0.15; Site 2 = 0.13 ).

Conclusion

At current prices, the secondary crops chilli on permanent raised beds without tillage, or intercropped tomato-mungbean on wavy raised beds without tillage, provide a viable alternative to the current system of growing soybean on gogorancah on rainfed Vertisols of Southern Lombok..

Acknowledgements

This work was funded by the Australian Centre for International Agriculture Research. Field assistants and local farmers in Southern Lombok are fully thanked for their significant contribution. Thanks also to Dr Andrew Borrell for helpful comments on an early draft of the paper.

References

Garside AL, Borrell AK, Ockerby SE, Dowling AJ, McPhee and Braunack MV (1992). An irrigated rice-based cropping system fro tropical Australia. Proceedings of the 6^th Australian Agronomy conference, Armidale. NSW.

Hamilton G, Bakker D, Houlbrooke D, Hetherington R and Spann C (2003). Permanent raised beds prevent waterlogging and increase the productivity of dryland farming areas in Western Australia. Proceedings International Soil Tillage Conference Organization, 524-530.

Krisdayanti D (1996). Pengaruh Budidaya Sawah Terhadap Sifat Vertisol Lombok. Thesis Master. Fakultas Pascasarjana, Universitas Brawijaya, Malang, Indonesia.

Ma’shum, M., Mahrup, Sukartono, Kusnarta, IGM, and Silawibawa, IP (2003). Water capturing on various rainfed vertisol’s managements in southern lombok. Agroteksosos Journal. Fakultas Pertanian UNRAM.

Meindertsma JD (1997). In ‘Modeling of Farming Households in Lombok, Indonesia’. (Royal Tropical Institute, Nederlands).

USDA (1998). ‘Keys to Soil Taxonomy’, 8th edn. (USDA, USA).

Van Cooten DE and Borrell AK (1999). Enhancing food security in semi-arid Eastern Indonesia through permanent raised-bed cropping: a review. Australian Journal of Experimental Agriculture 39, 1035-1046.