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A study was conducted in the Sabal area, Sarawak, to evaluate the physicochemical properties of sandy-textured soils under smallholder agricultural land uses. Study sites were established under rubber, oil palm, and pepper land uses, in comparison to the adjacent secondary forests. The sandy-textured soils underlain in all agricultural land uses are of Spodosols, based on USDA Soil Taxonomy. The soil properties under secondary forests were strongly acidic with poor nutrient contents. Despite higher bulk density in oil palm farmlands, soil properties in rubber and oil palm land uses showed little variation to those in secondary forests. Conversely, soils under pepper land uses were less acidic with higher nutrient contents at the surface layer, especially P. In addition, soils in the pepper land uses were more compact due to human trampling effects from regular farm works at a localized area. Positive correlations were observed between soil total C and soil total N, soil exchangeable K, soil sum of bases, and soil effective CEC, suggesting that soil total C is the determinant of soil fertility under the agricultural land uses. Meanwhile, insufficient K input in oil palm land uses was observed from the partial nutrient balances estimation. In contrast, P and K did not remain in the soils under pepper land use, although the fertilizers application by the farmers was beyond the crop uptake and removal (harvesting). Because of the siliceous sandy nature (low clay contents) of Spodosols, they are poor in nutrient retention capacity. Hence, maintaining ample supply of organic C is crucial to sustain the productivity and fertility of sandy-textured soils, especially when the litterfall layers covering the E horizon were removed for oil palm and pepper cultivation.
The assessment on relationship between soil properties and edaphic factors in the reforestation site is important to provide information on soil productivity and type of species preferences on degraded site. Hence, this information was vital for planning rehabilitation program at degraded area. The objectives of this study were to identify the soil properties at reforestation sites for rehabilitation purpose in Sarawak and to differentiate the soil properties at the reforestation sites of different age stands planted with Shorea macrophylla. For the purpose of this study, study sites were established at a reforestation site located at Sabal Forest Reserve (SFR). Three study plots with the size of 50 m x 50 m were constructed at reforestation sites with planted Shorea macrophylla and at different age stands (3 years, 4 years and 31 years after establishment). In each study plot, soil samples were collected at 0-10 cm and 30-40 cm from random points located at on the lines planting using soil auger. Soil physicochemical analysis involved in this study includes soil texture analysis and soil bulk density (BD), pH (water), total carbon (TC), total nitrogen (TN), total organic carbon (TOC), exchangeable Aluminum and available phosphorus. The results showed that, all the soil at the studied site were sandy and strongly acidic in nature. The soil physicochemical properties showed the clear differences between the SB11, SB10 and SB83 sites and generally showed the differences with the age stand, respectively. The soil at SB83 site was strongly acidic and higher soil organic matter as well as higher available phosphorus as compared with the soil at SB11 and SB10. Meanwhile, soil at SB11 site has higher sand content than SB83 site. This study also suggested that Shorea macrophylla is the suitable species for reforestation activities in the future as it is fast growing species and improved soil physicochemical properties.
Shifting cultivation of upland rice has been widely practiced by rural population in Sarawak for self-subsistence. However, recent depletion of arable land for agriculture caused by drastic land use changes resulted in transition of traditionally practiced single year cultivation to continuous multiple years of cultivation practices. Thus, present study aimed to clarify the changes in soil physicochemical properties under the single and multiple cultivation of upland rice via shifting cultivation. The study area was located at Sabal area, Sarawak where majority of people are subsistence Iban farmer with upland rice as their main crop. Composite and undisturbed soil samples were collected at the depth of 0-10cm and 30-40cm from three random points at different stages of rice cultivation in both single and multiple cultivation farmlands, i.e. before burning (land clearing), after burning and after rice harvesting for the determination of soil physicochemical properties. Based on the household interview, the fallow length after each shifting cultivation cycle has been reduced to 5 to 7 years at the study area. Moreover, some farmers practiced continuous cultivation of rice for two consecutive years due to limited accessibility of arable land. The results of the soil analysis indicated that the soils at Sabal region were characterized by relatively sandy texture and low nutrient status in both single and multiple cultivation farmlands. Although no major differences were showed in soil physicochemical properties between the single and multiple cultivation sites, slope degrees appeared to influence the levels of soil Total C and soil Total N in these upland rice farmlands. Meanwhile, soils under multiple cultivation sites becoming acidic with lower exchangeable bases after subsequent rice cultivation. Reduction of fallow length along with continuous cultivation at the study area might result in insufficient regeneration of vegetation which in turn leads to low nutrient recovery for the next cultivation.
Population expansion and the need of cash income result in intensified upland agricultural practices globally. Even though efforts are progressing towards sustaining the agricultural practices in upland areas, however, limited studies discuss on the present condition of upland agricultural practice. This study discusses present soil fertility status and condition under various kinds of perennial cash crops farming (rubber, Hevea brasiliensis; pepper, Piper nigrum; oil palm, Elaeis guineensis; vegetables and fruits) in an upland area of Sarawak, Malaysia towards providing fundamental information and future perspective of the current farming practice. The study was conducted at Kruin village in Sabal, Serian. Soil samples were collected in each type of agricultural lands; pepper garden, oil palm field, rubber field, fruit orchard and vegetable garden at the depths of 0-10cm and 30-40cm for soil physicochemical analysis. The results showed that the soils are sandy in texture with acidic nature which results in high Al saturation. The clay content is low with approximately 13.8% at the study area. At different agricultural lands, soil exchangeable bases and total C were low and did not varied widely although some sites especially in the home garden showed significantly high level of exchangeable Ca. High level of exchangeable Ca in home garden probably due to the ash effect from addition of burnt materials and left over unburned materials such as charcoal from household waste. At pepper farm, bulk density and soil hardness were high, indicating regular farming practices such as harvesting and weeding have resulted in considerable soil compaction. Based on the soil analysis, it can be concluded that current farming practice does not show much impacts to the soil, the chemicals levels in the soils were low, indicating little use of agrochemicals in the farming practice. However, technologies such as intercropping and crop rotation should be integrated into current farming practice to conserve soil fertility towards a more sustainable upland agriculture in the future.
Rapid population expansion throughout decades has put tremendous pressure on the agricultural land resources across the globe including Malaysia. With increasing cases of land degradation, the awareness in conserving the soil resources slowly gained attention from policymakers and public society. Soil quality indicators were developed by scientists to quantify large-scale evaluation systems including integrated natural resource management framework and soil fertility capability (Sanchez et al. 2003). Soil Fertility Index (SFI) has been implemented by Moran et al. (2000) to determine the relationship between soil fertility and rate of secondary forest succession. Subsequently, Lu et al. (2002) improved the equation by introducing Soil Evaluation Factor (SEF) to evaluate the secondary forests succession at Brazil under different types of soils (Alfisols, Ultisols, and Oxisols). Few researchers have been adapted these indices to estimate the soil fertility and quality of secondary forests in Southeast Asia (Doi and Sakurai 2004; Arifin et al. 2008). Additionally, Panwar et al. (2011) further proposed these indices to determine the impact of different land uses including forest plantation, home garden, areca nut plantation and agricultural land on soil fertility of Entisols in India. However, the applicability of these indices in estimating the soil fertility under tropical upland soils has not been commonly practiced in Malaysia. Thus, this study aimed to determine the soil fertility at various agricultural land uses cultivated with rubber, oil palm and pepper using Soil Evaluation Factor (SEF) in comparison with the adjacent secondary forests at tropical uplands in Sarawak.
Shifting cultivation practices are regarded as the most important agricultural land-use in the marginal uplands of Sarawak for the livelihood of the rural communities. In response to various socio-economic consequences, previous practices on traditional form of shifting cultivation were altered into much sedentary farming practices. Soil productivity to sustain rice yield under current intensified forms of shifting cultivation should be of prime importance for food security among the local community at the marginal uplands of Sarawak. Therefore, this study was conducted to characterize soil properties influenced by the current intensified shifting cultivation practices at Sabal upland area, Sarawak. Along with the use of agrochemicals, shifting cultivation at Sabal area was conducted through single cultivation practices (10 to 15 years of fallow period and a cycle of rice cultivation) and multiple cultivation practices (5 to 7 years of fallow period and two cycles of rice cultivation). Before burning practices, soil pH was highly acidic (ranged from 4.28 to 4.72) in single cultivation sites; while multiple cultivation sites showed less acidic nature (soil pH ranged from 4.98 to 5.23) with relatively high secondary macronutrient contents, especially soil exchangeable Mg and Ca. No significant observation was found after burning practice in Total C and Total N of the soils at both sites. The level of soil exchangeable bases (K, Mg and Ca) and available P increased after the burning practices in single cultivation farmlands; while multiple cultivation sites showed lower to no increase in exchangeable bases and available P, partly attributed to the limited supply of nutrients from the aboveground biomass. After the harvesting of rice, soils at both sites tended to be more acidic and lower in macronutrient contents (K, Mg and Ca), primarily ascribable to crop uptake during the cultivation period. The average yield of rice in single cultivation sites and multiple cultivation sites were 721 kg/ha and 391 kg/ha, respectively. Our findings suggested that the usage of agrochemicals, particularly fertilizers in multiple cultivation sites are necessary for sustaining rice yield to restore the depleted macronutrients (especially K, Mg and Ca) after successive cultivation.
At present, the depletion in arable lands for shifting cultivation practices in Sarawak has led to modification of traditional swidden land into a sedentary form of agricultural practice. Along with incorporation of agrochemicals for crop cultivation and short term fallow system, such practice may lead to environmental degradation especially on the existing soil resources. This study aimed to clarified and access the agricultural land capability and current state of soil nutrient status under such agricultural practices; focusing on smallholder and subsistence agricultural practices by local farmers in Sarawak. The study was conducted at Sabal, Sarawak where majority of the communities are of Iban origin. Interviews were conducted to obtain baseline information on current agronomy practices by the local communities. Soil samples were collected in each type of agricultural lands namely; rubber, pepper, oil palm and upland rice for further soil physicochemical analysis. In addition, information on agriculture capability at all study sites was also discussed. Our findings outlined that Red –Yellow Podzolic soils covered most of the study areas with some areas intersperse with Grey-White Podzolic and Podzols soils. In addition, Alluvial soils and Gley soils only occupied small patches of the study areas and were located along the river. Soils collected on all study sites fell between Class 3 to Class 4 under Agricultural Land Capability Classification. Smallholder agricultural practices with diversified cash crops farming in combination with subsistence agriculture are the common practice at the study area. Soil analysis indicated that the soils in Sabal region were acidic in nature and sandy in texture, giving rise to low CEC levels. In general, no substantial differences were found in the soil physicochemical properties at all the study areas. The soils under all study sites were low in nutrient contents even though fertilizers were added consistently to the soils to aid the yield of the crops. However, pepper farmlands showed significantly higher bulk density and soil hardness compared to other farmlands indicating considerable compaction caused by regular farmworks. Our result suggest that current agricultural practices at Sabal area showed no significant negative impact to the soils as most agricultural sites were localized and surrounded by secondary forest. Meanwhile, field adaptation of effective fertilizer management to different crops by farmers was observed as farmers were able to sustain the crop yield with minimal fertilizers application.