This study discusses soil fertility under perennial cash crop farming (para rubber, Hevea brasiliensis ; black pepper, Piper nigrum ; oil palm, Elaeis guineensis ) conducted by local farmers and an oil palm estate in an upland area of Sarawak, Malaysia, in comparison with the surrounding secondary forests. In the farmlands of the local farmers, rubber farming was conducted without fertilizer application, while 2–5 t ha −1 of NPK compounds were applied annually on pepper farms. Soils under rubber farming were acidic with poor nutrient contents, resembling soils in secondary forests. In pepper farms, soils were less acidic and showed high nutrient contents, especially with respect to available P and exchangeable Ca. This trend became stronger with increasing farming duration. Fertilizers applied around pepper vines appeared to migrate and spread across the fields. Bulk density and hardness of surface soils were higher in pepper farms than in secondary forests, indicating soil compaction due to field works. In the oil palm estate, annual fertilizer application rates were moderate at 0.4–0.8 t ha −1 of NPK compound fertilizers. However, the soil properties in the oil palm estate were similar to those of the small-scale pepper farms. Close to the bases of the palms where fertilizers usually are applied, the contents of exchangeable Ca and available P were high. Nutrient uptake by the dense root systems of the palms seemed to prevent excessive loss of nutrients through leaching. Loss of soil organic matter and deterioration of soil physical properties were brought about by terrace bench construction, but the soils seemed to recover to some extent over time. In conclusion, technologies such as intercropping and the appropriate allocation of different crops to specific locations as well as the proper selection and dosage of fertilizers should be developed and adopted to improve fertilizer efficiency and prevent water pollution due to fertilizer wash-off from farmlands. Keywords Para rubber Black pepper Oil palm Soil fertility Sarawak Upland farming 1 Introduction In the upland of Sarawak, Malaysia, local farmers grow para rubber ( Hevea brasiliensis ) and black pepper ( Piper nigrum ) as perennial cash crops in addition to upland rice as their staple food by shifting cultivation practices. According to Crumb (2007) , rubber farming was introduced at the beginning of the 20th century. It was adopted preferentially by farmers applying shifting cultivation, as it could easily be incorporated into cropping/fallow systems by planting its seedlings simultaneously or in sequence with upland rice. On the other hand, pepper farming began in the 1870s but became widespread only after the Second World War because of the high requirements for labor and agrochemical input. One characteristic of rubber and pepper production in Sarawak is that it has been conducted mainly by smallholders supported by the government's agricultural policies. Recently, with increasing need for cash income in a monetary economy, the significance of cash crop farming has increased. As a result, the shifting cultivation for rice production, formerly the most important agricultural activity and consequently, the central element of traditional local farming societies ( Jensen, 1965; Freeman, 1970 ), changed into a mere component of a more diverse upland farming system ( Crumb, 1993 ). This tendency toward commercialization was strengthened by various kinds of subsidy schemes provided by the Department of Agriculture of the state since the 1970s. Meanwhile, since the 1970s and 1980s, large-scale oil palm ( Elaeis guineensis ) plantations have been developed rapidly by public agencies of the federal and state governments as well as by private companies ( Ngidang, 2002; Crumb, 2007 ). Some local farmers possess their own small-scale oil palm farm, sometimes supported by subsidies. The total areas under perennial cash crops in Sarawak were estimated to be 156,731 ha for rubber, 12,930 ha for pepper, and 508,307 ha for oil palm in 2004, which accounted for 16.8, 1.4, and 54.5% of the total agricultural land, respectively (Department of Statistics, Malaysia). The areas covered by rice (excluding fallow land) amounted to 60,354 ha for lowland and 66,065 ha for upland varieties. The area used for oil palm farming expanded from 116,036 ha in 1995 to 508,307 ha in 2004 while those of other crops stagnated or declined slightly. The farmlands utilized for rice and cash crops as well as oil palm farming tend to be located along roadsides or rivers because of easy access and transportation ( Hansen and Mertz, 2006 ), resulting in an increasing intensity of land use at such favorable sites. In the traditional shifting cultivation, upland rice was grown only once after slashing and burning of secondary forest that was more than 10–15 years old; afterwards, the field was turned to fallow. Nowadays, the fallow period is around 5 years and upland rice is cultivated two to three times in a row ( Kendawang et al., 2005 ). Chemical fertilizers are widely used, especially in pepper and oil palm farming. This transformation from traditional shifting cultivation with low external input toward more sedentary farming practices with high input may affect soil fertility and, in consequence, the sustainability of the upland agricultural system. The transformation and present situation of upland agriculture in Sarawak have been studied mostly from socioeconomic viewpoints ( Best, 1988; Cooke, 2002; Ngidang, 2002; Hansen, 2005; Crumb, 2007; Ichikawa, 2007 ). Regarding crop production, numerous field trials have been carried out in peninsular Malaysia and Sarawak to optimize land management practices including fertilizer application (see, for example, Broughthon, 1977 for rubber, Raj, 1972 for pepper, Agamuthu and Broughton, 1985 and Khalid et al., 2000 for oil palm). The impacts of soil erosion were examined in the context of...

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.

Global demand for high-quality rice and healthy food has increased, especially to the affluent and health-conscious consumers. Red rice has been consumed because of its health benefits. Red rice has met the concepts of productivity and quality that emerged to supply the demands for products that improve the eating pattern of its consuming population. Red rice is based on food industries especially for nutrition-based food products and baby food products. For the case on Malaysia, limited domestic supplies of red rice have led to full dependency on imported red rice supplies in the country. Recent statistics showed that the Sarawak state can be one of the potential areas for the development of red rice production due to its vast land resources; proper guidelines which suit the agroecosystem in Sarawak for cultivation of red rice are essential. As for rice production in general, proper application of fertilizers enhances the yield and to a certain extent sustains soil productivity. Considering the needs to establish a proper fertilizing program especially for red rice production in Sarawak, a preliminary study was conducted to evaluate the yield and yield components of red rice variety (MRM 16) with three levels of NPK fertilizers (Treatment 1, control; Treatment 2, 60 : 35 : 40; Treatment 3, 120 : 70 : 80; and Treatment 4, 180 : 105 : 120 (proportions of N, P₂O₅, and K₂O·ha⁻¹, respectively)). The experiment was conducted in the pot trial during main season 2016 (December 2016–April 2017). The yield parameters including rice yield, panicle no./m², 1000-grain weight, spikelet number per panicle, and percentage of filled spikelets were collected. The results showed that yield was not significantly affected by the increment of the NPK fertilizer added at a rate of more than 60 kg/ha N, 35 kg/ha P, and 40 kg/ha K (T2). From the study, it was observed that the yield and yield components of red rice variety (MRM 16) were best in T2 (60 kg/ha N, 35 kg/ha P, and 40 kg/ha K).