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International Journal of Agronomy
Volume 2018 (2018), Article ID 9312537, 6 pages
Review Article

Introducing Natural Farming in Black Pepper (Piper nigrum L.) Cultivation

1Research and Development Division, Malaysian Pepper Board, 93916 Kuching, Sarawak, Malaysia
2Department of Crop Science, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia (UPM), Bintulu Campus, 97008 Bintulu, Sarawak, Malaysia
3Institute of Tropical Agriculture and Food Security (ITAFoS), Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia
4Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia

Correspondence should be addressed to Kevin Muyang Tawie Sulok

Received 30 October 2017; Accepted 4 January 2018; Published 1 February 2018

Academic Editor: Maria Serrano

Copyright © 2018 Kevin Muyang Tawie Sulok et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper reviews the role of Natural Farming as an ecological farming method to produce organically grown food of safe and high quality and at the same time improve soil quality and soil health. Currently, there is a dearth of information on the effects of Natural Farming approach on black pepper farms particularly in Sarawak, Malaysia. Previous studies on other crops had indicated positive outcome using the Natural Farming method. Thus, this paper discusses the essential role of effective microorganisms in Natural Farming and their potential in pepper cultivation. Through the action of effective microorganisms, this approach should be able to transform a degraded soil ecosystem into one that is fertile and has high nutrients availability. The mixed culture of effective microorganisms applied must be mutually compatible and coexist with one another to ensure its favorable establishment and interaction in the soil. Therefore, it is anticipated that introducing Natural Farming in black pepper cultivation can enhance the predominance of effective microorganisms in the soil, which in turn could lead to promising growth and yield of the crop.

1. Introduction

Current trends in pepper cultivation, fertilizers, and wide-scale applications of broad-spectrum organophosphate pesticides could result in a degrading ecological environment besides shortening the lifespan of pepper vines [1]. Therefore, as part of the National Commodity Policy of Malaysia heads towards an environment-friendly industry, introducing Natural Farming in pepper cultivation will be part of an effort by the Malaysian Pepper Board, Malaysia, to support green development. Moreover, as the global demand for organic farm produce increases, there is a need to develop an agricultural practice which is sound and sustainable for the betterment of both the environment and humans living in it.

Natural Farming is a term used to describe an ecological farming approach to produce organic based food crops [2, 3] (Talaat et al., 2017). It is a natural agriculture alternative which promotes lower production cost and at the same time is able to achieve product of high quality and yield with lower or without the usage of inorganic fertilizers and pesticides [4]. As the approach is closely related to soil fertility, introducing Natural Farming to enhance the predominance of beneficial and effective microorganisms can help to improve and maintain soil biological, chemical, and physical properties (Fukuoka, 2009) [5].

The role of using beneficial microorganisms in Natural Farming is in increase because many people are being aware of the hazards associated with consuming products with chemical substances. Nevertheless, enhancing food security through this approach in Malaysia is still a not well-established option due to lack of technical knowledge in the required subject. The desired effects for applying Natural Farming fertilizers to soils can vary, at least initially. In some soils, a single application may be enough to produce the expected results, whereas for other soils, repeated applications may be ineffective [6]. The reason for this is that, in some soils, it takes longer time for the introduced microorganisms to adapt to a new set of ecological and environmental conditions and to become well established as a stable, effective, and predominant part of the indigenous soil microflora. Megir and Paulus [1] observed that in most black pepper farms, intense use of farming chemicals causes the ecosystem to be degraded and therefore not suitable for newly introduced microbial communities to live in. Megir and Paulus [1] added that these microbes may not be able to withstand the intolerable pH, moisture, and temperature conditions of degraded soils. Hence, the proper and regular addition of organic amendments is often an important part of any strategy to ensure the survival of newly introduced microorganisms [5]. To this end, there is strong belief that Natural Farming can ensure very productive pepper farming, clean environment, increase profits of pepper growers, and at the same time make healthy and fresh organic produces affordable for everyone. Thus, this paper discusses the essential role of effective microorganisms in Natural Farming and their potential in pepper cultivation.

2. Fertilization Practice in Pepper

Pepper has high demand for nutrients [7]. It requires large quantities of nutrients to maintain significant growth and yield. It has been estimated that the nutrient uptake of a mature stand of pepper amounts to 202 kg N, 13 kg P, 156 kg K, 18 kg Mg, and 68 kg Ca per hectare per year [8]. Studies by the Malaysian Pepper Board [9] and Yap [8] estimated pepper yield by conventional practice was approximately 6 tons per hectare per year, whereas that of the yield associated with organic farming practice resulted in approximately 5 tons per hectare per year [8]. In Malaysia, the costs of buying compound inorganic fertilizers for pepper vines of different maturity stage are shown in Table 1. Mature vines or pepper aged three years and above requires more chemical or inorganic fertilizers than immature vines; therefore, more cost is involved. Hence, it is important to note that naturally cultivated pepper should be able to reduce the dependency on expensive inorganic fertilizers. Natural Farming approach must be able to convert a degraded soil ecosystem full of harmful microbes to one that is productive and contains useful microorganisms which in turn could contribute to high nutrients availability.

Table 1: Cost of fertilization associated with pepper cultivation.

3. Sustainable Agriculture through Natural Farming

The term Natural Farming or nature farming is not simply farming without chemical fertilizers and pesticides, but rather it is organic farming with the added dimension of exploiting beneficial microorganisms to enhance soil quality and soil health [10, 11]. Sustainable agriculture can be defined as a set of practices that conserve resources and the environment without compromising human needs. In line with the concept of sustainable agriculture and development, Natural Farming approach qualifies as one of its main pillars (Talaat et al., 2017). Sun et al. [11] stated that intimate understanding of the local ecology is necessary for successful agriculture, and it may be important to extend this knowledge to the smallest of lifeforms.

4. Soil Microflora Associated with Natural Farming

Microorganisms are effective only when they are presented with suitable and optimum conditions for metabolizing their substrates including available water, oxygen (depending on whether the microorganisms are obligate aerobes or facultative anaerobes), pH, and temperature of their environment. The important consideration here is the careful selection of a mixed culture of compatible, effective microorganisms properly cultured and provided with acceptable organic substrates [12, 13].

In Natural Farming, these beneficial microorganisms can be grown to high populations and then applied to soils that also have a large stable population of beneficial microorganisms, especially facultative anaerobic bacteria [14]. The desired effects appear only after they are established, become dominant, and remain stable and active in the soil. It has been difficult to study the time required for the inoculated microorganisms to be effective due to variable conditions in soils including unanticipated changes in soil pH, temperature, and moisture [1]. However, it will have required at least a year for a conventional black pepper farm to be fully established as a naturally organic farm with wealth of inoculated beneficial microorganisms in soils [2]. Park and DuPonte [2] added that repeated monthly applications, especially during the first cropping season, can markedly facilitate early establishment of the introduced beneficial microorganisms.

Van Bruggen and Finckh [15] also reported that even when a beneficial microorganism is isolated from a soil, cultured in the laboratory, and reinoculated into the same soil at a very high population, it is immediately subjected to competitive and antagonistic effects from the indigenous soil microflora and its numbers soon decline. Studies by Van Der Heijden et al. [16] and Rashid et al. [17] mentioned that one of the essential requirements for the inoculated microorganisms to be well established was the introduction of mixed cultures instead of a single inoculum. Zimmerman (2008) and Thies et al. [18] found that amending soil with biochar can also enhance the effectiveness of beneficial or effective microorganisms as it provides conducive environment for the microbes to live in. Thies et al. [18] added that the tiny perforations in the biochar provide shelter for the inoculated microorganisms to house themselves. Thus, the possibility of shifting the “microbiological equilibrium” of a soil and controlling it to favor the growth, yield, and health of crops is greater if mixed cultures of beneficial microorganisms introduced are physiologically and ecologically compatible. If so, then it is also highly probable that they will exercise considerable control over the indigenous soil microflora which, in due course, would likely be transformed into or replaced by a “new” soil microflora [16].

5. Effective Microorganism (EM)

Effective Microorganism (EM), generally in liquid form, contains a variety of lactic acid bacteria, yeasts, and phototrophic bacteria that can be applied as inoculants to increase the microbial diversity of soil ecosystem [12, 1921]. Talaat et al. [22] observed that EM contains selected species of microorganisms including predominant populations of lactic acid bacteria and yeasts, smaller numbers of photosynthetic bacteria, actinomycetes, and other types of organisms. All of these microorganisms are mutually compatible with one another and can coexist in liquid culture. Keymer and Lankau [14] added that usually EM shows best results in situations where the natural balance of microorganisms has been severely disrupted or where agricultural farming inputs are in short supply. In situations where natural microorganism populations are reasonably intact, or where a balanced supply of inputs is available, the addition of EM does not make significant difference.

Zuraihah et al. [21] noted that the exact mechanism of how EM acts and interacts in the soil-plant ecosystem is not known. However, there is evidence that supports a number of theories concerning the action of EM. Further studies done by Van Bruggen and Finckh [15] reported the beneficial effects of EM which include suppression of soil-borne pathogens, increased decomposition rate of organic waste, increased availability of mineralized nutrients to plants, enhancement of microbial activities, increased nitrogen fixation, and reduced requirement of chemical fertilizers, pesticides, and fungicides. Shin et al. [5] added that EM helps to speed up the natural composting process, without many of the side effects of foul odours and pests. Figure 1 shows the function of EM in the soil-plant ecosystem which was illustrated by Higa [19].

Figure 1: Functions of effective microorganisms in the soil in “Microorganisms for Agriculture and Environmental Preservation”, Higa [19], Nou-bun Kyo (in Japanese).

Sharma et al. [23] reported an increase in humus content of a soil amended with organic materials and inoculated with EM. Although there was little difference in the chemical analyses of the soil among treatments, EM enhanced or improved the growth of plants over those of the control and fertilizer-treated plants. The beneficial effect of EM was attributed to the utilization of plant root exudates and the solubilization and mineralization of certain soil nutrients into plant available forms [23]. In other experiments, pure cultures of lactic acid bacteria were unable to promote significant differences in the humus content or chemical content of the soil.

6. Biochar as Soil Amendment

Biochar is produced with the intent to be applied to soil as a means of improving soil productivity, carbon (C) storage, or filtration of percolating soil water [24]. Biochar is produced by thermal decomposition of organic material under limited supply of oxygen (O2) and at relatively low temperatures (<700°C) [25]. The potential of biochar to improve plant growth is related to changes in the physicochemical properties of soils that lead to overall increases in microbial activity [26, 27]. When conditioning soils, it is possible to enhance the effectiveness of beneficial or effective microorganisms by adding biochar, or a similar material with tiny perforations, in which the microbes can house themselves (Zimmerman, 2008) [18].

Agegnehu et al. [28] listed some extensive scientific evidence demonstrating that additions of low application rates of biochar into bedding plant container media in the greenhouse, or as amendments to field soils, improve plant growth and yields significantly, regardless of nutrient supply. For example, Vaccari et al. [29] reported increases in the rates of germination, growth, and yields of tomato plants grown in a range of concentrations of a soil commercial container medium amended with biochar. Dunlop et al. [30] demonstrated improvements in the germination and growth of petunias, marigolds, bell pepper, and tomatoes in response to similar charcoal activated carbon amendments into bedding plant container media.

7. Composts as Soil Amendment

Beneficial or effective microorganisms (EM) including yeast, mold fungi, lactic acid bacteria (LAB), photosynthetic bacteria, and actinomycetes [19] microbial groups are responsible for decomposing a variety of organic materials for use in agriculture [31]. These microorganisms are very common in composts [31]. Composts inoculated with EM improve yields and nutrient uptake significantly for a variety of crops including wheat [11], soybean [6], rice [23], and cotton [32] more than plants grown with noninoculated composts. Talaat et al. [22] stated that improved productivity in crops treated with EM-inoculated composts compared with untreated composts is related to hastened decomposition of organic compounds into plant available nutrients. Sharma et al. [23] added that EM compost is a good source of nutrients for crops, which can provide favorable conditions for the growth of crops, promoting the mobilization of insoluble nutrients and activating the beneficial microorganisms in soils.

Significant effects of composts on soils depend on the type and rate of compost, soil C, pH, cation exchange capacity (CEC), and other components of soil fertility. The application of composts to soils can alter soil organic matter status [33, 34] as this is associated with the release of nutrients such as N through mineralization [35]. This process improves both the growth and yield of the plant. Besides decreasing soil bulk density, Agegnehu et al. [28] added that application of compost can increase soil pH, soil organic content (SOC), N content, available P, K, Ca, Mg, Na, and S. Compost addition to soil has also been shown to increase yield of crops similarly to, or beyond the effects of, mineral fertilizer application [36]. However, annual application of high doses of compost had an inhibitory effect on enzyme activity and crop yields [37].

8. Role of Natural Farming to Improve Pepper Cultivation

Smith et al. [13] opined that the foundation of Natural Farming production lies in the health of the soil. A fertile soil provides essential nutrients to the growing crop and helps support a diverse and active biotic community. The soil in Natural Farming production is often referred to as living soil. There is a wealth of microorganisms including bacteria, fungi, algae, and protozoa as well as macrofauna such as earthworms, snails, slugs, insects, spiders, centipede, and millipede living in it. Fungi such as mycorrhizae and bacteria (Rhizobia), Azotobacter, and earthworms are known to contribute to the fertility of the soil.

Pepper is a nutrient demanding crop, especially during fruit setting. For optimal growth and yield, it requires sufficient amounts of macronutrients and micronutrients. A pepper grower who practices Natural Farming must be able to recognise nutrient deficiency symptoms so that remedial measures are timely taken [1, 11, 14]. Hunt et al. [26] reported that fermented plant juice (FPJ) and fermented fruit juice (FFJ) from organic materials incorporated with biochar can provide fertile soil for the vines to grow well and bear fruit. All crop residues and farm wastes available on the farm including branches and leaves from pepper vines can be recycled, so that soil fertility is restored and maintained. It is the process of transforming organic materials of plant origin into humus. The FPJ and FFJ can act as fertilizers as well as a soil conditioners [6]. Although a study by Paulus and Anyi Wan [38] showed that pepper yield obtained from organic farming was lower compared with that of the conventional practice of using chemical based farming input, on the production cost per yield basis, it provides higher benefit-cost ratio of 1.67 compared with that of conventional practice with benefit-cost ratio of 1.44.

9. Conclusion

The proper selection and dosage of Natural Farming liquid fertilizers should be studied and adopted to improve nutrient efficiency. If the microorganisms comprising the mixed culture can coexist and are physiologically compatible and mutually complementary, and if the initial inoculum density is sufficiently high, there is a high probability that these microorganisms will become established in the soil and will be effective as an associative group, whereby such positive interactions would continue. Therefore, it is important to set up and properly sustain pepper cultivation practices under Natural Farming to reduce investment on chemical based inputs and at the same time lower the environmental hazard caused by pesticides, weedicides, fungicides, and inorganic fertilizers.

Conflicts of Interest

The authors declare that there are no conflicts of interest regarding the publication of this paper.


The authors acknowledge the support of the Research and Development Division, Malaysian Pepper Board, Sarawak, Malaysia, and Universiti Putra Malaysia for this review paper.


  1. G. Megir and A. D. Paulus, Pepper Production Technology in Malaysia, L. K. Fong and S. S. Liang, Eds., Malaysian Pepper Board, Sarawak, Malaysia, 2011.
  2. H. Park and M. W. DuPonte, “How to cultivate Indigenous Microorganisms,” Biotechnology, vol. 9, pp. 1–7, 2008. View at Google Scholar
  3. S. A. Miller, D. M. Ikeda Weinert, E. Weinert Jr. et al., Fermented Plant Juice, University of Hawai’I, College of Tropical Agriculture and Human Resources, Honolulu, Hawaii, 2013.
  4. H. A. Hamed, Y. A. Moustafa, and S. M. Abdel-Aziz, “In vivo efficacy of lactic acid bacteria in biological control against Fusarium oxysporum for protection of tomato plant,” Life Science Journal, vol. 8, no. 4, pp. 462–468, 2011. View at Google Scholar · View at Scopus
  5. K. Shin, G. van Diepen, W. Blok, and A. H. C. van Bruggen, “Variability of Effective Micro-organisms (EM) in bokashi and soil and effects on soil-borne plant pathogens,” Crop Protection, vol. 99, pp. 168–176, 2017. View at Publisher · View at Google Scholar · View at Scopus
  6. A. Javaid and R. Bajwa, “Field evaluation of effective microorganisms (EM) application for growth, nodulation, and nutrition of mung bean,” Turkish Journal of Agriculture and Forestry, vol. 35, no. 4, pp. 443–452, 2011. View at Publisher · View at Google Scholar · View at Scopus
  7. C. Zu, Z. Li, J. Yang et al., “Acid soil is associated with reduced Yield, root growth and nutrient uptake in black pepper (Piper nigrum L.),” Agricultural Sciences, vol. 05, no. 05, pp. 466–473, 2014. View at Publisher · View at Google Scholar
  8. C. A. Yap, “Determination of nutrient uptake characteristics of black pepper (Piper nigrum L.),” Journal of Agricultural Science and Technology, vol. 6, pp. 86–89, 2012. View at Google Scholar
  9. Malaysian Pepper Board, Laporan Kajian Verifikasi Hasil Lada, Malaysian Pepper Board, Sarawak, Malaysia, 2017.
  10. Z. Zuraini, G. Sanjay, and M. Noresah, “Effective Microorganism (EM) technology for water quality restoration and potential for sustainable water resources and management,” in Proceedings of the International Congress on Environmental Modelling and Software Modelling for Environments Sake, Fifth Biennial Meeting Held between 5th–8th, Ontario, Canada, 2010.
  11. P.-F. Sun, W.-T. Fang, L.-Y. Shin, J.-Y. Wei, S.-F. Fu, and J.-Y. Chou, “Indole-3-acetic acid-producing yeasts in the phyllosphere of the carnivorous plant Drosera indica L,” PLoS ONE, vol. 9, no. 12, Article ID e114196, 2014. View at Publisher · View at Google Scholar · View at Scopus
  12. C. T. Lee, M. N. Ismail, F. Razali, I. I. Muhamad, M. R. Sarmidi, and A. K. Khamis, “Application of effective microorganisms on soil and maize,” Journal of Chemical and Natural Resources Engineering, pp. 1–13, 2008. View at Google Scholar
  13. D. L. Smith, S. Subramanian, J. R. Lamont, and M. Bywater-Ekegàrd, “Signaling in the phytomicrobiome: Breadth and potential,” Frontiers in Plant Science, vol. 6, no. 709, 2015. View at Publisher · View at Google Scholar · View at Scopus
  14. D. P. Keymer and R. A. Lankau, “Disruption of plant–soil–microbial relationships influences plant growth,” Journal of Ecology, vol. 105, no. 3, pp. 816–827, 2017. View at Publisher · View at Google Scholar · View at Scopus
  15. A. H. C. Van Bruggen and M. R. Finckh, “Plant Diseases and Management Approaches in Organic Farming Systems,” Annual Review of Phytopathology, vol. 54, pp. 25–54, 2016. View at Publisher · View at Google Scholar · View at Scopus
  16. M. G. A. Van Der Heijden, R. D. Bardgett, and N. M. van Straalen, “The unseen majority: soil microbes as drivers of plant diversity and productivity in terrestrial ecosystems,” Ecology Letters, vol. 11, no. 3, pp. 296–310, 2008. View at Publisher · View at Google Scholar
  17. M. I. Rashid, L. H. Mujawar, T. Shahzad, T. Almeelbi, I. M. I. Ismail, and M. Oves, “Bacteria and fungi can contribute to nutrients bioavailability and aggregate formation in degraded soils,” Microbiological Research, vol. 183, pp. 26–41, 2016. View at Publisher · View at Google Scholar · View at Scopus
  18. J. E. Thies, M. C. Rillig, and E. R. Graber, “Biochar effects on the abundance, activity and diversity of the soil biota,” in Biochar for Environmental Management: Science, Technology and Implementation, pp. 327–388, 2015. View at Google Scholar
  19. T. Higa, “34, Nou-bun Kyo,” in Microorganisms for Agriculture and Environmental Preservation, p. 33, In Japanese, 1991. View at Google Scholar
  20. A. Ghasemzadeh and H. Z. E. Jaafar, “Effect of CO2 enrichment on synthesis of some primary and secondary metabolites in ginger (Zingiber officinale Roscoe),” International Journal of Molecular Sciences, vol. 12, no. 2, pp. 1101–1114, 2011. View at Publisher · View at Google Scholar · View at Scopus
  21. I. I. Zuraihah, Z. Aini, and M. Faridah, “Effects of IMO and EM application on soil nutrients, microbial population and crop yield,” Journal of Tropical Agriculture and Food Science, vol. 40, no. 2, pp. 257–263, 2012. View at Google Scholar
  22. N. B. Talaat, A. E. Ghoniem, M. T. Abdelhamid, and B. T. Shawky, “Effective microorganisms improve growth performance, alter nutrients acquisition and induce compatible solutes accumulation in common bean (Phaseolus vulgaris L.) plants subjected to salinity stress,” Plant Growth Regulation, vol. 75, no. 1, pp. 281–295, 2015. View at Publisher · View at Google Scholar · View at Scopus
  23. A. Sharma, T. N. Saha, A. Arora, R. Shah, and L. Nain, “Efficient Microorganism Compost Benefits Plant Growth and Improves Soil Health in Calendula and Marigold,” Horticultural Plant Journal, vol. 3, no. 2, pp. 67–72, 2017. View at Publisher · View at Google Scholar
  24. M. I. Bird, C. M. Wurster, P. H. de Paula Silva, N. A. Paul, and R. de Nys, “Algal biochar: Effects and applications,” GCB Bioenergy, vol. 4, no. 1, pp. 61–69, 2012. View at Publisher · View at Google Scholar · View at Scopus
  25. M. I. Bird, “Test procedures for biochar analysis in soils,” in Biochar for Environmental Management: Science, Technology and Implementation, J. Lehmann and S. Joseph, Eds., pp. 677–714, Routledge, London, UK, 2nd edition, 2015. View at Google Scholar
  26. J. Hunt, M. DuPonte, D. Sato, and A. Kawabata, “The basics of Biochar: a natural soil amendment,” Soil and Crop Management, vol. 30, pp. 1–6, 2010. View at Google Scholar
  27. P. Blackwell, S. Joseph, P. Munroe et al., “Influences of Biochar and Biochar-Mineral Complex on Mycorrhizal Colonisation and Nutrition of Wheat and Sorghum,” Pedosphere, vol. 25, no. 5, pp. 686–695, 2015. View at Publisher · View at Google Scholar · View at Scopus
  28. G. Agegnehu, P. N. Nelson, and M. I. Bird, “Crop yield, plant nutrient uptake and soil physicochemical properties under organic soil amendments and nitrogen fertilization on Nitisols,” Soil & Tillage Research, vol. 160, pp. 1–13, 2016. View at Publisher · View at Google Scholar · View at Scopus
  29. F. P. Vaccari, A. Maienza, F. Miglietta et al., “Biochar stimulates plant growth but not fruit yield of processing tomato in a fertile soil,” Agriculture, Ecosystems & Environment, vol. 207, pp. 163–170, 2015. View at Publisher · View at Google Scholar · View at Scopus
  30. S. J. Dunlop, M. C. Arbestain, P. A. Bishop, and J. J. Wargent, “Closing the loop: Use of biochar produced from tomato crop green waste as a substrate for soilless, hydroponic tomato production,” HortScience, vol. 50, no. 10, pp. 1572–1581, 2015. View at Google Scholar · View at Scopus
  31. P. Partanen, J. Hultman, L. Paulin, P. Auvinen, and M. Romantschuk, “Bacterial diversity at different stages of the composting process,” BMC Microbiology, vol. 10, article 94, 2010. View at Publisher · View at Google Scholar · View at Scopus
  32. A. Khaliq, M. K. Abbasi, and T. Hussain, “Effects of integrated use of organic and inorganic nutrient sources with effective microorganisms (EM) on seed cotton yield in Pakistan,” Bioresource Technology, vol. 97, no. 8, pp. 967–972, 2006. View at Publisher · View at Google Scholar · View at Scopus
  33. D. Fischer and B. Glaser, Synergisms between Compost and Biochar for Sustainable Soil Amelioration, Management of Organic Waste, S. E. Kumar, Ed., InTech, Shanghai, China, 2012.
  34. H. Schulz and B. Glaser, “Effects of biochar compared to organic and inorganic fertilizers on soil quality and plant growth in a greenhouse experiment,” Journal of Plant Nutrition and Soil Science, vol. 175, no. 3, pp. 410–422, 2012. View at Publisher · View at Google Scholar · View at Scopus
  35. J. E. Sanchez, T. C. Willson, K. Kizilkaya, E. Parker, and R. R. Harwood, “Enhancing the mineralizable nitrogen pool through substrate diversity in long term cropping systems,” Soil Science Society of America Journal, vol. 65, no. 5, pp. 1442–1447, 2001. View at Publisher · View at Google Scholar · View at Scopus
  36. J. Kimpinski, C. E. Gallant, R. Henry, J. A. Macleod, J. B. Sanderson, and A. V. Sturz, “Effect of Compost and Manure Soil Amendments on Nematodes and on Yields of Potato and Barley: A 7-Year Study,” Journal of Nematology, vol. 35, no. 3, pp. 289–293, 2003. View at Google Scholar · View at Scopus
  37. I. Marcote, T. Hernández, C. García, and A. Polo, “Influence of one or two successive annual applications of organic fertilisers on the enzyme activity of a soil under barley cultivation,” Bioresource Technology, vol. 79, no. 2, pp. 147–154, 2001. View at Publisher · View at Google Scholar · View at Scopus
  38. A. D. Paulus and L. Anyi Wan, Pepper Production Technology in Malaysia, L. K. Fong and S. S. Liang, Eds., Malaysian Pepper Board, Sarawak, Malaysia, 2011.