1. Black, C. A., Evans, D. D., White, J. L., Ensminger, L. E., and Clark, F. E. 1965. Methods of soil analysis, part 2, Chemical and microbiological properties. American Society of Agronomy.
2. Bremner, J. M., and Mulvaney, C. S. 1965. Nitrogen-Total. In: Methods of soil analysis: part 2, Chemical and Microbiological Properties. Page, A. L. (Ed). 1982. Second Edition. American Society of Agronomy Inc. Madison, Wisconsin USA. Agronomy Series 9 (2): 596-622.
3. Briones, M. J. I., Barreal, M. E., Harrison, A. C., and Gallego, P. P. 2011. Earthworms and nitrogen applications to improve soil health in an intensively cultivated kiwifruit orchard. Applied Soil Ecology 49: 158-166.
4. Chaoui, H. I., Zibilske, L. M., and Ohno, T. 2003 .Effects of earthworm casts and compost on soil microbial activity and plant nutrient availability. Soil Biology and Biochemistry 35: 295-302.
5. Clark M. S., Horwath W. R., Shennan C., and Scow, K. M. 1998. Changes in soil chemical properties resulting from organic and low-input farming practices. Agronomy Journal 90: 662-671.
6. Corwin, D. L., and Lesch, S. M. 2005. Apparent soil electrical conductivity measurements in agriculture. Computer, Electronic and Agriculture 46: 11-44.
7. Eghball, B., and Power, J. F. 1999. Composted and non-composted manure application to conventional and no-tillage system: corn yield and nitrogen uptake. Agronomy Journal 91: 819-825.
8. Eigenberg, R. A., Doran, J. W., Nienaber, J. A., Ferguson, R. B., and Woodbury, B. L. 2002. Electrical conductivity monitoring of soil condition and available N with animal manure and a cover crop. Agriculture, Ecosystems and Environment 88: 183-193.
9. Emam, Y. 2003. Cereal farming. Shiraz university publication. (in Persian).
10. Franzen, D., Long, D., Sims, A., Lamb, J., Casey, F., Staricka, J., Halvorson, M., and Hofman, V. 2011. Evaluation of methods to determine residual soil nitrate zones across the northern Great Plains of the USA. Precision Agriculture 12 (4): 594-607.
11. Gajda, A. M., Doran, J. W., Weinhold, B. J., Kettler, T. A., Pikul, Jr. J. L., and Cambadella, C. A. 2000. Soil quality evaluations of alternative and conventional management systems in the Plains. In: Lal R., Kimble J. F., Follett, R. F., Stewart B. A. (Eds.), Methods of Assessment of Soil Carbon, CRC Press, Boca Raton, FL.
12. Hoyle, F. C., and Murphy, D. V. 2011. Influence of organic residues and soil incorporation on temporal measures of microbial biomass and plant available nitrogen. Plant and Soil 347: 53-64.
13. Jaynes, D. B., Colvin, T. S., and Ambuel, J. 1995. Yield mapping by electromagnetic induction. p. 383-394. In: P.C. Robert et al. (ed.) Site-specific management for agricultural systems. ASA, CSSA, and SSSA, Madison, WI.
14. Johnson, C. K., Doran, J. W., Eghball, B., Eigenberg, R. A., Wienhold, B. J., and Woodbury, B. L. 2003. Status of soil electrical conductivity studies by central states researchers. American Society of Agricultural Engineers Annual International Meeting, Las Vegas.
15. Johnson, C. K., Eskridge, K. M., and Corwin, D. L. 2005. Apparent soil electrical conductivity: applications for designing and evaluating field-scale experiments. Computers and Electronics in Agriculture 46: 181-202.
16. Kamkar, B., and Mahdavi-Damghani, A. 2008. Principles of sustainable agriculture. Academic Jihad publication. Mashhad. (in Persian).
17. Kanchikerimath, M., and Singh, D. 2001. Soil organic matter and biological properties after 26 years of maize-wheat-cowpea cropping as affected by manure and fertilization in a combisol India. Agriculture Ecosystem and Environment 86: 155-162.
18. Kennedy, I. R., Choudhury, A. T. A. M., and Kecskes, M. L. 2004. Non-symbiotic bacterial daizotrophs in crop-farming systems: can their potential for plant growth promotion be better exploited? Soil Biology and Biochemistry 36: 1229-1244.
19. Kitchen, N. R., Sudduth, K. A., and Drummond, S. T. 1999. Soil electrical conductivity as a crop productivity measure for claypan soils. Journal of Production Agriculture 12: 607-617.
20. Kizilkaya, R., and Hepsen, S. 2007. Microbiological properties in earthworm cast and surrounding soil amended with various organic wastes. Communications in Soil Science and Plant Analysis 38: 2861-2876.
21. Lee, J. 2010. Effect of application method of organic fertilizer on growth, soil chemical properties and microbial densities in organic bulb onion production. Scientia Horticulturae 124: 299-305.
22. Majidian, M., Ghalavand, A., Karimian, N., and Kamkar-Haghighi, A. 2008. Effect of different levels of nitrogen, manure and irrigation on corn yield and yield components. Crops product Journal 2: 67-85. (in Persian with English abstract).
23. Manna, M. C., Jha, S., Ghosh, P. K., and Acharya, C. L. 2003. Comparative efficacy of three epigic earthworms under different deciduous forest litters decomposition. Bioresource Technology 88: 197-206.
24. Marinari, S., Masciandaro, G., Ceccanti, B., and Grego, S. 2000. Influence of organic and mineral fertilizers on soil biological and physical properties. Bioresource Technology 72: 9-17.
25. Mirzaee-Talarposhti, R., Kambozia, J., Sabahi, H., and Mahdavi-Damghani, A. 2009. Effect of organic fertilizers on soil physico-chemical properties and yield of tamato (Lycopersicon esculentum). Iranian Journal of Field Crops Research 7 (1): 257-268. (in Persian with English abstract).
26. Nelson, D. W., and Sommers, L. E. 1982. Total carbon, organic carbon and organic matter. In: Page, A. L., Miller, R. H., and Keeney, D. R. (Eds.), Methods of Soil Analysis, American Society of Agronomy. Madison, Wisconsis: 539-580.
27. Pang, X. P., and Letey, J. 2000. Organic farming: challenge of timing nitrogen availability to crop nitrogen requirements. Soil Science Society of American Journal 64: 247-253.
28. Patriquin, D. G., Blaikie, H., Patriquin, M. J., and Yang, C. 1993. On-farm measurements of pH, electrical conductivity and nitrate in soil extracts for monitoring coupling of nutrient cycles. Biology, Agriculture and Horticulture 9: 231-272.
29. Rezaeenejad, Y., and Afyooni, M. 2001. Effect of organic matters on soil chemical properties, elements uptake by corn and corn yield. Agriculture and Natural Resources Sciences and Technologies 4 (4): 19-28. (in Persian with English abstract).
30. Sharma, P., Shukla, M. K., and Mexal, J. G. 2011. Spatial variability of soil properties in agricultural fields of southern New Mexico. Soil Science, Article in Press.
31. Sudduth, K. A., Kitchen, N. R., Hughes, D. F., and Drummond, S. T. 1995. Electromagnetic induction sensing as an indicator or productivity on claypan soils. p. 671-681. In: P.C. Robert et al. (Eds.) Site-specific management for agricultural systems. ASA, CSSA, and SSSA, Madison, WI.