We tested the effects of triple superphosphate (TSP) and Minjingu phosphate rock (MPR), when applied at phosphorus (P) rates of 50 or 250？kg？P？ha？1 in a factorial combination with urea or Tithonia diversifolia green manure as nitrogen sources, on P availability and maize yields for two seasons at Nyabeda and Khwisero in Kenya. Phosphorus availability was determined by the Olsen method or sequential fractionation. There was no significant difference in Olsen P as influenced by TSP and MPR at 50？kg？P？ha？1 irrespective of the N source at both sites in both seasons. However, at 250？kg？P？ha？1, TSP gave significantly higher Olsen P than MPR. The labile P fractions generally followed the same trend as the Olsen P. Maize yields increased with increasing amount of P applied. Generally, there was no significant difference between TSP and MPR on maize yields irrespective of the N source. The Olsen-P, Resin-P, and sodium bicarbonate inorganic P correlated well with maize yields when TSP was used but the correlations between these P tests and maize yields for MPR were not consistent and therefore their use on soils treated with MPR should be exercised with caution. 1. Introduction More than 80% of the soils in the densely populated highlands of western Kenya are inherently low in P and this seriously limits the productivity of maize which is the staple food crop in the area [1]. Although judicious application of inorganic P fertilizers is recognized as the most effective method for alleviating P deficiencies, their high cost, inaccessibility, and erratic and unprofitable crop responses limit their use, particularly on smallholder farms [2]. Much research on soil fertility management in western Kenya has therefore been devoted to testing nutrient inputs that are thought to be inexpensive, locally available, and sustainable, as alternatives to conventional fertilizers. The use of organic materials (OMs) and phosphate rocks (PR) has in particular received considerable research attention in recent years [3–5]. This has been given impetus by a paradigm shift in soil fertility management towards the integrated soil fertility management (ISFM). In this strategy, the use of organic and inorganic nutrient sources in combination is advocated on smallholder farms [6] with the OMs being utilized mainly as sources of N, because of their low P content, while inorganic fertilizers are used to supply P. In addition, to increase the range of OMs that smallholder farmers can use in integrated soil fertility management (ISFM), some nontraditional sources of nutrients such as
References
[1]
B. Jama and P. van Straaten, “Potential of East African phosphate rock deposits in integrated nutrient management strategies,” Annals of Brazilian Academy of Sciences, vol. 78, no. 4, pp. 781–790, 2006.
[2]
S. M. Nandwa and M. A. Bekunda, “Research on nutrient flows and balances in East and Southern Africa: state-of-the-art,” Agriculture, Ecosystems and Environment, vol. 71, no. 1–3, pp. 5–18, 1998.
[3]
P. A. Opala, J. R. Okalebo, and C. Othieno, “Comparison of effects of phosphorus sources on soil acidity, available phosphorus and maize yields at two sites in western Kenya,” Archives of Agronomy and Soil Science, vol. 59, no. 3, 2013.
[4]
S. T. Ikerra, E. Semu, and J. P. Mrema, “Combining Tithonia diversifolia and minjingu phosphate rock for improvement of P availability and maize grain yields on a chromic acrisol in Morogoro, Tanzania,” Nutrient Cycling in Agroecosystems, vol. 76, no. 2-3, pp. 249–260, 2006.
[5]
M. W. Waigwa, C. O. Othieno, and J. R. Okalebo, “Phosphorus availability as affected by the application of phosphate rock combined with organic materials to acid soils in western Kenya,” Experimental Agriculture, vol. 39, no. 4, pp. 395–407, 2003.
[6]
N. Sanginga and P. L. Woomer, Integrated Soil Fertility Management in Africa: Principles, Practices and Development Process, Tropical Soil Biology and Fertility Institute of the International Centre for Tropical Agriculture, Nairobi, Kenya, 2009.
[7]
B. Jama, C. A. Palm, R. J. Buresh et al., “Tithonia diversifolia as a green manure for soil fertility improvement in western Kenya: a review,” Agroforestry Systems, vol. 49, no. 2, pp. 201–221, 2000.
[8]
G. Nziguheba, C. A. Palm, R. J. Buresh, and P. C. Smithson, “Soil phosphorus fractions and adsorption as affected by organic and inorganic sources,” Plant and Soil, vol. 198, no. 2, pp. 159–168, 1998.
[9]
A. A. Rivaie, P. Loganathan, J. D. Graham, R. W. Tillman, and T. W. Payn, “Effect of phosphate rock and triple superphosphate on soil phosphorus fractions and their plant-availability and downward movement in two volcanic ash soils under Pinus radiata plantations in New Zealand,” Nutrient Cycling in Agroecosystems, vol. 82, no. 1, pp. 75–88, 2008.
[10]
M. J. Hedley, J. W. B. Stewart, and B. S. Chauhan, “Changes in inorganic and organic soil phosphorus fractions induced by cultivation practices and by laboratory incubations,” Soil Science Society of America Journal, vol. 46, no. 5, pp. 970–976, 1982.
[11]
H. Tiessen and J. O. Moir, “Characterization of available P by sequential extraction,” in Soil Sampling and Methods of Analysis, M. R. Carter, Ed., pp. 75–86, Lewis Publications, Boca Raton, Fla, USA, 1993.
[12]
A. Samadi, “Contribution of inorganic phosphorus fractions to plant nutrition in alkaline-calcareous soils,” Journal of Agricultural Science and Technology, vol. 8, pp. 77–89, 2006.
[13]
S. R. Olsen, C. V. Cole, F. S. Watanabe, and L. A. Dean, “Estimation of available phosphorus in soils by extraction with sodium bicarbonate,” U.S.D.A. Circular 939, 1954.
S. H. Chien, W. R. Clayton, and G. M. McClellan, “Kinetic dissolution of phosphate rocks in soils,” Soil Science Society of America Journal, vol. 44, pp. 260–264, 1980.
[16]
R. E. White, “Recent developments in the use of phosphate fertilizer on New Zealand pastures,” Journal of the Australian Institute of Agricultural Science, vol. 2, pp. 25–32, 1989.
[17]
A. K. N. Zoysa, P. Loganathan, and M. J. Hedley, “Comparison of the agronomic effectiveness of a phosphate rock and triple superphosphate as phosphate fertilisers for tea (Camellia sinensis L.) on a strongly acidic Ultisol,” Nutrient Cycling in Agroecosystems, vol. 59, no. 2, pp. 95–105, 2001.
[18]
R. J. Buresh, P. C. Smithson, and D. T. Hellums, “Building soil phosphorus capital in Africa,” in Replenishing Soil Fertility in Africa, R. J. Buresh, P. A. Sanchez, and F. Calhoun, Eds., pp. 114–149, Soils Science Society of America special publication, Madison, Wis, USA, 1997.
[19]
F. Iyamuremye and R. P. Dick, “Organic amendments and phosphorus sorption by soils,” Advances in Agronomy, vol. 56, pp. 139–185, 1996.
[20]
P. A. Sanchez, K. D. Shepherd, M. J. Soule et al., “Soil fertility replenishment in Africa: an investment in natural resource capital,” in Replenishing Soil Fertility in Africa, R. J. Buresh, P. A. Sanchez, and F. Calhoun, Eds., pp. 1–46, Soils Science Society of America special publication, Madison, Wis, USA, 1997.
[21]
A. Paniagua, M. J. Mazzarino, D. Kass, L. Szott, and C. Fernandez, “Soil phosphorus fractions under five tropical agro-ecosystems on a volcanic soil,” Australian Journal of Soil Research, vol. 33, no. 2, pp. 311–320, 1995.
[22]
H. Tiessen, J. W. B. Stewart, and C. V. Cole, “Pathways of phosphorus transformations in soils of differing pedogenesis,” Soil Science Society of America Journal, vol. 48, no. 4, pp. 853–858, 1984.
[23]
J. R. Okalebo, K. W. Gathua, and P. L. Woomer, Laboratory Methods of Soil and Plant Analysis. A Working Manual, TSBF-CIAT, SACRED Africa, KARI, SSEA, Nairobi, Kenya, 2nd edition, 2002.
[24]
C. N. Gachengo, C. A. Palm, B. Jama, and C. Othieno, “Tithonia and senna green manures and inorganic fertilizers as phosphorus sources for maize in Western Kenya,” Agroforestry Systems, vol. 44, no. 1, pp. 21–36, 1998.
[25]
P. K. Mutuo, P. C. Smithson, R. J. Buresh, and R. J. Okalebo, “Comparison of phosphate rock and triple superphosphate on a phosphorus- deficient Kenyan soil,” Communications in Soil Science and Plant Analysis, vol. 30, no. 7-8, pp. 1091–1103, 1999.
[26]
A. Abunyewa, E. K. Asiedu, and Y. Ahenkorah, “Fertilizer phosphorus fractions and their availability to maize on different land forms of vertisols in the coastal savanna zone of Ghana,” West African Journal of Applied Ecology, vol. 5, pp. 63–73, 2004.
[27]
P. A. Sánchez and J. G. Salinas, “Low-input technology for managing oxisols and ultisols in tropical America,” Advances in Agronomy, vol. 34, pp. 279–406, 1981.
