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Influence of Tithonia diversifolia and triple superphosphate on dissolution and effectiveness of phosphate rock in acidic soil
Author(s) -
Savini Isaac,
Smithson Paul C.,
Karanja Nancy K.,
Yamasaki Hideo
Publication year - 2006
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200521931
Subject(s) - tithonia , chemistry , dissolution , solubility , oxisol , nuclear chemistry , phosphate , zoology , soil water , agronomy , geology , biochemistry , biology , soil science , organic chemistry
An incubation and a pot experiment were conducted to evaluate the dissolution and agronomic effectiveness of a less reactive phosphate rock, Busumbu soft ore (BPR), in an Oxisol in Kenya. Resin (anion and anion + cation)‐extractable P and sequentially extracted P with 0.5 M NaHCO 3 , 0.1 M NaOH, and 1 M HCl were analyzed. Dissolution was determined from the increase in anion resin (AER)–, NaHCO 3 ‐, and NaOH‐extractable P in soil amended with PR compared with the control soil. Where P was applied, resin P significantly increased above the no‐P treatment. Busumbu‐PR solubility was low and did not increase significantly in 16 weeks. Anion + cation (ACER)‐extractable P was generally greater than AER‐P. The difference was greater for PR than for triple superphosphate (TSP). The ACER extraction may be a better estimate of plant P availability, particularly when poorly soluble P sources are used. Addition of P fertilizers alone or in combination with Tithonia diversifolia (TSP, BPR, TSP + Tithonia , and BPR + Tithonia ) increased the concentration of labile inorganic P pools (NaHCO 3 ‐ and NaOH‐P i ). Cumulative evolved CO 2 was significantly correlated with cumulative N mineralized from Tithonia (r, 0.51, p < 0.05). Decrease in pH caused NH $ _4^+ $ ‐N accumulation while NO $ _3^- $ ‐N remained low where Tithonia was incorporated at all sampling times. However, when pH was increased, NH $ _4^+ $ ‐N declined with a corresponding rise in NO $ _3^- $ ‐N. Tithonia significantly depressed soil exchangeable acidity relative to control with time. A significant increase ( p < 0.05) was observed for P uptake but not dry‐mass production in maize where BPR was applied. The variations in yield and P uptake due to source and rates of application were statistically significant. At any given P rate, highest yields were obtained with Tithonia alone. Combination of Busumbu PR with TSP or Tithonia did not enhance the effectiveness of the PR. The poor dissolution and plant P uptake of BPR may be related to the high Fe content in the PR material.