Improving CIPR efficiency using CIPR-TSP mixtures
1998
Rosmaria, A.K. | Siva, K.B. | Aminuddin Hussin
Most Malaysian soils are acidic and have a high phosphate-fixing capacity which renders low soil phosphorus (P) status. Direct use of Christmas Island Phosphate Rock (CIPR) to alleviate such a problem is an economical option when compared to use of soluble P fertiliser i.e Triple Super Phosphate (TSP). Comparatively, however, CIPR is less reactive and efficient in releasing P for plant uptake. One way of overcoming this limitation is by mixing CIPR with soluble P fertiliser, which yields phosphoric acid and calcium phosphate. Since the solubility of phosphate rock increases under acidic regime(high H subscript + concentration), the phosphoric acid produced should potentially increase the solubility of CIPR. A study was conducted to evaluate the effect of CIPR and TSP mixtures on P and calcium (Ca) recovery from two Malaysian soils of differing pH. Treatments employed included single applications of either CIPR or TSP at rates ranging from 100 to 300 mg/kg for the former and 50-200 for the latter. Mixtures of TSP-CIPR were applied in ratios of 1:1 and 1:3. Recovery of P and Ca was recorded over time up to 90 days after treatment. Results indicated that TSP-CIPR mixtures increased P release when compared to single application of CIPR in both soils. Increased release of Ca from the mixtures was evident only in the acid soil. Release of P increased with increase in mixture concentration and were more pronounced in mixtures bearing a ration of 1:1. The mixtures, however, did not yield added benefits in P and Ca release when compared with summed values derived from single applicatons of CIPR and TSP.
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