Comparison of water‐insoluble phosphate fertilisers with superphosphate—a review

Abstract

A series of experiments was carried out in England and Wales in the period 1972-1982, to compare the relative effectiveness of various commercially available water-insoluble phosphate fertilisers with that of superphosphate. Most of the trials were on permanent grassland, but a few used barley and swedes as test crops. Ground Gafsa rock P, although only approximately 50% as effective as superphosphate in the year of application, gave somewhat higher responses in the following (residual) 2 years on unlimed, acid grassland. In these circumstances, grinding finer than 150 pm did not appear to be worth the extra cost. Granulation of finely ground Gafsa rock P slightly reduced its effectiveness for grass in the first year, but markedly reduced its efficiency for cereals. Mixtures of medium grade basic slag and Moroccan rock P were only slightly inferior to high grade basic slag, but mixtures of low grade slag and ground rock P (Moroccan or Gafsa) were somewhat less effective than the finely ground Gafsa rock P, especially in the first year. Granulated ground underacidulated rock P (Gafsa or Moroccan), was as effective as very finely ground Gafsa rock P, however a bulk blend of granulated Gafsa rock P and triple superphosphate was more effective than Gafsa rock P, but less so than superphosphate in the first year. Calcined aluminium calcium P was the least effective of the fertilisers tested, being especially slow in action, and only 25% as effective as superphosphate in the first year.

How effective are Calciphos and Phospal?

“…The residual value of superphosphate relative to freshly applied superphospate decreases by about 50% between year 1 and year 2, and less rapidly thereafter [2,8]. The residual value of both Calciphos and Phospal expressed relative to residual superphosphate increases [12,22,24,28,36]. A similar trend was observed for C900 [4].…”

“…Many high RE values were determined for Phospal from field experiments (data from reference 35) giving a mean value of 0.91. However in other field experiments [12,13], Phospal was much less effective than superphosphate in the year of application. It was not always possible to calculate RE values from some of the published data on both Calciphos and Phospal because no yield results are listed for treatments receiving no P fertilizer applications [20,22,36].…”

“…The circles are 90% confidence regions for the canonical variate means. (12) 0.62 (m2) RESP (X3) -0.55 (13) 0.37 (m3) LEVEL (X4) 0.69 (14) 1.36 (m4) % variance 74% 18%…”

“…Since only one or two levels of applied P were used in most experiments from which we were able to calculate RE values for Phospal, a comparison of the two methods of evaluation is not possible. However, the effectiveness of Phospal has been reported to be much less than that of freshly applied superphosphate in pot experiments [33,37], small plot experiments [38] and field experiments [12,13,281.…”

Partially acidulated phosphate rock as fertiliser and dissolution in soil of the residual rock phosphate

“…Results from greenhouse studies using New Zealand soils (Raj an 1982(Raj an , 1986) and overseas studies (McLean et al 1964;Hammond et al 1980;Garbochev 1981;Marwaha 1983;Davies 1984;Hagin & Katz 1985) suggest that consistent agronomic effectiveness requires reactive PRs for partial acidulation. North Carolina PR is a highly reactive rock (Chien & Hammond 1978) and is imported in large quantities into New Zealand.…”