A glasshouse comparison of 6 phosphate fertilisers

Abstract

In a glasshouse experiment the effectiveness of Chatham Rise phosphorite (CRP) as a source of phosphorus (P) for perennial ryegrass and white clover on 6 contrasting soils was compared with single superphosphate, North Carolina phosphate rock (NCPR), Sechura phosphate rock (SPR) from Peru, Tennessee phosphate rock (TPR), and calcined Christmas Island 'C' grade phosphate rock (Calciphos). The 6 P sources are ranked in the following order of effectiveness for ryegrass under glasshouse conditions: superphosphate ~ NCPR ~ SPR > CRP > > Calciphos > > TPR. A marked difference was found in the ability of the 2 plant species to use P from a phosphate rock (PR). SPR was as effective as superphosphate on clover. This was particularly pronounced when the comparison was based upon P uptake data rather than yield data. In fact there was no difference between superphosphate, SPR, and CRP when P uptake by clover was used as the measure of effectiveness. When P uptake by ryegrass was used to assess agronomic performance rather than ryegrass yield data, the reactive PR materials, NCPR, SPR, and CRP were far less effective than superphosphate. The results indicate that both dry matter yield and P uptake data are required to fully evaluate the agronomic effectiveness of PRo Extrapolation of the results of this glasshouse experiment to field situations is discussed.

Crop (Maize) Response to Direct Application of Local Phosphate Rock on Selected Acid Soils of Tanzania

“…Accordingly, the relative agronomic effectiveness (RAE) of MPRs is less than 100% (Table 3). The better performance of TSP-treated soils can be attributed to higher solubility (faster reaction) of TSP compared to MPRs in agreement with the commonly found slower dissolution of PRs than of TSP (Mackay, Syers, and Greig 1984;Hammond, Chien, and Easterwood 1986). Slower dissolution results in lower soil solution concentration, and hence reduced availability and plant growth, which is aggravated on P-deficient soils with strong phosphate-fixing components due to competition between plants and soil adsorbents.…”

Effects of Organic and Inorganic Materials on Soil Acidity and Phosphorus Availability in a Soil Incubation Study

“…This is ascribed to the higher solubility of TSP compared to the PRs whose dissolution is usually low and slow [31]. The OMs generally gave higher Olsen P values than the PRs at comparable total P rates.…”

Seasonal patterns of phosphate uptake in relation to comparisons between fertilizers

“…that the relative effectiveness of phosphate sources of low solubility increases with time e.g. [11,16,17]. More often comparisons between phosphates have been made over only a single time interval so that no opportunity occurred to detect this effect.…”

“…However no procedure gives an absolute measure of the relative effectiveness [17] of one fertilizer compared with another. When using the respective P uptakes it needs to be assumed that the use of native soil P is unaltered by the addition of fertilizers; at comparable yields with different fertilizers, the error from this assumption should not greatly affect fertilizer comparisons.…”