Double Superphosphate Research Articles

Fertility Studies on a Sandy Loam in Semi-Arid Tanzania

SUMMARYInitial and residual effects of phosphorus, lime and potassium were studied on Natal Common and Dodoma Bold groundnuts. Double superphosphate (D.S.P., 42% P2O5) considerably increased yields of the first two crops. Lime was noticeably beneficial on Dodoma Bold but less so on Natal Common, while K depressed yields of both when applied without P. The LPK treatment yielded best with each variety, but initially P alone was most economic. Comparing D.S.P., Tororo superphosphate (T.S.P., 21% P2O5, 13% S) and Minjingu phosphate (M.P., 15% citric soluble P2O5), T.S.P. gave the best response (625 lb/acre over 3 years), more than double that of equivalent P2O5 as D.S.P. T.S.P.'s superiority is attributed mainly to its sulphur content. Though initially inferior, M.P. proved as good as D.S.P. over 3 years. 224 lb/acre T.S.P. in alter-nate years is recommended. After two or three crops, light applications of lime and potassium together would be beneficial.

Fertility Studies on a Sandy Loam in Semi-Arid Tanzania

SummaryN and P fertilizers applied to maize had considerable effects over a five-year period, especially when both were given. Initial applications of 47 lb/acre/P2O5with annual dressings of 58 lb N, produced a mean yield increase of 55 per cent above the control. K gave little response in the first three years, but thereafter became more important. 1120 lb ammonium sulphate nitrate caused striking reductions in soil pH, Ca, Mg, K, total and organic P but increases in exch. Mn and soluble P. 112 lb double superphosphate increased the total and organic P and 65 lb K2O reduced organic P. Organic carbon suffered a mean loss of 33 per cent over five years. Recommendations are made regarding P2O5, N and K on this soil.

A study of the interaction of P, K, S, Mg, Mo, and B fertilisers, and ground limestone, applied to grass-clover pasture

Abstract Results are presented of two multi-factorial field experiments on permanent pasture with six fertilisers and ground limestone. The trials were carried out at Marton Experimental Area and at Invermay Research Station, Mosgiel. Treatments were:—high versus low rates of ground limestone, muriate of potash, and double superphosphate; and some against nil rates of elemental sulphur, magnesium carbonate, borax, and sodium molybdate. All treatments except limestone and sodium molybdate were applied annually by top-dressing.

Determination of free phosphoric acid in superphosphate

Abstract Water soluble phosphoric acid in ordinary superphosphate and double (or triple) superphosphate consists of mainly monocalcium phosphate, but it also contains one to several per cent free phosphoric acid. Both free acid and water are the essential components in order to know the change in curing or to estimate the reduction of posphoric acid in manufacture of mixed fertilizer.

The effect of different phosphate fertilisers on soil pH and the consequent effect on phosphate retention

Summary A comparison has been made of the degree of phosphate retention by yellow-brown loam of different phosphate fertilisers—superphosphate, double superphosphate, potassium dihydrogen phosphate and diarn-monium phosphate. The soils used were of low, medium and high phosphorus status. The addition of the phosphate to the soil suspension alters the pH, and the differences between the pH values of the suspensions are sufficient to account for the differences in phosphate retention. To determine how long these differences in pH persist, a low and a high phosphorus status soil were topdressed in a laboratory experiment at 90 lb P/acre and the pH of the surface soil measured over a period of three months. Changes of over one pH unit were recorded after topdressing, and it is considered that, even under light topdressing in the field, these pH changes would occur in the immediate vicinity of the phosphate particles and affect the concentration of phosphate in the soil solution and the utilisation of the appl...

Studies on physico-chemical relations of soil and water

The paper deals with effects of ammonium sulphate (N), potassium sulphate (K) and double superphosphate (P), singly and in combinations (total 8 treatments) on the water retentive force of the soil at different moisture contents.

Ammoniation of Double Superphosphate

Ammoniation of Double Superphosphate

Observations on the Analysis of Double Superphosphate

Observations on the Analysis of Double Superphosphate