Response of spring wheat to phosphorus and sulphur starter fertilizers of differing acidification potential

Phosphorus (P) availability is often restricted in alkaline soils. The objective of this study was to determine if the plant availability of P from liquid ammonium polyphosphate fertilizer (APP) would be enhanced when blended with fluid sulphur (S) sources of differing acidification potential. Eight field studies with 'Butte 86' hard red spring wheat (Triticum aestivum L.) were conducted in 1995 and 1996 in eastern North Dakota, USA, comparing no P, 9.8 kg/ha of P, and 9.8 kg P/ha plus 11.2 kg S/ha from different S sources. The S sources were elemental sulphur (ES), ammonium sulphate (BS), ammonium bisulphite (ABS), ammonium thiosulphate (ATS), potassium thiosulphate (KTS) and potassium sulphate (KS). The P and S fertilizers were banded with the seed at planting. Phosphorus fertilization gave a typical 'starter effect', stimulating tillering, early growth and P uptake. Phosphorus uptake at the 4-5 leaf stage was increased by addition of acid-forming S fertilizers to the APP. Grain yield response to P applied with the seed was typically 400 kg/ha. The enhanced P uptake observed at the 4-5 leaf stage when certain S sources were added to APP did not lead to additional grain yield. Wheat grain yield in North Dakota comes almost entirely from the contributions of the main stem, T1 and T2 tillers, and initiation of these tillers was essentially complete when APP alone was banded with the seed.