Phosphorus Source and Surface Fluid Band Spacing Effects on Irrigated Alfalfa

• Published in: Soil Science Society of America journal Vol. 73; no. 2; pp. 367 - 374
• Main Authors: Koenig, Richard, Winward, Dean, Reid, Chad, Barnhill, James, Pace, Mike, Heaton, Kevin
• Format: Journal Article
• Language: English
• Published: Madison Soil Science Society 01-03-2009; Soil Science Society of America; American Society of Agronomy
• Subjects: Advantages; Agronomy. Soil science and plant productions; Alfalfa; alkaline soils; Ammonium; ammonium polyphosphates; application methods; band placement; Biological and medical sciences; broadcast application; calcareous soils; chemical concentration; Crops; Dry matter; dry matter accumulation; Earth sciences; Earth, ocean, space; Exact sciences and technology; fertilizer application; Fundamental and applied biological sciences. Psychology; liquid fertilizers; Loam soils; Medicago sativa; monoammonium phosphate; nutrient availability; nutrient uptake; phosphorus fertilizers; plant growth; plant tissues; Soil science; soil test values; Soil testing; Soils; spatial variation; Studies; Surficial geology; yields; Utah; Soil science; Earth science
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj2008.0197

Subsurface banding of P fertilizer is more effective than broadcast and incorporation for annual crops on P-deficient sites. Subsurface banding in established alfalfa (Medicago sativa L.) may damage plants. This study compared spring-applied, broadcast dry monoammonium phosphate (MAP) and fluid ammonium polyphosphate (APP), and APP applied in surface bands with 15-, 30-, or 60-cm spacing, at rates equivalent to 0.5x and 1x the soil test recommendation for yield, tissue P concentration, and P uptake at six sites. There was no difference in soil test P measured after the first cutting between broadcast MAP or APP. Yield responses to P occurred at all sites and ranged from a low of 0.7 Mg ha-1 (7%) averaged across P rate, to 2.6 Mg ha-1 (46%) at the 0.5x rate and 5.4 Mg ha-1 (95%) at the 1x rate above the 0 kg P ha-1 treatment. Yield was higher with MAP than with APP for five of 19 individual harvests, while total yield was 1.0 Mg ha-1 higher with MAP than with APP at one site-year. Phosphorus source effects on P concentration and uptake were similar to those on dry matter yield. There was a linear decrease in yield with increasing band spacing for one site-year and a quadratic response for another. Responses to band spacing in tissue P concentration for nine harvests suggest that band spacing of 15 and 30 cm may enhance P availability relative to broadcast or 60-cm spacing. In only one site-year did we find a yield advantage of MAP over APP, or of surface band over broadcast APP.