Published online by Cambridge University Press: 27 March 2009
1. A spring top-dressing of 0·5 cwt.nitrogen/acre was applied to winter wheat as urea or ammonium nitrate in a single spray at 30 gal./acre or as solid fertilizer applied to the soil. A weed-killer, 2,4-dichlorophenoxyacetic acid, was applied in the nitrogen spray or separately in spray to plots that received solid fertilizer.
2. Uptake of nitrogen by the crop from solid fertilizer was about twice that from fertilizers applied in sprays. Solid fertilizer increased yield slightly more than did sprays.
3. Ammonium nitrate and urea had the same effects, both when applied in sprays and when applied as solid to the soil.
4. 2,4-D decreased the amount of weed slightly, but had no effect on yield of wheat.
5. The interactions between weed-killer and method of applying nitrogen were small; the response to nitrogen in dry weight of straw, including weeds, in one experiment, and of shoots in another experiment, was decreased by 2,4-D when nitrogen was applied in spray but not when it was applied as solid fertilizer.