Published online by Cambridge University Press: 27 March 2009
Field experiments of modern design that included carrots were first made at Woburn in 1934, to compare the value of nitrogen in dried poultry manure with ammonium sulphate. The experiments were repeated at several centres and continued until 1939. Most other crops responded well to nitrogen but in only one of the five experiments containing carrots did ammonium sulphate at 3 cwt/acre increase the root yield, and in two it significantly depressed yield. Ammonium sulphate tended to lessen plant numbers, but it increased the yield of tops (Rothamsted Experimental Station, 1934)