Abstract: | The nitrate and percentage organic nitrogen contents of 14 vegetable and two arable crops were measured after they had been grown with different levels of N-fertiliser. Foliage crops always contained substantial quantities of nitrate which increased with increase in the rate of N-fertiliser application. Grain of legumes and cereals, storage roots of carrots, parsnips and sugar beet, and onion bulbs and leeks contained no detectable amounts of nitrate even when N-fertiliser application rates were very high. Storage roots of red beet, swede and white turnip contained more than 3 mg NON g?1 dry weight when grown with exceptionally high levels of fertiliser-N but contained very little when grown with the optimum amount of fertiliser-N or less. An equation was developed that linked NON to percentage organic-N for those parts of plants that could accumulate nitrate. It gave good fits to the data from seven crop species grown at a range of different levels of N-nutrition. It is estimated from the foregoing data and a survey of household food consumption that the average British person consumes about 60 mg NON week?1 in field vegetables. If N-fertilisers were withheld consumption would be about 30 mg and if excess were applied it would be about 120 mg NON week?1. |