A single harvest method using horticultural maturity rating data was tested in 2 years of Ν application field trials with broccoli. Using analysis of variance with the maturity data as covariates, it was possible to evaluate how broccoli yield response to Ν was influenced through the effect of Ν on maturity. This single harvest method simplified field operations and facilitated interpretation of Ν uptake data. Nitrogen treatments did not significantly alter maturity of broccoli in either year. Broccoli yield increased with up to 250 kg·ha –1 of Ν in both years. Sweet corn, which was grown adjacent to the broccoli in the first year, did not respond to similar applications. Nitrogen did not preferentially increase vegetative growth of broccoli, but in one year increased head yield. Nitrogen accumulated in the head of broccoli. The corn crop accumulated extra Ν in the vegetation and this was assumed to be luxury uptake. The difference in response to Ν of corn and broccoli was assumed to be the result of a difference in Ν use or uptake efficiency rather than overall demand, since the total above-ground uptake by corn and broccoli was quite similar.
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Kowalenko et al. (1987) studied this question.