Three ammonium‐tagged fertilizers, two nitrate‐tagged fertilizers, and N‐tagged urea were added to three soils in green house pots. Plant uptake of surface‐applied fertilizer N was measured by growing four crops over a period of 314 days. In another experiment, tagged ammonium sulfate, ammonium nitrate, and aqueous ammonia, were compared using band application. With surface application, uptake of fertilizer N in plant tops varied from 35 to 71%, with nitrate sources showing the higher values. Residual N in soil ranged from 18 to 41%, and its availability decreased with successive crops. All ammonium sources suffered some loss with surface application, especially aqueous ammonia, but losses were negligible with band application. Availability of soil N was influenced to some extent by the nature of the fertilizer applied. From 5 to 13% of the soil N was utilized by four crops.
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Broadbent et al. (1968) studied this question.