Growth traits and yields of maize (Zea mays) are described for varying fertilizer treatments (fresh cow manure, composted manure, inorganic NPK). Relative N-uptake is 9, 28, and 46% for compost, fresh manure and NPK, respectively. Growth rate and yields are correlated significantly with plant tissue nitrate at 30 days, which diminished in the order NPK>fresh manure>control> compost. Similarly, leaf nitrate at silking stage of maize decreases in the same order, with compost giving lowest soluble N levels. Total-N in grain at harvest does not differ significantly between the treatments, however. It is concluded that rapid early nitrogen release contributes to a high yield but elevated plant nitrate and nitrate remaining in soil after harvest are consequences which must be weighed against it. The difficulties inherent in estimating N-release from organic sources are discussed.