15N-Aided Studies on Effects on Maize and Balance Sheets of Different Form of N Fertilizer

Abstract

              A field experiment using the ¹⁵N technique was conducted on a Reddish Brown Lateritic soil to compare the effects of N fertilizer in the forms of ammonium, nitrate and urea on growth, yields and absorption of some nutrient elements of maize (Zea mays, L) as well as to compare the balance sheets of these forms of fertilizer.

              Ammonium sulfate [(NH₄)₂SO₄], potassium nitrate [KNO₃] and urea were comparable in promotion on growth, yield production, and absorption of N, P, K, Ca, and Mg of maize and distribution of N, K and Mg in different parts of plant but were different in distribution of P, Ca and Mg in some parts of plant. The accumulation of N from ammonium, nitrate and urea in some plant parts were different.

              The recoveries of N from ammonium, nitrate and urea by maize were comparable (25.0-25.95%). The total amounts of fertilizer N remaining in the soil from ammonium (69.7%) and nitrate (68.7%) fertilizers were comparable but larger than that from urea (51.1%). The amounts of N remaining in the 0-15 cm soil layer were in the order: from ammonium>from nitrate>from urea. The amount of N remaining in the 15-30 cm soil layer were: from NO₃>from NH₄ = from urea. The amounts of N remaining in the 30-60 cm soil layer from the three forms of N fertilizer were comparable. Leaching losses of the three forms of N fertilizer were also comparable. Gaseous loss of N from urea was higher than those from ammonium and nitrate. Considering the immediate effects on maize yield and the recovery of the fertilizer N, it would be appropriate to say that (NH₄)₂SO₄, KNO₃ and urea were equally recommendable. However, the comparative residual effects of these fertilizers and improvement in the efficiency of urea when applied by deep placement remained to be seen.