Nitrogen Fertilizer Potential of an Experimental Urea Formaldehyde 1

An experimental urea formaldehyde (UFC) having less of its nitrogen in the hot water insoluble and thus a higher availability index than the commercial one (UF) was developed by Chemicals and Phosphates Ltd., Haifa, Israel. It was expected that UFC would act as a slow release fertilizer, releasing more of its nitrogen to plants and in a shorter time than UF and thus increasing the nitrogen recovery by plants. In an incubation experiment in a silty clay soil the rates of nitrification of UFC and UF agreed well with the availability indices. In a greenhouse experiment on three soils (silty clay, sandy loam, and sand), with five levels of application, and five crops, [oats ( Avena sativa), barley ( Hordeum vulgare ), rhodes grass ( Chloris gayana ), rhodes grass and oats], UFC was compared to UF and ammonium nitrate (AN). Accumulative N‐uptake by plants at the 1.0 g N/3 kg soil level, on the three soils, was highest in ihe AN treatment and higher in the UFC than in the UF treatments (1.26 vs. 1.16 vs. 0.83, 1.04 vs. 0.97 vs. 0.66, and 0.52 vs. 0.38 vs. 0.25 g N/pot), indicating that the UFC may be more efficient as a nitrogen source than the UF. In another similar greenhouse experiment, with a crop sequence of barley, rhodes grass, rhodes grass, rhodes grass, oats, but combined with leaching, the UFC showed the highest nitrogen recovery by plants, when compared to UF and ammonium nitrate. At the 1.0 g N/pot application level the accumulative N‐uptake on the silty clay soil was 0.80 vs. 0.57 vs. 0.59, respectively, on the sandy loam 0.55 vs. 0.35 vs. 0.44, and on the sand 0.37 vs. 0.22 vs. 0.27. The experimental urea formaldehyde produced a higher nitrogen uptake by plants than the commercial one, indicating a higher nitrogen recovery, both under leaching and nonleaching conditions.