Nitrogen Utilization Efficiency in Melons Using Soluble and Slow Release Fertilizers

Abstract

A field experiment was conducted at the Maricopa Agricultural Center on a Casa Grande sandy loam soil to compare the nitrogen (N) utilization efficiency achieved using slowrelease and conventional nitrogen fertilizers under subsurface drip irrigated melon production conditions. 'Mirage' watermelon, 'Laguna' cantaloupe and 'Gallicum' honeyloupe were used as the test crops. Single, preplant applications of three slow - release products (methylene urea, coated ammonium sulfate and coated urea) were compared with the use of urea -ammonium nitrate added in either one or three split applications. The total amount of N applied to all treated plots was 100 lbs. per acre. Whole plant samples were taken four times during the season to determine N uptake patterns. Petioles from the youngest fully expanded leaves were sampled on four dates throughout the season to monitor the N status of all plots. At harvest, total and marketable melon yields were determined. In general, the methylene urea treatment was superior to the use of coated (NH₄)₂SO₄ which in turn was far superior to the coated urea product. The split UAN and preplant UAN treatments had the highest numerical values for total N uptake for all three melon types. However, these values were usually not statistically different from the N uptake in response to the three slow- release N treatments. The type of water delivery system may have reduced the potential advantages of using slow-versus fast-release N fertilizers.