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This article in SSSAJ

  1. Vol. 59 No. 1, p. 145-150
     
    Received: Jan 3, 1994
    Published: Jan, 1995


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doi:10.2136/sssaj1995.03615995005900010023x

Nitrogen and Water Interactions in Trickle-Irrigated Watermelon

  1. J. W. Pier and
  2. T. A. Doerge 
  1. Dep. of Biological Systems Engineering, Univ. of Nebraska, 233 LW Chase Hall, Lincoln, NE 68583-0726
    Dep. of Soil and Water Science, Univ. of Arizona, 429 Shantz Bldg. no. 38, Tucson, AZ 85721

Abstract

Abstract

Rising water costs and concern for groundwater contamination by NO3 and other agricultural chemicals are forcing growers in arid regions to improve irrigation and N fertilization efficiency. Applying N and water through a subsurface drip irrigation system in conjunction with in-season monitoring techniques for assessing crop water and N status has the potential to greatly improve water and N use efficiency. The objectives of this research were to: (i) investigate the interactive effects of water and N applied through a subsurface trickle irrigation system on watermelon [Citrullus lanatus (Thumb.) Matsum and Nakai var. lanatus] fruit yield and on the potential for leaching losses of NO3, and (ii) determine the optimum range of soil water tension for subsurface trickle-irrigated watermelon. Field experiments were conducted during 1990 and 1991 on a reclaimed Casa Grande soil (fine-loamy, mixed, hyperthermic Typic Natrargid) in southern Arizona. Levels of target soil water tensions and fertilizer N were arranged in a factorial design to determine fruit yield response surfaces. Tensiometers at 0.3- and 0.6-m depth were used to monitor soil water tension throughout the growing season. Marketable watermelon yield showed a pronounced positive water × N interaction in both years of the study. Predicted marketable yields were 90 Mg ha−1 when mean soil water tension was 6 kPa and applied N was between 200 and 270 kg ha−1 in 1990 and a predicted yield maximum of 102 Mg ha−1 at 7.2 kPa and 336 kg N ha−1 in 1991. Scheduling of irrigations using feedback from tensiometers proved very useful in providing optimum amounts of water while avoiding conditions that favor N loss through leaching or denitrification.

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